Indian Journal of Horticulture

Onion (Allium cepa. L.) is open pollinated and highly heterozygous crop. Hence, there are chances of mixtures or mislabeling of seeds. The grow out tests for testing the purity of seeds are time consuming and the life of onion seed under normal storage conditions is one to one and a half year only. Several biotechnological tools are available but due to its breeding system, under or over-polymorphism regions often appear in RAPD and AFLP techniques. Several co-dominant simple sequence repeats or microsatellites (SSRs) have been reported in onion. Fourteen short day and 2 long day cultivars were evaluated at 24 microsatellite loci. Twenty-one primer pairs were polymorphic and 64 different alleles were scored. Percentage of same fragments between two cultivars was also compared as a measure of similarity. Nashik Red and Poona Red cultivars showed 100% similarity and were indistinguishable. Cultivars N-53 and Bombay Red showed 95% similar fragments. It was followed by Arka Niketan and Poona Red (91.3% similar fragments) and Arka Niketan and Nashik Red (90.5% similar fragments pair), which were quite close. Alisa Craig showed maximum diversity with about 70% dissimilar fragments pairs compared to other cultivars and 25.7% similar fragment pairs with Brigham Yellow Globe. Some fragments were unique and were only present or absent in a cultivar at particular loci and they can be used as cultivar specific markers for rapid discrimination. Jaccard's coefficient for SSRs was also estimated and cultivars were grouped into 5 main groups on the basis of their relatedness. Exotic cultivars Alisa Craig and Brigham Yellow Globe were different compared to the Indian cultivars. Nashik Red and Poona Red were indistinguishable and similarly N-53 and Bombay Red were quite close. The results of this study will also be helpful in selecting the diverse parents (inbreds) for the development of suitable hybrids of onion, for the DNA fingerprinting of the cultivars and promising germplasm for their protection under Plant Cultivar Protection Act.