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2021 Vol. 20 No. 7 Previous Issue    Next Issue

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Crop Science
Horticulture
Plant Protection
Animal Science · Veterinary Medicine
Agro-ecosystem & Environment
Agricultural Economics and Management
Short Communication


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Tomato brown rugose fruit virus (ToBRFV) is a new emerging tobamovirus and causes serious threat to the tomato industry. Since it was firstly reported by Jordan in 2015, ToBRFV has spread to America, Asia, and Europe. The photo, provided by Prof. Li Xiangdong from the Shandong Agricultural University, China, shows the brown rugose necrotic lesion symptoms induced by ToBRFV on tomato fruits. See pages 1871–1879 in details.


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Crop Science

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Receptor-like kinase OsASLRK regulates methylglyoxal response and content in rice LIN Fa-ming, LI Shen, WANG Ke, TIAN Hao-ran, GAO Jun-feng, DU Chang-qing 2021, 20(7): 1731-1742.  DOI: 10.1016/S2095-3119(20)63258-0 Abstract ( )   PDF in ScienceDirect   Receptor-like kinases (RLKs) are essential for plant abiotic stress responses.  Methylglyoxal (MG) is a cellular metabolite that is often considered to be a stress signal molecule.  However, limited information is available about the relationship between RLKs and MG.  Here, we addressed the function of a receptor-like kinase, OsASLRK, in the MG response and content in rice.  A typical MG-responsive element (AAAAAAAA) exists in the promoter region of the OsASLRK gene.  RT-qPCR analysis indicated that the transcript level of OsASLRK was significantly increased by exogenous MG in a time- and dosage-dependent fashion.  GUS staining also confirmed that the expression of OsASLRK in rice root was enhanced by exogenous MG treatment.  Genetic analysis suggested that the Osaslrk mutant displays increased sensitivity to MG and it showed higher endogenous MG content under exogenous MG treatments, while OsASLRK-overexpressing rice plants showed the opposite phenotypes.  Diaminobenzidine (DAB) staining, scavenging enzyme activities and GSH content assays indicate that OsASLRK regulates MG sensitivity and content via the elevation of antioxidative enzyme activities and alleviation of membrane damage.  Therefore, our results provide new evidence illustrating the roles that receptor-like kinase OsASLRK plays in MG regulation in rice.

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Heredity and gene mapping of a novel white stripe leaf mutant in wheat LI Hui-juan, JIAO Zhi-xin, NI Yong-jing, JIANG Yu-mei, LI Jun-chang, PAN Chao, ZHANG Jing, SUN Yu-long, AN Jun-hang, LIU Hong-jie, LI Qiao-yun, NIU Ji-shan 2021, 20(7): 1743-1752.  DOI: 10.1016/S2095-3119(20)63345-7 Abstract ( )   PDF in ScienceDirect   Spotted leaf (spl) mutant is a type of leaf lesion mimic mutants in plants.  We obtained some lesion mimic mutants from ethyl methane sulfonate (EMS)-mutagenized wheat (Triticum aestivum L.) cultivar Guomai 301 (wild type, WT), and one of them was named as white stripe leaf (wsl) mutant because of the white stripes on its leaves.  Here we report the heredity and gene mapping of this novel wheat mutant wsl.  There are many small scattered white stripes on the leaves of wsl throughout its whole growth period.  As the plants grew, the white stripes became more severe and the necrotic area expanded.  The mutant wsl grew only weakly before the jointing stage and gradually recovered after jointing.  The length and width of the flag leaf, spike number per plant and thousand-grain weight of wsl were significantly lower than those of the WT.  Genetic analysis indicated that the trait of white stripe leaf was controlled by a recessive gene locus, named as wsl, which was mapped on the short arm of chromosome 6B by SSR marker assay.  Four SSR markers in the F2 population of wsl×CS were linked to wsl in the order of Xgpw1079–Xwmc104–Xgwm508-wsl–Xgpw7651 at 7.1, 5.2, 8.7, and 4.4 cM, respectively and three SSR markers in the F2 population of wsl×Jimai 22 were linked to wsl in the order of Xgwm508–Xwmc494–Xgwm518-wsl at 3.5, 1.6 and 8.2 cM, respectively.  In comparison to the reference genome sequence of Chinese Spring (CS), wsl is located in a 91-Mb region from 88 Mb (Xgwm518) to 179 Mb (Xgpw7651) on chromosome 6BS.  Mutant wsl is a novel germplasm for studying the molecular mechanism of wheat leaf development.

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Construction of a high-density adzuki bean genetic map and evaluation of its utility based on a QTL analysis of seed size WANG Li-xia, WANG Jie, LUO Gao-ling, YUAN Xing-xing, GONG Dan, HU Liang-liang, WANG Su-hua, CHEN Hong-lin, CHEN Xin, CHENG Xu-zhen 2021, 20(7): 1753-1761.  DOI: 10.1016/S2095-3119(20)63343-3 Abstract ( )   PDF in ScienceDirect   Adzuki bean (Vigna angularis (Willd.) Ohwi & Ohashi) is an annual cultivated leguminous crop commonly grown in Asia and consumed worldwide.  However, there has been limited research regarding adzuki bean genetics, which has prevented the efficient application of genes during breeding.  In the present study, we constructed a high-density genetic map based on whole genome re-sequencing technology and validated its utility by mining QTLs related to seed size.  Moreover, we analyzed the sequences flanking insertions/deletions (InDels) to develop a set of PCR-based markers useful for characterizing adzuki bean genetics.  A total of 2 904 markers were mapped to 11 linkage groups (LGs).  The total length of the map was 1 365.0 cM, with an average distance between markers of 0.47 cM.  Among the LGs, the number of markers ranged from 208 (LG7) to 397 (LG1) and the total distance ranged from 97.4 cM (LG9) to 155.6 cM (LG1).  Twelve QTLs related to seed size were identified using the constructed map.  The two major QTLs in LG2 and LG9 explained 22.1 and 18.8% of the total phenotypic variation, respectively.  Ten minor QTLs in LG4, LG5 and LG6 explained 3.0–10.4% of the total phenotypic variation.  A total of 9 718 primer pairs were designed based on the sequences flanking InDels.  Among the 200 selected primer pairs, 75 revealed polymorphisms in 24 adzuki bean germplasms.  The genetic map constructed in this study will be useful for screening genes related to other traits.  Furthermore, the QTL analysis of seed size and the novel markers described herein may be relevant for future molecular investigations of adzuki bean and will be useful for exploiting the mechanisms underlying legume seed development.

