GLIOCLADIUM VIRENS MUTANT FOR THE MANAGEMENT OF DAMPING OFF OF CABBAGE CAUSED BY RHIZOCTONIA SOLANI KUEHN
| Apurba Das (adas273427@gmail.com) |
| Plant Pathology, Assam Agricultural University |
| July, 2013 |
| PhD. Scholar DEPARTMENT OF PLANT PATHOLOGY ASSAM AGRICULTURAL UNIVERSITY JORHAT, ASSAM |
Abstract |
| The antagonistic fungal isolates have been found to be effective for the management of damping-off of vegetables and other crops. However, most of them are very much sensitive to carbendazim which is often used as a seed-dressing fungicide to eliminate the seed-borne as well as soil borne fungal pathogens. The aim of the present investigation was to develop UV-irradiated carbendazim tolerant mutants of Gliocladium virens (Synm: Trichoderma virens). Three stable mutants of a bio-control agent, G. virens (GvM1, GvM2 and GvM3) have been generated by exposing to UV radiation at 260 nm for different time periods (viz., 60, 80 and 100 minutes). The mutants differed from the wild type strain in phenotype, growth rate, sporulation, antagonistic potential and fungicide tolerance. The new biotype possessed tolerance to carbendazim upto 50 ppm, while the wild type fails to grow even at 10 ppm concentration. Further, molecular characterization of the wild and mutant of G. virens confirmed the genetic difference among the isolates. The phylogenetic analysis of the wild and mutant of G. virens revealed that the mutant types were more similar with Trichoderma harzianum isolates of other region. Antagonistic activities of these three mutants were tested against Rhizoctonia solani, a causal agent of damping off of cabbage. The maximum reduction of radial growth of the pathogen was shown by GvM1 (59.67%) which was followed by GvM2 (51.93%), GvM3 (44.29%) and Gv-Wild (36.87%). In an another test, sclerotial growth and development of R. solani was dwindled significantly when mutant GvM2 was inoculated with R. solani in MSM (4%) as compared to wild G. virens (Gv-Wild). Colonization of wild and mutant of G. virens was studied in pot condition at room temperature, in terms of viable propagules, where it was observed that colony forming unit (cfu) was significantly higher for GvM1 (29.37x 105 cfu/ml), which was followed by GvM2 (16.25x105 cfu/ml), GvM3 (14.25x 105 cfu/ml) and Gv-Wild (4.37x105 cfu/ml). In pot experiment, maximum reduction of total pre and post emergence damping off in both sterilized and unsterilized soil was achieved when the seeds were treated with the best mutant (GvM1) (16.68% and 23.41%) which was followed by seed treatment with Gv-Wild in both sterilized and unsterilized soil (25.77% and 34.61%). The Root and shoot length of the treated seedlings were found to be increased with the same treatment. |
