MAHATMA, M.K.KAPADIA, CHINTAN V.2016-04-292016-04-292012-05http://krishikosh.egranth.ac.in/handle/1/65654One of the key approaches for disease prevention and control in castor (Ricinus communis L.) is to develop a disease resistant variety; this can be achieved through tagging of resistance genes. In this study, a total of two putative resistance gene analogues (RGAs) have been isolated and characterized from resistant castor genotype (SKP-84) using primers targeted at the conserved motifs of the known R gene in the database. Homology and % identity searches of the isolated RGA sequences with the NCBI GenBank database showed that p6.4 had 89% identity to the disease resistance like proteins in castor and 23 had 100% identity with I2C disease resistant proteins in tomato. Phylogenetic analysis indicated that the RGAs clustered with R genes found in Arabidopsis and Tomato. The findings will be useful for studying of resistance mechanism in castor to Fusarium. Induction of plant defence against pathogen attack is regulated by a complex network of different signals. Thus changes in various biochemical defences including antioxidant enzymes, phenolic compounds andpathogenesis related (PR) proteins were investigated the roots of resistant and susceptible genotypes of castor at 0, 24, 48 and 72 h.a.i. by Fusarium oxysporium significantly increased the SOD and POX activities in the roots of susceptible genotypes, while the catalase activities were appreciably higher in the roots of resistant genotypes at different stages. Constitutive levels of APX and PPO were higher in the resistant genotypes. Also, activities of PAL and β 1, 3 glucanase significantly increased in the roots of resistant genotypes after infections. Rate of increment of MDA content was higher in resistant genotypes after infection. Analysis of isozyme electrophoresis revealed that interaction between plant and fungi invoked various isozymes at 48 hours of infection. The isozyme banding pattern of SOD, POX, PPO and esterase were studied during plant pathogen interaction and showed some induced isozymes.SOD 3 was observed only in resistant genotypes at 24 h.a. i . except , Geeta. Simi larly induction of POX 5 was observed only in resistant genotypes at 48 hours of infection, though the intensity of POX 5 was very less. Expression analysis of regulatory genes of ethylene and spermidine biosynthesis using RT-PCR revealed higher expression of S-adenosyl methionine decarboxylase, ACC Synthase and sepermidine synthase in the roots of resistant genotypes at 4, 6 and 8 h.a.i., which shows role of ethylene as signal molecule in disease resistance.These results reflect cascade of signals activated by fungi which leading to the activation of defence system in castor against wilt pathogen.enenzymes, planting, genes, diseases, biological phenomena, genotypes, proteins, castor (genus), fungi, vegetablesThesis