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Effects of temperature and solar radiation on yield of good eating-quality rice in the lower reaches of the Huai River Basin, China ZHOU Nian-bing, ZHANG jun, FANG Shu-liang, WEI Hai-yan, ZHANG Hong-cheng 2021, 20(7): 1762-1774.  DOI: 10.1016/S2095-3119(20)63561-4 Abstract ( )   PDF in ScienceDirect   We studied the effects of temperature and solar radiation on rice yield with the aim of understanding the temperature and solar radiation requirements for high yield rice production in the lower reaches of the Huai River, China.  Field experiments were conducted with two medium-maturing japonica rice (MMJR) varieties and four late-maturing japonica rice (LMJR) varieties in 2017 and 2018.  Seeds were sown on May 10 (T1), May 17 (T2), May 24 (T3), May 31 (T4), June 7 (T5), June 14 (T6), and June 21 (T7).  The whole growth duration (WGD) of rice was shortened when sowing date was delayed, especially for the duration from sowing to heading (S–H).  The effective accumulated temperature (EAT), mean daily temperature (Tmean), cumulative solar radiation (CSR), and mean daily solar radiation (Rmean) over the WGD decreased when sowing date was delayed.  Compared with T1, yields in T2, T3, T4, T5, T6, and T7 decreased by 0.12–0.35, 0.45–0.89, 0.74–1.56, 1.41–2.24, 2.16–2.90, and 2.69–3.64 t ha−1, respectively.  There was a significant positive correlation between rice yield and EAT in different growth stages.  Temperature was the main factor that affected the yield of good eating-quality rice in the lower reaches of the Huai River.  We found that a relatively high yield can be obtained when the optimal Tmean for medium-maturing japonica rice (MMJR) and late-maturing japonica rice (LMJR) was 25.8–27.0°C and 26.6–27.1°C in the stages from sowing to heading (S–H), and 20.3–23.3°C and 20.3–22.1°C in the stages from heading to maturity (H–M), respectively.  The optimal sowing dates for MMJR and LMJR in the lower reaches of the Huai River were May 15–31 and May 15–18, respectively.

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Difference in corn kernel moisture content between pre- and post-harvest LI Lu-lu, MING Bo, XUE Jun, GAO Shang, WANG Ke-ru, XIE Rui-zhi, HOU Peng, LI Shao-kun 2021, 20(7): 1775-1782.  DOI: 10.1016/S2095-3119(20)63245-2 Abstract ( )   PDF in ScienceDirect   The harvest method of shelling corn (Zea mays L.) kernels in the field decreases labor costs associated with transporting, drying and threshing the crop.  However,  it was previously found that the kernel moisture content increased after field harvest, which decreased the value of corn kernels.  To identify the reasons underlying the increase, we conducted a multi-year and -area trial in the Huang-Huai-Hai Plain, China and performed a staged-harvest test at several phases of kernel dry-down.  The test investigated a range of parameters such as the kernel moisture content pre- and post-harvest, the kernel breakage rate, the amount of impurities, and the moisture content of various other plant tissues.  An analysis of 411 pairs of pre- and post-harvest samples found that kernel moisture content after harvest was 2.2% higher than that before harvest.  In the staged-harvest test, however, a significant increase was only observed when the kernel moisture content before harvest was higher than 23.9%.  The increase in post-harvest kernel moisture content was positively associated with the pre-harvest kernel moisture content, breakage rate and impurity rate.  Typically, at harvest time in this region, there is a significant fraction of immature crops with a high moisture content, resulting in kernels that are prone to breakage or impurities that ultimately lead to increases in water content after harvest.  Therefore, we suggest using hybrids that quickly wither late in the growing stage.  Additionally, farmers should delay harvest in order to minimize the pre-harvest kernel moisture content and thus reduce breakages and impurities, thereby improving the quality of kernels after harvest and the efficiency of corn kernel farming in China.

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The effect of elevating temperature on the growth and development of reproductive organs and yield of summer maize SHAO Rui-xin, YU Kang-ke, LI Hong-wei, JIA Shuang-jie, YANG Qing-hua, ZHAO Xia, ZHAO Ya-li, LIU Tian-xu 2021, 20(7): 1783-1795.  DOI: 10.1016/S2095-3119(20)63304-4 Abstract ( )   PDF in ScienceDirect   Compared to other crops, maize production demands relatively high temperatures. However, temperatures exceeding 35°C lead to adverse effects on maize yield.  High temperatures (≥35°C) are consistently experienced by summer maize during its reproductive growth stage in the North China Plain, which is likely to cause irreversible crop damage.  This study investigated the effects of elevating temperature (ET) treatment on the yield component of summer maize, beginning at the 9th unfolding leaf stage and ending at the tasseling stage.  Results demonstrated that continuous ET led to a decrease in the elongation rate and activity of silks and an elongated interval between anthesis and silking stages, and eventually decreased grain number at ear tip and reduced yield.  Although continuous ET before tasseling damaged the anther structure, reduced pollen activity, delayed the start of the pollen shedding stage, and shortened the pollen shedding time, it was inferred, based on phenotypical and physiological traits, that continuous ET after the 9th unfolding leaf stage influenced ears and therefore may have more significant impacts.  Overall, when maize plants were exposed to ET treatment in the ear reproductive development stage, the growth of ears and tassels was blocked, which increased the occurrence of barren ear tips and led to large yield losses.

