Screening F1 Advanced Sweetpotato [Ipomoea batatas (L) LAM] Segregating Populations for Early Bulking, Dry Matter Content and Optimum Harvesting Time in Umudike, South-East Nigeria

Abstract

Sweetpotato is an important carbohydrate root crop grown mainly for its storage roots for processing into various sweetpotato products due to its dry matter content.  Twenty three (23) sweetpotato genotypes was conducted at the Western experimental field of NRCRI, Umudike in 2020 and 2021 to select potential early storage root bulking and maturing genotypes with high dry matter content for early cultivation genotypes. Objectives were to identify precise time for harvesting each genotype, select genotypes for extra-early, early, medium and late maturity for various end users. The experiment was laid out in a randomized complete block design with three replications. Each plot measured 4 x 3 m and comprised 4 ridges. Ten genotypes were used as samples per plot per genotype. The sweetpotato seed were cut 25 cm long, with at least 4 nodes, which were inserted two nodes on the crest of the ridges in a slanting position and spaced 1m between ridges and 0.3m apart along the row on the ridges. Ten (10) sweetpotato plants per plot were harvested at interval of 4 weeks after planting (WAP). Plant attributes studied were number of marketable roots at 8, 12, 16 and 20 weeks after planting and number of unmarketable roots. The yield data were subjected to analysis of variance and their means separated with standard error of difference at the probability level of 0.05. Four harvest dates for the sweetpotato genotypes were proposed; very early maturing, early maturing, intermediate and late maturing.  The proposed dates were: 8, 12, 16 and 20 Weeks After Planting (WAP). Standard error of difference was used to assign genotypes to a harvest group/date. Results obtained indicated that Sweetpotato genotypes vary in their marketable root bulking and maturity dates, and harvesting at 8WAP would render the storage roots immature and unmarketable.  Some genotypes required more than 16WAP to reach maturity. It is therefore, recommended that harvesting should be at 16 WAP.  Assigning genotypes to a given harvest date is important for areas of short growing seasons as a result of short rainfall, areas of high disease infestation, areas with high market demand, for industrial uses depending on type of utility of the storage roots. Genotypes with dry matter of 28% are acceptable to most consumers.