Table of Content

16 February 2022, Volume 55 Issue 4

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CROP GENETICS & BREEDING·GERMPLASM RESOURCES·MOLECULAR GENETICS

Evaluation of Rice Blast Resistance and Genetic Structure Analysis of Rice Germplasm in Heilongjiang Province

ZHANG YaLing, GAO Qing, ZHAO Yuhan, LIU Rui, FU Zhongju, LI Xue, SUN Yujia, JIN XueHui

Scientia Agricultura Sinica. 2022, 55(4):  625-640.  doi:10.3864/j.issn.0578-1752.2022.04.001

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【Objective】Rice blast seriously threatens rice production in Heilongjiang Province and the breeding and utilization of anti-blast varieties are the most economical, safe and effective measures to control it. This study explored the resistance of rice varieties in Heilongjiang Province; clarified the resistance effect of disease resistance genes, and provided a basis for the selection and utilization of germplasm resources of rice blast in Heilongjiang Province. 【Method】 In the autumn of 2018, 134 rice strains were collected from the main rice area in Heilongjiang Province, and the resistance of 50 dominant rice varieties was analyzed. For the reported 35 rice blast resistance genes, a comparison was made between the varieties and positive control varieties. Sequencing results of some positive control varieties were compared with the reference sequence published in the National Centre for Biotechnology Information to analyze the existence of rice blast resistance genes in the corresponding varieties. Through the correlation analysis of gene aggregation type and breed resistance performance, the genotypes related to the resistance performance of rice varieties in Heilongjiang Province were clarified. 【Result】 Among 50 rice varieties in Heilongjiang Province, Longgeng 20 had the best resistance (R). Longgeng 67, Longken 202, Longgeng 40, Longgeng 31, Longgeng 57 and Longgeng 43 had moderate disease resistance; whereas, 43 varieties such as Jiahe 1 had relatively low resistance. Through the analysis of variety combination resistance, we found that 33 pairs of Longgeng 20 + Longgeng 67 had a high RAC（resistance association coefficient) value, low VAC (virulence association coefficient) value and good combined disease resistance. The matching structure showed potential for application. The identification of resistance genes carried by specific primers showed that Pish, Pi36, Pi33 and Pi-CO39 were detected, and Pi63, Ptr, Pi37, Pi64, pi21, Pi9, Pi54, Pikh, Pia, Pikp, Pi35, Pikm and Pik were between 50%-100% of occurences frequency, indicating that such genes were widely used in rice breeding in Heilongjiang Province. The detection rate of Pita, Pib, Pii, Pi5, Piz-t, Pi50 and Pi2 was between 10% and 50%; Pid2 was detected in in two varieties, and Pigm was detected in Jigeng 88. However, Pit, Pid3, Bsr-d1, Pi25, Pid3-A4, Pi56, Pi1, Pike and Pb1 were not detected in the cultivars, indicating that such genes are less distributed in rice varieties in Heilongjiang Province. The variety genotype analysis found that the varieties carried 12-19 resistant genes, with a total of 58 genotypes, indicating that the test varieties had rich blast resistance gene combination types. By analysis, the single gene and gene polymerization with disease resistance showed that the distribution frequency of Pi2, Piz-t, Pi50, Pi5 and Pii corresponded to frequency of resistance. We found that the more varieties carrying resistance genes, the higher the frequency resistance, and six varieties that carrying Pi2+Piz-t+Pi50+α polymerization types showed resistance. 【Conclusion】 Our results have demonstrated the following: the resistance of rice germplasm resources in Heilongjiang province is low; combination planting of different varieties could be usefully applied; the distribution of blast resistance genes is different in the participating varieties; Pi2, Piz-t, Pi50, Pi5 and Pii play a leading role in disease resistance, and Pi2+Piz-t+Pi50+α gene polymerization type could contribute to improving rice blast resistance.

Evaluation of Edible Quality of Roasted Peanuts and Indexes Screening

BIAN NengFei, SUN DongLei, GONG JiaLi, WANG Xing, XING XingHua, JIN XiaHong, WANG XiaoJun

Scientia Agricultura Sinica. 2022, 55(4):  641-652.  doi:10.3864/j.issn.0578-1752.2022.04.002

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【Objective】The objective of this study was to explore the evaluation methods of edible quality of roasted peanuts, screen identification indexes, establish prediction model, and provide basis for peanut edible quality breeding. 【Method】The kernels of 51 peanut varieties (lines) with different quality types were used as experimental materials. A total of 27 edible quality indexes related to tastes, appearances, textures and nutrition of roasted kernels were measured. Correlation analysis and principal component analysis were used to comprehensively evaluate the edible quality of roasted peanut kernels. Cluster analysis was used to classify edible quality of 51 peanut varieties (lines). Regression analysis were used to establish predictive model and index screening. 【Result】27 indexes had different ranges of variation in 51 peanut varieties (lines), with coefficients of variation ranging from 5.86% to 39.65%. There were significant or extremely significant related indexes for each individual index. The correlation coefficients of 175 groups reached significant level, and the 140 groups reached extremely significant level. The 27 individual indexes were converted into 5 independent comprehensive indexes through principal component analysis, and their contribution rates respectively were 35.70%, 20.63%, 10.07%, 8.19% and 6.38%, representing the information of 80.97% of all data. The comprehensive evaluation analysis showed that the average F value of the roasted edible quality of 51 peanut varieties (lines) was 0.76. Xuhuatian 29 had the highest F value (F=1.51) and the best roasting edible quality. Xuhua 15 had the lowest F value (F=0.03) and the worst roasting edible quality. The correlation analysis showed that 21 indexes were significantly correlated with F value. Cluster analysis was performed on the comprehensive value F of peanut roasting edible quality, and 51 varieties (lines) were divided into 3 categories. The first category was of good edible quality, including 4 varieties of Xuhuatian 29, Jihuatian 1, Linhua 16 and Xuhuatian 30. The second category was of general edible quality and contained 33 varieties (lines). The third category was of poor edible quality and contained 14 varieties (lines). Using stepwise regression analysis method, the prediction model of roasting edible quality was established as: Y=0.979+ 0.021X₇+0.081X₂₁+0.009X₂₀-0.034X₁₉-0.074X₂₇ (R²=0.953). Then, 5 identification indexes were screened, which were the hundred kernel weight, sucrose content, protein content, fat content and behenic acid content. The analysis of characteristics showed that the four varieties with good roasting edible quality had medium to high hundred kernel weight, high sucrose content, medium protein content, low fat content, and low to medium behenic acid content. According to the prediction model, this category varieties still need to be improved to increase protein content and reduce behenic acid content. 【Conclusion】Hundred kernel weight, sucrose content, protein content, fat content and behenic acid content could be used to identify the edible quality of roasted peanuts. It is determined that high-quality roasted peanut varieties should have the characteristics of medium to large kernels, high oleic acid content, high sucrose content, high protein content, low fat content and low behenic acid content.

