Variability of early bulking and related characters in sweetpotato (Ipomoea batatas (L.) Lam)

Date

3-1996

Abstract

Parental clones and Fls of a 5 x 5 diallel cross were evaluated for earliness in root bulking measured as root yield increments at different times of harvest namely, 60, 90, 120 and 150 days after planting (DAP) at the Benguet State University (BSU) and the University of the Philippines Los Banos (UPLB), during the 1994 wet season and during the 1994-95 dry season.

Storage root bulking in sweetpotato varied among the 15 genotypes evaluated in all environments (location-season combinations) at every harvest date. All of them exhibited high yield increment from 60 to 90 DAP. In BSU, bulking was early and fast during the wet season but became slower during the dry season probably due to lower temperature and insufficient amount of water available to the plant during this period. In UPLB, faster and early root bulking was detected during the dry season because of higher temperature n' longer exposure of the plant to solar radiation than the wet season. Significant regression coefficients for almost all genotypes evaluated indicate linear response of storage root yield to dates of harvest. Higher total root yield during the wet season than the dry season was produced in BSU while the reverse was observed in UPLB. The same trend was noted for marketable root yield, number of roots per plant and average root weight.

Marketable root yield and average root weight generally increased with time of harvest in all environments. production of leaves in sweetpotato continued throughout its entire growth period. Higher harvest indices were recorded among genotypes as a result of longer growing period received by the plant and as a manifestation of greater assimilate partitioning into the enlarging roots.

The root dry matter and starch contents increased with root maturity which varied among genotypes. Total free sugar was comparable among genotypes in all environments except during the wet season in UPLB.

Considering all the characters investigated in this study, crosses involving some parent clones or parent clones themselves such as Binicol, NPSP 48 and UPLSP 1 showed outstanding performance suggesting that they can be used as parents in producing early and high yielding sweetpotato genotypes.

Highly significant variation among genotypes (i.e. among parents and among crosses) was detected for almost all characters considered in this study which indicated significant genetic effects. Significant differences between parents and crosses were noted only for harvest index, dry matter content and starch content during the wet season in BSU; total leaf area during the dry season in BSU; and harvest index, total leaf number, dry matter content and starch content during the wet season in UPLB, reflecting heterosis which is also attributable entirely to non-additive genetic effects.

Combined analysis of variances over four environments showed that genotype x environment interactions were present and significant for average root weight and harvest index throughout all harvest periods except at 60 and 150 DAP for average root weight. This indicate that sweetpotato genotypes performed differently in different environments, however, a stable genotype in terms of average root weight can be found in sweetpotato at 60 and 150 DAP. UPLSp 1 outperformed all other genotypes in terms of average root weight over environments across harvesting dates while Binicol x NPSp 48 recorded the highest harvest index over environments from 60 to 120 DAP. At 150 DAP, Binicol and its crosses gave comparable and significantly higher harvest index than all other genotypes tested. Sweetpotato performed significantly better in UPLB during the dry season planting than in all other three test environments.

Document Type

Dissertation

Degree

Doctor of Philosophy in Plant Breeding

College

Graduate School (GS)

Adviser/Committee Chair

Ruben L. Villareal

Co-adviser

Azucena L. Carpena

Committee Member

Tito J. Rimando, Randy A. Hautea

Language

English

LC Subject

Sweet potatoes, Sweet potatoes--Storage

Location

UPLB Main Library Special Collections Section (USCS)

Call Number

LG 996 1996 A42 T35

Notes

Doctor of Philosophy (Plant Breeding)

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