Research Projects

Onion (Allium cepa L.; Family: Alliaceae) is a spice-cum-bulbous vegetable crop with significant commercial and therapeutic values. India is the second largest producer of onion with annual production of 19.4 million tonnes. However, onion productivity in recent times has been greatly affected by stemphylium vesICARium infection that causes stemphylium Leaf Blight (sLB) disease. sLB together with purple blotch accounts for nearly 85% yield losses. Management of sLB through application of fungicides and bio-controls haven't been very effective. Host-resistance breeding has not met with tangible success due to lack of sLB resistant onion varieties. In this condition, molecular markers could be the most promising tools for identification of novel resistant cultivars. Yet, the absence of dependable molecular markers is a major drawback in the sLB resistance breeding. Moreover, the molecular mechanism governing the onion-sLB interaction and the characterization of sLB resistance locus in onion is yet to be ascertained. Therefore, the development of robust markers linked to sLB resistance locus for utilization in marker-aided selection is the need of the hour. The advent of high-throughput sequencing has made the single nucleotide polymorphisms (sNPs) as the robust group of genetic markers. With high distribution density and genetic stability across the genome, sNPs can facilitate rapid identification of alleles for disease resistant traits. sNPs have been recently linked to purple blotch (PB) resistance in Allium cepa. However, robust markers linked to sLB resistance is yet to be characterized in onion. A comprehensive detection of sNP markers using reduced representation library (RRL) sequencing together with bulk-segregant analysis and their subsequent usage in the fine mapping of the sLB resistance traits will be crucial in the rapid and early identification of sLB resistant onion genotypes and their effective application in molecular breeding programmes. Thus, the present project was formulated to achieve the main objective of fine mapping the sLB resistance locus using sNP markers and their utilization in onion breeding through marker-assisted selection.