Current Status and Perspectives of Innovation Studies Related to Foxtail Millet Seed Industry in China

JIA GuanQing, DIAO XianMin

Scientia Agricultura Sinica. 2022, 55(4):  653-665.  doi:10.3864/j.issn.0578-1752.2022.04.003

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Seed industry was the ‘chip’ of agricultural development, and original innovation have played essential roles in maintaining stable development of modern agriculture. The No. 1 central document of China released in 2021 has put forward requirements of original innovation researches essential for supporting further developments of Chinese crop seed industry. Foxtail millet is a traditional crop species cultivated for both forage and grain food consumption in China, and to date, foxtail millet was still widely planted as minor cereals in China with the largest scale of field production and commercial consumption across the globe. Foxtail millet was originated from China and cultivated for thousands of years to ensure development of Chinese agricultural culture and field crop production. Original innovation in foxtail millet has promoted initial development of foxtail millet seed industry based on operation of herbicide-resistant varieties in recent decades, including breakthroughs in areas of heterosis utilization, herbicide resistant breeding, dwarfing variety creation and genomics study of this important crop species. Achievements of fundamental researches including germplasm characterization, development of breeding tools, coordination and regulation of vital traits, seeds propagation and truth identification of commercial varieties have provided more opportunities for further development of the seed industry of foxtail millet. However, challenges of seed industry development still exist in China, including deficiency of excellent germplasms, backward breeding approaches, inharmonious of yield and quality characters, unclear criterion of seed propagation and market supervision problems. Future direction of original innovation studies related to foxtail millet seed industry were as follows: 1) Large scale breeding systems constructed from utilizations of crop phenomics and genomic modification technologies, double haploid breeding and genome selection tools, identification and pyramiding of superior haplotypes; 2) Seeds production, store and quality supervision systems constructed from techniques of development and water content of commercial seeds, and establishment of molecular fingerprints and efficient utilization of heterosis in foxtail millet; 3) Construction of innovation system through integrating education, research and promotion sectors of seed industry and stimulate personnel training in China.

TILLAGE & CULTIVATION·PHYSIOLOGY & BIOCHEMISTRY·AGRICULTURE INFORMATION TECHNOLOGY

Beneficial Effects of Precision Drill Sowing with Low Seeding Rates in Machine Transplanting for Hybrid Rice to Improve Population Uniformity and Yield

WANG YaLiang, ZHU DeFeng, CHEN RuoXia, FANG WenYing, WANG JingQing, XIANG Jing, CHEN HuiZhe, ZHANG YuPing, CHEN JiangHua

Scientia Agricultura Sinica. 2022, 55(4):  666-679.  doi:10.3864/j.issn.0578-1752.2022.04.004

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【Objective】 The aim of this study was to clarify the beneficial effect of precision drill sowing (PS) in machine transplanting for improving the population uniformity and yield of hybrid rice under low seeding rate, and to establish the theory and technology for machine transplanting with sparse sowing and fewer seedling in machine transplanting with flat seedling of hybrid rice. 【Method】 Indica-japonica hybrid rice ‘Yongyou 1540’ was used in this study, and the experiment was conducted at Chonghua country (Yuhang district) and experimental base of China National Rice Research Inistitute (Fuyang district) at the same time. PS was layout set at 18 horizontal hills×40 vertical hills in the standard seedling tray for machine transplanting. The sowing amount per hill in seedling tray was set as 2.5 seeds (43.2 g/tray, T₁), 3.5 seeds (60.5 g/tray, T₂), and 4.0 seeds (69.1 g/tray, T₃), and the same seeding rates in traditional broadcast sowing (BS) for machine transplanting were set as the control. Then, the seed distribution, seedling quality, machine planting quality, dry matter accumulation in rice population, the uniformity of the number of productive tillers and yield formation were investigated. 【Result】(1) Compared with BS, PS improved the uniformity of seed distribution in seedling tray. (2) PS significantly enhanced rice seedling quality, and increased the dry matter accumulation and uniformity of seedling. PS increased the seedling uniformity by 47.5% on average among different seeding rates than that under BS, which presented a more beneficial effect with low seeding rates. (3) Compared with BS, PS reduced the missing hill percent in machine transplanting by 8.9 percentage point on average, and PS enhanced the uniformity of seedling number transplanted per hill by 87.8% on average, meanwhile, the percentage of hills with 2-3 seedling transplanted was the highest at T₂ under PS. (4) PS increased the number of tillers at tillering peak stage to increase the number of productive panicles in rice population. Among the different seeding rate treatments, PS increased the number of productive tillers by 6.7% on average, meanwhile, which enhanced the uniformity of the number of productive tillers by 40.2%, in which T₂ presented the highest productive tillers and productive tillers uniformity, meanwhile PS enhanced the leaf area index and dry matter accumulation of rice population. (5) PS enhanced the rice yield by 9.0% on average compared with BS by increasing in the number of productive tillers, in which T₂ presented the highest yield. With the increasing of seeding rate, the increasing rate of yield under PS in contrast to BS presented a reduction tendency, while a decreasing was observed in the contribution rate of machine-transplanted seedlings to yield. (6) Correlation analysis showed that the population uniformity of the number of productive tillers positive correlated to leaf area index, dry matter accumulation and rice yield. 【Conclusion】Precision drill sowing in machine transplanting improved the uniformity of seed distribution, reduced the missing hill percent, increased the uniformity of seedling transplanted per hill, therefore contributed to enhance the rice population uniformity and yield. Precision drill sowing was an effective method to achieve higher yield with flat seedling in machine transplanting under low seeding rates of hybrid rice.

