Identification of resistant sources of castor against Fusarium wilt disease

Castor is an important oilseed crop grown in India. However, its cultivation is seriously affected by several diseases, e.g. wilt disease caused by Fusariumoxysporum f. sp. ricini being economically relevant. Host plant resistance is the best option for the management of this disease. A total of 524 castor genotypes were screened against wilt disease under sick plot conditions for five years from 2013-2014 to 2017-2018. The wilt sick plot was maintained with a inoculum load of 2 x 10(3 )CFU/gm of soil and the genotypes were screened alongside resistant (48-1) and susceptible (JI-35) cultivars. It was observed that 109 castor genotypes were susceptible to wilt with more than 50% wilt incidence whereas, 32 genotypes; i.e., DCS-86, DCS-118, DCS-108, DCS-105, DCS-107, DPC-17, DPC-18, DPC-21, DPC-23, DPC-24, DPC-25, M-571, DPC-28, PMC-9, PMC-11, PMC-14, PMC-15, PMC-16, PMC-17, PMC-24, PMC-38, PMC-55, PMC-60, PVT- 11-3, PVT-11-18, PVT-11-17, PVT-11-21, PVT-12-4, PVT-12-6, PVT-12-72 and PVT-11-26 recorded < 20% wilt incidence during the consecutive years of testing. Three wilt-resistant parental lines of castor IPC-21/DPC-21(INGR No.21107), M-571 (INGR No. 21230), and ICS-200 (INGR No. 21157) were identified and registered by the Plant Germplasm Registration Committee. Among the screened parental lines, PMC-14 showed a resistant reaction of 10-16.7% to wilt for three years and was used as a parent ICS-164 (PMC-14) in developing wilt-resistant hybrid ICH-66, which was released for cultivation in five states of India, namely, Andhra Pradesh, Telangana, Tamil Nadu, Karnataka and Odisha. The resistant lines identified in this study could be used for breeding wilt-resistant castor hybrids.