Diversity and high nitrogenase activity of endophytic diazotrophs isolated from Oryza rufipogon Griff.

Diversity and nitrogenase activity of endophytic diazotrophs colonized in the wild rice Oryza rufipogon Griff grown in Boluo, Huilai County in Guangdong Province and Lingshui County in Hainan Province were studied. Thirty-seven isolates obtained from Oryza rufipogon were identified as putative endophytic nitrogen-fixing bacteria by ARA （acetylene reduction assay） test and further confirmed by PCR amplification of nifH gene fragments. All obtained strains have ARA activity and the same sized nifH gene fragments. Above the similarity level of 80%, the obtained isolates were assigned as Group Ⅰ to Ⅷ by the clustering of IS-PCR fingerprints. The SDS-PAGE whole-cell protein patterns were similar to those of IS-PCR fingerprints. Components and contents of fatty acid methyl esters （FAMEs） were used to differentiate the representative strains （Ls13, Ls8, BL1, BL12, HL6, Ls4） from Group Ⅰ to Group Ⅵ. The six representative strains showed significant difference in contents and components of cellular fatty acid methyl ester. 16S rDNA sequencing analysis showed that strains of Group Ⅰ to Ⅶ were located in Enterobacteraceae （y-proteobacteria）. Strains of Group Ⅰ and Group Ⅱ were closely related to Klebsiella sp.; Strain Ls8 of Group Ⅱ was a little far away from the genus of Pantoea （homology level 96% with Pantoea agglomerans）, which may represent a new species or genus in Enterobacteraceae; Strains of Groups Ⅳ and Ⅴ belonged to different Enterobacter sp.; Strain Ls4 and Ls 9 representing Group Ⅵ were close to Citrobacter amalonaticus with 98% sequence similarity; Strain Ls15 of Group Ⅶ showed 98% sequence identity with Pantoea sp.; Strains of Group Ⅷ were assigned to the genus Ideonella （β-proteobacteria）. Based on the above results, endophytic diazotrophs isolated from O. rufipogon showed great diversity and some diazotrophs showed high nitrogenase activity with 42.52 μmol/mL. h C2H4. Inoculation to rice tests indicated that the isolated endophytic diazotrophs significantly promoted the rice growth.     

Identification of an S5n allele in Oryza rufipogon Griff. and its effect on embryo sac fertility

Oryza rufipogon exhibits abundant genetic diversity and contains many elite genes. In this work, a total of 441 accessions of O. rufipogon were genetically examined using the functional marker S5n, revealing that 18 accessions carried the S5n allele with a heterozygous genotype (S5nS5i/j). Of these accessions, 14 were from Guangdong Province, 2 from Guangxi Zhuang Autonomous Region, 1 from Hainan Province and 1 from Jiangxi Province. Further sequence analysis spanning both sides of the deletion in S5n allel...     

一个水稻苗期白化致死突变体asl6的鉴定及其基因定位

经60Coγ诱变处理粳稻嘉花1号得到一个稳定遗传苗期白化致死突变体asl6(albino seedling lethality 6).与野生型(WT)相比,该突变体从发芽出苗起一直表现白化,四叶期逐渐死亡,叶合色素含量几乎没有且没有完整的叶绿体结构.通过qRT-PCR分析发现,与叶绿体发育、叶绿素合成及光合作用相关的基因表达量明显下调.对利用asl6突变体与培矮64S杂交获得的F2代分离群体进行遗传分析,发现该突变表型受单个隐性核基因控制.利用图位克隆技术将该asl6基因定位于第2号染色体的InDel分子标记ID31982与SSR分子标记MM5712之间约293 kb的区域内.目前,该范围内没有叶色相关基因的报道,可能为一新的调控水稻叶绿体发育的基因.     

一个新水稻低温敏感叶色突变体tcm11的鉴定及基因定位

对粳稻嘉花1号经~(60)Coγ诱变处理获得的稳定遗传低温敏感叶色突变体tcm11(thermo-sensitive chloroplast mutant 11)进行了表型鉴定与遗传分析.在20℃条件下,该突变体三叶期之前幼苗均表现为黄色,光合色素含量明显下降,叶绿体发育不完整,从第4叶开始逐渐转为浅黄绿色直至最后死亡.而在32℃条件下,其表型与野生型相比没有明显差异,具有低温敏感属性.通过对培矮64S与tcm11杂交的F_2代分离群体进行遗传分析,发现该低温敏感突变体性状是受单个隐性核基因(tcm11)控制,利用图位克隆技术对tcm11进行定位,将其定位在第11号染色体的InDel分子标记ID13252与SSR分子标记MM1361之间一个约1 566 kb的区域内.这也为后续的研究奠定了基础.     

Identification of a novel tillering dwarf mutant and fine mapping of the TDDL（T） gene in rice （Oryza sativa L.）

Rice plant architecture is an important agronomic trait that affects the grain yield. To understand the molecular mechanism that controls plant architecture, a tillering dwarf mutant with darker-green leaves derived from an indica cultivar IR64 treated with EMS is characterized. The mutant, designated as tddl（t）, is nonallelic to the known tiilering dwarf mutants. It is controlled by one recessive nuclear gene, TDDL（T）, and grouped into the dn-type dwarfism according to Takeda＇s definition. The dwarfism of the mutant is independent of gibberellic acid based on the analyses of two GA-mediated processes. The independence of brassinosteroid （BR） and naphthal-3-acetic acid （NAA） of the tddl（t） mutant, together with the decreased size of parenchyma cells in the vascular bundle, indicates that the TDDL（7） gene might participate in another hormone pathway. TDDL（T） is fine mapped within an 85.51 kb region on the long arm of rice chromosome 4, where 20 ORFs are predicted by RiceGAAS （http：//ricegaas.dna.affrc. go.jp/rgadb/）. Further cloning of TDDL（T） will benefit both marker assisted selection （MAS） of plant architecture and dissection of the molecular mechanism underlying tillering dwarf in rice.     

