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A mapping population, recombinant inbred lines (RILs), was developed from the cross of aphid susceptible cv. PL426 and resistant genotype BK 9816 to identify genetic loci conferring corn leaf aphid (CLA) Rhopalosiphum maidis (Fitch) resistance in barley. RILs showed wide range of aphid infestation (2.2–65.0 aphids/tiller) indicating quantitative inheritance of aphid resistance. All the traits related to aphid resistance, viz. aphid fecundity, chlorophyll content and tiller dry weight of plants, also showed quantitative variation. RILs were further genotyped by sequencing to identify SNPs covering whole barley genome. A total of 605 high-quality bin-mapped SNPs were positioned in seven linkage groups with a total map length of 1208.9 cM and average marker distance of 2.02 cM. Composite interval mapping identified five different quantitative trait loci (QTLs) on chromosomes 1H, 3H, 5H and 6H associated with aphid resistance and related traits. Two QTLs on chromosome 6H, QCLA.pau-6H.1 and QCLA.pau-6H.2, were mapped at genetic intervals of 1.7 cM and 4.9 cM, respectively. QCLA.pau-6H.1 explained 9.76 percent of phenotypic variation for aphid count and 12.78 percent for aphid score. Similarly, QCLA.pau-6H.2 explained 10.96 percent of phenotypic variation for aphid score. The QTL for chlorophyll content and tiller dry weight spanned the same region of QCLA.pau-6H.2, explained 13.08 and 13.20 percent phenotypic variation, respectively. Another QTL associated with chlorophyll content was mapped on chromosome 3H at 3.6-cM interval explained 12.90 percent phenotypic variation. In addition, QTL regions were also identified for aphid resistance and related traits on chromosome 1H and 5H. [ABSTRACT FROM AUTHOR]

Key message: Here, we report identification of a large effect QTL conferring Mungbean yellow mosaic India virus resistance introgressed from ricebean in blackgram variety Mash114. The tightly linked KASP markers would assist in marker-assisted-transfer of this region into Vigna species infected by MYMIV. Until recently, precise location of genes and marker-assisted selection was long thought in legumes such as blackgram due to lack of dense molecular maps. However, advances in next-generation sequencing based on high-throughput genotyping technologies such as QTL-seq have revolutionized trait mapping in marker-orphan crops. Using QTL-seq approach, we have identified a large-effect QTL for resistance to Mungbean yellow mosaic India virus (MYMIV) in blackgram variety Mash114. MYMIV is devastating disease responsible for huge yield losses in blackgram, greengram and other legumes. Mash114 showed consistent and high level of resistance to MYMIV since last nine years. Whole genome re-sequencing of MYMIV-resistant and susceptible bulks derived from RILs of cross KUG253 X Mash114 identified a large-effect QTL (qMYMIV6.1.1) spanning 3.4 Mb on chromosome 6 explaining 70% of total phenotypic variation. This region was further identified as an inter-specific introgression from ricebean. Linkage mapping using KASP markers developed from potent candidate genes involved in virus resistance identified the 500 kb genomic region equaling 1.9 cM on genetic map linked with MYMIV. The three KASP markers closely associated with MYMIV originated from serine threonine kinase, UBE2D2 and BAK1/BRI1-ASSOCIATED RECEPTOR KINASE genes. These KASPs can be used for marker-assisted transfer of introgressed segment into suitable backgrounds of Vigna species. [ABSTRACT FROM AUTHOR]

