Authors:C. Bharathimatha, Sabitha Doraiswamy, R. Rabindran, P. Renukadevi and R. Velazhahan
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.
Authors:G. V. Sible, T. Marimuthu, R. Rabindran and R. Velazhahan
Pretreatment of rice leaves with 20 per cent cow dung water extract (CDWE) was found to reduce bacterial blight disease of rice to about 50 per cent. The suppression of the disease by the extract was not due to direct inhibition of the pathogen. Pretreatment of rice leaves with cow dung water extract as foliar spray induced the accumulation of phenolics and enhanced the activities of peroxidase, chitinase and ß-1,3-glucanase. The induced defense mechanisms might have played a role in reducing the disease.
Authors:K. Manickam, Sabitha Doraiswamy, T. Ganapathy and R. Rabindran
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.
Authors:R. Vivekananthan, R. Sudhagar, M. Ravi, T. Ganapathy, K. Thiyagarajan and R. Rabindran
The wild rice species (Oryza rufipogon, O. latifolia), thermogenic male sterile lines (TGMS) and Cuddalore rice accessions were evaluated for their reaction to the sheath rot pathogen (Sarocladium oryzae) under field conditions. The resistant TGMS line TS 47, Jeragasala 1, 2 and 3 (Cuddalore accessions) exhibited reduced disease symptoms. These field-screened cultivars were further confirmed for their resistance under in vitro conditions. The efficiency to grow in the toxin-containing medium was appraised. The medium was supplemented with toxin as crude, diluted preparation and culture filtrate. All the field identified genotypes except TS 47 showed better callus proliferation in vitro. Indeed they produced plantlets in toxin free medium further confirm their resistance. The germination test conducted in toxin containing culture tube also endorsed the suitability of Jeragasala 1, 2 and 3 as resistance donor. In addition, the difference in the protein profile of disease susceptible and resistant cultivars has been investigated by SDS-PAGE. A 80 kDa protein was present in relatively high concentration in resistant cultivars although the specific band was also present in susceptible genotypes, but in lower intensity.