Novel alleles for commercially important traits exist in the exotic germplasm of crops, including wild relatives and landraces ( Wang et al., 2017). The widespread production area of cultivars with Indianhead heritage is therefore 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. Under controlled environment screening conditions, isolates have also 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. lentis isolates has contributed to the breakdown of AB resistance of lentil cultivars with similar genetic background, particularly those that derive resistance from cv. However, the emergence of highly aggressive A. In Australia, prominent variety releases, such as PBA Northfield, Nipper, PBA Jumbo2 and PBA Hurricane XT with improved AB resistance ( Rodda et al., 2017 Pulse Australia, 2020), gave hope of a genetic solution to this problem. Use of resistant cultivars is considered an effective control measure in combination with appropriate cultural methods and application of fungicides ( Hawthorne et al., 2015). lentis spread frequently occur ( Gossen and Morrall, 1983 Kaiser, 1992). Yield losses of up to 70% are common where conditions favorable for A. Globally, AB is considered the most widespread and economically important disease in lentil crops ( Erskine et al., 1993 Ye et al., 2002). A major constraint 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). However, lentil productivity is highly inconsistent and ranged between 0.8 and 2.4tonnes/ha in the last decade ( Faostat, 2021). Owing to the demand and export value, Australian lentil production scaled to 255,185 MT in 2018, an increase of over 85% compared to 3,000 MT produced in 1990 ( Faostat, 2021). Lentil ( Lens culinaris Medikus), a member of the Fabaceae legume family, is cultivated across the world for its high dietary benefits. 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. The identified QTL regions harbored putative candidate genes potentially associated with defense responses to A. Another QTL was identified on LG2 with phenotypic variance of 9.6%. 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. A genetic linkage map was constructed from single-nucleotide polymorphism markers generated using a genotyping-by-sequencing transcript approach. 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. Successful introgression entails an understanding of the genetic basis of resistance. However, the breakdown of AB resistance in cultivars, such as Northfield and Nipper, suggests the need for introgression of new and diverse resistance genes. Cultivation of AB resistant cultivars, alongside agronomic management including fungicide application, is the current most economically viable control strategy.
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