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High plant density increases seed Bt endotoxin content in Bt transgenic cotton CHEN Yuan, LIU Zhen-yu, HENG Li, Leila I. M. TAMBEL, CHEN De-hua 2021, 20(7): 1796-1806.  DOI: 10.1016/S2095-3119(20)63232-4 Abstract ( )   PDF in ScienceDirect   Plant density is the cultivation practice usually employed to manipulate boll distribution, boll setting and yield in cotton production.  In order to determine the effect of plant density on the insecticidal protein content of Bacillus thuringiensis (Bt) cotton plants, a study was conducted in Yangzhou University of China in 2015 and 2016.  Five plant densities (PD1–PD5, representing 15 000, 30 000, 45 000, 60 000, and 75 000 plants ha–1) were imposed on two Bt cotton cultivars, Sikang 1 (the conventional cultivar, SK-1) and Sikang 3 (the hybrid cultivar, SK-3).  The boll number per plant, boll weight and boll volume all decreased as plant density increased.  As plant density increased from 15 000 to 75 000 plants ha–1, seed Bt protein content increased, with increases of 66.5% in SK-1 and 53.4% in SK-3 at 40 days after flowering (DAF) in 2015, and 36.8% in SK-1 and 38.6% in SK-3 in 2016.  Nitrogen (N) metabolism was investigated to uncover the potential mechanism.  The analysis of N metabolism showed enhanced soluble protein content, glutamic-pyruvic transaminase (GPT) and glutamate oxaloacetate transaminase (GOT) activities, but reduced free amino acid content, and protease and peptidase activities with increasing plant density.  At 20 DAF, the seed Bt toxin amount was positively correlated with soluble protein level, with correlation coefficients of 0.825** in SK-1 and 0.926** in SK-3 in 2015, and 0.955** in SK-1 and 0.965** in SK-3 in 2016.  In contrast, the seed Bt protein level was negatively correlated with free amino acid content, with correlation coefficients of –0.983** in SK-1 and –0.974** in SK-3 in 2015, and –0.996** in SK-1 and –0.986** in SK-3 in 2016.  To further confirm the relationship of Bt protein content and N metabolism, the Bt protein content was found to be positively correlated with the activities of GPT and GOT, but negatively correlated with the activities of protease and peptidase.  In conclusion, our present study indicated that high plant density elevated the amount of seed Bt protein, and this increase was associated with decreased boll number per plant, boll weight and boll volume.  In addition, altered N metabolism also contributed to the increased Bt protein content under high plant density.

Horticulture

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Integration of the metabolome and transcriptome reveals the metabolites and genes related to nutritional and medicinal value in Coriandrum sativum WU Tong, FENG Shu-yan, YANG Qi-hang, Preetida J BHETARIYA, GONG Ke, CUI Chun-lin, SONG Jie, PING Xiao-rui, PEI Qiao-ying, YU Tong, SONG Xiao-ming 2021, 20(7): 1807-1818.  DOI: 10.1016/S2095-3119(20)63358-5 Abstract ( )   PDF in ScienceDirect   Coriandrum sativum (Coriander) or Chinese parsley is a culinary herb with multiple medicinal effects, which is widely used in cooking and traditional medicine.  It is enriched with essential oils and anti-oxidant compounds with unknown significance.  To explore the untapped reservoir of Coriander, we studied the transcriptome and metabolic profiles from three developmental stages.  Here, we identified 10 tyrosine metabolic pathway-related genes (TMPRGs), six porphyrins and chlorophyll metabolic pathway-related genes (PCMPRGs), and five Vitamin E metabolic pathway-related genes (VEMPRGs).  These genes were associated with the early development of Coriander.  Our analysis suggests that these pathways are involved in the production of critical phenolic metabolites.  Furthermore, we constructed the interaction network between these pathway-related genes and transcription factors (TFs), which supported the regulatory pathways for phenolic metabolites.  Interestingly, we identified several nutritional or medicinally relevant metabolites, including 59 phenols, two polyamines, 12 alkaloids, and one terpenoid.  The higher concentrations of metabolites were from caffeic acid, agmatine, and its derivatives.  We found higher levels of caffeic acid and agmatine at 30 days compared to 60 or 90 days.  This study provides evidence to stimulate further investigation of the role of these metabolites in medicinal and nutritional research.

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Transcriptome analysis for understanding the mechanism of dark septate endophyte S16 in promoting the growth and nitrate uptake of sweet cherry WU Fan-lin, QU De-hui, TIAN Wei, WANG Meng-yun, CHEN Fei-yan, LI Ke-ke, SUN Ya-dong, SU Ying-hua, YANG Li-na, SU Hong-yan, WANG Lei 2021, 20(7): 1819-1831.  DOI: 10.1016/S2095-3119(20)63355-X Abstract ( )   PDF in ScienceDirect   Sweet cherry is one of the most popular fresh fruits in the world.  Previously, we isolated a soilborne dark septate endophyte (DSE) strain, S16, which promoted the growth of Gisela 5 sweet cherry rootstock.  However, little is known about the molecular mechanism of the effect of S16 on the growth of sweet cherry.  In this study, the physiological parameters and transcript profiles of sweet cherry roots were analyzed under S16 treatment compared with a control to elucidate the molecular mechanisms of the effect of this strain on sweet cherry growth.  After inoculation with S16, sweet cherry seedlings exhibited more vigorous growth.  Moreover, we identified 4 249 differentially expressed genes (DEGs) between S16-treated plants and the control.  Many of the DEGs are involved in pathways related to plant growth, such as cellular metabolic and plant hormone pathways.  Additionally, some genes involved in nitrate regulation were also enriched; and these genes may be involved in the regulation of nitrate uptake in plants.  Physiological index detection demonstrated that S16 could improve the nitrate assimilation of sweet cherry via NO3– transporters. This RNA-seq dataset provides comprehensive insight into the transcriptomic landscape to reveal the molecular mechanisms whereby the DSE influences the growth of sweet cherry.

