Thesis Abstract and Dissertation Abstracts
Studies on the collar rot of betelvine (Piper betle L.)
Abstract Category: Science
Course / Degree: Ph. D.
Institution / University: Lucknow University, India
Published in: 2002
Survey of betelvine growing districts of Uttar Pradesh and bordering areas of Madhya Pradesh, it was observed that the collar/foot rot disease caused by Sclerotium rolfsii affected these plantations. The disease severity ranged from 20-80 %, with some new conservatories (an area covered with grasses on all the four sides specially prepared for betelvine cultivation on commercial scale) showing disease severity up to 90 %. The first visible symptom of collar rot disease was observed as yellowing or wilting of lower leaves. Later on, the yellowing progressed to upper leaves. The fungal mycelium first appeared at the base of the vines near the soil line. The pathogen then grew upwards covering the stem with a cottony-white mass of mycelia. Later on, water-soaked and grey lesion appeared on the vines, which turned brown, resulting in the rotting of whole plant system. A large number of small, light brown, mustard-seed like sclerotia developed in the collar zone. After the pathogen established itself, its subsequent advancement and production of mycelia and sclerotia were quite rapid. The infected vines, which were 3-4 weeks old ultimately toppled down and died.
The pathogen was isolated from infected plant parts of betelvine from different locations. Five different morphological groups of Sclerotium rolfsii were observed depending on their cultural growth, sclerotial size and production. Of these five isolates, NBSr-3 produced maximum number of small sized sclerotia and it was found to be more pathogenic to different cultivars of betelvine. The pathogenicity was proved by inoculating the mycelia and sclerotia of the pathogen on host plant in pots and on stem and leaves of betelvine under in vitro conditions. The symptoms similar to those produced on betelvine in field were observed both under in vitro and in vivo conditions.
Of the different cultivars screened under in vivo and in vitro conditions for disease resistant cv. Desawari was found to be the most susceptible with Ayurvedic Bangla being least susceptible. Therefore cv. Desawari was selected as host for disease management trials.
Three of the five isolates of Sclerotium rolfsii were induced to produce basidiospores under in vitro conditions when inoculated on PDA amended rhizome powder of Cyperus rotundus. The production of basidiospores by these isolates indicated that they were heterokaryons whereas the other two isolates which did not form the athelial stage in culture were homokaryons. Isolate NBSr-3 could not produce the athelial stage in field conditions as the required atmospheric conditions were not available.
Thirteen essential oils were screened for their antifungal efficacy against Sclerotium rolfsii, the collar rot pathogen of betelvine. All the oils showed inhibition in the mycelial growth and reduction in mycelial weight of Sclerotium rolfsii under in vitro conditions. Citronella, clove and geranium oils proved to be the most effective as they completely checked the growth of Sclerotium rolfsii at all the test concentrations both in liquid and solid media. The essential oil of patchouli proved to be the least effective in inhibiting the growth of pathogen. However, none of oils tested were found to be cidal in nature. It is concluded that these oils can be used for controlling collar rot disease in field conditions after further quantification and standardization.
Ten fungicides were screened in vitro for controlling the growth of Sclerotium rolfsii. All the fungicides effectively checked the mycelial growth of the pathogen with Contaf and Vitavax proving to be more effective among these fungicides. Bavistin and Mopsin were also effective in reducing the mycelial growth of S. rolfsii. Six fungicides were selected on the basis of their effect on Sclerotium rolfsii in vitro for disease control experiments under field conditions. Mopsin proved to be the superior in controlling the collar rot disease in field as it gave 100 % disease control at 0.10 % concentration during both the years of experiment.
Soil solarization was used to observe its effect on the viability of sclerotia, the overwintering structure of collar rot pathogen, of Sclerotium rolfsii. The experiment was conducted in earthen pots (12" diameter). The sclerotia were filled in cotton bags and buried at different depths in these pots which were later covered with single and double layer of clear plastic mulch (CPM) (25 µm thickness). It was observed that the temperature of the soil was raised considerably at different depths more so under double layer of CPM. The rise in temperature was more in the month of May 2001 than in June 2001. This rise in temperature reduced the viability of sclerotia after one week. In all the treatments involving sclerotia buried at 10 cm and beyond no sclerotia were viable after one week. However, at a depth of 5 cm under single CPM, the sclerotial viability was reduced to 10 %. The viability in the control (no covering with CPM) remained 100 % even after one week.
Two strains of Pseudomonas fluorescens viz. NBRI-N6 and NBRI-N were tested for their effect on the collar rot disease of betelvine. The disease control by either of these two strains was not significant over control but a consortium of the two strains showed significant disease control (77.83 %). There was significant increase in the yield of betelvine leaves when the vines were treated with either of the two strains of P. fluorescens or a consortium thereof. The increase in yield was better in the vines treated with NBRI-N6 in comparison to other two treatments. Thus the fluorescent pseudomonas increased the yield of betelvine significantly in all the treatments over but the disease control was significant only in the consortium of two strains.
Different species of Arbuscular Mycorrhizal fungi were also tested in field for observing their effect on the yield of betelvine and collar rot disease. It was observed that though all the treatments significantly improved the yield of Piper betle, the disease control was non-significant, the maximum control being 38.07 % in the vines treated with Glomus mosseae in the first year and 29.29 in the vines treated with G. fasciculatum and G. mosseae. The maximum increase in vine height was observed due to treatment of vines with G. mosseae in both the years whereas G. fasciculatum increased the number of mature leaves which could be plucked from the vines for sale after a period of 290 days. Thus different species of mycorrhiza though can be used for increasing the yield of vine, their effect on the reducing the collar rot disease was not significant.
In the present investigation twenty strains of Trichoderma and one of Gliocladium viz. G. (=Trichoderma) virens were screened in vitro for their effect on the mycelial growth and sclerotial viability of Sclerotium rolfsii. It was observed that all the strains inhibited the growth of Sclerotium rolfsii in dual culture; the inhibition ranged from 59.26 % to 88.28 %. The sclerotial viability was also significantly reduced due to attack by different antagonistic fungi. This reduction in viability may be due mycoparasitism and/or antibiosis as is evident from the observations made under microscope (coiling of mycelium of antagonist around the sclerotia and its ultimate destruction) and in dual culture plates (formation of distinct inhibition zones). Four potential strais viz. T. harzianum (MTCC Nos. 3841, 3842 and 3843) and G. virens (MTCC No. 794) were selected for disease management trials in the conservatory. All the four strains reduced the disease incidence considerably. At higher rates of application of fungal antagonists no disease was observed thus 10 % disease control was achieved. In addition all the strains increased the yield of betelvine significantly over both inoculated and uninoculated control during both the years of experiment.
Thesis Keywords/Search Tags:
betelvine, soil solarization, collar rot disease, biological control
This Thesis Abstract may be cited as follows:
Singh, A. 2002. Studies on the collar rot of betelvine (Piper betle L.). Ph. D. Thesis, Lucknow University, Lucknow. p. 187
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Submission Details: Thesis Abstract submitted by Anand Singh from India on 31-Dec-2004 08:52.
Abstract has been viewed 7792 times (since 7 Mar 2010).
Anand Singh Contact Details: Email: an_ab@rediffmail.com
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