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Genome-wide association studies (GWAS) have been used widely to analyze the genetic control of complex traits in crops. In the present study, seven related phenotypic traits were analyzed in combination to study their association with 41,101 SNPs in 201 maize inbred lines that had been evaluated in seven environments (year/location combinations) under water-stressed (WS) or well-watered (WW) regimes. By comparing the association signals with a fixed P value, GWAS showed that the number of association signals identified varied among traits and in different environments. Data that were missing under the severe water stress treatment had a great impact on the results of this GWAS. A total of 206 significant SNPs were associated with 115 candidate genes for drought tolerance and related traits including final grain yield, total number of ears per plot, kernel number per row, plant height, anthesis-silking interval, days to anthesis (DtA), and days to silking (DtS). Among these, four genes were associated with at least two different related traits, and six genes associated with traits were detected in at least two environments under water stress. Nine candidate QTL identified by GWAS were also discovered, three of which co-located to a consensus QTL region meta-analyzed by linkage mapping for drought tolerance. Some regulatory genes related to abiotic stress responses might also make a strong contribution to drought tolerance. The comprehensive information presented here regarding consensus QTL combined with candidate genes derived from GWAS provides an important reference tool for improving maize drought tolerance. [ABSTRACT FROM AUTHOR]

Genetic factors controlling quantitative inheritance of grain yield and its components have been intensively investigated during recent decades using diverse populations in maize ( Zea mays L.). Notwithstanding this, quantitative trait loci (QTL) for kernel row number (KRN) with large and consistent effect have not been identified. In this study, a linkage map of 150 simple sequence repeat (SSR) loci was constructed by using a population of 500 F2 individuals derived from a cross between elite inbreds Ye478 and Dan340. The linkage map spanned a total of 1478 cM with an average interval of 10.0 cM. A total of 397 F2:3 lines were evaluated across seven diverse environments for mapping QTL for KRN. Some QTL for grain yield and its components had previously been confirmed with this population across environments. A total of 13 QTL for KRN were identified, with each QTL explaining from 3.0 to 17.9% of phenotypic variance. The gene action for KRN was mainly additive to partial dominance. A large-effect QTL ( qkrn7) with partial dominance effect accounting for 17.9% of the phenotypic variation for KRN was identified on chromosome 7 near marker umc1865 with consistent gene effect across seven diverse environments. This study has laid a foundation for map-based cloning of this major QTL and for developing molecular markers for marker-assisted selection of high KRN. [ABSTRACT FROM AUTHOR]

Abstract: Sugarcane mosaic virus (SCMV) causes considerable damage to maize (Zea mays L.) in China. Characterization of resistance gene(s) serves as the basis for effective selection in resistance breeding programs. The objective of this study was to identify novel genes conferring resistance to SCMV from maize germplasm in China. A total of 21 BC2F3 populations derived from 8 maize intercross combinations were artificially inoculated with SCMV under field conditions. The numbers of resistant and susceptible plants in the BC2F3 population Ye 478 × Hai 9-21 were consistent with the theoretical 1:3 phenotypic ratio, suggesting that a recessive gene derived from the resistant parent Hai 9-21 was responsible for resistance to SCMV. Bulked segregant analysis (BSA) and simple sequence repeat (SSR) marker analysis were used to verify the recessive resistance gene that was designated scm3. Gene scm3 was located in bin 3.04–3.05, flanked by SSR markers umc1965 and bnlg420 with genetic distances of 45.7 and 6.5 cM, respectively. Four additional linked markers were detected, which were associated with scm3 gene in the order of umc1965–scm3–bnlg420–umc1307–umc2265–bnlg2241–umc2166. [Copyright &y& Elsevier]