This study attempted to monitor the development of microbial communities and reveal the correlation between the soil microbial community and soil nutrient factors over different years following the replanting of peach trees.  The replanted soil (RS) and nonreplanted soil (NRS) were collected from peach orchards with different growth years (1, 3, 5, 7, 9, 11, and 13 years) in the same region.  The soil bacterial and fungal community diversities were analyzed by high-throughput sequencing technology.  Redundancy analysis (RDA) was used to show the correlation between the soil microbial community and environmental variables.  The alpha diversities of the bacterial and fungal communities indicated that RS contained a higher abundance of bacterial and fungal operational taxonomic units (OTUs) than NRS.  NMDS and ANOSIM analyses showed that the soil bacterial and fungal communities were significantly (P<0.01) affected by planting years, and that the main changes occurred in the first and ninth planting years.  The presence of the bacterial orders Sphingobacteriales, Burkholderiales and Actinomycetales changed significantly after replanting.  Some bacteria associated with bioremediation, such as Burkholderiales and Intrasporangiaceae, and some harmful pathogens, such as Penicillium and Ophiostomatales, significantly increased after replanting (LDA score>3.0).  In addition, the soil nutrient contents were lower in RS than in NRS in the early stage (1–5 years), and the RDA showed that bacterial and fungal phyla are closely associated with environmental variables, including the potential of hydrogen (pH), ammonium nitrogen (AN), available phosphorus (AP) and available potassium (AK).  These results lead to a deeper understanding of the microbial responses to replanting in peach orchards. 

Understanding the heterosis in multiple environments between different heterotic groups is of fundamental importance in successful maize breeding.  A total of 737 hybrids derived from 41 maize inbreds were evaluated over two years, with the aim of assessing the genetic diversity and their performance between heterotic groups under drought-stressed (DS) and well-watered (WW) treatments.  A total of 38 737 SNPs were employed to assess the genetic diversity.  The genetic distance (GD) between the parents ranged from 0.05 to 0.74, and the 41 inbreds were classified into five heterotic groups.  According to the hybrid performance (high yield and early maturity between heterotic groups), the heterosis and heterotic patterns of Iowa Stiff Stalk Synthetic (BSSS)×Non-Stiff Stalk (NSS), NSS×Sipingtou (SPT) and BSSS×SPT were identified to be useful options in China’s maize breeding.  The relative importance of general and specific combining abilities (GCA and SCA) suggests the importance of the additive genetic effects for grain yield traits under the WW treatment, but the non-additive effects under the DS treatment.  At least one of the parental lines with drought tolerance and a high GCA effect would be required to achieve the ideal hybrid performance under drought conditions.  GD showed a positive correlation with yield and yield heterosis in within-group hybrids over a certain range of GD.  The present investigation suggests that the heterosis is due to the combined accumulation of superior genes/alleles in parents and the optimal genetic distance between parents, and that yield heterosis under DS treatment was mainly determined by the non-additive effects.

Watermelon (Citrullus lanatus (Thunb.) Matsum. & Nakai) is an important cucurbit crop grown worldwide.  Watermelon fruit quality, fertility, and seed-setting rate are closely related to male flower development.  In this study, the different developmental stages of flower buds of the watermelon cultivar ‘Xinteda Zhengkang 9’ were distinguished by cytological observation, and transcriptome sequencing analysis was performed subsequently.  Acetocarmine staining of anthers was performed and the longitudinal and transverse diameters of the unopened male flower buds were measured.  Cytological observations of anthers at different developmental stages showed that the anther grew from the tetrad to the mature stage, and the longitudinal and transverse diameters of the flower buds increased.  The length of the male flower buds also changed significantly during development.  Transcriptome sequencing analysis at four periods, the tetrad (A group), mononuclear (B group), dikaryophase (C group), and mature stages (D group).  A total of 16 288 differentially expressed genes (DEGs) were detected in the four stages, with the prolongation of developmental stages, the number of DEGs increased gradually in the comparison groups, there was 2 014, 3 259, 4 628, 1 490, 3 495 and 1 132 DEGs revealed in six comparison groups (A-vs.-B, A-vs.-C, A-vs-D, B-vs.-C, B-vs.-D, and C-vs.-D), respectively.  Gene Ontology (GO) and KEGG enrichment analysis showed that the DEGs were mainly enriched in cellular component and starch and sucrose metabolism, phenylpropanoid biosynthesis and pentose sugar, etc.  Finally, we completely screened 59 DEGs in the six comparison groups, interestingly, we found one pollen-specific protein (Cla001608) that was significantly down-regulated (the value of log₂Fold Change up to 17.32), which indicated that it may play an important role in the development of male flowers.  This work provides insight into the molecular basis of the developmental stages of male flowers in watermelon and may aid in dominant cross breeding.

