Assessment of genetic diversity among rhizoctonia root rot resistant soybean genotypes

Rhizoctonia root rot caused by Rhizoctonia solani [Kühn teleomorph Thanatephorus cucumeris (Frank) Donk] is one of the most destructive diseases of soybean in India. Very little is known about the diversity among resistant sources in this crop. The aim of present study is to assess the genetic diversity and use allele mining approach to characterize and utilize the naturally occurring resistance diversity in soybean. Five moderately resistant cultivars along with four gamma induced moderately resistant mutants and five high yielding susceptible cultivars were evaluated by 49 simple sequence repeats (SSR) and 20 inter simple sequence repeats (ISSR) markers. A total of 126 (117 polymorphic) and 164 (113 polymorphic) bands were detected by SSR and ISSR markers respectively. Several SSR makers e.g., Sat_076, Sat_246, Satt119 and Satt 433 discriminated the susceptible and resistant cultivars. SSR marker Satt 177, which is reported to be associated with resistance to rhizoctonia root rot also amplified specific alleles in susceptible and resistant cultivars. SSR and ISSR marker data sets showed positive correlation (Mantel test r = 0.69) in the UPGMA cluster analysis, grouping the susceptible cultivars along with resistant cultivars. The partition of the variation among and within susceptible and resistant cultivars showed great variation among individual rather than between the groups.