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The variation of phyllosphere bacterial and fungal communities along elevation gradients may provide a potential link with temperature, which corresponds to an elevation over short geographic distances. At the same time, the plant growth stage is also an important factor affecting phyllosphere microorganisms. Understanding microbiological diversity over changes in elevation and among plant growth stages is important for developing crop growth ecological theories. Thus, we investigated variations in the composition of the rice phyllosphere bacterial and fungal communities at five sites along an elevation gradient from 580 to 980 m above sea level (asl) in the Ziquejie Mountain at the seedling, heading, and mature stages, using high-throughput Illumina sequencing methods. The results revealed that the dominant bacterial phyla were Proteobacteria, Actinobacteria, and Bacteroidetes, and the dominant fungal phyla were Ascomycota and Basidiomycota, which varied significantly at different elevation sites and growth stages. Elevation had a greater effect on the α diversity of phyllosphere bacteria than on that phyllosphere fungi. Meanwhile, the growth stage had a great effect on the α diversity of both phyllosphere bacteria and fungi. Our results also showed that the composition of bacterial and fungal communities varied significantly along elevation within the different growth stages, in terms of both changes in the relative abundance of species, and that the variations in bacterial and fungal composition were well correlated with variations in the average elevation. A total of 18 bacterial and 24 fungal genera were significantly correlated with elevational gradient, displaying large differences at the various growth stages. Soluble protein (SP) shared a strong positive correlation with bacterial and fungal communities (p < 0.05) and had a strong significant negative correlation with Serratia, Passalora, unclassified_Trichosphaeriales, and antioxidant enzymes (R > 0.5, p < 0.05), and significant positive correlation with the fungal genera Xylaria, Gibberella, and Penicillium (R > 0.5, p < 0.05). Therefore, it suggests that elevation and growth stage might alter both the diversity and abundance of phyllosphere bacterial and fungal populations.

Utilization of resistant varieties is the most economical and effective strategy to control bacterial blight (BB) and brown planthopper (BPH) in rice. Yuehui9113 is a widely used elite restorer line with high combining ability, and one of its hybrids, C815S/Yuehui9113, has been designated as a check variety for late season single-cropping rice; however, both of the parental lines are susceptible to BB and BPH. To simultaneously improve resistance to both BB and BPH in Yuehui9113 and F1 hybrids derived from it, one BB resistance gene (Xa21) and two BPH resistance genes (Bph14 and Bph15) were pyramided in Yuehui9113 using a marker-assisted backcrossing (MABC) strategy coupled with phenotypic selection in this study. Evaluation of BB and BPH resistance showed that all improved restorer lines that were homozygous for the resistance genes, and their derived F1 hybrids crossed with C815S, were at least moderately resistant to fourteen Xanthomonas oryzae pv. oryzae (Xoo) strains except for strain FuJ. They were also resistant or highly resistant to BPH, except for the improved line BX9113-06 and its hybrid C815S/BX9113-06, suggesting that BB and BPH resistances were significantly improved compared with the parent Yuehui9113 and the original hybrid C815S/Yuehui9113. Evaluation of agronomic traits and plot yields in 2014 and 2016 suggested that the improved lines BX9113-01 and BX9113-12 and their hybrids with C815S are superior or similar to the original parental line Yuehui9113 and the original hybrid C815S/Yuehui9113 with respect to important agronomic traits, and the two hybrids showed higher yield potential than the control hybrid C815S/Yuehui9113. The results of this study show that introgression of the Xa21, Bph14, and Bph15 genes can significantly improve resistance to BB and BPH in Yuehui9113 and its hybrids. Thus, the improved restorer lines BX9113-01 and BX9113-12 will play an important role in breeding hybrid rice with high levels of resistance to BB and BPH in the Yangtze River valley of China.