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Development and application of microsatellite markers within transcription factors in flare tree peony (Paeonia rockii) based on next-generation and single-molecule long-read RNA-seq LIU Na, CHENG Fang-yun, GUO Xin, ZHONG Yuan 2021, 20(7): 1832-1848.  DOI: 10.1016/S2095-3119(20)63402-5 Abstract ( )   PDF in ScienceDirect   Tree peonies native to China are a precious crop with ornamental, medicinal and edible oil properties, of which flare tree peony (Paeonia rockii) is one of the most significant germplasms in Paeonia.  The development and application of expressed sequence tag-simple sequence repeat (EST-SSR) markers are very valuable for genetic and breeding applications, but EST-SSR resources for the genus Paeonia are still limited.  In this study, we first reported the development of SSRs within transcription factors (TFs) in P. rockii based on next-generation sequencing (NGS) and single-molecule long-read sequencing (SMLRS).  A total of 166 EST-SSRs containing six nucleotide repeat types were identified from 959 candidate TFs associated with yield, with an average of one SSR per 5.83 unigenes.  In total, 102 (61.45%) pairs of primers produced amplification products in the two RNA-seq cultivars.  Among them, 58 (56.86%) pairs of primers from 18 gene families (AP2, bHLH, HSF, etc.) were identified to be polymorphic both in the parents of a linkage mapping population and in eight randomly selected accessions of P. rockii.  Further, the 58 EST-SSRs indicated a high level of informativeness with PIC values ranging from 0.32 to 0.91 (mean 0.70) after assessment in 37 tree peony accessions.  Transferability studies indicated that the amplification ratio of the 58 pairs of primers ranged from 89.66 to 100% across seven species of Paeonia.  In addition, a genetic relationship study was performed in 62 accessions.  Cluster analysis using the neighbour-joining (NJ) tree demonstrated that major clusters corresponded to the known pedigree trees.  Taken together, these newly developed EST-SSRs have a potential use in the conservation of tree peony germplasm and marker-assisted selection (MAS) breeding.

Plant Protection

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The TaFIM1 gene mediates wheat resistance against Puccinia striiformis f. sp. tritici and responds to abiotic stress SHI Bei-bei, WANG Juan, GAO Hai-feng, ZHANG Xiao-juan, WANG Yang, MA Qing 2021, 20(7): 1849-1857.  DOI: 10.1016/S2095-3119(20)63276-2 Abstract ( )   PDF in ScienceDirect   Fimbrin, a regulator of actin cytoskeletal dynamics that participates in numerous physiological and biochemical processes, controls multiple developmental processes in a variety of tissues and cell types.  However, the role of fimbrin in pathogen defense of wheat and the mechanisms have not been well studied.  Here, we investigated that the expression of TaFIM1 gene of wheat was significantly induced in response to avirulent race of Puccinia striiformis f. sp. tritici (Pst) and silencing of TaFIM1 by virus-induced gene silencing method.  The results show that silencing of TaFIM1 resulted in a reduction of resistance against the stripe rust indicated by both phenotypes and a histological examination of Pst growth.  Additionally, the expression level of TaFIM1 gene was up-regulated under abiotic stresses.  These findings suggest that TaFIM1 functions as a positive regulator of pathogen resistance of wheat plants and response to abiotic stress.  Our work may show new light on understanding the roles of fimbrin in wheat.

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Extracellular superoxide dismutase VdSOD5 is required for virulence in Verticillium dahliae TIAN Li, HUANG Cai-min, ZHANG Dan-dan, LI Ran, CHEN Jie-yin, SUN Wei-xia, QIU Nian-wei, DAI Xiao-feng 2021, 20(7): 1858-1870.  DOI: 10.1016/S2095-3119(20)63353-6 Abstract ( )   PDF in ScienceDirect   Plants produce reactive oxygen species (ROS) to defend pathogens.  To counteract this attack, certain pathogens express superoxide dismutases (SODs) to scavenge host-derived ROS.  However, the roles of SODs in Verticillium dahliae, an important vascular pathogen, are not clear.  Our previous study has shown that a putative extracellular SOD (VdSOD5) of V. dahliae is significantly induced by culturing in cotton tissues, suggesting that VdSOD5 may play an important role in host–pathogen interactions and virulence.  Here, we showed that VdSOD5 encoded a superoxide dismutase with a co-factor copper-binding site and a functional signal peptide that can conduct protein secretion in an invertase-mutated yeast strain.  The mutations in VdSOD5 (ΔVdSOD5) did not change the normal vegetative growth and conidial production but reduced the virulence of V. dahliae on susceptible host cotton.  Further studies showed that the transcription of VdSOD5 was significantly up-regulated during the early stage of infection, and the loss-of-function of VdSOD5 decreased culture filtrate and fungal tissue SOD activities of V. dahliae by 74 and 28%, respectively.  Compared to the wild-type strain Vd991, the ΔVdSOD5 showed the same sensitivity to the intracellular ROS generator menadione.  Furthermore, nitroblue tetrazolium (NBT) staining demonstrated that VdSOD5 functioned in the detoxification of superoxides generated by host roots during infection.  These results suggest that VdSOD5 of V. dahliae is an important virulence factor, secreted out of cells to combat host-derived ROS.