Chickpea yield is severely affected by drought stress, which is a complex quantitative trait regulated by multiple small-effect genes. Identifying genomic regions associated with drought tolerance component traits may increase our understanding of drought tolerance mechanisms and assist in the development of drought-tolerant varieties. Here, a total of 187 F8 recombinant inbred lines (RILs) developed from an interspecific cross between drought-tolerant genotype GPF 2 (Cicer arietinum) and droughtsensitive accession ILWC 292 (C. reticulatum) were evaluated to identify quantitative trait loci (QTLs) associated with drought tolerance component traits. A total of 21 traits, including 12 morpho-physiological traits and nine rootrelated traits, were studied under rainfed and irrigated conditions. Composite interval mapping identified 31 QTLs at Ludhiana and 23 QTLs at Faridkot locations for morphological and physiological traits, and seven QTLs were identified for root-related traits. QTL analysis identified eight consensus QTLs for six traits and five QTL clusters containing QTLs for multiple traits on linkage groups CaLG04 and CaLG06. The identified major QTLs and genomic regions associated with drought tolerance component traits can be introgressed into elite cultivars using genomics-assisted breeding to enhance drought tolerance in chickpea. [ABSTRACT FROM AUTHOR]

Heat stress during reproductive stages has been leading to significant yield losses in chickpea (Cicer arietinum L.). With an aim of identifying the genomic regions or QTLs responsible for heat tolerance, 187 F8 recombinant inbred lines (RILs) derived from the cross GPF 2 (heat tolerant) × ILWC 292 (heat sensitive) were evaluated under late-sown irrigated (January-May) and timely-sown irrigated environments (November-April) at Ludhiana and Faridkot in Punjab, India for 13 heat tolerance related traits. The pooled ANOVA for both locations for the traits namely days to germination (DG), days to flowering initiation (DFI), days to 50% flowering (DFF), days to 100% flowering (DHF), plant height (PH), pods per plant (NPP), biomass (BIO), grain yield (YLD), 100-seed weight (HSW), harvest index (HI), membrane permeability index (MPI), relative leaf water content (RLWC) and pollen viability (PV)) showed a highly significant difference in RILs. The phenotyping data coupled with the genetic map comprising of 1365 ddRAD-Seq based SNP markers were used for identifying the QTLs for heat tolerance. Composite interval mapping provided a total of 28 and 23 QTLs, respectively at Ludhiana and Faridkot locations. Of these, 13 consensus QTLs for DG, DFI, DFF, DHF, PH, YLD, and MPI have been identified at both locations. Four QTL clusters containing QTLs for multiple traits were identified on the same genomic region at both locations. Stable QTLs for days to flowering can be one of the major factors for providing heat tolerance as early flowering has an advantage of more seed setting due to a comparatively longer reproductive period. Identified QTLs can be used in genomics-assisted breeding to develop heat stress-tolerant high yielding chickpea cultivars. [ABSTRACT FROM AUTHOR]

Ascochyta blight (AB) and botrytis grey mould (BGM) are the most devastating fungal diseases of chickpea worldwide. The wild relative of chickpea, C. reticulatum acc. ILWC 292 was found resistant to BGM whereas, GPF2 (Cicer arietinum L.) is resistant to AB. A total of 187 F8 Recombinant Inbred Lines (RILs) developed from an inter-specific cross of GPF2 × C. reticulatum acc. ILWC 292 were used to identify quantitative trait loci (QTLs) responsible for resistance to AB and BGM. RILs along with parents were evaluated under artificial epiphytotic field/laboratory conditions for two years. Highly significant differences (P < 0.001) were observed for reaction to both pathogens in both years. Parents and RILs were genotyped-bysequencing to identify genome wide single nucleotide polymorphism (SNPs). A total of 1365 filtered and parental polymorphic SNPs were used for linkage map construction, of which, 673 SNPs were arranged on eight linkage groups. Composite interval mapping revealed three QTLs for AB and four QTLs for BGM resistance. Out of which, two QTLs for AB and three QTLs for BGM were consistent in both years. These QTLs can be targeted for further fine mapping for deployment of resistance to AB and BGM in elite chickpea cultivars using marker-assisted-selection. [ABSTRACT FROM AUTHOR]

