Browsing by Author "Balakrishnan, B"

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Etiology and biological control of sheath rot disease of rice
(Department of Plant Pathology, College of Agriculture, Vellayani, 1995) Mini, George; Balakrishnan, B
Sympotmatology and etiology of sheath rot disease of rice was investigated and attempts were made in the biological control of the disease. The sheath rot disease of rice initiated as brown oblong lesions on the flag leaf sheath were surrounded by light yellow halo initially. On maturity, these lesions turned dark brown with grey centres. Slight brown discolouration was also seen on the second and third leaf sheaths. Panicles were found choked inside the sheath or partially emerged with discoloured grains. The pathogen was isolated from diseased rice varieties collected from seven different locations and from ten different varieties. Out of these six isolates of Sarocladium oryzae and four isolates of associated fungi were selected based on the symptomatolgical variations for further study. Slide cultures of the above isolates were prepared and the morphological studies on the nature of mycelium, conidiophore formation, conidial ontogeny and their measurements were recorded. All the isolates were similar in many characters except slight variation in conidiophore length and the length of conidia. Pathogenicity tests done on eight varieties showed that S. oryzae and the associated fungi inoculated could produce disease symptoms. The nature of symptoms varied with virulence of the pathogen and rice varieties. Combined inoculation of S. orysae and the associated fungi in variety Jaya gave typical symptoms, than their individual action on symptom development. 15 showed the maximum virulence in all the varieties. Inoculation of the pathogen showed that all the varieties were susceptible to the different isolates of the pathogen tested. Variety Jaya showed the maximum disease intensity. Studies on the viability of the pathogen in infected grains showed that the pathogen could remain viable for six months in paddy grains. But the frequency of occurrence was found to be reduced from the 3rd month onwards of the storage. Pathogen was viable in the soil up to three months steadily and after that their frequency of occurrence was reduced both at 2cm and 6cm depths. Cultural characters of the fungus was studied by growing the fungus both in liquid and solid media. Studies on the growth of the pathogen in different solid media showed that different isolates respond varyingly under different media conditions. Czapek’s agar, Oat meal agar and carrot agar were found to be the best media which supported maximum radial growth of the fungus. Among the different liquid media tested Czapek’s medium was found to be the best followed by Richard’s medium and Coon’s medium. Mannitol was found to be the best carbon source followed by starch and sucrose. Ammonium nitrate and sodium nitrate ranked first in the nitrogen sources. Effect of different spectra of light was studied on growth and sporulation of S. oryzae. All the light spectra viz., red, blue and green showed a reduction in the growth. Blue light induced maximum sporulation while red light showed least effect. Studies on the inhibition of spore germination using plant extracts showed that all the plant extracts tested viz., Neem, Carlic, Phyllanthus and Ocimum had inhibitory effect on the spore germination of the pathogen. Studies on Biological control showed that fungi namely, Chaetomium sp., Pestalotia sp. etc. and bacterial species namely Pseudomonas fluorescens strain 2 and 87 were antagonistic against Sarocladium oryzae under in vitro conditions. Under in vivo conditions Chaetomium sp. was found to minimise the disease maximum among the fungal isolates followed by the bacterial strains P. fluorescens strain 2 and 87.
Improvement of strains and production technologies for paddy straw mashrooms(volvariella spp.)
