Exploitation of heterosis in sweetpotato (Ipomoea batatas L. (Lam)) via progeny testing and use of molecular markers
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Date
NOVEMBER, 2016
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Abstract
Genetic diversity and heterosis (mid and better parent heterosis) was assessed in a West African breeding population by using 15 simple sequence repeat markers in 28 parents exclusively and other 10 parents with their 30 progenies in sweetpotato. The polymorphism information content (PIC) of the SSR primers used revealed that all of them were polymorphic except IB-297 and J116 A with PIC less than 50% for the 10 parents and their progenies and 6 primers (IB-248, IBS-10, IBS-18, IBR-12, IBR-16 and IBR-19) out of 15 were polymorphic for the 28 parents. These results mean that most of the primers used in this work can be used for parent and progeny diversity study in sweetptatoto. The progenies were produced from biparental crosses, and heterosis was estimated in some pre-harvest and harvest traits, harvest index and some quality traits. Parents PG12086-18, Nanungungungu and Apomuden occur most in the crosses. Some of the crosses exhibited high heterosis. Correlation among total yield and pre-harvest, harvest and quality traits revealed highly significant positive correlations between total yield and marketable roots, root size, number of marketable roots and harvest index. Vine vigour was also correlated significantly and positively with the weight of marketable roots, root size, number of plants harvested, percentage dry matter, iron and starch contents. Virus severity was significantly correlated negatively with the number of plants at maturity, percentage dry matter, iron content, percentage protein and starch content but not significant with total yield, weight of marketable roots, root size and number of marketable roots. The weevil damage was significantly correlated negatively with total yield, weight of marketable roots, root size, number of marketable roots and harvest index, and Percentage dry matter correlated significantly and positively with iron content, percentage protein, starch and zinc contents. The diversity study showed that the parents could be grouped into five clusters. The progenies from distantly related parent such as Nanungungungu x Bohye, Nanungungungu x Faara, Nanungungungu x Hi-starch, Faara x Nanungungungu, Nanungungungu x PG12086-18, Apomuden x Sauti and CIP440390 x PG12086-18 exhibited high heterosis for total yield, harvest index and the quality traits; and Nanungungungu x Otoo, Sauti x Nanungungungu, Apomuden x Hi-starch, PG12086-18 x Apomuden, Apomuden x Faara and Apomuden x PG12086-18 exhibited high heterosis for some yield related traits and quality traits. This study showed that all the progenies were not close to their parents due to the high somatic transformation in sweetpotato which is a source of genetic variation among genotypes.
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A thesis submited to the Department of Crop and Soil Sciences, Kwame Nkrumah University of Science and Technology, Kumasi, Ghana, in partial fulfillment of the requirements for the degree of Master of Philosophy in Plant Breeding,