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Biological and molecular characterization of tomato brown rugose fruit virus and development of quadruplex RT-PCR detection YAN Zhi-yong, ZHAO Mei-sheng, MA Hua-yu, LIU Ling-zhi, YANG Guang-ling, GENG Chao, TIAN Yan-ping, LI Xiang-dong 2021, 20(7): 1871-1879.  DOI: 10.1016/S2095-3119(20)63275-0 Abstract ( )   PDF in ScienceDirect   Tomato brown rugose fruit virus (ToBRFV) is a novel tobamovirus firstly reported in 2015 and poses a severe threat to the tomato industry.  So far, it has spread to 10 countries in America, Asia, and Europe.  In 2019, ToBRFV was identified in Shandong Province (ToBRFV-SD), China.  In this study, it was shown that ToBRFV-SD induced mild to severe mosaic and blistering on leaves, necrosis on sepals and pedicles, and deformation, yellow spots, and brown rugose necrotic lesions on fruits.  ToBRFV-SD induced distinct symptoms on plants of tomato, Capsicum annumm, and Nicotiana benthamiana, and caused latent infection on plants of Solanum tuberosum, Solanum melongena, and N. tabacum cv. Zhongyan 102.  All the 50 tomato cultivars tested were highly sensitive to ToBRFV-SD.  The complete genomic sequence of ToBRFV-SD shared the highest nucleotide and amino acid identities with isolate IL from Israel.  In the phylogenetic tree constructed with the complete genomic sequence, all the ToBRFV isolates were clustered together and formed a sister branch with tobacco mosaic virus (TMV).  Furthermore, a quadruplex RT-PCR system was developed that could differentiate ToBRFV from other economically important viruses affecting tomatoes, such as TMV, tomato mosaic virus, and tomato spotted wilt virus.  The findings of this study enhance our understanding of the biological and molecular characteristics of ToBRFV and provide an efficient and effective detection method for multiple infections, which is helpful in the management of ToBRFV.

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Functional analysis of the orphan genes Tssor-3 and Tssor-4 in male Plutella xylostella LI Tian-pu, ZHANG Li-wen, LI Ya-qing, YOU Min-sheng, ZHAO Qian 2021, 20(7): 1880-1888.  DOI: 10.1016/S2095-3119(21)63655-9 Abstract ( )   PDF in ScienceDirect   Orphan genes are genes with no sequence homologues in other species.  Here, we identified two orphan genes, namely, Tssor-3 and Tssor-4, in Plutella xylostella.  Both genes contained a signal peptide sequence, suggesting their functions as secreted proteins.  Expression pattern analysis based on real-time quantitative PCR (qPCR) showed that both orphan genes were specifically expressed in all male gonads except the testes.  The expression of both the orphan genes peaked at the male adult stage.  Immunofluorescence assays suggested that the two proteins were seminal proteins, indicating their potential roles in male reproductive regulation.  To further explain their functions, we knocked down the expression of these two genes by RNA interference (RNAi).  The results showed that the expression of Tssor-3 and Tssor-4 was significantly downregulated at 24 h after injection compared to that of the controls.  Biological assays showed that the number of laid eggs and the hatching rate of offspring eggs were significantly reduced when the expression of Tssor-3 and Tssor-4 was reduced, suggesting that the two orphan genes played a role in male fertility in P. xylostella.  Our results provide evidence that orphan genes are involved in male reproductive regulation, which is important for male fitness during evolution.

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Potential influence of carbohydrate and amino acid intake by adults on the population dynamics of Cnaphalocrocis medinalis (Lepidoptera: Crambidae) LI Chuan-ming, XU Jian, LIU Qin, HAN Guang-jie, XU Bin, YANG Yi-zhong, LIU Xian-jin 2021, 20(7): 1889-1897.  DOI: 10.1016/S2095-3119(20)63419-0 Abstract ( )   PDF in ScienceDirect   Cnaphalocrocis medinalis is a key lepidopteran pest of rice.  However, little is known about the nutritional requirements of the adult or the effects of adult-derived nutrients on reproduction.  The aim of the present study was to evaluate the effects of carbohydrates and amino acids on the reproductive and demographic parameters of C.?medinalis.  Different feeding solutions significantly influenced adult survival and reproduction.  All the sources of carbohydrates used in the treatments (fructose, glucose, and sucrose) were sufficient to increase adult longevity and fecundity, and benefited the development of ovaries in the adult stage.  The positive impact of carbohydrates on lifetime fecundity was due to the prolonged oviposition period and the increased daily fecundity.  The intrinsic rate of increase (rm) of C.?medinalis increased from 0.103 in water-fed individuals to approximately 0.138 when adults were fed with solutions containing carbohydrates.  In contrast, amino acid intake by adult insects exhibited no effect on the longevity, fecundity, ovarian development or population growth, even showing an impact of decreasing longevity of females.  As nectar secreted by the flowering plant is generally rich in sugars, the potential effects of nectar on the adults of C.?medinalis and other pests have to be considered during the development of biological control by applying flowering plants as a microhabitat and food source for natural enemies in rice fields.

