Fine mapping of an adult-plant resistance gene to powdery mildew in soybean cultivar Zhonghuang 24

Powdery mildew(PM),caused by the fungus Microsphaera diffusa,causes severe yield losses in soybean[Glycine max(L.)Merr.]under suitable environmental conditions.Identifying resistance genes and developing resistant cultivars may prevent soybean PM damage.In this study,analysis of F_(1),F_(2),and F8:11 recombinant inbred line(RIL)populations derived from the cross between Zhonghuang 24(ZH24)and Huaxia 3(HX3)indicated that adult-plant resistance(APR)to powdery mildew in the soybean cultivar(cv.)ZH24 was controlled by a single dominant locus.A high-density genetic linkage map of the RIL population was used for fine mapping.The APR locus in ZH24 was mapped to a 281-kb genomic region on chromosome 16.Using 283 susceptible plants of another F2 population,the candidate region was finemapped to a 32.8-kb genomic interval flanked by the markers InDel14 and Gm16_428.The interval harbored five genes,including four disease resistance(R)-like genes,according to the Williams 82.a2.v1 reference genome.Quantitative real-time PCR assays of candidate genes revealed that the expression levels of Glyma.16g214300 and Glyma.16g214500 were changed by M.diffusa infection and might be involved in disease defense.Rmd_B13 showed all-stage resistance(ASR)to PM in soybean cv.B13.An allelism test in the F2 segregating population from the cross of ZH24 × B13 suggested that the APR locus Rmd_ZH24 and the ASR locus Rmd_B13 may be allelic or tightly linked.These results provide a reference marker-assisted selection in breeding programs.

Natural variation of GmFATA1B regulates seed oil content and composition in soybean

Soybean(Glycine max) produces seeds that are rich in unsaturated fatty acids and is an important oilseed crop worldwide. Seed oil content and composition largely determine the economic value of soybean. Due to natural genetic variation, seed oil content varies substantially across soybean cultivars. Although much progress has been made in elucidating the genetic trajectory underlying fatty acid metabolism and oil biosynthesis in plants, the causal genes for many quantitative trait loci(QTLs) regulating seed oil content in soybean remain to be revealed. In this study, we identified Gm FATA1B as the gene underlying a QTL that regulates seed oil content and composition, as well as seed size in soybean. Nine extra amino acids in the conserved region of Gm FATA1B impair its function as a fatty acyl–acyl carrier protein thioesterase, thereby affecting seed oil content and composition. Heterogeneously overexpressing the functional Gm FATA1B allele in Arabidopsis thaliana increased both the total oil content and the oleic acid and linoleic acid contents of seeds. Our findings uncover a previously unknown locus underlying variation in seed oil content in soybean and lay the foundation for improving seed oil content and composition in soybean.

GmRmd1 encodes a TIR-NBS-BSP protein and confers resistance to powdery mildew in soybean

Dear editor,Powdery mildew(PMD)is a widespread,fungal-borne disease that impacts crop yield worldwide.In soybean,PMD is caused by the fungal pathogen,Microsphaera diffusa.The most efficient and economic strategy for PMD management with minimal environmental impact is through the deployment of resistance genes(Dangl et al.,2013;Hafeez et al.,2021).Although resistant genes against PMD have been identified in some crops,identification of those in soybean remains elusive.Several independent reports have consistently mapped the PMD-resistance locus to the end of Chr 16(Kang and Mian,2010;Jun et al.,2012;Jiang et al.,2019),however,the underlying gene that confers PMD resistance in soybean has yet to be cloned.Identification of the resistance-to-M.diffusa 1(Rmd1)gene is critical for the breeding of resistant soybean varieties,and thus control of PMD in this important crop.