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.

Fine mapping and genetic analysis of resistance genes,Rsc18,against soybean mosaic virus

Soybean mosaic virus(SMV) affects seed quality and production of soybean(Glycine max(L.) Merr.) worldwide.SC18 is one of the dominant SMV strains in South China,and accession Zhonghuang 24 displayed resistance to SC18.The F_(1),F_(2) and 168 F_(11) recombinant inbred lines(RILs) population derived from a hybridization between Zhonghuang 24(resistant,R) and Huaxia 3(susceptible,S) were used in this study.According to the segregation ratios of the F_(2) generation(3 R:1 S) and the recombinant inbred lines(RILs) population(1 R:1 S),one dominant locus may regulate the resistance to SC18 in Zhonghuang 24.By using composite interval mapping(CIM),Rsc18 was mapped to a 415.357-kb region on chromosome 13.Three candidate genes,including one NBS-LRR type gene and two serine/threonine protein type genes,were identified according to the genetic annotations,which may be related to the resistance to SC18.The q RT-PCR demonstrated that these genes were up-regulated in the R genotype compared to the control.In conclusion,the findings of this research enhanced the understanding about the R genes at the Rsc18 locus.Moreover,our results will provide insights for designing molecular markers to improve marker-assisted selection and developing new varieties with resistance to SC18.

Identification and validation of stable and novel quantitative trait loci for pod shattering in soybean[Glycine max(L.)Merr.]

Pod shattering is an important domesticated trait which can cause great economic loss of crop yield in cultivated soybean.In this study,we utilized two recombinant inbred line populations(RILs,CY,Huachun 2×Wayao;GB,Guizao 1×B13)to identify quantitative trait loci(QTLs)associated with pod shattering in soybean across multiple environments.A total of 14 QTLs for pod shattering were identified in the two RIL populations,which had LOD scores ranging from 2.64 to 44.33 with phenotypic variance explanation(PVE)ranging from 1.33 to 50.85%.One QTL qPS16-1,located on chromosome 16,included a well-known functional gene Pod dehiscence 1(Pdh1)that was reported previously.Ten new putative QTLs were validated in two RIL populations,and their LOD scores were between 2.55 and 4.24,explaining 1.33 to 2.60%of the phenotypic variation.Of which four novel QTLs(qPS01-1,qPS03-2,qPS05-1,and qPS07-1)could be detected in two environments where nine genes had specific changes in gene expression.Although the nine genes may have significant effects on pod shattering of soybean,their detailed functions still need to be further explored in the future.The results of this study will facilitate a better understanding of the genetic basis of the pod shattering-resistant trait and benefit soybean molecular breeding for improving pod shattering resistance.

Earthworm rather than biochar and sodium silicate addition increased bacterial diversity in mining areas subjected to chemical fertilization

The addition of biochar,sodium silicate,or earthworm is a feasible practice to repair soils disturbed by mining activities,and the reclamation is largely based on the alteration of the diversity and structure of soil bacteria.The objectives of this study were to assess the relative importance of these supplements on soil bacterial community diversity and structure in reclaimed mine areas.A field experiment with soybean was carried out in mining areas to assess the efficiency of nitrogen,phospho-rus and potassium(NPK)fertilizers plus those supplements on soil bacterial community structure and diversity by the 16S rRNA sequencing method.Soil chemical properties were analyzed to their effects on the bacterial community structure.The results showed that the application of nitrogen,phosphorus and potassium(NPK)fertilizers significantly increased bacterial diversity,and a further increase was observed in NPK plus biochar,sodium silicate or earthworm addition.Furthermore,a higher number of genera were found in the NPK plus biochar and NPK plus earthworm treatments than that in the control,NPK and NPK plus sodium silicate treatments.The bacterial community was significantly associated with nutrients,such as carbon(C)and nitrogen(N).Moreover,soil organic carbon(SOC)and pH were the most dominant factors in shaping the soil bacterial community structure and diversity.Our data indicate that the addition of earthworms to soil rather than biochar and sodium silicate was the best strategy to mitigate the detrimental effects of mining activities on soil bacterial diversity.

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.