Using genome-wide SNP association mapping, a total of 77 and 7 loci were identified for rice bacterial blight and bacterial leaf streak resistance, respectively, which may facilitate rice resistance improvement. Bacterial blight (BB) and bacterial leaf streak (BLS) caused by Gram-negative bacteria Xanthomonas oryzae pv. oryzae (Xoo) and X. oryzae pv. oryzicola (Xoc), respectively, are two economically important diseases negatively affecting rice production. To mine new sources of resistance, a set of rice germplasm collection consisting of 895 re-sequenced accessions from the 3000 Rice Genomes Project (3 K RGP) were screened for BB and BLS resistance under field conditions. Higher levels of BB resistance were observed in aus/boro subgroup, whereas the japonica, temperate japonica and tropical japonica subgroups possessed comparatively high levels of resistance to BLS. A genome-wide association study (GWAS) mined 77 genomic loci significantly associated with BB and 7 with BLS resistance. The phenotypic variance (R2) explained by these loci ranged from 0.4 to 30.2%. Among the loci, 7 for BB resistance were co-localized with known BB resistance genes and one for BLS resistance overlapped with a previously reported BLS resistance QTL. A search for the candidates in other novel loci revealed several defense-related genes that may be involved in resistance to BB and BLS. High levels of phenotypic resistance to BB or BLS could be attributed to the accumulation of the resistance (R) alleles at the associated loci, indicating their potential value in rice resistance breeding via gene pyramiding. The GWAS analysis validated the known genes underlying BB and BLS resistance and identified novel loci that could enrich the current resistance gene pool. The resources with strong resistance and significant SNPs identified in this study are potentially useful in breeding for BB and BLS resistance.

Using genome-wide SNP association mapping, a total of 77 and 7 loci were identified for rice bacterial blight and bacterial leaf streak resistance, respectively, which may facilitate rice resistance improvement. Bacterial blight (BB) and bacterial leaf streak (BLS) caused by Gram-negative bacteria Xanthomonas oryzae pv. oryzae (Xoo) and X. oryzae pv. oryzicola (Xoc), respectively, are two economically important diseases negatively affecting rice production. To mine new sources of resistance, a set of rice germplasm collection consisting of 895 re-sequenced accessions from the 3000 Rice Genomes Project (3 K RGP) were screened for BB and BLS resistance under field conditions. Higher levels of BB resistance were observed in aus/boro subgroup, whereas the japonica, temperate japonica and tropical japonica subgroups possessed comparatively high levels of resistance to BLS. A genome-wide association study (GWAS) mined 77 genomic loci significantly associated with BB and 7 with BLS resistance. The phenotypic variance (R

Microbial communities associated with the plant phyllosphere and endosphere can have both beneficial as well as detrimental effects on their hosts. There is an ongoing debate to which extend the phyllosphere and endosphere microbiome assembly is controlled by the host plant how pronounced cultivar effects are. We investigated the bacterial and fungal communities from the phyllosphere and endosphere of 10 different rice cultivars grown under identical environmental conditions in the frame of a targeted approach to identify drivers of community assembly. The results indicated that the endophytic bacterial communities were clearly separated into two groups. The α-diversity and microbial network complexity within Group I were significantly lower than in Group II. Moreover, the genera Nocardioides, Microvirga, and Gaiella were significantly more abundant in Group II and only present in the interaction networks of this group. These three genera were significantly correlated with α- and β-diversity of the endophytic bacterial community and thus identified as major drivers of the endosphere community. We have identified keystone taxa that shape endophytic bacterial communities of different rice cultivars. Our overall findings provide new insights into plant-microbe interactions, and may contribute to targeted improvements of rice varieties in the future.