Accumulated Temperature Requirement for Field Stalk Dehydration After Maize Physiological Maturity in Different Planting Regions

HUANG ZhaoFu, LI LuLu, HOU LiangYu, GAO Shang, MING Bo, XIE RuiZhi, HOU Peng, WANG KeRu, XUE Jun, LI ShaoKun

Scientia Agricultura Sinica. 2022, 55(4):  680-691.  doi:10.3864/j.issn.0578-1752.2022.04.005

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【Objective】Under the background of mechanical grain harvesting, the purpose of this study was to determine the accumulated temperature requirements of maize in different planting regions after physiological maturity by dehydration to the suitable harvest date, so as to provide the theoretical guidance for selecting suitable grain harvesting varieties, and rationally arrange agricultural operations and improve mechanical utilization efficiency in each planting region. 【Method】From 2014 to 2018, 141 maize varieties with different maturity periods selected to observe the dynamic changes of grain moisture content at typical test points in the northwest maize region (NW), the north maize region (NM) and Huang-huai-hai maize region (HM). Combining with meteorological date, the accumulated temperature requirements of maize field stalk dehydration to 25% and 20% grain moisture content after the physiological maturity were analyzed in different production regions. 【Result】The grain moisture content was different at physiological maturity in different production regions. The average grain moisture content was 28.5%, 29.9% and 29.6% in HM, NW and NM, respectively. Correlation analysis showed that there was no significant correlation between the growth period of different varieties and the grain moisture content at physiological maturity. The accumulated temperature of grain moisture content from physiological maturity to 25%, 20% and grain moisture content at physiological maturity were used as indexes. By using the two-way average method, the tested varieties were divided into 4 types, including low accumulated temperature demand and high moisture content (I), high accumulated temperature demand and high moisture content (II), low accumulated temperature demand and low moisture content (III), and high accumulated temperature and low moisture content (IV). For the northwest China, north China and northeast China, III and IV could be selected, but IV varieties needed to reserve enough accumulated temperature to dehydrate in the field. While the summer maize with growing twice a year in the Huanghuaihai region, III varieties could better coordinate the production and allocation of wheat and maize, and make full use of the excess temperature that could be used for grain dehydration. 【Conclusion】 Because of different dehydrating conditions such as temperature, the days when grain moisture content from physiological maturity to 25%, 20% showed that the northwest maize region was longer than the north maize region and Huang-huai-hai maize region. Grain moisture content and harvest quality can be effectively reduced by selecting the accumulated temperature varieties suitable for different regions and scientifically setting the harvest date.

Spatial and Temporal Difference Analysis of Wheat Yield and Yield Components in Henan Province Based on GIS

XIONG ShuPing, GAO Ming, ZHANG ZhiYong, QIN BuTan, XU SaiJun, FU XinLu, WANG XiaoChun, MA XinMing

Scientia Agricultura Sinica. 2022, 55(4):  692-706.  doi:10.3864/j.issn.0578-1752.2022.04.006

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【Objective】The aim of the study was to clarify the main direction of further improving wheat grain yield in the different wheat regions of Henan province by analyzing the temporal and spatial differences of wheat yield and yield components. 【Method】The spatial distribution maps of wheat grain yield and yield components in four wheat regions of Henan province from 2017 to 2020 were drawn based on the field monitoring data of fixed wheat monitoring stations in Henan province, and the optimal model was selected by geographic information system (GIS), and then the differences and relationships among different wheat regions were analyzed. 【Result】The wheat yield and yield components were different between different wheat regions. Among them, the yield and the spike number in North Henan and Central Henan were significantly higher than those in South Henan and West Henan, and the North Henan’s were the most, while the West Henan’s were the least. However, the kernels per ear showed that the production regions in Central Henan, South Henan and North Henan were significantly more than West Henan’s, and the most in Central Henan, while the least in West Henan. The 1000-grains weight in North Henan was the most, while South Henan was the lowest. The wheat yield, spike number, kernels per ear, and 1000-grains weight in Central Henan and South Henan (Luohe, Zhoukou, Zhumadian, etc.) were often more than that of other places in Henan, and this performance were stable between years. Correlation analysis showed that the relationship between the three elements of yield and yield in different wheat regions was inconsistent. Specifically speaking, the 1000-grains weight, the kernels per ear and the spike number in the North Henan and Central Henan regions had the largest correlation with the yield. However, the relationship with yield in East Henan and South Henan were appeared as: the spike number was the largest, the 1000-grains weight was the second, and the kernels per ear was the smallest. Path analysis was carried out on the three elements of yield and yield in those four wheat regions, which further showed that there were differences in the contribution of the yield components to yield. More precisely, the spike number and kernels per ear contributed the most to the yield in North Henan, with a direct path coefficient of 0.67. The contribution of yield components to yield in Central Henan and South Henan regions was spike number> kernels per ear> 1000-grain weight; while in West Henan, the greatest was the spike number, followed by 1000-grain weight, and the kernels per ear was the least; the direct path coefficients were 0.69, 0.45 and 0.39, respectively. Meanwhile, the indirect diameter coefficient showed that enhancing the yield increase effect of the 1000-grain weight was better than that of the kernels per ear in North Henan, Central Henan, and South Henan regions, but the West Henan was better by enhancing the kernels per ear. 【Conclusion】There were large differences in wheat yield and yield components in Henan different wheat regions and between years. At the same time, the three components of wheat yield in different wheat regions had different contributions to yield. Therefore, in term of further tapping the potential of wheat production for Henan province, it should be accurately classified by regions and years. As far as the conditions of this experiment concerned, based on stabilizing the spike number in the Henan province wheat regions, the production regions of North Henan, Central Henan, and South Henan should focus on further tapping the potential of 1000-grain weight, while the West Henan improving the yield increase effect of the kernels per ear were better than that of the 1000-grain weight.

