Abstract
Australian lentil production is affected by several major biotic constraints including Ascochyta blight (AB), caused by Ascochyta lentis, a devastating fungal disease. Cultivation of AB resistant cultivars, alongside agronomic management including fungicide application, is the current most economically viable control strategy. However, the breakdown of AB resistance in cultivars, such as Northfield and Nipper, suggests the need for introgression of new and diverse resistance genes. Successful introgression entails an understanding of the genetic basis of resistance. In this context, a biparental mapping population derived from a cross between a recently identified AB resistant accession ILWL 180 (Lens orientalis) and a susceptible cultivar ILL 6002 was produced. A genetic linkage map was constructed from single-nucleotide polymorphism markers generated using a genotyping-by-sequencing transcript approach. Genetic dissection of the mapping population revealed a major quantitative trait loci (QTL) region nested with three QTLs on linkage group 5 and explained 9.5–11.5 percent (%) of phenotypic variance for AB resistance. Another QTL was identified on LG2 with phenotypic variance of 9.6%. The identified QTL regions harbored putative candidate genes potentially associated with defense responses to A. lentis infection. The QTL analysis and the candidate gene information are expected to contribute to the development of diagnostic markers and enable marker-assisted resistance selection in lentil breeding programmes.
Highlights
Lentil (Lens culinaris Medikus), a member of the Fabaceae legume family, is cultivated across the world for its high dietary benefits
Significant differences for ascochyta blight (AB) resistance were found between the parents, ILWL 180 (Leaf lesion score at 28 dpi = 0.66 ± 0.50%, mean Area under disease progress curve (AUDPC) = 11; Stem lesion score at 28 dpi = 7.77 ± 2.21%, mean AUDPC = 122) and ILL 6002 (Leaf lesion score at 28 dpi = 72.66 ± 4.37%, mean AUDPC = 907; Stem lesion score at 28 dpi = 63.33 ± 4.09%, mean AUDPC = 1,078) following inoculation with the highly aggressive isolate FT13038 at 14, 21 and 28 dpi (p < 0.001; Figures 1A–C)
The genomic region between 51,406,761 and 210,272,490 bp on LcChr6 chromosome was previously reported to be associated with AB resistance (Sudheesh et al, 2016a; Polanco et al, 2019). These results indicate that the larger proportion of the resistance at seedling stage is conditioned by common loci and that may be potentially conserved within Genus Lens and further agree with Polanco et al (2019) that common genes are involved in defense responses to A. lentis infection
Summary
Lentil (Lens culinaris Medikus), a member of the Fabaceae legume family, is cultivated across the world for its high dietary benefits. Lens orientalis Contributes Ascochyta Blight Resistance to lentil productivity is yield reduction resulting from infection by the fungal disease ascochyta blight (AB) caused by Ascochyta lentis, estimated to cost the Australian lentil industry 16.2 million AUD per year (Murray and Brennan, 2012). The emergence of highly aggressive A. lentis isolates has contributed to the breakdown of AB resistance of lentil cultivars with similar genetic background, those that derive resistance from cv. Under controlled environment screening conditions, isolates have been reported to have caused a susceptible reaction in cultivars (PBA Jumbo and PBA Blitz) with Indianhead pedigree (Davidson et al, 2016) and in cv. The widespread production area of cultivars with Indianhead heritage is likely under current selection pressure, underlining the critical need for inclusion of novel and diverse resistance alleles/genes into the breeding programme to enhance the durability of resistance sources to AB
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