In this study, the characteristic of three transformants named as B1C106-1, B1C106-2, and B1C106-3 were studied that carried three innate resistant genes Bph14, Bph15, and Xa23, and two enthetic resistant genes Cry1Ca# and Bar. The five resistant genes were all verified by PCR and the two enthetic genes were identified in single copy insertion by Southern blot. At tillering stage, the Cry1C and PAT (phosphinothricin acetyl transferase) protein contents in leaf, sheath, and stem of T2 generation were in the similar pattern: leaf>stem>sheath, and showed significant difference (P

In our previous study, an early season rice restorer line B2A68 expressing Cry2Aa# gene was obtained. In order to evaluate the performance of B2A68’s hybrids, a total of six hybrids from crossing B2A68 with six thermo-sensitive genic male sterile (TGMS) lines of early season rice were compared for expression level of Cry2Aa protein, as well as in insect resistance, agronomic traits and grain quality with their non-Bt null controls. Our results showed that the highest Cry2Aa protein content among B2A68's hybrids was detected in leaf, where the Cry2Aa content was nearly three times of that in stem. The Cry2Aa content of B2A68 was significantly higher than those of its derived hybrids, indicating the Cry2Aa# gene was incompletely dominant in hybrids. The hybrids with Cry2Aa# gene exhibited higher plant protection against rice leaf roller than the hybrids without Cry2Aa# gene in field. Significant differences were observed in plant height, panicle length, number of grains per panicle, seed set, 1000-grain weight and yield per plant between hybrids with Cry2Aa# gene and hybrids without Cry2Aa# gene in 2013 or 2014. There were significant differences in chalky grain rate and chalkiness degree between paternal lines B2A68 and D68, and between hybrids with Cry2Aa# gene and hybrids without Cry2Aa# gene. All of the differences in agronomic traits and grain quality varied among parental lines and hybrids. In this paper, three hybrids with high lepidopteran resistance, high yield, elite agronomic traits and acceptable grain quality was selected out, that could serve as elite resistant hybrids to control lepidopteran pests in early season rice production.

Development of resistant varieties is one of the most economical and effective strategies to prevent rice from bacterial blight disease (BB) and brown planthopper (BPH), the two main pests jeopardizing rice production. The hybrid rice Tianyouhuazhan (TianfengA/Huazhan) has been widely used in rice production in China, but this hybrid is susceptible to BB and BPH. In this study, one BB resistance gene ( Xa23 ) and two BPH resistance genes ( Bph14 and Bph15 ) were simultaneously introgressed into the restorer line Huazhan to improve the BB and BPH resistance of Tianyouhuazhan using marker-assisted backcrossing (MABC) strategy coupled with phenotypic selection. The results of identification of BB and BPH resistance revealed that almost all of the improved restorer lines and their derived hybrids showed high resistance (HR) or resistance (R) to BB and BPH. Almost all of the agronomic traits of improved restorer lines and their hybrids were similar to those of their respective original versions in field trial, except the 1000-grain weight of improved hybrids showed an extremely significant increase than that of Tianyouhuazhan. Plot yields test in 2013 and 2014 suggested that two improved hybrid combinations named as TianfengA/R43-06 and TianfengA/R43-07 had higher grain yields per plot than Tianyouhuazhan and other improved hybrids. These results clearly indicate that pyramiding of Xa23 , Bph14 and Bph15 genes is a useful approach for improving BB and BPH resistance, two hybrid combinations TianfengA/R43-06 and TianfengA/R43-07 could replace Tianyouhuazhan for extension in BB and/or BPH epidemic area in China.

One sequence tagged site marker Sub1-1 and twice submergence stress method were used in selection of submergence tolerant homozygous line from Sub-1BS, a submergence tolerant, bentazon sensitive and photoperiod-sensitive and/or thermo-sensitive genic male sterile line that developed by our laboratory. The results revealed that the original Sub-1BS was heterozygous in Sub1A-1 locus even though it was identical in almost all of agronomical traits and the segregation of Sub1A-1 was in accordance with Mendelian law based on chi-square test. And then the original Sub-1BS was divided into two groups: one was of Sub1A-1 introgression and the other was not; and the two groups were tested by twice submergence stress method. After the first submergence stress that lasted for 12 d, the average plant heights were significant difference at the 1% level between the two groups. After recovery for 10 d, the second submergence stress sustained for 18 d was carried on; and the group with Sub1A-1 gene was found apparently tolerant than the other group in submergence tolerance.