Genetic analysis and gene mapping of a narrow leaf mutant in rice ( Oryza sativa L.)

A narrow leaf mutant was obtained after T-DNA transformation conducted on a rice variety Zhonghua 11. Several abnormal morphological characteristics, including semi-dwarf, delayed flowering time, narrow and inward rolling leaves, and lower seed-setting, were observed. The rate of net photosynthesis (under saturate light) of flag leaves in the mutant was significantly lower than that of the wild type. Moreover, the leaf transpiration rate and stomatal conductance in the mutant flag leaf were lower than those of the wild type at the grain filling stage. It was found that the mutant phenotype was not caused by the T-DNA insertion. Genetic analysis showed that the mutant was controlled by a single recessive gene, designated as nal3(t). A genetic linkage map was constructed using a large F₂ mapping population derived from a cross between nal3(t) and an indica variety Longtefu B with 6 polymorphic markers on chromosome 12 identified from 366 SSR markers by the BAS method. Gene nal3(t) was mapped between the markers RM7018 and RM3331. Fine mapping of nal3(t) locus was conducted with 22 newly developed STS markers based on the sequence diversity around the region harboring nal3(t) between Nipponbare and 93–11, and nal3(t) was finally mapped to a 136-kb region between the STS markers NS10 and RH12-8. Supported by National High Technology Research and Development Program of China (863 Program) (Grant No. 2006AA10A102), National Natural Science Foundation of China (Grant No. 30600349) and Natural Science Foundation of Zhejiang Province (Grant No. Y306149)     

上海市11种常规粳稻抗稻瘟病基因分子标记检测

利用分子标记检测技术,对9种参加2020年上海市水稻区域试验的品种和2种本课题组新培育的新品系的共10个抗稻瘟病基因位点进行了检测.结果显示,Pi37,Pi41,Pi-d23个基因在11种水稻中出现的频率达100％,Pi2,Pi5,Pi9,Pi36,Pikm和Pib抗性基因在11种水稻中出现的频率分别为18.18％,9...     

Conditional and unconditional mapping of quantitative trait loci underlying plant height and tiller number in rice (Oryza sativa L.)grown at two nitrogen levels

In this study, we used 127 double haploid (DH) lines to analyze agricultural traits of rice. The DH lines, derived from a ZYQ8 (indica)/JX17 (japonica) cross by anther culture, contained 160 RFLP and 83 SSR markers. Unconditional and conditional quantitative trait loci (QTL) mapping was conducted to analyze plant height (PH) and tillers per plant (TP) at ?ve growth stages that were grown at two nitrogen levels. Fourteen PH and 13 TP unconditional QTL were identified in the di?erent growth stages, including 19 QTL from high-nitrogen (HN) and 14 QTL from low-nitrogen (LN) conditions. The conditional QTL for 14 genomic regions under LN/HN conditions showed that there was a significant effect on PH and TP across the different stages. Only one conditional QTL, ph2-3, was unable to be detected in unconditional mapping. More QTL were detected in the ?rst four rice growth stages than in the final stage. Furthermore, a line from the DH mapping population, DH78, was identified in extreme phenotypes of PH and TP that exhibited dwarfism and less-tiller (dft) characters. The gene dft1 was mapped to chromosome 2 using a backcrossed population of DH78/JX17 through a mapbased cloning strategy. The location of dft1 coincided with the mapping region of the small-LOD peak, QTL ph2 and tp2, which were identified in plants grown in low-nitrogen conditions. Further backcrossing and fine-mapping successfully delimited the dft1 locus to a 91 kb region.     

Fine mapping of the red plant gene R1 in upland cotton(Gossypium hirsutum)

Sub 16 is a substitution line with G. hirsutum cv. TM-1 genetic background except that the 16th chromosome (Chr. 16) is replaced by the corresponding homozygous chromosome of G. barbadense cv. 3-79, and T586 is a G. hirsutum multiple gene marker line with 8 dominant mutation genes. The R ₁ gene for anthocyanin pigmentation was tagged in Chr. 16 in T586. The objective of this research was to screen SSR markers tightly linked with R ₁ by using the F₂ segregating population containing 1259 plants derived from the cross of Sub 16 and T586 and the backbone genetic linkage map from G. hirsutum×G. barbadense BC₁ newly updated by our laboratory. Genetic analysis suggested that the segregation ratio of red plants in the F₂ population fit Mendelian 1:2:1 inheritance, confirming that the red plant trait was controlled by an incomplete dominance gene. Preliminary mapping of R ₁ was conducted using 237 randomLy selected F₂ individuals and JoinMap v3.0 software. Then, a fine map of R1 was constructed using the F₂ segregating population containing 1259 plants, and R ₁ was located between NAU4956 and NAU6752, with only 0.49 cM to the nearest maker loci (NAU6752). These results provided a foundation for map-based cloning of R ₁ and further development of cotton cultivars with red fibers by transgenic technology. Supported by National Natural Science Foundation of China (Grant No. 30730067) and Programme of Introducing Talents of Discipline to Universities (Grant No. B08025)