A modified and effective stem inoculation technique for artificial screening against Sclerotinia sclerotiorum in mustard

Abstract

AbstractSclerotinia stem rot (SR) disease emerged as a potential threat in most mustard‐growing regions globally. Sclerotinia sclerotiorum, a necrotrophic pathogen, causes considerable damage to the crop under congenial environments. The sclerotia even under adverse conditions can survive up to 5 years in the soil. The use of resistant sources is the only mean to combat the pathogen. The development of an effective inoculation technique can facilitate the identification of new sources of resistance rapidly. Investigations on resistant sources using Potato Dextrose Agar (PDA) medium for artificial stem inoculation are ongoing under the All India Coordinated Research Project (AICRP) on rapeseed‐mustard for many years but no resistant sources could been identified. In the present study, two non‐injury stem inoculation techniques using sorghum grains and PDA medium as a basal medium were tested on 11 brassica entries for up to three consecutive years. Results revealed that sorghum grain‐based inoculum was found efficient for disease development and lesion formation in brassica entries compared with PDA‐based inoculum. Among the entries, a maximum disease incidence of 42.3% was recorded in entry DRMR 5206 followed by DRMRSJ‐20, DRMRSJ‐22 and DRMR 2017‐8 with 42.1%, 41.8% and 41.3% SR incidence, respectively. In PDA disc inoculation maximum SR incidence of 30.8% was observed in DRMRSJ‐26 followed by DRMR 5206, DRMRSJ‐25 and DRMRSJ‐2017‐18 with 27.5%–24.9%, respectively. Lesion length was more in entries inoculated with fungal mycelium multiplied on sorghum grains compared with the PDA disc inoculation method. The statistical analysis and results of p‐value (<.00001) showed a significant difference between tested methodologies. Thus, the sorghum grain‐based inoculation technique is an appropriate, economic and effective non‐injury inoculation technique for artificial screening against S. sclerotiorum in the mustard crop. This technique can be used to screen a large number of brassica entries more efficiently with less labour and time.