Browsing by Author "Sivaprasad, P"

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Control of collar rot and root-knot of cowpea with VA mycorrhizae
(Department of Plant Pathology, College of Agriculture, Vellayani, 1993) Deepti N Varadan; Sivaprasad, P
The objective of the present study was to evaluate VA mycorrhizae as a biocontrol agent against collar rot caused by Rhizoctonia solani and root-knot nematode Meloidogyneincognita in cowpea. Three different pot culture experiments were conducted. The first two were conducted to assess the effectiveness of VA mycorrhizal fungi viz. Glomus fasciculatum, G. mosseae and Acaulospora morroweae to suppress the pathogen R. solani and the nematode M. incognita. The results of the first two experiments revealed that G. fasciculatum is the best VA mycorrhizal fungus in terms of reducing the disease intensity (collar rot) and nematode population. Artificial inoculation with VA mycorrhizae significantly increased mycorrhizal colonization, nodulation, fresh weight, dry weight, plant height and leaf number of plants. A. morroweae was found to be a comparatively weaker symbiont in terms of increasing growth and suppressing the pathogens. Based on these results G. fasciculatum was used for further studies. Analysis of total phenols was done under conditions of interaction of G. fasciculatum, R. solani and M. incognita. Plants inoculated with VA mycorrhiza always showed a higher phenol content compared with the plants not inoculated with mycorrhiza. There was a significant positive correlation between mycorrhizal colonization and phenol content of plant tissue. Hence, the VA mycorrhizal mediated disease tolerance could be attributed to the enhanced phenol accumulation. The present investigation reveals that VA mycorrhizal technology has much potential as a biological tool for the management of root pathogens of cowpea. However, for practical application, the appropriate organism, for the host/environment should be chosen.
Development of inoculant cultures of azospirillum for rice (Oryza sativa L.) in Kuttanad
(Department of Plant Pathology, College of Agriculture, Vellayani, 1996) Sasikumar, S; Sivaprasad, P
Hardening and ex vitro establishment of rose plantlets
(Kerala Agricultural University, 1997) Wilson; Nayar, N K; Sivaprasad, P
Plantlets regenerated by in \ilro techniques under high humidity and low temperature in an artificial medium did not survive by direct planting out in small pots. An improvised structure made of wooden frame and polyethylene cover helped to maintain high humidity to ex vitro plantlets. Attempts made to get successful field establishment with different potting media and nutrient solutions did not give any positive results. Successful hardening and ex vitro establishment of plantlets were achieved by surface inoculation of different species of vesicular arbuscular mycorrhizae {VAM). Inoculation with Glomus etunicatum (Becker and Gerd) recorded the highest survival rate of 66.67 per cent, and took minimum days for flowering.
Histochemical changes in nodules of Cajanus cajan (L.) Mill sp. inoculated with vesicular- Arbuscular Mycorrhizal Fungus and Rhizobium
(Kerala Agricultural University, 1988) Sivaprasad, P; Joshi, S S; Rai, P V
Symbiosis of Glomus fasciculatum (Thaxter sensu Gerd) and Trappe, Rhizobium and Ca/anus cajan (L.) Millsp. was studied in relation with bacteroidal zone and polysaccharide accumulation in nodule tissue. Tripartite symbiosis enhanced the area of bacteroidal zone in nodule tissue and size of bacteroidal cell and nucleus. Association of vesicular-arbuscular rnycorrhizal fungus alone had maximum polysaccharide accumulation in the nodule tissue. Dual inoculation with rnicrosymbionts showed very little polysaccharide accumulation
Integration of bioinoculant technology with micropropagation of black pepper (Piper nigrum L.) and standardization of production of arbuscular mycorrhizal fungi (AMF) in transformed roots
(Department of Plant Pathology, College of Agriculture, Vellayani, 2004) Simi, R; Sivaprasad, P
The present investigation was undertaken to evaluate the effect of inoculation with various microbial inoculants such as arbuscular mycorrhizal fungi (AMF), Azospirillum and fluorescent pseudomonads in different combinations on establishment, growth and foot rot tolerance of micropropagated black pepper plantlets and also to standardize transformed root culture technique using Agrobacterium rhizogenes for AMF inoculum production in selected host plant. A general improvement in growth and establishment of the plantlets was observed due to inoculation with AMF, Pseudomonas and Azospirillum. The combined inoculation of the three microbial inoculants showed a significant effect on survival rate and growth characteristics such as plant height and leaf area. There was significant effect on physiological and biochemical characteristics of the plantlets such as stomatal conductance, leaf temperature, relative water content, total phenol, orthodihydroxy phenol, total soluble protein and total carbohydrate content due to inoculation with microbial inoculants which favoured better survival, growth and disease tolerance of the plantlets. All the treatments involving AMF showed a minimum stomatal conductance at early stages of hardening and later it was steadily increased and reached the maximum. The leaf temperature was found to decrease due to treatments with microbial inoculants. Inoculation with the organisms resulted in consistently high values of relative water content at different stages of observation. Combination involving all the three organisms recorded maximum. The total phenol content in plant tissues was highly stimulated by AMF followed by Azospirillum and Pseudomonas. The orthodihydroxy phenol, total soluble protein and total carbohydrate content of the plantlets were also significantly improved by inoculation with all the three organisms. Foot rot disease incidence and intensity was significantly reduced by inoculation with Pseudomonas either singly or in combination with others. AMF alone or in combination also showed relatively low mortality due to foot rot disease. Azospirillum was not effective in suppressing foot rot disease. In the attempt made to make use of transformed root culture technique using Agrobacterium rhizogenes for AMF inoculum production, cucumber was found as the most sensitive host plant. The co-culturing of transformed root with AMF through root colonization was not successful. Further studies are needed to analyse the physiological reasons for the failure of AMF colonization in transformed roots. The present investigation vividly showed that inoculation with microbial inoculants – AMF, Pseudomonas and Azospirillum – is highly beneficial to tissue culture plantlets of black pepper and significant increase in survival rate, growth and tolerance to foot rot disease was achieved. The treatment combination involving all the three organisms was most effective.