In vitro gynogenesis is an important tool used in haploid or homozygous double-haploid plant breeding.  However, because of low repeatability, embryoid induction rate and quality, the molecular mechanisms remain poorly understood.  Heat shock treatment can promote the transformation of the gametophytic pathway into the sporophyte pathway, which induces the occurrence of haploid.  In this study, unfertilized ovaries were heat shocked for 0 h (A0) before flowering and for 0 h (A1), 4 h (A3), 8 h (A5), 12 h (A7), and 24 h (A8), respectively, at 37°C at the first day of the flowering stage.  The ovule enlargement rate was increased from 0% at 25°C to 96.8% at 37°C (24 h treatment).  Thus, we aimed to investigate the gene expression patterns in unfertilized ovules of watermelon after different periods of heat shock by using RNA-Seq technology.  The results showed that compared with A3, A5, A7, and A8, the biosynthesis of amino acid, glycine, serine and threonine metabolic pathways in A1 has changed significantly.  This indicated that heat shock treatment affected the synthesis and transformation of amino acids during ovule expansion.  The transcriptome data suggested gene expressions of ovule growth were significantly changed by heat-specific influences.  The results provide new information on the complex relationship between in vitro gynogenesis and temperature.  This provides a basis for further study of the mechanism of heat shock affecting the expansion of watermelon ovule. 

     Heterosis is an important biological phenomenon, and it has been used to increase grain yield, quality and resistance to abiotic and biotic stresses in many crops. However, the genetic mechanism of heterosis remains unclear up to now. In this study, a set of 184 chromosome segment substitution lines (CSSLs) population, which derived from two inbred lines lx9801 (the recurrent parent) and Chang 72 (the donor parent), were used as basal material to construct two test populations with the inbred lines Zheng 58 and Xun 9058. The two test populations were evaluated in two locations over two years, and the heterotic loci for plant height and ear height were identified by comparing the performance of each test hybrid with the corresponding CK at P<0.05 significant level using one-way ANOVA analysis and Duncan’s multiple comparisons. There were 24 and 29 different heterotic loci (HL) identified for plant height and ear height in the two populations at two locations over two years. Three HL (hlPH4a, hlPH7c, hlPH1b) for plant height and three (hlEH1d, hlEH6b, hlEH1b) for ear height were identified in the CSSLs×Zheng 58 and CSSLs×Xun 9058 populations as contributing highly to heterosis performance of plant height and ear height across four environments. Among the 29 HL identified for ear height, 12 HL (41.4%) shared the same chromosomal region associated with the HL (50.0%) identified for plant height in the same test population and environment.

Wheat grain natural transverse sections of 12 periods were observed and analyzed using scanning electron micrographs technology and Bio-Quant system IV image analyzer in order to detect the developing process of A- and B-type starch granules. In addition, the chemical composition and starch granule-bound proteins (SGPs) of A- and B-type starch granules were tested and analyzed. The results showed that A-type starch granules in wheat began from 3 d post anthesis (DPA) till grain maturing and B-type starch granules occured after 15 DPA till grain maturing. Approximately 98.5% of chemical compositions in both A- and B-type starch granules were amylose and amylopectin, and more than half of which were amylopectin. The amylopectin contents, average chain length, and chain length distribution (degree of polymerization> 40) of amylopectin in A-type starch granules were significant higher than that of B-type starch granules. SGP-145, SGP- 140, and SGP-26 kD were associated with A-type starch formation in wheat grain.