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ThesisItem Open Access Genetic variability and path coefficient studies on fodder yield and its components in oats( Avena sativa. L.)(Department of Agricultural Botany, Rajasthan college of Agriculture, University of Udaipur, 1976) Sukumaran, Nair PThesisItem Open Access Cytotoxic and clastogenic effects of some insecticides in allium cepa, L(Department of Agricultural Botany, College of Horticulture, Vellanikkara, 1983) Jayaprakash Naik, B; KAU; Vijayakumar, N KIn the present investigation, the cytotoxic and clastogenic effects of three very commonly used insecticides, namely, aldrin, carbofuran and phorate were tested in Allium cepa, L., a test system. Four concentrations of each insecticides were used for the study. These concentrations were fixed taking into consideration of their field dose of application in insect control. The treatment periods fixed were 12, 24 and 48 hours. The mitotic index was computed from 4000 cells and indices of each division phases were also computed. The chromosome abnormalities were scored from about 100 to 150 cells of each phases in each treatments. Aldrin was found to be drastically mitodepressive compared to carbofuran and phorate. While phorate increased mitotic index in the lowest dose, carbofuran showed only marginal reduction. However, both the compounds reduced mitotic index in higher doses and the field doses. Aldrin exhibited a dose and period responsiveness, while carbofuran and phorate could not with regard to mitotic index. The study also revealed that aldrin is an effective toxicant on both genetic material and proteins. The various chromosome abnormalities noticed were stickiness, bridges, laggards, blurred chromosome borders, chromatin bridge, micronuclei, non-orientation of metaphase, precocious movement in anaphase, chromatin bodies, irregular anaphase, star metaphase, strays, beaked nuclei, break, C-metaphase and unequal nuclei in their decreasing order of occurrence. Unlike aldrin, carbofuran and phorate could not induce anomalies to a significant level in the lowest doses tried, 0.0075 and 0.02 per cent respectively. Chromosome bridge being the most frequent abnormality found in carbofuran, which was followed by stickiness and laggards. The frequency of abnormalities found in field and higher doses were more or less same. Phorate, on the other hand showed linear relationship in inducing chromotoxicities with respect to concentrations and period of treatment. The major types of abnormalities recorded were bridges, breaks and stickiness. The results showed that all the insecticides tried were capable of affecting the genetic material as well as protein, but to different degrees depending on concentrations. It can be tentatively concluded that they cannot be considered completely safe at the field dose of application on the cellular constituents of the organism. The results call for extensive testing of these chemicals in other test systems also.ThesisItem Open Access Genetic variability and correlation studies in cocoa(Department of Agricultural Botany, College of Horticulture, Vellanikkara, 1983) Gregory, Zachariah; KAU; Kumaran, KInvestigation on the generic variability and correlation studies in cocoa were undertaken in the Department of Agricultural Botany, College of Horticulture, Vellanikkara during the period from July 1980 to August 1981 in a well established cocoa garden at Alpara in Trichur district, to elucidate information on the extent of variability and the degree of association existing among the 26 important plant, pod and bean characters, in a group of 135 cocoa tress, variety Forastero. Considerable variability was noted among all the characters of the sexually reproduced population of cocoa trees. Number of flowers per unit length on the trunk, number of pods per tree per year, weight of pod, volume of pod and wet weight of beans per pod showed maximum variability. Shell percentage and seed index manifested considerable variability among the bean characters. Phenotypic coefficient of variation (P.C.V.), genotypic coefficient of variation (G.C.V.) and heritability were estimated for 7 pod and bean characters. Both (P.C.V.) and (G.C.V.) were highest for attributes such as thickness of pod husk, number of beans per pod and weight of pod. Moderately high heritability was observed for weight of pod, thickness of pod husk and number of germinated beans. Volume of beans showed the lowest heritability. Yield from trees was found to be positively correlated with 6 of the characters studied, while number of germinated beans per pod and pod value were negatively correlated with yield. Out of the eight characters, pod value had the maximum contribution to yield. Number of pods per tree per year was found strongly associated with yield. Seed index and trunk girth also were positively and significantly correlated with yield. Phenotypic (rp) correlations among seven characters indicated that number of beans per pod was positively correlated with weight of pod. Positive correlations were also established between volume of beans and wet weight of beans per pod. Among the seven characters observed for genetypic (rg) correlations, wet weight of beans showed positive correlation with diameter of the pod and pod weight. Positive phenotypic as well as genotypic correlations were established in the case of wet weight of beans per pod with number of beans per pod and volume of beans. Number of beans per pod in turn, showed positive correlation with weight of pod at both levels. From the present studies it was evident that characters like diameter of pod, wet weight of beans per pod, number of beans per pod, number of germinated beans per pod, volume of pod, volume of bean, pod value, number of cushions on trunk, trunk girth, number of pods per tree per year and seed index have direct influence on the yield of cocoa. These traits can be considered while selecting cocoa trees for using in breeding programmes.
