Date of Award

1982

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Abstract

Genetic study on sweet potato resistance to the soil rot disease, Streptomyces ipomoea and other characters was conducted from 1979 through 1981. In control crosses, L(,3)-64 was incompatible with L(,4)-62 and L(,4)-112 with L(,4)-131. The average pod set for all progenies was 16.95%. Additive genetic effects were more important than non-additive in the inheritance of resistance. Resistant families were only produced from crosses between resistant parents and most progenies from crosses of moderatley resistant x resistant, resistant x susceptible and moderately resistant x susceptible parents produced moderately resistant segregates. Polycross progenies from resistant parents, L(,4)-131 and L(,6)-135, had families with low indices of 10.06% and 13.25%, respectively. Moderately resistant parent, L(,4)-112 had a mean severity index of 22.91% and the susceptible parent, L(,3)-77 had 34.66%. Heritability estimates as an average for all control crossed progenies were 56.24% for vine rating and 18.10% for soil rot severity index. Heritability estimates as an average of all polycross progenies were 37% for vine rating with an expected gain from selection of 15.61% and 43.38% for soil rot severity index with an expected gain from selection of 51.12%. Heritability estimates for number of marketable roots, weight of marketable roots, dry matter and flesh color of sweet potatoes for the 1979-1980 test were 13.92%, 32.87%, 15.16% and 48.66%, respectively, and for the 1980-1981 test, heritability estimates for total number of fleshy roots, total weight of fleshy roots, number of marketable roots, weight of marketable roots, dry matter and flesh color were 16.17%, 20.14%, 14.97%, 19.28%, 38.80% and 18.60%, respectively. Highly significant negative correlation coefficients were found between soil rot severity index and vine rating, total number of roots, total weight of roots, number of marketable roots and weight of marketable roots per hill. Highly significant positive correlation coefficients were found between number of roots and weight of roots and between flesh color and dry matter in both years.

Pages

143

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