(Department of Plant Pathology, College of Agriculture, Vellayani, 2004) Pramod, R; Balakrishnan, B
Improvement on the techniques for the cultivation and preservation of tropical species of mushrooms
(Department of Plant Pathology, College of Agriculture, Vellayani, 1994) Balakrishnan, B; Chandrasekharan Nair, M
Intensive collections made from certain selected areas of Kerala yielded a total of eight species of Pleurotus, one species each of Volvariella and Tricholoma, namely V. esculenta and T. lobayense respectively from the native flora. Various species collected were identified and based on the preliminary observations made on their adaptability for large scale cultivation, among the Pleurotus two species have been selected for detailed study along with the other standard cultures procured from various mushroom research centres of the country. The native isolate of T. lobayense in the present study is the first record of the species from Kerala. Detailed studies have been done on various aspects of cultivation of pleurotus spp. With a view to improve the already known technologies so as to suit the conditions of Kerala. The two native species of pleurotus selected have been domesticated and compared with other standard cultures on their performance. Based on the observations made in the seasonal influence, yield and market qualities the species most suited for large scale cultivation in Kerala have been identified. Alternative local substrates for cultivation of oyster mushrooms have been identified and their processing technology standardized. Effective nutritional supplements for increased yield, method for speedy induction of sporocarp, after care method for the once harvested beds for further flushes, effective method for cultivation etc. have been worked out for large scale cultivation of Pleurotus spp. In Kerala. Commonly available low cost substrates in spawn production have been identified and their technologies standardized. Influence of light on spawn growth, influence of storing environment on growth and shelf life of spawn etc. have been studied. Technology for preparation of an instant liquid spawn developed and also a modified method for speedy and low cost production of spawn using polypropylene cover as the container has been standardized. The effect of coconut milk in blending culture media for enhanced growth of various Pleurotus spp. and the effect of coconut milk in their biomass production have been proved. In the strain improvement programme, a substrate influenced mutant of Pleurotus sajor-caju for better yield, a resistant/tolerant strain against the most destructive weed mould Trichoderma viride and an interstock hybrid with desirable traits have been developed. Type of pests and their control etc. have been worked out. The effect of chemical pasteurization of the substrates on checking the weed mould infestation during spawn run and the use of lime powder for spot treatment of beds in the management of T. viride have been proved. Post harvest technology for preservation of both raw and dehydrated forms of mushrooms has been standardized. The native strains of other tropical mushrooms locally collected namely V. esculenta and T. lobayense have been identified based on the detailed description of the same. The performance of the native strain, V. esculenta under cultivation has been compared with that of the standard species, V. volvacea and a technique for cultivation of T. lobayense has been standardized for first time in this part of the country.
Severe leaf blight of palmyra palm (Borassus Flabelliformis) caused by Pestalotiopsis palmarum in Kerala
(Kerala Agricultural University, 1982) Balakrishnan, B; Karunakaran, P; Chandrasekharan Nair, M
Strain improvement in oyster mushroom (Pleurotus spp.)
(Department of Plant Pathology, College of Agriculture, Vellayani, 1998) Anitha, R; Balakrishnan, B
Attempts were made to collect native flora of Pleurotus spp., by doing intensive surveys for the same during monsoon periods. Among the various isolates made two efficient ones were identified and described namely, Pleurotus eous and P. petaloides. Evaluation of growth and fruiting behaviour of these isolates done following the standard method and it is proved that these isolates were amenable for large scale cultivation under Kerala conditions. The two selected isolates along with the other standard cultures procurred from various mushroom research centres of the country were subjected to detailed observations. Strain improvement programmes have been done following strain mixing hybridization and mutation techniques. One recombined strain was developed through strain mixing which has got good yield and intermediate sporocarp characters between the parents. Physical mutation was done by irradiating them with gamma radiation. Among the mutants three effective mutants were selected for their better sporocarp yield, steady yielding character and resistance against insect pests and competitor weed moulds. In the chemical mutation, one mutant having small sporocarp with long stipe and other mutant having sporocarp with very few spores have been developed. In hybridization, one hybrid was developed by pairing compatible mono spore cultures of two different species of Pleurotus which have got maximum desirable characters among the developed hybrids. Cultural characters of the selected isolates were studied and the effect of coconut milk in enhancing mycelial growth were proved. Periodical observatiori of the incidence of insect pests and competitor weed moulds in the mutants, hybrids and native isolates have been worked out. Studies on quality parameters and consumer acceptability have proved that the native isolates were comparatively better to the other species of Pleurotus obtained from various mushroom research centres of the country. Organoleptic studies of selected hybrids and mutants have been proved that they have better acceptability in the market as compared to the standard species, Pleurotus sajor-caju.
Symptomatology etiology and control of sheath rot disease of rice caused by Acrocylindrium oryzae
(Department of Plant Pathology, College of Agriculture, Vellayani, 1981) Balakrishnan, B; Chandrasekharan Nair, M
Sheath rot disease of rice caused by Acrocylindrium oryzae was investigated. The fungus was found to infect rice plants at boot leaf stage. The leaf sheath covering the panicle was found to be comparatively more susceptible to the fungus than the sheath of other leaves. Severe infection caused choising of the whole penicle insids the sheath itself before emergence. The pathogen was isolated from infected tissues of host plants and brought into pure culture. Comparative studies of air isolates of Acrocylindrium oryzae from four rice varieties and two weed hosts did not show much appreciable difference in their morphological characters except light variations in the hyphal thickness and smaller conidial size from those on weed hosts.