Screening Wild Brassica Species Against Alternaria Brassicicola (Schw.) Wiltsh for Breeding Alternaria Leaf Spot Resistance in Brassica Vegetables

Abstract Alternaria leaf spot (ALS) is a major disease of Brassica crops, and it causes huge economic losses to both the cultivated oilseed-and vegetable- Brassicas . The present study was aimed to develop a non-destructive robust method for screening of wild Brassica species and to find resistant wild species against Alternaria brassicicola (Schw.) Wiltsh available in the germplasm. For this, 38 wild Brassica species were screened at adult plant stage by an in vitro detached leaf inoculation method in three consecutive years i.e. 2019-20, 2020-21 and 2021-22. The new screening protocol provides favourable environment (temperature 25±2 °C; relative humidity >90%) for the pathogen and retained the host leaves in condition (by placing sucrose 5% w/v in petiolar base) for disease development. The consistency in reactions of the species against A. brassicicola during all three years of testing indicates the robustness of the protocol. Further, the multiple parameters were recorded on leaf condition and disease response of the wild species. Complete resistance was observed in Capsella while resistance in Lepidium , Camelina and Biscutella . Both Capsella bursa pastoris (L.) Medik (early) and C. bursa pastoris (late) were symptomless resistant. Camelina sativa (L.) Crantz, Diplotaxis erucoides (L.) DC and Diplotaxis gomez-campoi Mart.-Laborde were found to be resistant against A. brassicicola . The significant correlation between disease parameters indicates the robustness and effectiveness of the screening protocol for wild Brassica species.