Screening of Landraces of Cluster Bean for Powdery Mildew Disease Resistance and Molecular Characterization of Selected Landraces

Abstract

Background: Cluster bean (Cyamopsis tetragonoloba) is a major legume crop. Powdery mildew is a devastating foliar disease affecting cluster beans. Fungicides are recommended for disease management; however, their use is costly and environmentally harmful. Aim: The present study was undertaken to identify resistant landraces of cluster bean as an eco-friendly and sustainable alternative for managing powdery mildew.     Study Design: Thirty-two landraces were screened against powdery mildew under natural epiphytotic conditions in the field to identify the resistance landrace. Place and Duration: Department of Plant Biotechnology, College of Agricultural Biotechnology, Loni, between June 2024 and December 2024 Methodology: The disease severity was recorded at 25 days and 50 days after infection. Five leaves from the lower, middle, and upper part of the plant were graded by using 0-9 scale. RAPD markers were used to characterize five landraces: two resistance landraces (P5 and P6), two susceptibility landraces (AS1 and AS4), and one control landrace (Phule Guar). Scoring of amplified fragments was done. Jaccard's similarity coefficient was used to determine pairwise genetic similarities between Cluster bean ladraces. Result: After 50 DAI, only ten landraces were found to be resistant. However, twenty-two landraces were found to be highly susceptible, with a maximum grade of nine on the (0–9) scale.  Five RAPD primers were screened which successfully discriminated the landraces. The similarity coefficient value ranged from 0.34 to 0.63 across five landraces indicating a high degree of genetic variation. The dendrogram analysis revealed that five cluster bean landraces may be classified into two major clusters: A and B. Only the control variety, Phule Guar, belonged to cluster B, indicating that it differed from the collected guar landrace. Cluster A1.1 contains AS4 and AS1, both of which were susceptible in nature but produced high yields. In contrast, landrace P6 from cluster A1.2 was resistant to powdery mildew disease but produced lower yields. Landrace P5 belonged to cluster A2, which was more diversified than AS4, AS1, and P6 landraces, as well as resistant and high yielding. This work will help to improve genetic resource conservation and management, as well as the establishment of sophisticated breeding programs for clusterbean.