Animal Science · Veterinary Medicine

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Genome-wide scan for selection signatures based on whole-genome re-sequencing in Landrace and Yorkshire pigs WANG Kai, WU Ping-xian, CHEN De-juan, ZHOU Jie, YANG Xi-di, JIANG An-an, MA Ji-deng, TANG Qian-zi, XIAO Wei-hang, JIANG Yan-zhi, ZHU Li, QIU Xiao-tian, LI Ming-zhou, LI Xue-wei, TANG Guo-qing 2021, 20(7): 1898-1906.  DOI: 10.1016/S2095-3119(20)63488-8 Abstract ( )   PDF in ScienceDirect   We performed a genome-wide scan to detect selection signatures that showed evidence of positive selection in the domestication process by re-sequencing the whole genomes of Landrace and Yorkshire pigs.  Fifteen annotated elements with 13 associated genes were identified using the Z-transformed FST (Z(FST)) method, and 208 annotated elements with 140 associated genes were identified using the Z-transformed heterozygosity (ZHp) method.  The functional analysis and the results of previous studies showed that most of the candidate genes were associated with basic metabolism, disease resistance, cellular processes, and biochemical signals, and several were related to body morphology and organs.  They included PPP3CA, which plays an essential role in the transduction of intracellular Ca2+-mediated signals, and WWTR1, which plays a pivotal role in organ size control and tumor suppression.  These results suggest that genes associated with body morphology were subject to selection pressure during domestication, whereas genes involved in basic metabolism and disease resistance were subject to selection during artificial breeding.  Our findings provide new insights into the potential genetic variation of phenotypic diversity in different pig breeds and will help to better understand the selection effects of modern breeding in Landrace and Yorkshire pigs.

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Effects of rearing system (floor vs. cage) and sex on performance, meat quality and enteric microorganism of yellow feather broilers WANG Lai-di, ZHANG Yang, KONG Ling-ling, WANG Zhi-xiu, BAI Hao, JIANG Yong, BI Yu-lin, CHANG Guo-bin, CHEN Guo-hong 2021, 20(7): 1907-1920.  DOI: 10.1016/S2095-3119(20)63420-7 Abstract ( )   PDF in ScienceDirect   This study investigated the effects of floor and cage rearing systems on performance, meat quality, and enteric microorganisms of male and female yellow feather broilers.  Two hundred Xueshan chickens (42 days old; 100 of each sex) were divided into four groups, according to sex and rearing system (stainless-steel cage or litter floor).  Male and cage-reared broilers exhibited better (P<0.001) performance and higher (P≤0.001) eviscerated percentage than female and floor-reared broilers.  The interaction between rearing system and sex had an effect (P<0.05) on the percentage of breast and thigh muscles.  Female floor-reared broilers presented the highest (P<0.02) percentage of breast and thigh muscles among all the groups.  In both sexes, the abdominal fat content in cage-reared broilers was higher (P<0.01) than that in floor-reared broilers.  Female cage-reared broilers exhibited better (P<0.05) meat quality of breast muscle than other groups.  An analysis of welfare observations indicated that the feather quality of floor-reared broilers was better (P<0.01) than that of cage-reared broilers, whereas the gait scores were not significantly affected (P>0.05) by rearing system.  The enteric microbiota assessment by 16S rRNA amplicon-based sequencing showed that Firmicutes, Proteobacteria, and Bacteroidetes were the most prevalent phyla in both rearing systems, and that the cecum was relatively stable in terms of microbiome composition.  Floor-reared broilers exhibited a richer diversity of bacteria in the intestinal tract than cage-reared broilers, while alpha diversity was not significantly different (P>0.05) among the groups.  The ratio of Bacteroidetes to Firmicutes and the abundance of Helicobacter and Romboutsia could potentially affect the production of broilers.  These findings indicate that cage rearing improved the production of male Xueshan broilers, which may be due to the difference in enteric microbiota between cage and floor rearing systems.

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Susceptibility breakpoint for cefquinome against Escherichia coli and Staphylococcus aureus from pigs ZHANG Hui-lin, ZHAO Yi-yang, ZHOU Zi-chong, DING Huan-zhong 2021, 20(7): 1921-1932.  DOI: 10.1016/S2095-3119(20)63572-9 Abstract ( )   PDF in ScienceDirect   Cefquinome is the only fourth-generation cephalosporin used solely for veterinary applications.  In this study, we established the wild-type cut-off (COWT) and pharmacokinetic/pharmacodynamic cut-off (COPD) of cefquinome against Escherichia coli and Staphylococcus aureus.  A total of 210 E. coli and 160 S. aureus isolates were collected from pigs in Guangdong Province between 2014 and 2018.  The minimum inhibitory concentrations (MICs) were determined using a microdilution broth method.  MIC50 and MIC90 were 0.06 and 0.25 μg mL–1 for E. coli and 0.5 and 1 μg mL–1 for S. aureus, respectively.  Statistical analysis and the ECOFFinder Program showed that the COWT for cefquinome against E. coli and S. aureus were 0.125 and 2 µg mL–1, respectively.  The resistance rates were 11.9% for E. coli and 6.25% for S. aureus.  Based on a 5 000-subject Monte Carlo simulation, the COPD value for cefquinome against E. coil and S. aureus was 0.25 µg mL–1 under the recommended dose (2 mg kg–1, twice a day for 3 days), confirming that infections caused by strains with MIC≤0.25 μg mL–1 could be effectively treated.  Following adjustment of the dosing regimen to 4.5 mg kg–1, effective treatment (>90) was achieved for S. aureus infections with MIC90 1 μg mL–1.  This susceptibility breakpoint determination is significant for resistant surveillance and cefquinome dosage guidance against E. coli and S. aureus in pigs.