PLANT PROTECTION

Development of Artificial Inoculation Methodology for Evaluation of Resistance to Fusarium Crown and Root Rot and Screening of Resistance Sources in Tomato

WANG MengRui, LIU ShuMei, HOU LiXia, WANG ShiHui, LÜ HongJun, SU XiaoMei

Scientia Agricultura Sinica. 2022, 55(4):  707-718.  doi:10.3864/j.issn.0578-1752.2022.04.007

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【Objective】The objective of this study is to explore the resistance identification technology of Fusarium crown and root rot (FCRR), carry out the resistance identification and analysis of tomato germplasm resources and varieties, enrich the available tomato resources resistant to FCRR, and to lay the foundation for the cultivation of tomato varieties that resistant to FCRR. 【Method】In the present study, four parameters that influence the inoculation effect including inoculum concentration, seedlings stage, environmental temperature and inoculation methods were studied using susceptible line Heinz 1706 infected with Fusarium oxysporum f. sp. radicis-lycopersici (Forl). Subsequently, 100 tomato materials were identified through artificial inoculation at seedling stage as well as the molecular markers linked to the resistance gene. 【Result】The disease incidence and disease index of FCRR increased in a certain range along with the increase of inoculum concentration, and the actual levels of plant resistance could be revealed with the inoculum of 10⁷spores/mL, for which the disease incidence and disease index were 100% and 89.2, respectively. The disease index was not significantly different among different seedling ages when the host was inoculated at 2 to 5 leaf stage. The effects of different environmental temperatures after inoculation on the disease index of FCRR were significantly different and the lower temperature (20℃) condition was more favorable to the occurrence of FCRR. The incidence and disease index were higher and the effect was stable using root dipping and root irrigation methods, which were significantly better than stem injection. The result of inoculation identification suggested that 38 materials showed resistance to FCRR among 100 tomato materials, which could be used for breeding or production in tomato for FCRR resistance. In addition, among the reported markers linked to Frl, SCAR_Frl has the lowest accuracy of 51%, while C2-25 has the accuracy of 59% and the accuracy of PNU-D4 is 83%, which is expected to be used in marker-assisted selection (MAS) for FCRR resistance. 【Conclusion】The established assessment system can identify levels of the resistance to FCRR in tomato seedlings, which can be used for identification and screening of tomato materials.

Proliferation of Two Types Prophage of ‘Candidatus Liberibacter asiaticus’ in Diaphorina citri and their Pathogenicity

HUANG JiaQuan,LI Li,WU FengNian,ZHENG Zheng,DENG XiaoLing

Scientia Agricultura Sinica. 2022, 55(4):  719-728.  doi:10.3864/j.issn.0578-1752.2022.04.008

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【Background】In China, citrus Huanglongbing is a destructive disease associated with ‘Candidatus Liberibacter asiaticus’ (CLas), which currently threatening the sustainable development of citrus industry. Previous studies had identified three types of prophage sequences in the genome of CLas strains. Prophage group typing analysis revealed that the Type 2 prophage strains and Type 1+3 prophage strains dominated in Guangdong Province. However, the difference in propagation capacity of these two strains of CLas in Asian citri psyllid (Diaphorina citri) and pathogenicity of these two strains leading by insect transmission remains unknown. 【Objective】The objective of this study is to assess the difference in proliferation capacity between Type-2-CLas and Type-1+3-CLas in D. citri and the pathogenicity variations between them on Citrus reticulata Blanco cv. Shatangju. 【Method】The buds with different strains of CLas were grafted to healthy Shatangju. Fifty nymphal and fifty adult D. citri were caged on the young shoots of infected Shatangju to acquire different strains of CLas for 6, 12, and 18 days, respectively. Real-time quantitative PCR (qPCR) was used to detect and analyze the difference in the acquisition rate and quantity of Type-2-CLas and Type-1+3-CLas between the nymphal stage and the adult stage of D. citri. Further, twenty adult D. citri infected with Type-2-CLas or Type-1+3-CLas were placed on the young shoots of healthy Shatangju to inoculate for two weeks, respectively. The D. citri were collected and detected by qPCR. The general information of infection rate and quantity of CLas was collected. Symptom development of Shatangju and titers of CLas in leaves were monitored each month. Morphological change of leaves phloem and parenchyma cell was visualized by light microscopy 360 days after inoculation. 【Result】There was no significant difference between acquisition rate and quantity of Type-2-CLas and Type-1+3-CLas detected in D. citri that fed on the infected plant at the nymphal stage. In contrast to fed as nymphs, the acquisition rate and quantity of Type-2-CLas were significantly higher than Type-1+3-CLas when D. citri fed on infected plant at the adult stage. The leaves presented more severe mottled symptom after inoculation with Type-2-CLas at 120 d after D. citri removal. The immature leaves at young shoots had an obstacle on turning green, presenting leathery, small size, and yellowing which was infected with Type-2-CLas. The symptoms on Type-1+3-CLas infected plants were presented as typical mottled leaves and leathery. Anatomical analyses indicated that Type-2-CLas caused more severe damage to phloem and accumulated more starch in parenchyma cell even if the titer of Type-1+3-CLas was closed to Type-2-CLas. 【Conclusion】Compared to Type-1+3-CLas, Type-2-CLas was more capable of invading and proliferating in adult D. citri, accompanied by a higher titer of CLas which indirectly proved the high contagious capacity of Type-2-CLas. The young leaves infected with Type-2-CLas presented symptoms of uniform yellowing, small size, while infected with Type-1+3-CLas showed lightly mottled and leathery. Type-2-CLas destroyed more phloem cells and caused severe starch accumulation, indicating that Type-2-CLas had stronger pathogenicity to citrus than Type-1+3-CLas.

