Cultivated lentil suffers yield loss from stemphylium blight, caused by Stemphylium botryosum Wallr. Identification of sources of stemphylium blight resistance and knowledge of the mode of inheritance of resistance are important for developing resistant cultivars. The interspecific recombinant inbred line (RIL) population developed from a cross between the moderately resistant parent Lens culinaris cv. ‘Eston’ and the resistant parent L. ervoides (Brign.) Grande accession IG 72815 was evaluated for stemphylium blight resistance under controlled conditions at the University of Saskatchewan, Saskatoon, Canada, and under field conditions at the Pulses Research Centre (PRC), Ishurdi, Bangladesh. We hypothesized that resistance from both parents will lead to transgressive segregation indicative of pyramiding of resistance genes from the same. However, no resistant transgressive segregants were observed in the RIL population. A large proportion (50%) of the RILs had disease severity levels similar to the resistant parent IG 72815 in experiments conducted under natural disease pressure in Bangladesh. Under controlled conditions in Saskatoon, 38% of RILs had resistance levels similar to IG 72815. Across all environments, 14 RILs consistently had resistance levels similar to IG 72815. The distribution of disease severity scores for all RILs indicated polygenic inheritance of stemphylium blight resistance in the population. RILs with consistent resistant reactions should prove useful for lentil improvement programmes. This will contribute to increasing the productivity of lentil crops in North America and the Indo-Gangetic region, which account for more than 68% of world lentil production.
Genetically accessible variation to some of the abiotic and biotic stresses are limited in the cultivated lentil (Lens culinaris Medik.) germplasm. Introgression of novel alleles from its wild relative species will be useful for enhancing the genetic improvement of the crop. L. ervoides, one of the wild relatives of lentil, is a proven source of disease resistance for the crop. Here we introduce a lentil advanced backcross (LABC-01) population developed in cultivar ‘CDC Redberry’ background, based on L. ervoides alleles derived from an interspecific recombinant inbred population, LR-59-81. Two-hundred and seventeen individuals of the LABC-01 population at BC2F3:4 generation were screened for the race 0 of anthracnose (Colletotrichum lentis) and stemphylium blight (Stemphylium botryosum) under controlled conditions. The population showed significant variations for both diseases and the transfer of resistance alleles into the elite cultivar was evident. It also segregated for other traits such as days to flowering, seed coat colour, seed coat pattern and flower colour. Overall, we showed that LABC-01 population can be used in breeding programmes worldwide to improve disease resistance and will be available as a valuable genetic resource for future genetic analysis of desired loci introgressed from L. ervoides.
Stemphylium blight caused by Stemphylium botryosum, is a foliar disease of lentil. It affects the productivity and milling quality of lentil crops, mainly in South Asia and Canada. Development of stemphylium blight resistant cultivars by introgression of resistance alleles from crop wild relatives of lentil, such as Lens ervoides, is one strategy of disease control. The objective of this study was to identify genomic regions associated with stemphylium blight resistance by combining linkage mapping and marker-trait association analysis. A total of 182 genotypes of a lentil advanced backcross population (LABC-01) developed from the backcross of the interspecificL. culinaris ´ L. ervoides line LR-59-81 (donor) and cultivar CDC Redberry (recurrent) and 101 diverse lentil accessions selected by stratified random sampling from a lentil diversity panel were genotyped and evaluated for stemphylium blight reactions. Quantitative trait locus (QTL) analysis identified four loci contributing to stemphylium blight resistance on lentil chromosomes 2, 4 and 5. Marker trait association analysis detected five significant single nucleotide polymorphism (SNP) markers associated with stemphylium blight resistance within QTLs regions and seven SNP markers outside the QTLs regions on chromosomes 1, 2, 3, 5, and 7. The markers associated with stemphylium blight resistance may be useful for marker-assisted selection of resistant cultivars after validation.
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