Agro-ecosystem & Environment

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Response of carbon footprint to plastic film mulch application in spring maize production and mitigation strategy CHEN Bao-qing, Shahar BARAM, DONG Wen-yi, HE Wen-qing, LIU En-ke, YAN Chang-rong 2021, 20(7): 1933-1943.  DOI: 10.1016/S2095-3119(20)63278-6 Abstract ( )   PDF in ScienceDirect   Producing more food with a lower environmental cost is one of the most crucial challenges worldwide.  Plastic mulching has developed as one of the most dominant practices to improve crop yields, however its impacts on greenhouse gas (GHG) emissions during the production life cycle of a crop are still unclear.  The objective of this work is to quantify the impacts of plastic film on GHG emissions and to reduce GHG emissions with innovative agronomic practices.  Carbon footprint per unit of area (CFa), per unit of maize grain yield (CFy), and per unit of economic output (CFe) were evaluated for three maize cultivation systems: a no mulch system, a conventional plastic mulching system (PM) and a biennial plastic mulching pattern, namely a ‘one film for 2 years’ system (PM2), during 2015–2018 in a maize field located on the Loess Plateau of China.  The results suggested that PM induced a 24% improvement in maize yields during the four experimental years compared to a no-mulch treatment (NM).  However, PM dramatically increased the CFa by 69%, 59% of which was created by the input of the plastic film material, and 10% was created by increases in the soil N2O emissions.  The yield improvements from PM could not offset the increases in CFa, and CFy and CFe were both increased by 36%.  Shifting from PM to PM2 did not reduce crop yields, but it led to a 21% reduction in CFa and 23% reductions in CFy and CFe due to the reduced input amount of plastic film, decreased soil N2O emissions, and less diesel oil used for tillage.  Compared to NM, CFy and CFe were only 5% higher in PM2.  This study highlights the necessity of reducing the amount of plastic film input in the development of low-carbon agriculture and shifting from conventional PM cultivation to PM2 could be an efficient option for mitigating GHG emissions while sustaining high crop yields in plastic mulched fields.

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Monthly composites from Sentinel-1 and Sentinel-2 images for regional major crop mapping with Google Earth Engine LUO Chong, LIU Huan-jun, LU Lü-ping, LIU Zheng-rong, KONG Fan-chang, ZHANG Xin-le 2021, 20(7): 1944-1957.  DOI: 10.1016/S2095-3119(20)63329-9 Abstract ( )   PDF in ScienceDirect   Rapid and accurate access to large-scale, high-resolution crop-type distribution maps is important for agricultural management and sustainable agricultural development.  Due to the limitations of remote sensing image quality and data processing capabilities, large-scale crop classification is still challenging.  This study aimed to map the distribution of crops in Heilongjiang Province using Google Earth Engine (GEE) and Sentinel-1 and Sentinel-2 images.  We obtained Sentinel-1 and Sentinel-2 images from all the covered study areas in the critical period for crop growth in 2018 (May to September), combined monthly composite images of reflectance bands, vegetation indices and polarization bands as input features, and then performed crop classification using a Random Forest (RF) classifier.  The results show that the Sentinel-1 and Sentinel-2 monthly composite images combined with the RF classifier can accurately generate the crop distribution map of the study area, and the overall accuracy (OA) reached 89.75%.  Through experiments, we also found that the classification performance using time-series images is significantly better than that using single-period images.  Compared with the use of traditional bands only (i.e., the visible and near-infrared bands), the addition of shortwave infrared bands can improve the accuracy of crop classification most significantly, followed by the addition of red-edge bands.  Adding common vegetation indices and Sentinel-1 data to the crop classification improved the overall classification accuracy and the OA by 0.2 and 0.6%, respectively, compared to using only the Sentinel-2 reflectance bands.  The analysis of timeliness revealed that when the July image is available, the increase in the accuracy of crop classification is the highest.  When the Sentinel-1 and Sentinel-2 images for May, June, and July are available, an OA greater than 80% can be achieved.  The results of this study are applicable to large-scale, high-resolution crop classification and provide key technologies for remote sensing-based crop classification in small-scale agricultural areas.

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Winter wheat yield estimation based on assimilated Sentinel-2 images with the CERES-Wheat model LIU Zheng-chun, WANG Chao, BI Ru-tian, ZHU Hong-fen, HE Peng, JING Yao-dong, YANG Wu-de 2021, 20(7): 1958-1968.  DOI: 10.1016/S2095-3119(20)63483-9 Abstract ( )   PDF in ScienceDirect   Assimilating Sentinel-2 images with the CERES-Wheat model can improve the precision of winter wheat yield estimates at a regional scale.  To verify this method, we applied the ensemble Kalman filter (EnKF) to assimilate the leaf area index (LAI) derived from Sentinel-2 data and simulated by the CERES-Wheat model.  From this, we obtained the assimilated daily LAI during the growth stage of winter wheat across three counties located in the southeast of the Loess Plateau in China: Xiangfen, Xinjiang, and Wenxi.  We assigned LAI weights at different growth stages by comparing the improved analytic hierarchy method, the entropy method, and the normalized combination weighting method, and constructed a yield estimation model with the measurements to accurately estimate the yield of winter wheat.  We found that the changes of assimilated LAI during the growth stage of winter wheat strongly agreed with the simulated LAI.  With the correction of the derived LAI from the Sentinel-2 images, the LAI from the green-up stage to the heading–filling stage was enhanced, while the LAI decrease from the milking stage was slowed down, which was more in line with the actual changes of LAI for winter wheat.  We also compared the simulated and derived LAI and found the assimilated LAI had reduced the root mean square error (RMSE) by 0.43 and 0.29 m2 m–2, respectively, based on the measured LAI.  The assimilation improved the estimation accuracy of the LAI time series.  The highest determination coefficient (R2) was 0.8627 and the lowest RMSE was 472.92 kg ha–1 in the regression of the yields estimated by the normalized weighted assimilated LAI method and measurements.  The relative error of the estimated yield of winter wheat in the study counties was less than 1%, suggesting that Sentinel-2 data with high spatial-temporal resolution can be assimilated with the CERES-Wheat model to obtain more accurate regional yield estimates.