SOIL & FERTILIZER·WATER-SAVING IRRIGATION·AGROECOLOGY & ENVIRONMENT

Effects of Crop Residue Decomposition on Soil Inorganic Nitrogen and Greenhouse Gas Emissions from Fluvo-Aquic Soil and Shajiang Black Soil

ZHANG XueLin, WU Mei, HE TangQing, ZHANG ChenXi, TIAN MingHui, LI XiaoLi, HOU XiaoPan, HAO XiaoFeng, YANG QingHua, LI ChaoHai

Scientia Agricultura Sinica. 2022, 55(4):  729-742.  doi:10.3864/j.issn.0578-1752.2022.04.009

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【Objective】The purpose of this study was to examine the effects of crop residue decomposition on soil available nitrogen (N) and nitrous oxide (N₂O) emissions, and provide a theoretical basis for reasonable N fertilizer rate in agricultural soils to promote residue decomposition, to increase soil available nutrients, and to reduce N₂O emissions. 【Method】The indoor soil incubations with nylon decomposition bag were conducted to study the effects of crop residue types (wheat and maize), soil types (fluvo-aquic soil: AS and Shajiang black soil: LS) and N fertilizer rates (N0: 0; N1: 180 kg N·hm^-2; N2: 360 kg N·hm^-2) on soil N₂O emission. A control (CK) without residue addition and N fertilizer input was also established for the two soil types. Inorganic N content, N₂O and CO₂ flux, and soil enzyme activity were measured in incubated soil. 【Result】Compared with CK, soil inorganic N content under N0 decreased significantly, which was decreased by 0.8 mg·g^-1 for 1 g wheat residue addition or 0.4 mg·g^-1 for 1 g maize residue addition. Compared with AS, soil inorganic N content in LS reduced by 16% with wheat residue addition, by 41% with maize residue addition. Compared with wheat residue addition, soil inorganic N content in AS and LS increased by 111% and 252% with maize residue addition, respectively. Compared with CK, both soil N₂O and CO₂ flux increased with wheat residue or maize residue addition, and the total accumulation of soil N₂O flux under N0 treatment increased by 70% and 47% with wheat residue and maize residue addition, by 346% and 154% for CO₂ accumulation, and by 53% and 71% for global warming potential, respectively. Compared with AS, soil N₂O flux in LS reduced by 38% and 61% with wheat residue and maize residue addition, by 12% and 51% for the accumulation of N₂O flux, and by 28% and 16% for the accumulation of CO₂ flux, respectively. And the global warming potential in LS increased by 13% with the wheat residue addition in comparison with that in AS, while declined by 44% with maize residue addition. Compared with wheat residue addition, the accumulation of soil N₂O flux with maize residue addition increased by 88% in AS, and by 6% in LS, and reduced by 21% and 6% for the accumulation of soil CO₂ flux in AS and LS, respectively. And the global warming potential with maize residue addition was 91% higher than that of wheat residue addition under the conditions of different N fertilizer rates and soil types. Compared with N0 and N2, soil N₂O flux and their global warming potential under N1 treatment reduced significantly with wheat residue or maize residue addition in LS. Compared with CK, soil invertase activity increased with wheat residue or maize residue addition in both AS and LS, while which declined for soil Catalase and O₂ content. Compared with wheat residue addition, soil urease activity, Catalase, and invertase activities declined with maize residue addition. Compared with AS, soil urease and catalase activities in LS reduced with wheat residue or maize residue addition, while soil O₂ content increased. The catalase activities and O₂ content was significantly and negatively related with soil N₂O flux. 【Conclusion】The decomposition of wheat residue and maize residue reduced soil inorganic N content while increasing soil N₂O flux. Soil inorganic N content and N₂O flux with maize residue addition were higher than that of wheat residue. Emissions of N₂O from Fluvo-aquic soil with wheat or maize residue addition was higher than that from Shajiang black soil. When combined with suitable N fertilizer rate, neither residues additions in Shajiang black soil increased N₂O flux and global warming potential. These results suggested that, in the field, comprehensive management methods by returning residue to soil should consider the residue type, soil type and rate of N fertilization.

SOIL & FERTILIZER·WATER-SAVING IRRIGATION·AGROECOLOGY & ENVIRONMENT

Effects of the Mixted-cropping of Chinese Milk Vetch and Rape on Soil Nitrous Oxide Emission and Abundance of Related Functional Genes in Paddy Fields

YANG BinJuan,LI Ping,HU QiLiang,HUANG GuoQin

Scientia Agricultura Sinica. 2022, 55(4):  743-754.  doi:10.3864/j.issn.0578-1752.2022.04.010

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【Objective】The aim of this study was to determine how a green manure mixted-cropping affected nitrous oxide (N₂O) emissions from soil and the abundance of related functional genes in paddy field soil. The ultimate aim of this research was to identify a green manure mixted-cropping that had high and stable yields and reduces emissions, and was suitable for cultivation in the double-rice areas of southern China. 【Method】The effects of mixted-cropping of Chinese milk vetch and rape at different ratios (single Chinese milk vetch, single rape, 3/4 Chinese milk vetch +1/4 rape, 1/2 Chinese milk vetch +1/2 rape, and 1/4 Chinese milk vetch +3/4 rape) on N₂O emissions and the abundance of related functional genes in paddy field soil were determined and compared. 【Result】(1) The crop species affected N₂O emissions. The N₂O emissions were similar among the different treatments. Among them the N₂O emissions from winter crop soil were mainly concentrated at its flowering stage, and those during the rice growing period were concentrated at the tillering, filling, and maturity stages of early and late rice crops. On the whole, the N₂O emissions from paddy fields were lower N₂O in the early rice season than that in the late rice season. The overall N₂O emissions flux in the paddy fields was higher in 2018 than that in 2019. (2) There was no significant difference in N₂O cumulative emission of early rice under different treatments. The cumulative N₂O emissions from a single seeding treatment were lower than those from mixed treatments over two consecutive years. The annual cumulative N₂O emissions were lowest under CK1 in 2019. Among all the mixed treatments, the 3/4 Chinese milk vetch +1/4 rape treatment had the lowest annual cumulative N₂O emissions. (3) In general, the copy number of amoA-AOA and amoA-AOB genes was higher in the soil of late rice than that in the soil of early rice, and the copy number of AmoA-AOA was up to two orders of magnitude higher in late rice soil than in early rice soil. The copy numbers of nirS, nirK and nosZ were higher in the soil of late rice crops than that in the soil of early rice crops, and the copy number of nirS was up to two orders of magnitude higher than those of nirK and nosZ in late rice soil. The mixted-cropping of Chinese milk vetch and rape increased the abundance amoA-AOA and amoA-AOB genes in soil, and amoA-AOA was the dominant functional gene. It also increased the abundance of nirS, nirK and nosZ genes in soil, and nirS gene was the dominant gene. The copy number of genes related to denitrification was one to three orders of magnitude higher than the copy number of genes related to nitrification, indicating that denitrification made a larger contribution to N₂O emissions. 【Conclusion】Overall, the 3/4 Chinese milk vetch + 1/4 rape-early rice-late rice was the best mixed planting system, because it had the best combination of low N₂O emissions as well as high yield and high fertility.

