Browsing by Author "Tripathi, Atma Nand"
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ThesisItem Open Access Studies on variability in Fusarium moniliforme Sheldon, from different crop species seeds and its sensitivity towards different biopesticides(G.B. Pant University of Agriculture and Technology, Pantnagar - 263145 (Uttarakhand), 2009-06) Tripathi, Atma Nand; Singh, U.S.Fusarium moniliforme Sheldon is an economically important seed-borne fungus which has a very wide host range and produce toxins. It causes the serious “bakanae” (Foot-rot) disease in rice, seedling blight, stalk and ear rot in maize and sorghum. Present studies were undertaken on phenotypic and genetic variability in thirty isolates of F. moniliforme isolated from 12 different crop species including 4 isolates from Indian Type Culture Collection (ITCC) New Delhi, India. All 30 test isolates were categorized into four major classes on the basis of colony characters (colony colour and texture), however, three major classes were formed on the basis of pigmentation. A comparison of five test media revealed that Potato Dextrose Agar (PDA) is most suitable for the fungal growth. Zonation was observed only on Cook Rose Bengal Agar (CRBA) medium. Two isolates (FmE5 and 11) showed saltation on the PDA culture plates. All isolates showed abundant sporulation except isolates FmI21 and 25, which were weak sporulants on PDA. Genetic variability among test isolates were studied with three molecular marker techniques viz. RAPD (43 random primers), ISSR (5 primers) and SSR (13 pairs of primers). At 60% level of similarity, RAPD, ISSR and SSR resulted in 30, 24 and 20 clusters, respectively, among 30 isolates. The three marker systems invariably showed large variation among all the 30 isolates of F. moniliforme. Jaccard’s similarity indices were higher for ISSR (0.90) followed by SSR (0.88) and RAPD (0.69). The average number of polymorphic bands per primer was higher in case of ISSR (8) as compared to that in RAPDs (7.27) and SSRs (5). The polymorphism information content (PIC) was also highest with ISSR (0.737) followed by RAPD (0.735) and SSR (0.568). The average expected gene diversity (Hi) value was higher for SSRs (0.292) which could detect greater average expected gene diversity than RAPDs (0.216) and ISSRs (0.214). The cophenetic correlation (r) were 0.916, 0.880, 0.854 and 0.913 indicating very good fit of the cluster analysis for RAPD, ISSR SSR and combined (RAPD+ ISSR + SSR). Among the molecular markers pairs highest Pearson correlation coefficient (r) was (0.88) between RAPD and SSR. While the total variation of first eight principal coordinate analysis (PCoA) for RAPD, ISSR and SSR was estimated as 43.21, 58.12 and 56.93%, respectively. Out of 61 primers used in the study, eight primers resulted in unique bands (four in RAPD, two in ISSR and two in SSR) as each one of them amplifying unique band in single isolate. These primers can be used for identification of specific isolate of F. moniliforme. A total of 314 scorable bands were obtained using 43 random primers with all 30 isolates. Out of which, 313 were polymorphic and only one band was monomorphic which was most interesting part of the studies. The results revealed that RAPD marker was best for discrimination among all the isolates studied, hence may be considered more efficient markers technique for F. moniliforme. In general, the isolates from the same host species could not grouped together in the same cluster. The knowledge of variability in the isolates within a region, country and among the countries as well as variability in the isolates of one crop host to another will be helpful for development of suitable management strategies. In vitro inhibition of various test isolates of F. moniliforme using biocontrol agents (TH38, TH39 & TH43) and essential oils (lemongrass, citronella and palmarosa) were studied. Bangle method used to evaluate antagonistic potential of three isolates viz. TH38, TH39 and TH43 of T. harzianum against 30 different isolates of F. moniliforme. The order of efficacy of Trichoderma isolates was assessed by the inhibition zone against test isolates of F. moniliforme was TH38 > TH43 > TH38. Three essential oils were evaluated for their in vitro antifungal efficacy using poisoned food technique at 1200, 1500, 1800 & 2000 ppm. The order of efficacy of essential oils assayed by per cent of mycelial growth inhibition against test isolates of F. moniliforme was lemongrass > citronella > palmarosa oil. These biopesticides (biocontrol agents and essential oils) can be further evaluated for use as broad spectrum seed treatment for the ecofriendly management of the disease. Variability among the test isolates on the basis of genotypic, phenotypic and sensitivity studies did not form similar pattern of clustering and was in poor congruence with their host preference as well as geographical locations.ThesisItem Open Access Variability studies on ralstonia solanacearum (E.F. Smith) Yabuuchi et al. in Himachal Pradesh(CSKHPKV, Palampur, 2004) Tripathi, Atma Nand; Sood, A.K.