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Simple method for extracting the seasonal signals of photochemical reflectance index and normalized difference vegetation index measured using a spectral reflectance sensor Jae-Hyun RYU, Dohyeok OH, Jaeil CHO 2021, 20(7): 1969-1986.  DOI: 10.1016/S2095-3119(20)63410-4 Abstract ( )   PDF in ScienceDirect   A spectral reflectance sensor (SRS) fixed on the near-surface ground was developed to support the continuous monitoring of vegetation indices such as the normalized difference vegetation index (NDVI) and photochemical reflectance index (PRI).  NDVI is useful for indicating crop growth/phenology, whereas PRI was developed for observing physiological conditions.  Thus, the seasonal change patterns of NDVI and PRI are two valuable pieces of information in a crop-monitoring system.  However, capturing the seasonal patterns is considered challenging because the vegetation index values estimated by the reflection from vegetation are often governed by meteorological conditions, such as solar irradiance and precipitation.  Further, unlike growth/phenology, the physiological condition has diurnal changes as well as seasonal characteristics.  This study proposed a novel filtering method for extracting the seasonal signals of SRS-based NDVI and PRI in paddy rice, barley, and garlic.  First, the measurement accuracy of SRSs was compared with handheld spectrometers, and the R2 values between the two devices were 0.96 and 0.81 for NDVI and PRI, respectively.  Second, the experimental study of threshold criteria with respect to meteorological variables (i.e., insolation, cloudiness, sunshine duration, and precipitation) was conducted, and sunshine duration was the most useful one for excluding distorted values of the vegetation indices.  After data processing based on sunshine duration, the R2 values between the measured vegetation indices and the extracted seasonal signals of vegetation indices increased by approximately 0.002–0.004 (NDVI) and 0.065–0.298 (PRI) on the three crops, and the seasonal signals of vegetation indices became noticeably improved.  This method will contribute to an agricultural monitoring system by identifying the seasonal changes in crop growth and physiological conditions.

Agricultural Economics and Management

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Farmers’ risk preference and fertilizer use QIAO Fang-bin, HUANG Ji-kun 2021, 20(7): 1987-1995.  DOI: 10.1016/S2095-3119(20)63450-5 Abstract ( )   PDF in ScienceDirect   This study examines the role of farmers’ risk attitudes toward fertilizer use in cotton production in China.  Contradicting previous studies, this paper theoretically shows that the relationship between farmers’ risk aversion and fertilizer use is not always monotonic.  Field survey data were collected to test this relationship using the Cobb–Douglas production function.  Results suggest that when the elasticity of fertilizer use and the probability of achieving the desired effects from fertilizer use are high, risk-averse farmers apply more fertilizer than risk-taking farmers.  Conversely, when the elasticity of fertilizer use and the probability of achieving the desired effects are low, risk-taking farmers apply more fertilizer than risk-neutral or risk-averse farmers.

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Mechanization and efficiency in rice production in China SHI Min, Krishna P. PAUDEL, CHEN Feng-bo 2021, 20(7): 1996-2008.  DOI: 10.1016/S2095-3119(20)63439-6 Abstract ( )   PDF in ScienceDirect   Agricultural mechanization and custom machine services have developed rapidly in China, which can influence rice production efficiency in the future.  We calculate technical efficiency, allocative efficiency, and scale efficiency using data collected in 2015 from a face-to-face interview survey of 450 households that cultivated 3 096 plots located in the five major rice-producing provinces of China.  We use a one-step stochastic frontier model to calculate technical efficiency and regress the efficiency scores on socio-demographic and physical land characteristics to find the influencing variables.  Variables influencing technical efficiency are compared at three different phases of rice cultivation.  We also calculate technical efficiency by using the Heckman Selection Model, which addresses technological heterogeneity and self-selection bias.  Results indicate that: (1) the average value of technical efficiency using a one-step stochastic frontier model was found to be 0.74.  When self-selection bias is accounted for using the Heckman Selection Model, the average value of the technical efficiency increases to 0.80; (2) mechanization at the chemical application phase has a positive effect on technical efficiency, but mechanization does not affect efficiency at the plowing and harvesting phases; (3) machines are overused relative to both land and labor, and high machine input use on the small size of landholding has resulted in allocative inefficiency; (4) rice farmers are overwhelmingly operating at a sub-optimal scale.  Future policies should focus on encouraging farmland transfer in rural areas to achieve scale efficiency and allocative efficiency while promoting mechanization at the chemical application phase of rice cultivation to improve technical efficiency.

Short Communication

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Monilinia fructicola on loquat: An old pathogen invading a new host YIN Liang-fen, ZHANG Shu-qin, DU Juan, WANG Xin-yu, XU Wen-xing, LUO Chao-xi 2021, 20(7): 2009-2014.  DOI: 10.1016/S2095-3119(20)63375-5 Abstract ( )   PDF in ScienceDirect   Monilinia fructicola has been widely reported as the causal agent of brown rot disease on many Rosaceae family fruits worldwide.  It has been reported on stone fruits, e.g., peach, plum, cherry, apricot and mume; as well as pome fruits, e.g., apple, pear and hawthorn.  Loquat is a member of the Eriobotrya genus in subfamily Maloideae along with apple, pear and hawthorn.  So far, loquat has not been reported as the host of any Monilia species.  In June 2019, brown rot symptoms were observed on loquat fruits in an orchard in Wuhan, Hubei Province, China.  Thirty single spore isolates were obtained and identified as M. fructicola based on morphological characteristics and molecular analysis.  This is the first report of loquat brown rot disease caused by Monilia species in the world.  Furthermore, upon artificial inoculation, all three Monilia species from peach in China, i.e., M. fructicola, M. mumecola and M. yunnanensis, could cause typical brown rot disease on loquat fruits.  At the same time, M. fructicola isolates from loquat showed virulence similar to those isolates from peach when the pathogenicity test was conducted on peach fruits.  These results suggested that loquat could be infected by other Monilia species and that isolates from loquat also have potential to damage other Rosaceae family fruits in practice.