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  • Author or Editor: T. Ganapathy x
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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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Treatment of acibenzolar-S-methyl (bionTM), salicylic acid and the saprophytic bacterium Pseudomonas fluorescens exhibited induced systemic resistance in Sorghum bicolor (cv. Rio) to Sugarcane mosaic virus (SCMV) isolates from sugarcane. The treatments significantly slowed down the SCMV titre in plants during the initial growth phase. The enhanced induction of total phenols, phenylalanine ammonia lyase (PAL), peroxidase (PO) and polyphenol oxidase (PPO) might have contributed for the induced systemic resistance triggered by various biotic and abiotic inducers. More induction of PO and PPO isozymes were noticed upon application of these inducers. In the present studies, there was a significant decrease of SCMV titre as evidenced by ELISA in these treatments. Among the treatment methods, foliar application was highly effective in case of the abiotic elicitors bion and salicylic acid whereas with P. fluorescens seed treatment was effective.

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Authors: D. Ladhalakshmi, M. Ramiah, T. Ganapathy, M. Krishna Reddy, S. E. Khabbaz, S. Karunakaran and A. Kamalakannan

A new necrosis viral disease was observed in blackgram, showed brown necrotic rings along with veinal and stem necrosis. The virus was mechanically inoculated on the local lesion host, cowpea cv. 152 and maintained in the local lesion host throughout the study. Yield studies under pot culture experiment showed 10- to 30-day-old plants were highly susceptible and the yield became almost nil. By using Transmission Electron Microscope (TEM) and indirect Direct Antigen Coated-Enzyme Linked Immuno-Sorbent Assay (DAC-ELISA) studies the virus was identified as Tobacco streak virus (TSV). The ultraviolet absorbance of the purified virus was measured and the ratio of A260/A280 was determined as 1.41. Polyclonal antiserum was raised against blackgram necrosis virus in New Zealand white rabbit and the titre value was determined as 1: 200. Direct antigen coating-ELISA was used to detect the virus concentration in various plant parts and stem portion recorded maximum virus concentration. TSV in blackgram was not transmitted through seeds.

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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.

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