HORTICULTURE

Interpretation of the Case of Bud Sports Selection to Promote the High-Quality and Efficient Development of the World’s Apple and Citrus Industry

CHEN XueSen, YIN HuaLin, WANG Nan, ZHANG Min, JIANG ShengHui, XU Juan, MAO ZhiQuan, ZHANG ZongYing, WANG ZhiGang, JIANG ZhaoTao, XU YueHua, LI JianMing

Scientia Agricultura Sinica. 2022, 55(4):  755-768.  doi:10.3864/j.issn.0578-1752.2022.04.011

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This review summarized the research progress of plant epigenetics and fruit tree bud sports selection, and analyzed the classic cases of bud sports selection promoting the high-quality and efficient development of the word’s apple and citrus industries. The main results were summarized as follows: (1) Epigenetics caused by DNA methylation and histone modification, etc., was widely involved in various plant growth and development processes and adversity stress responses; (2) The selection of fruit tree bud sports was the best among the best. It had six characteristics, such as high efficiency, reproducibility, stability, diversity and pleiotropy, epigenetic characteristics, and practical effects. At present, more than 600 varieties of fruit tree bud sports have been selected, such as apples and citrus; (3) In response to the problems of the four varieties of Fuji, Delicious, Navel Oranges and Satsuma Mandarin, a series of new varieties have been bred using continuous multi-generation bud sports selection technology, forming a huge variety group and promoting the high-quality and efficient development of the industry. Therefore, two aspects should be further studied in the future: one is to further strengthen the mechanism of fruit tree bud sports and to promote the innovation of breeding technology; The second is to further enhance the awareness of the innovation of fruit tree bud sports selection and to further strengthen the understanding of the importance of the fruit tree industry, and the technical route of combining Mendelian inheritance and epigenetic inheritance should be adopt, combining conventional and molecular technology as well as hybrid breeding and bud sports selection, so as to increase the research efforts of fruit tree bud sports selection and new varieties breeding, and provide varieties support for the high-quality development of the fruit tree industry.

Study on the Chemical Constituents of Yongchun Foshou Oolong Tea Based on Metabolomics

PENG JiaKun, DAI WeiDong, YAN YongQuan, ZHANG Yue, CHEN Dan, DONG MingHua, LÜ MeiLing, LIN Zhi

Scientia Agricultura Sinica. 2022, 55(4):  769-784.  doi:10.3864/j.issn.0578-1752.2022.04.012

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【Objective】 Oolong teas made with different tea cultivars have a great difference in flavor and chemical components. In this study, non-targeted metabolomics, absolute quantitative analysis, and multivariate statistics analysis were used to investigate the chemical differences among Yongchun Foshou (YCFS), Tieguanyin (TGY) and Shuixian (SX) oolong tea and to screen characteristic chemical components of YCFS oolong tea, as well as to study the influence of tea cultivars on chemical components and sensory quality of oolong tea. 【Method】 Camellia sinensis cv. Foshou was used as the main research sample and Camellia sinensis cv. Tieguanyin and Camellia sinensis cv. Shuixian were used as the controls. Three tea cultivars were manufactured into fresh-scent, strong-scent and aged-scent oolong teas. Ultra-high performance liquid chromatography-quadrupole-time-of-flight mass spectrometry (UHPLC-Q-TOF/MS) was used for non-targeted metabolomics analysis to screen differential compounds in the oolong teas made from different cultivars. In addition, ultra-high performance liquid chromatograph, amino acid analyzer and ultra-high performance liquid chromatography-quadrupole-orbitrap-mass spectrometry (UHPLC-Q-Orbitrap-MS) was applied for absolute quantifications of main chemical constituents and differential compounds in oolong teas made from different tea cultivars. 【Result】 Compared with the control oolong teas of same scent type, YCFS oolong tea had relatively higher contents in total amino acid and theanine. The contents of total catechins and caffeine were not significantly different among the 3 cultivars in fresh-scent and strong-scent oolong teas, which were the highest in YCFS in aged-scent oolong teas. The content of gallic acid was SX>YCFS>TGY in 3 scent types oolong teas. Metabolomics analysis combined with multivariate statistics analysis showed that the compound patterns in oolong teas made from different tea cultivars were significantly different. In fresh-scent, strong-scent and aged-scent oolong teas, there were 50, 59 and 47 differential compounds between YCFS and control cultivar, respectively. Among them, 23 differential compounds were common, including 14 flavone (flavonol) glycosides, 5 catechins and their derivatives, 1 lipid, 1 alkaloid, 1 organic acid and 1 amino acid. Further quantitative analysis of 20 main flavone (flavonol) glycosides showed that the contents of 14 flavone (flavonol) glycosides were the highest in YCFS oolong teas, whose contents were 1.4 to 14.6-fold of that in TGY oolong teas and were 1.3 to 18.0-fold of that in SX oolong teas. Among four kinds of flavone (flavonol) glycosides, quercetin glycosides were the main flavone (flavonol) glycosides with higher contents than glycosides of kaempferol, myricetin and apigenin. Sensory evaluation combined with chemical composition results showed that the higher contents of flavone (flavonol) glycosides did not significantly enhance the astringency of YCFS oolong tea infusions. 【Conclusion】 The metabolomics method effectively characterized the component differences in oolong teas made from different tea cultivars in this study. There were obvious differences in compound patterns among YCFS, TGY and SX oolong teas. Flavone (flavonol) glycosides were the most significantly differential compounds. The higher content of flavone (flavonol) glycosides was a major chemical feature of YCFS oolong tea and was expected to be used as a discriminant index for the identification of oolong tea cultivar in the future.

