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Castor is an industrially economic and valuable oilseed crop cultivated worldwide. There is a constant upsurge in demand for its oil. But wilt caused by Fusarium spp. is a devastating disease that severely affects the productivity depending upon the crop stage. Stable high yielding pistillate lines serve as donors in heterosis breeding programme and for further biotechnological advancements. Genetic characterization of wilt resistance indicated the role of duplicate dominant epistasis in YTP 1 × TMV 5, complementary epistasis in DPC 9 × JP 65 and JP 65 × SKI 215, duplicate recessive epistasis in YRCP 1 × DPC 9. Monogenic recessive nature of wilt resistance was reported in other four cross combinations viz., YRCP 2 × JP 65, SKP 84 × JP 65, YRCP 2 × DPC 9 and YRCP 2 × SKP 84. Magnified images taken using LED phase contrast microscope portrayed the presence of microconidia and macroconidia and Scanning Electron Microscope (SEM) image analysis showed the presence of intact internal cell structures in resistant check (48−1) while the cell structures were disturbed with mycelial growth in the susceptible check (JI 35). Among 21 pistillate lines screened, seven viz., DPC 9, DPC 16, SKP 84, JP 96, GEETA, M 574 and M 619–1 were resistant. By screening P1, P2, F1, F2, BC1F1 (P1) and BC1F1 (P2) generations of eight crosses under field and pot test method, the stable pistillate line DPC 9 was found to be wilt resistant. F1 generation plants expressed 100% susceptibility indicating the recessive nature of wilt resistance. JP 65 × SKI 215 and YRCP 1 × DPC 9 showed the minimum incidence comparing other F2 populations. The backcross (YRCP 1 × DPC 9) × DPC 9 was found to possess the lowest wilt incidence compared to other populations under field and green house condition. Hence the identified lines could be better used to develop wilt resistant high yielding hybrid and for further identifying and introgressing genomic regions conferring wilt resistance to high yielding popular variety through linkage/QTL mapping technique.

A drought-resistant plant with high adaptability to various climatic and soil conditions is castor (Ricinus communis L.). There is currently a significant expectation of increased castor oil demand on the global market. When it comes to crop development, there are a variety of factors to take into account for each growing region, especially when it is preferable to fit the castor crop to specific tillage practices and intercropping system. In this veneration, the current study's goal was to determine the effects of various tillage methods and legume crop-based intercropping system in rainfed regions. The field experiments were conducted in 2021-2022 and 2022-2023 at Tapioca and Castor Research Station, Tamil Nadu Agricultural University, Yethapur. The experimental treatments consisted of conventional tillage and minimum tillage as main plot and castor based inter cropping system @ 1:3 ratio viz., Castor + Greengram, Castor + Cowpea, Castor + Groundnut and Sole Castor as subplot treatments and conducted in split plot design with three replications. The pooled results of a two-year study of different tillage practices in legume crop based intercropping systems in rainfed conditions showed no significant difference among tillage practices relevant to growth, yield attributing characters, seed yield and biomass yield, however higher values were registered under conventional tillage practices over minimum tillage. Higher seed yield of both base (1152 kg ha-1) and inter crop (481 kg ha-1) were documented in conventional tillage practices over minimum tillage. With respect to inter cropping, higher base crop (castor) yield of 1058 kg ha-1 was recorded under castor + groundnut inter cropping system, which was observed to be on par with sole castor (1020 kg ha-1), and castor + greengram (907 kg ha-1). Recorded highest Castor equivalent yield in castor + groundnut (1:3) intercropping, grown under a conventional tillage system. Moreover, the maximum benefit-cost ratio was recorded in castor + groundnut (1:3) intercropping, over sole castor cropping. The highest Castor Equivalent Yield (CEY) in a conventional tillage system was observed in a castor + groundnut (1:3) intercropping system. [ABSTRACT FROM AUTHOR]

Castor is one of the non - edible oilseed crop cultivated all over the world. Knowledge on genetic divergence is the foremost important tool for the initiation of any successful breeding programme. The present investigation aims to reveals the nature and magnitude of diversity that exist among the 70 castor genotypes based on 11 biometrical traits, using Mahalanobis D2 statistics. Based on the genetic distance, 70 castor genotypes were grouped into seven different clusters. Among the characters studied, seed yield per plant (45.96 per cent) had major contribution to the total divergence. The maximum interclusters distance was recorded between genotypes cluster IV and cluster VI. The maximum intera- cluster distance was observed in the cluster VII (28.28). Thus, selection of genotypes from diverse clusters for future hybridization programme as a parental genotypes will helps to obtain segregants.