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  • Author or Editor: Sabitha Doraiswamy x
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Seed extracts of 50 plant species belonging to different families were evaluated for their ability to inhibit growth of Trichoderma viride in vitro. Of the various seed extracts, the seed extracts of Harpullia cupanioides (Roxb) belonging to Sapindaceae family exhibited very high antifungal activity. The seed extract of H. cupanioides strongly inhibited the growth of Rhizoctonia solani, Curvularia lunata, Colletotrichum musae and Alter­naria alternata. Seed extract of H. cupanioides retained its antifungal acti­vity even after heating at 100 °C for 10 min or autoclaving at 121 °C for 20 min. For partial purification of antifungal proteins, H. cupanioides seed extract was subjected to ammonium sulphate fractionation followed by gel filtration on Sephadex G-200 column. The fractions from sephadex G-200 were individually tested for their antifungal activity against T. viride. SDS-PAGE analysis of the fractions from Sephadex-G200 column indi­cat­ed that the fractions with antifungal activity contained a 68-kDa band as well as other low molecular weight protein bands. The N-terminal amino acid sequence of the 68-kDa protein (13 residues) was determined by Edman degradation. However, comparison with sequences in the GenBank database (Swiss Prot) did not reveal any homology with known protein sequences.

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Authors: S. Ravi, Sabitha Doraiswamy, V. Valluvaparadisan and C. Jeyalakshmi

French bean seed samples were collected from different parts of Tamil Nadu including both tropical and temperate region including four cultivars viz.,Arkakomal,Premier,Rajmash DPU 88-4 and Watex.The variety Watex was found to maximum per cent seed infection of C.lindemuthianum with more discolorations.Among the various techniques adopted for detection,agar plate method was found to be best and yielded maximum per cent seed infection.Direct correlation was obtained between seed discoloration and per cent seed infection.The pathogen was found to be present mostly in seed coat and cotyledon and rarely in embryonic axis.The artificial inoculation of 45-day-old plants resulted in maximum disease incidence,resultant seed infection and minimum seed yield /plant and 100 grain weight.

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A polymerase chain reaction (PCR) assay was used to detect the Indian iso­late of banana bunchy top virus at early stages of infection in banana suckers before symptom expression. The viral DNA was detected from a single viruliferous banana aphid (Pentalonia nigronervosa) at 1.0 kb. The six plant species viz., Zingiber officinale, Colocasia esculenta, Cathe­ranthus roseus, Canna indica, Hedychium coronarium and Alphi­nium sp. upon inoculation with BBTV showed negative results in PCR assay. Using PCR assay the BBTV could be detected in meristem tip cultured banana plants before symptom expression. In field condition the meristem tip cultured banana plants expressed BBTV symptom 45 days after planting.

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Seed extract of Harpullia cupanioides was tested against infection by Tomato spotted wilt virus (TSWV), Rice tungro virus (RTV) and Cowpea aphid borne mosaic virus (CABMV). Seed extract of H. cupanioides (10%) when sprayed on test plants 24 h before virus inoculation significantly inhibited virus infections. Percentage inhibition of TSWV in local lesion host by 10% seed extract of H. cupanioides was found to be 90.9. Pre-inoculation application of 10% seed extract of H. cupanioides provided 87.5% inhibition of CABMV infection. The seed extract (10%) sprayed rice plants recorded RTV infection of 48% as against 100% in control.

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