Fine-mapping of a candidate gene for web blotch resistance in Arachis hypogaea L.

Peanut(Arachis hypogaea L.)is a globally important oil crop.Web blotch is one of the most important foliar diseases affecting peanut,which results in serious yield losses worldwide.Breeding web blotch-resistant peanut varieties is the most effective and economically viable method for minimizing yield losses due to web blotch.In the current study,a bulked segregant analysis with next-generation sequencing was used to analyze an F2:3 segregating population and identify candidate loci related to web blotch resistance.Based on the fine-mapping of the candidate genomic interval using kompetitive allele-specific PCR(KASP)markers,we identified a novel web blotch resistance-related locus spanning approximately 169 kb on chromosome 16.This region included four annotated genes,of which only Arahy.35VVQ3 had a non-synonymous single nucleotide polymorphism in the coding region between the two parents.Two markers(Chr.16.12872635 and Chr.16.12966357)linked to this gene were shown to be co-segregated with the resistance of peanut web blotch by 72 randomly selected recombinant inbred lines(RIL),which could be used in marker-assisted breeding of resistant peanut varieties.

Identifi cation of a novel male sterile wheat mutant dms conferring dwarf status and multi-pistils

Plant height and fertility are two important traits of wheat (Triticum aestivum L.), whose mutants are ideal materials for studies on molecular mechanisms of stem and lforal organ development. In this study, we identiifed a dwarf, multi-pistil and male sterile (dms hereafter) wheat mutant from Zhoumai 18. Simple sequence repeat (SSR) marker assay with 181 primer pairs showed that only one locus of GWM148-2B was divergent between Zhoumai 18 and dms. There were three typical phenotypes in the progeny of dms, tal (T;ca. 0.8 m), semi-dwarf (M;ca. 0.6 m) and dwarf (D;under 0.3 m) plants. Morphological investigation indicated that the internode length of M was shortened by about 20–50 mm each;the internode number of D was 2 less than that of T and Zhoumai 18, and its internode length was shorter also. The pol en vigor and hybridization test demonstrated that dms mutant was male sterility. Segregated phenotypes in progeny of M suggested that the multi-pistils and sterility were control ed by one recessive gene locus which was designated as dms temporarily, and the plant height was control ed by a semi-dominant gene locus Dms. Therefore, progeny individuals of the dms had three genotypes, DmsDms for tal plants, Dmsdms for semi-dwarf plants and dmsdms for dwarf plants. The mutant progenies were individual y selected and propagated for more than 6 generations, thus a set of near isogenic lines of T, M and D for dms were developed. This study provides a set germplasms for studies on molecular mechanisms of wheat stem and spike development.

Genetic mapping and expressivity of a wheat multi-pistil gene in mutant 12TP

We identified a wheat(Triticum aestivum L.) multi-pistil mutant from an F_2 breeding population in 2012, named 12 TP(three pistils in one floret). Genetic analysis showed that one dominant gene locus controlled the multi-pistil trait. Using homozygous normal and multi-pistil lines(near-isogenic lines; NILs) derived from the original mutant 12 TP, a simple sequence repeat(SSR) marker assay located the 12 TP locus on chromosome arm 2 DL. Four SSR markers were linked to 12 TP and their order was Xcfd233→Xcfd62-12 TP→Xwmc41→Xcfd168 at 15.85, 10.47, 2.89, and 10.37 cM, respectively. The average genetic expressivity of the trait ‘three pistils in one floret' was more than 98% in seven homozygous 12 TP lines; however, the average genetic expressivity in heterozygous F_1 plants was about 49%. Thus, the 12 TP is a semi-dominant gene locus, which differ from all previously reported multi-pistil mutants. Mutant 12 TP is a new useful germplasm for study of wheat floral development and for breeding of high yield wheat.

Heredity and gene mapping of a novel white stripe leaf mutant in wheat

Spotted leaf(spl)mutant is a type of leaf lesion mimic mutants in plants.We obtained some lesion mimic mutants from ethyl methane sulfonate(EMS)-mutagenized wheat(Triticum aestivum L.)cultivar Guomai 301(wild type,WT),and one of them was named as white stripe leaf(wsl)mutant because of the white stripes on its leaves.Here we report the heredity and gene mapping of this novel wheat mutant wsl.There are many small scattered white stripes on the leaves of wsl throughout its whole growth period.As the plants grew,the white stripes became more severe and the necrotic area expanded.The mutant wsl grew only weakly before the jointing stage and gradually recovered after jointing.The length and width of the flag leaf,spike number per plant and thousand-grain weight of wsl were significantly lower than those of the WT.Genetic analysis indicated that the trait of white stripe leaf was controlled by a recessive gene locus,named as wsl,which was mapped on the short arm of chromosome 6 B by SSR marker assay.Four SSR markers in the F2 population of wsl×CS were linked to wsl in the order of Xgpw1079–Xwmc104–Xgwm508-wsl–Xgpw7651 at 7.1,5.2,8.7,and 4.4 c M,respectively and three SSR markers in the F2 population of wsl×Jimai 22 were linked to wsl in the order of Xgwm508–Xwmc494–Xgwm518-wsl at 3.5,1.6 and 8.2 c M,respectively.In comparison to the reference genome sequence of Chinese Spring(CS),wsl is located in a 91-Mb region from 88 Mb(Xgwm518)to 179 Mb(Xgpw7651)on chromosome 6 BS.Mutant wsl is a novel germplasm for studying the molecular mechanism of wheat leaf development.

Identification of genetic loci for grain yield-related traits in the wheat population Zhongmai 578/Jimai 22

The identification of stable quantitative trait locus(QTL)for yield-related traits and tightly linked molecular markers is important for improving wheat grain yield.In the present study,six yield-related traits in a recombinant inbred line(RIL)population derived from the Zhongmai 578/Jimai 22 cross were phenotyped in five environments.The parents and 262 RILs were genotyped using the wheat 50K single nucleotide polymorphism(SNP)array.A high-density genetic map was constructed with 1501 non-redundant bin markers,spanning 2384.95 cM.Fifty-three QTLs for six yield-related traits were mapped on chromosomes 1D(2),2A(9),2B(6),2D,3A(2),3B(2),4A(5),4D,5B(8),5D(2),7A(7),7B(3)and 7D(5),which explained 2.7-25.5%of the phenotypic variances.Among the 53 QTLs,23 were detected in at least three environments,including seven for thousand-kernel weight(TKW),four for kernel length(KL),four for kernel width(KW),three for average grain filling rate(GFR),one for kernel number per spike(KNS)and four for plant height(PH).The stable QTLs QKl.caas-2A.1,QKl.caas-7D,QKw.caas-7D,QGfr.caas-2B.1,QGfr.caas-4A,QGfr.caas-7A and QPh.caas-2A.1 are likely to be new loci.Six QTL-rich regions on 2A,2B,4A,5B,7A and 7D,showed pleiotropic effects on various yield traits.TaSus2-2B and WAPO-A1 are potential candidate genes for the pleiotropic regions on 2B and 7A,respectively.The pleiotropic QTL on 7D for TKW,KL,KW and PH was verified in a natural population.The results of this study enrich our knowledge of the genetic basis underlying yield-related traits and provide molecular markers for high-yield wheat breeding.