Management of foot rot of black pepper (piper nigrum L.) with va mycorrhiza and antagonists
(Department of Plant Pathology, College of Agriculture, Vellayani, 1998) Christin Robert, P; Sivaprasad, P
Management of rhizome rot and root-knot of ginger (Zingiber officinale R.) using V A mycorrhizal fungi and antigonists
(Department of Plant Pathology, College of Agriculture, Vellayani, 1997) Joseph, P J; Sivaprasad, P
Management of rhizome rot, the most destructive disease of ginger incited by Pythium aphanidermatum (Edson)Fitz. using native arbuscular mycorrhizal fungi (AMF) and antagonists was attempted. The extensive survey in the ginger growing belts of the state revealed a definite negative relationship between AMF development and disease incidence. Based on preliminary evaluation with six AMF species, Glomus constrictum was selected as most efficient for disease suppresion, growth enhancement and yield and used as reference culture for the subsequent studies. The population of Heloidogyne incognita, a pre disposing factor for the disease, was reduced in the presence of all the six AMF species particularly with G. fasciculatum. Characterization studies of native AMF associated with ginger indicated that Glomus spp. were more frequent and G. fasciculatum was the most predominent species. Influence of soil types on the AMF occurrence in ginger was evident. Out of the fourteen native AMF developed from ginger rhizosphere, Mi-l and Mi-4, identified as Glomus species, were the most efficient isolates for rhizome rot suppression yield increase and growth enhancement in ginger. Eleven native antagonistic fungi, selected from in vitro evaluation, were screened in the green house and Ai-12, identified as Trichoderma viride, was the most effective isolate for suppression of rhizome rot, growth enhancement and yield of ginger. Ai-13 isolate, identified as Aspergillus fumigatus, was also effective for disease suppression. The isolates, Mi-l, Mi-4, Ai-12 and Ai-13 were tested for their combined effect in the green house. Dual inoculation of Ai-12 with Mi-l and Mi-4 resulted in remarkable synergistic interaction in reducing the disease and enhancing biomass and yield. Both single and dual inoculations of Ai-12, Mi-l and Mi-4 significantly reduced the disease and enhanced plant growth and yield in the field also. Isolate Ai-13 inhibited AMF development and increased disease in the green house and field. Application of AMF inoculum on ginger rhizome after starch coating was very effective for rapid and early colonization of AMF. Out of the various plant protection chemicals tested, thiram and carbofuran least affected the AMF and antagonist development. An effective management strategy of rhizome rot of ginger is evolved in the present study by combining appropriate native AMF (Mi-l and Mi-2) and antagonistic fungi (Ai-12) for inoculation of seed rhizomes at planting time. The present study forms the first report of detailed documentation of native AMF associated with ginger and extensive study on the utilisation of AMF. antagonists and their combined effect for the management of rhizome rot.
Mechanism of enhanced nodulation in vesicular-arbuscular mycorrhizal (Vam) pigeonpea (Cajanus cajan (L.) Mill sp.)
(Kerala Agricultural University, 1987) Sivaprasad, P; Rai, P V
Nodule and root initiation in Cajanus cajan plants inoculated with vesicular— arbuscular mycorrhizal fungus and Rhizobium was studied Mycorrhizal association enhanced the success of nodule formation with no significant difference in number of root initiated in a specific area. Further, there was increased cytokinin activity in stem exudate and root of mycorrhizal plants. Based on the observations a hypothesisis proposed for the mechanism of enhanced nodulation in mycorrhizal legumes.
Occurrence of endotropic mycorrhiza in rubber (Heavea brasiliensis muell. Arc.)
(Kerala Agricultural University, 1982) Sivaprasad, P; Rajendran Pillai, M V; Nair, M C
Response of cowpea Vigna unguiculata (L.) Walp. to Rhizobium seed inoculation
(Kerala Agricultural University, 1980) Sivaprasad, P; Shivappashetty, K
Field experiment was carried out at the Instructional Farm of the University of Agricultural Sciences, Bangalore to study the response of cowpea to seed inoculation with selected Rhizobium strains. Significant increase in yield, plant top dry weight and leghaemoglobin content of nodules were noticed in plants inoculated with the strains 8 and 12, Correlation studies showed significant correlation between leghaemoglobin content of nodules, plant top dry weight and final grain yield. No significant correlation was observed between nodule number and nitrogen content of plant top on Thirtieth day of growth and final grain yield.
Ultra structures of nodules of cajanus cajan (L) mill sp. Inoculated with vesicular-arbuscular mycorrhizal (Vam) fungus
(Kerala Agricultural University, 1988) Sivaprasad, P; Rai, V; Joshi, S S
Ultrastructural observations made on nodules of Cajanus cajan (L) Millsp. indicated that tha association of VA mycorrhizal fungus Glomus fasciculatum did not influence tha number of bacteroid formed per membrane envelop, which was always one. Both the transformed cell size and number of bacteroid/ Rhizobium pressnt in transformed cell were increased due to mycorrhizal association. Bacteroidal shape differed from the Rhizobium However, no such difference was noticed in size.