BIOCHEMICAL INVESTIGATIONS FOR FUSARIUM (Fusarium oxysporum f.sp. cumini) WILT RESISTANCE IN CUMIN (Cuminum cyminum L.)
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Date
2003
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AAU, Anand
Abstract
Cumin is an important spice crop, cultivated mainly in Gujarat, Rajasthan and in some parts of Uttar Pradesh and Punjab. Extensive loss occurs to cumin by the wilt disease causing fungus, Fusarium oxysporum f.sp. cumini which is very much devastating. Existing germplasm also does not contain a good source of resistance as it has a very narrow genetic base. Onset of pathogen attack causes alteration in physiological and biochemical pathways which can be viewed through the investigation at biochemical and molecular level. Our results suggested that higher levels of total phenols, total carbohydrates, cellulose, total proteins and total free amino acids both before and after infection in GC-3 suggested the role for each of these constituents in a resistant cultivar. On the other hand, higher levels of total soluble sugars and reducing sugars indicated susceptibility to wilt disease as observed in GC-1. Higher enzyme activities such as peroxidase, esterase, β-glucosidase, phenylalanine ammonia lyase and β-1,3- glucanase in GC-3 again suggested a better resistance mechanism against the disease. Genetic diversity studies revealed a close relationship between GC-1 and GC-3. Gene expression results suggested genotype specific expression, as very less number of transcripts induced were common to all the three genotypes. Out of 204 differentially expressed transcripts, 60 were repressed and the remaining 144 were induced transcripts. Repressed transcript may account for decrease in some of the biochemical constituents. Our protein profiles clearly indicated the genotype specific expression at protein level. Biochemical analysis of cumin callus from different explants suggested the role of different biochemical constituents in callus growth and organogenesis. Significantly higher total carbohydrates, total proteins, total free amino acids, proline, ascorbic acid along with significantly higher activities of enzymes such as peroxidase, polyphenol oxidase, esterase and PAL were characteristic of the callus from shoot tip of GC-2 which had better growth and organogenic potential. Protein profile also revealed that higher protein content in callus from shoot tip of GC-2 which was highly organogenic rather than the callus from hypocotyl. The treatment of callus by culture filtrate revealed that culture filtrate at 0.1% was very effective in retaining callus growth and regeneration capacity. Significantly higher total phenols, total carbohydrates and total proteins in culture filtrate treated calli and higher enzyme activities of peroxidase, esterase, PPO, PAL and β-glucosidase revealed a second role for these constituents in callus survival under applied pressure. Our proteomic results suggested that many proteins get induced/repressed as a result of culture filtrate treatment which may alter some of the biochemical pathways for their survival, growth and regeneration.
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BIOCHEMISTRY, Investigation