Integration of bioinoculant technology with micropropagation of black pepper (Piper nigrum L.) and standardization of production of arbuscular mycorrhizal fungi (AMF) in transformed roots
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Date
2004
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Department of Plant Pathology, College of Agriculture, Vellayani
Abstract
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.
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