Agronomical Characters and Nutritional Quality Analyses in Selected Potato (SOLANUM TUBEROSUM L.) Genotypes

Abstract

The research works embodied in this thesis were aimed to explore the extent of genetic variation among the selected potato genotypes for important agronomic and nutritional quality characters and their possible exploitation in varietal improvement programme for desirable traits. Field experiment was conducted with 32 potato genotypes following RCBD with three replications. Data were collected on days to first shoot emergence, foliage coverage, number of stems/plant, number of leaves/plant, plant height, chlorophyll content in leaf, number of tubers/plant, tuber weight/plant, single tuber weight and tuber yield/ha at early (70 DAP) and late (90 DAP) harvest. Collected data were analyzed using both 1st degree statistics such as mean, SE, analysis of variance, DMRT and 2nd degree statistics such as coefficient of variability, heritability, genetic advance, correlation coefficients and path coefficient analysis. Analysis of variance revealed significant differences among the 32 potato genotypes for all the studied characters that indicate the presence of wide range of genetic variation among them. Mean performances of different characters of 32 potato genotypes were also found significantly different as revealed by the DMRT test. Foliage coverage, number of stems/plant, number of leaves/plant, plant height, chlorophyll content in leaf, number of tubers/plant, tuber weight/plant, single tuber weight and tuber yield/ha showed moderate to high heritability along with high genetic advance as percentage of means. Correlation and path coefficient analyses revealed that foliage coverage, chlorophyll content in leaf and single tuber weight showed significant positive genotypic correlation with tuber yield as well as employed positive direct effect on tuber yield both at early and late harvest suggesting that the selection for these traits would be helpful for the improvement of tuber yield. Among the genotypes G9 (Granola) and G11 (Courage) were found to be the highest tuber yielder at early harvest and genotypes G20 (Cardinal), G22 (Diamont) and G28 (Ultra) showed the highest tuber yield at late harvest. Freshly harvested potatoes from each genotype were analyzed in laboratory for the quantitative estimation of 20 nutritional quality characters viz., moisture, dry matter, specific gravity, ash, pH, total soluble solids, titratable acidity, total phenolics, β-carotene, vitamin C, starch, soluble protein, total sugar, reducing sugar, non-reducing sugar, iron (Fe), phosphorous (P), calcium (Ca), potassium (K) and zinc (Zn) contents. Chemical analysis were done separately for early (70 DAP) and late (90 DAP) harvested tubers. Analysis of variance revealed the existence of significant variation for all nutritional characters among the potato genotypes studied. Mean performances of different quality characters of 32 potato genotypes were also found significantly different as revealed by the DMRT test. The results of PCV and GCV analyses revealed the presence of wide range of variation among the potato genotypes for the studied nutritional quality characters. Among the nutritional quality characters, dry matter, titratable acidity, total phenolics, vitamin C, starch, total sugar, reducing sugar, non-reducing sugar, soluble protein, Fe, P, Ca, K and Zn contents of tubers both at 70 and 90 DAP showed high heritability along with higher genetic advance as percentage of mean. The nutritional quality characters like dry matter, total phenolics, starch and minerals showed significant negative correlation with tuber yield/ha both at 70 and 90 DAP harvest and reducing sugar was negatively correlated with dry matter suggesting that the selection for these traits would be helpful for the improvement of nutritional quality of tuber. The results of principal component (PCA), principal coordinate (PCO), canonical variate (CVA) and cluster analyses revealed that the genotypes could be grouped into seven different clusters on the basis of 70 and 90 DAP harvesting situation. The results also revealed that the genotypes in cluster III were far diverse from genotypes of cluster VI (early harvest) and cluster V (late harvest) whereas the genotypes belong to cluster I and VII (early harvest) and II and VII (late harvest) were least diverse. Intra-cluster distances in both the harvesting time were being much lower than the inter cluster one’s, suggesting heterogeneous and homogeneous nature between and within groups, respectively. The highest inter genotypic distance indicated that there is scope for improvement of nutritional quality characters by hybridization. Genotypes in cluster I showed the maximum dry matter, total phenolics, starch, total sugar, reducing sugar, soluble protein, Fe and Ca contents, where as the genotypes in cluster III showed the best mean performance for K and Zn contents and the genotypes under cluster IV showed the highest vitamin C and P contents when harvested at 70 DAP. In case of tuber harvested at 90 DAP cluster I showed the highest starch, total sugar, reducing sugar and Ca contents. However, the genotypes under cluster II showed the highest vitamin C content but the genotypes in cluster III showed the highest K and Zn contents. The highest amount of dry matter, total phenolics, soluble protein, Fe and P contents were found in the genotypes under cluster IV. Dry matter, total phenolics, reducing sugar, soluble protein, Fe, P, Ca, K and Zn contents were found to be contributed effectively towards genetic divergence among the genotypes. Therefore, these traits would offer a good scope for the improvement of nutritional quality through rational selection of parental genotypes in future potato breeding. The genotypes G8 (Lady Rosetta), G12 (Hagrai), G13 (Indurkani), G21 (Vandarpur), G23 (JPR) and G24 (All Red) might be selected as better parents for improving different nutritional quality characters through hybridization programme with higher yielder genotypes like G9 (Granola) and G11 (Courage) for early and G20 (Cardinal), G22 (Diamont) and G28 (Ultra) for late harvest potato varieties.