Key message: A novel recessive bacterial blight resistance locus designated as a xa-45(t) was identified from Oryza glaberrima accession IRGC 102600B, transferred to O. sativa and mapped to the long arm of chromosome 8 using ddRAD sequencing approach. The identified QTL spans 80 kb region on Nipponbare reference genome IRGSP-1.0 and contains 9 candidate genes. An STS marker developed from the locus LOC_Os08g42410 was found co-segregating with the trait and will be useful for marker-assisted transfer of this recessive resistance gene in breeding programs. Bacterial blight, caused by Xanthomonas oryzae pv. oryzae, is one of the major constraints of rice productivity in Southeast Asia. In spite of having 44 bacterial blight resistance genes from cultivated rice and wild species, the durability of resistance is always at stake due to the continually evolving nature of the pathogen and lack of suitable chemical control. Here, we report high-resolution genetic mapping of a novel bacterial blight resistance gene tentatively designated as a xa-45(t) from an introgression line derived from Oryza glaberrima accession IRGC 102600B. This introgression line was crossed with the susceptible rice indica cultivar cv. Pusa 44 to generate F2 and F2:3 populations for inheritance and mapping studies. The inheritance studies revealed the presence of single recessive locus controlling resistance to the Xanthomonas pathotype seven. A high-density linkage map was constructed using double-digest restriction-associated DNA sequencing of 96 F2 populations along with the parents. The QTL mapping identified a major locus on the long arm of rice chromosome 8 with a LOD score of 33.22 between the SNP markers C8.26737175 and C8.26818765. The peak marker, C8.26810477, explains 49.8% of the total phenotypic variance and was positioned at 202.90 cM on the linkage map. This major locus spans 80 kb region on Nipponbare reference genome IRGSP-1.0 and contains 9 candidate genes. A co-segregating STS marker was developed from the LOC_Os08g42410 for efficient transfer of this novel gene to elite cultivars. [ABSTRACT FROM AUTHOR]

Bacterial blight (BB), caused by Xanthomonas oryzae pv. oryzae, is a major disease of rice managed largely through the deployment of resistance genes. Xa38, a BB resistance gene identified from Oryza nivara acc. IRGC 81825, was mapped on chromosome 4L in a 38.4-kb region. The closely linked markers for this gene, identified earlier, were simple sequence repeat marker RM17499 and sequence-tagged site markers developed from loci Os04g53060 and Os04g53120. Marker Os04g53060 is dominant while the other two markers show smaller size differences difficult to resolve accurately on agarose gel. Based on gene annotation, three nucleotide binding site-leucine-rich repeat genes present in the target region were cloned from O. nivara and sequenced. One of the loci, LOC_Os04g53050, had a 48-base-pair deletion in O. nivara acc. IRGC 81825 compared to the cultivated rice. Primers were designed around the deletion and the resulting marker is codominant and easy to score in agarose gel. The newly designed marker co-segregated with Xa38, amplifying products of 269 bp in O. nivara and 317 bp in cultivated rice. This marker could be more useful for marker-assisted selection than ones reported earlier. [ABSTRACT FROM AUTHOR]

BACKGROUND RESULTS CONCLUSION Yellow mosaic disease (YMD) is the most devastating disease of soybean under north Indian conditions. A recombinant inbred line population derived from SL 958 (R) × AGS 456 (S) was used to map the genes imparting YMD resistance. Genotyping by sequencing (GBS) of 148 individuals and the parents was used to identify polymorphic SNPs in the population. These were used to generate linkage maps and subsequently map the QTL.A QTL, MYMIV 1‐1.1, was mapped onto chromosome 6. The QTL was mapped at a genetic distance of 114.31 cM, with likelihood ratio of 81.34 (LOD 17.68), explaining 33.80% of the variation for the trait, with an additive effect of 1.22. MYMIV 1‐1.1 was flanked by SNPs Gm06_12614920 explaining 33.80% of variation and Gm06_12887789 explaining 31.04% of the variation. The QTL region spanned for a total of 2.798 Mbp.The QTL was mapped in an approximately 4 cM region. Flanking SNPs can be developed into linked markers for effective marker‐assisted selection. Out of the genes in the QTL region, Glyma.06G161700 (Suppressor of Gene Silencing/SGS3) is the strongest contender for the resistance gene. This is the first study documenting GBS‐based mapping of YMD resistance in soybean. © 2024 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]