Utilization of synthetic hexaploid Ipomoea trifida (H.B.K.) G. Don in sweetpotato (I. batatas (L.) Lam.) genetic improvement
1994
Vu Dinh Hoa
Results showed that backcross and intercross derivatives produced lower root yield than sweetpotato clones. Consistent significant differences in root yield and its components were observed between backcross-derived progeny and population of sweetpotato, suggesting the retention of negative alleles of the wild relative in the intercross derivatives. Majority of the backcross and intercross derivatives were poor yielders, but high yielding clones were present. In contrast to root yield, the lowest weevil damage to stem and roots was observed in intercross derivative, followed by backcross derived progeny. However, low weevil damage occurred frequently in clones with thin stems and/or poor root development. There were significant positive correlation between root yield and its components, particularly average root weight and weevil infestation in backcross and intercross-derived progeny. Weevil resistance found in this study was likely attributed to nonpreference mechanism and possibly, escape from infestation due to some attribute of the genotype. A no-choice test indicated that backcross and intercross derivatives were as susceptible to weevil damage as cultivated sweetpotato clones, suggesting that synthetic 6 x I. trifida does not carry sufficient genes conferring weevil resistance. Synthetic 6 x I. trifida presented no problems in terms of root yield because of the rapid rate of recovery of this trait by backcrossing, but appeared not to offer desirable attributes such as dry matter content and resistance to weevil. However, the narrow stem character of I. trifida which was shown by the I. batatas x I. trifida progeny may be incorporated into sweetpotato cultivars to reduce infestations of vines and subsequently the infestations of roots
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