FOOD SCIENCE AND ENGINEERING

Effects of Melatonin Treatment on Resistance to Black Spot and Postharvest Storage Quality of Pear Fruit

XIANG MiaoLian, WU Fan, LI ShuCheng, WANG YinBao, XIAO LiuHua, PENG WenWen, CHEN JinYin, CHEN Ming

Scientia Agricultura Sinica. 2022, 55(4):  785-795.  doi:10.3864/j.issn.0578-1752.2022.04.013

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【Objective】 The aim of this study was to explore the effects of melatonine (MT) treatment on postharvest black spot disease and storage quality of pear fruit, so as to provide the theoretical basis and reference for exogenous substances regulating postharvest disease and storage quality of pear fruit. 【Method】 ‘Cuiguan’ pears were used as the experimental material, which were sprayed with 0.1 mmol·L^-1 MT solution and then kept at room temperature for 48 h. The treated fruits were inoculated with two 1 mm diameter × 3 mm depth small holes along both sides of the fruit equator. Twenty µL Alternaria alternata spore suspension with 1.0×10⁶ spores/mL were injected into the two holes, and the sterile water treatment was used as control. The fruit was placed at 25℃ after inoculation, and then the lesion diameters and induced effects as well as the genes expression of defense enzymes, such as catalase (PpCAT), peroxidase (PpPOD), polyphenol oxidase (PpPPO), and copper-zinc superoxide dismutase (Cu-ZnSOD), and pathogenesis-related protein including chitinase (PpCHI) and β-1,3 glucanase (PpGLU), were analysed to demonstrate the effect and mechanism of MT-induced pear fruit against black spot disease. In addition, the pear fruits were sprayed with 0.1 mmol·L^-1 MT solution, and then stored at (5±1)℃, 85%-90% relative humidity for 42 d. The sterile water treatment was used as the control. The decay rate, weight loss rate, respiration rate, firmness, total soluble solids, titratable acid, vitamin C, total phenols and malondialdehyde contents were measured at fixed period, and the effect of MT treatment on the storage effect and quality of pear fruit were discussed. 【Result】 The lesion diameters of pear fruits inoculated with A. alternata gradually increased with the time, while the lesion diameters under MT treatment was significantly smaller than those under the control (P<0.05). The MT-induced resistance effects on pear fruits black spot were 29.16%, 45.03% and 23.26% on the 3rd, 5th and 7th day, respectively. The relative expression levels of PpCAT, PpPOD, PpPPO, Cu-ZnSOD, PpCHI and PpGLU in MT-treated group were significantly higher than those of the control group during 4-7 days post inoculation (dpi), and the maximum values of them were 1.35, 2.08, 2.28, 2.02, 2.89 and 3.45 times of control fruits, respectively. The induced expression of PpPOD, PpPPO and PpCHI indicated that MT treatment inducing resistance of pear fruit to black spot disease possible depended on these defense enzyme and pathogenesis-related proteins. For the low temperature storage, the fruit decay rate was not significantly different between MT treatment group and control group, which was probably caused by the inhibition growth of pathogen under low temperature. All of fruit firmness gradually decreased during storage, while the fruit firmness under MT treatment was higher than that under the control with 1.06 times of significant difference at 28 d. Furthermore, the fruit respiration rate increased in the early storage stage (7-14 d) and decreased in the later stage. In comparison with the control group, the effects of MT treatment inhibiting fruit respiration and delaying fruit senescence were more significantly in the early storage stage than in the later stage. In addition, MT treatment also significantly reduced the fruit weight loss rate, maintained the high levels of total soluble solids, and delayed the degradation of titratable acid and vitamin C. Also, it promoted the accumulation of total phenolic content, enhanced the fruit antioxidant capacity, inhibited the accumulation of MDA content, and reduced the damage of cell membrane lipid peroxidation. The above results indicated that MT might enhance fruit quality and storage resistance by regulating fruit sugar, acid, and cell wall metabolism. 【Conclusion】0.1 mmol·L^-1 MT treatment induced the resistance of pear fruit to black spot, stimulated the relative expression of defense enzymes and pathogenesis-related protein coded-genes, and finally improved the storage quality of pear fruit.

ANIMAL SCIENCE·VETERINARY SCIENCE·RESOURCE INSECT

Effects of 2-Hydroxy-4-(Methylthio)-Butanoic Acid on Rumen Fermentation and Microbiota in Holstein Female Calves

KONG FanLin,LI Yuan,FU Tong,DIAO QiYu,TU Yan

Scientia Agricultura Sinica. 2022, 55(4):  796-806.  doi:10.3864/j.issn.0578-1752.2022.04.014

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【Objective】2-Hydroxy-4-(Methylthio)-Butanoic Acid (HMBi) is widely used to satisfy the absent of methionine (Met) in ruminal diet. Although the characteristic of HMBi is a rumen protected product, there is still an amount of HMBi degraded in rumen, which should be taken seriously. Hence, this study was conducted to evaluate the effects of HMBi on rumen fermentation and microbiota. 【Method】The experiment was conducted for 97 days with 36 Holstein female calves aged about 84 day-old with (101±10) kg body weight, and those calves were allocated to 2 groups, including PC group (0.40% Met) and PCMet group (0.28% Met). The treatment was achieved by deducting HMBi in diet of PCMet group and made Met level 30% lower than that of PC group. The first 7 d were an adaptation to the diets and the next 90 d for sampling. The body weight was measured at 0 d and 90 d, respectivley. The dry matter intake was recorded daily throughout the whole trial period. The serum and rumen fluid samples from five calves in each group were sampled on day 90 to determine rumen fermentation parameters and microbial communities. 【Result】(1) Compared with PC group, the growth performance of PCMet group was not changed (P>0.05). The Met in serum of PCMet group had trend to be significantly decreased when compared with PC group (0.05<P<0.1); (2) The molar proportion of acetate and microprotein concentration in PCMet group was significantly decreased by Met deduction (P<0.05). There were no significant differences on concentrations of total volatile fatty acid and ammonia nitrogen between two groups (P>0.05). (3) The Shannon index of microbiota in PCMet group was lower than that in PC group (P<0.05). The PCoA and PREANOVA analysis showed the significant distinction between microbiota in two groups (P<0.05). Furthermore, the relative abundance of Firmicutes in PCMet group was decreased and the relative abundance of Bacteroidetes was increased when compared with PC group (P<0.05). At genus level, the relative abundance of Olsenella, [Ruminococcus] gauvreauii group, Acetitomaculum, [Eubacterium] nodatum group, and Coprococcus 1 were decreased in PCMet group (P<0.05). The correlation analysis showed that [Eubacterium] nodatum group and Acetitomaculum were significantly correlated with acetate and [Ruminococcus] gauvreauii group was significantly correlated with MCP (P<0.05, r>0.7). 【Conclusion】 The ruminal microbiota was inhibited by HMBi deduction, which led to the decrease of MCP and Shannon index. Among them, the acetogen was sensitive with HMBi. In conclusion, although HMBi was a rumen protected product, the part of HMBi degraded in rumen still had the ability to regulate rumen fermentation.

