Rajendran Pillai, M VSunitha Anie, CheriyanKAU2019-05-252019-05-252001http://krishikosh.egranth.ac.in/handle/1/5810104621PGAn experiment was conducted at the College of Horticulture, Vellanikkara on the "effect of Azospirillum and V A mycorrhiza on the growth of cocoa seedlings and incidence of seedling blight disease", during 1998-2000. The experiment was conducted using native isolates and commercial cultures of Azospirillum and V A mycorrhiza. The objective of the experiment was to find out whether there is any synergistic effect for the combined inoculation of Azospirillum and V A mycorrhiza in improving the growth and establishment of cocoa seedlings and to find out the efficacy of the inoculants in imparting resistance to seedling blight disease. The first experiment showed that there was a positive influence for both V A mycorrhiza and Azospirillum in improving the growth parameters. The height and number of leaves were maximum in native Azospirillum inoculated plants. Native mycorrhizal inoculation recorded maximum height of plant while the number of leaves was maximum in plants inoculated with commercial V A mycorrhiza inoculant. Combined inoculation of native Azospirillum and V A mycorrhiza ranked only second but it was on par with the best treatment combination. The native isolates of both the inoculants and their combination was found to increase the height to the maximum. Maximum number of leaves was noted in plants inoculated with commercial V A mycorrhiza. V A mycorrhizal inoculation did not influence the number of leaves. The results on the leaf length breadth ratio revealed that Azospirillum inoculation could influence the shape of leaves. It could be presumed that the linear nature of leaves is an indication on the efficiency of inoculated A zospirillum. Eventhough commercial Azospirillum was effective in improving the collar girth, the efficiency was slightly reduced when it was combined with native V A mycorrhiza. Commercial Azospirillum inoculation and the combination of native Azospirillum and native V A mycorrhiza were equally effective in improving the collar girth of cocoa seedlings to the maximum. The different treatments and their combinations affected the dry matter of the plant differently. VA mycorrhizal application was found to reduce the moisture content of the plant and make the plant more sturdy than succulent. This may be a factor that contributes to disease resistance of mycorrhizal plants. Due to the various treatments the moisture content of roots did not vary much. Native mycorrhiza was found better in improving nitrogen content of the plant compared to commercial mycorrhiza. But commercial Azospirillum was better than native Azospirillum in improving the nitrogen content of the plant. Absorption of phosphorus was maximum (0.16%) in native VA mycorrhizal inoculated plants. Both the mycorrhizal inoculants were found to increase the phosphorus content of the plants. Azospirillum inoculation did not affect the phosphorus content of the plants. Dual inoculation of commercial cultures of both the organisms was found equally effective with native Azospirillum application alone in potassium absorption. V AM infection percentage was also maximum in native V A mycorrhizal inoculated plants. Combined inoculation of native isolates of both the organisms influenced the mycorrhizal infection positively. Out of the ten parameters observed, the native Azospirillum isolate Al ranked first in nine of the parameters. Similarly native mycorrhizal isolate MI showed superiority in seven of the parameters tested proving the superiority of native isolates over commercial inoculants. In controlling the seedling blight disease of cocoa, it was found that dual inoculated plants showed a reduction in disease index by 0.77. In VA mycorrhiza treated plants reduction in disease index was 0.26. In Azospirillum treated plants there was a slight increase in disease index by 0.33. The disease reduction by dual inoculation was higher than that was achieved by the application of the fungicide potassium phosphonate. Among fungicides tested application of potassium phosphonate 0.3 per cent was better in controlling the seedling blight disease.ennullThesis