Effects of CaSR and CCK-1R Mediated Soybean Protein Hydrolysate on Appetite Using Mouse

WANG LÜYang,CUI LeiHong,FENG JiangYin,HONG QiuXia,YOU MeiJing,BAO HaoYu,HANG SuQin

Scientia Agricultura Sinica. 2022, 55(4):  807-815.  doi:10.3864/j.issn.0578-1752.2022.04.015

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【Objective】The study aimed to investigate the effects and mechanisms of soy protein hydrolysate (SPH) on the appetite in mice, so as to provide the new frame work guidelines for strategies towards manipulating feed intake in pigs. 【Method】In this study, the pepsin was used to hydrolyze soy protein to produce SPH. Firstly, the effects on short-term feed intake and the expressions of duodenal peptide sensing receptors calcium sensing receptor (CaSR), G protein-coupled receptor 93 (GPR9)3 and oligopeptide transporter 1 (PepT1) were investigated by intragastrically different concentrations of SPH in mice. Based on this, the CaSR inhibitor NPS2143 and the peripheral cholecystokinin-1 receptor (CCK-1R) inhibitor Devazepide were intraperitoneally injected, respectively, to investigate whether SPH inhibited feed intake by the CASR-CCK-CCK-1R-hypothalamus pathway. 【Result】The amount of 1.5g·kg^-1 SPH reduced the 0-1 h feed intake (P<0.05), and increased the CaSR expression (P<0.05). Compared with SPH group, the feed intake of SPH+NPS2143 group were increased at 0-1 h, and the plasma CCK levels were decreased, and there were no differences from the control group (0.05<P<0.5). Meanwhile, SPH reduced 0-1 h gastric emptying rate and increased the expression of hypothalamus anorexia nerve factor pro-opiomelanocortin (POMC) (P<0.05), while the effects disappeared in SPH+Devazepide group. However, SPH had no effect on the small intestine transit rate or the expression of the hypothalamic food-promoting factors neuropeptide Y (NPY) and agouti related peptide (AgRP). 【Conclusion】CaSR mediated SPH to promote CCK secretion, delayed gastric emptying rate through the peripheral CCK-1 receptor, and improved the expression of hypothalamic anorexia nerve factor POMC to suppress appetite.

Amino Acid of 225 in the HA Protein Affects the Pathogenicities of H1N1 Subtype Swine Influenza Viruses

YANG ShiMan, XU ChengZhi, XU BangFeng, WU YunPu, JIA YunHui, QIAO ChuanLing, CHEN HuaLan

Scientia Agricultura Sinica. 2022, 55(4):  816-824.  doi:10.3864/j.issn.0578-1752.2022.04.016

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【Objective】 The pathogenicities of influenza viruses are determined by multiple viral genes. The results of our previous study indicated that hemagglutinin (HA) gene substitutions of the two genetically similar H1N1 swine influenza viruses altered their pathogenicities in mice. This study aimed to further identify the key amino acids affecting viral pathogenicity. 【Method】 After analyzing the amino acid differences of HA protein between the two H1N1 viruses, the reassortant viruses bearing the single amino acid mutations were constructed using the site-directed mutagenesis primers, and their EID₅₀ values were determined. To determine the growth of the parental, reassortant and mutant viruses in vitro, MDCK cells and A549 cells were infected with the indicated viruses at a multiplicity of infection (MOI) of 0.001 and 0.1, respectively. The BALB/c mice was further intranasally (i.n.) inoculated with 10⁶ EID₅₀ of each virus, and three mice were euthanized at 3 days post-infection (dpi).The organs, including brain, nasal turbinate, lung, kidney and spleen, were collected from the mice and titrated in eggs to evaluate the viral replication abilities in vivo. The MLD₅₀ values of the indicated viruses were determined by inoculating i.n. groups of five mice with 10¹-10⁶ EID₅₀ of viruses. The body weight was measured daily for 14 dpi, and the mice that lost more than 25% of their original weight were euthanized for humane reasons. 【Result】 The HA proteins of the ZD71 and SY130 viruses differed at four amino acids at positions 4, 138, 144, and 225 (H3 numbering). Four reassortants were rescued, followed by whole-genome sequencing to ensure the absence of unwanted mutations. The viral replication abilities of the reassortant viruses (rZD71-HA/G225E and rSY130-HA/E225G) were significantly affected in MDCK, as well as in A549 cells, when G225E and E225G substitutions were introduced into the rZD71 and rSY130 virus, respectively. In contrast, the mutations of the other three amino acids had little effect on viral replication in vitro. Further mouse infection experiments also demonstrated that amino acid substitutions at site 225 of HA protein significantly affected the viral pathogenicities in mice. In particular, the substitution G225E increased the pathogenicity of rZD71-HA/G225E virus, with the MLD₅₀ value of rZD71-HA/G225E virus decreasing from 4.32 log₁₀EID₅₀ to 3.0 log₁₀EID₅₀, compared with that of rZD71 virus. And the virus replicated well not only in the nasal turbinate and lung, but also in the spleen and kidney. 【Conclusion】 A single amino acid at position 225 in the HA protein significantly affects the viral replication capacity and virulence of these two H1N1 swine influenza viruses. It is suggested that close monitoring for this residue should be paid in the future virological surveillance, so as to provide a scientific basis for better prevention and control of animal influenza, and even human influenza pandemic.