ABSTRACT

This study aimed at assessing the inheritance of important agronomic traits in full-sib families of orange-fleshed sweetpotato (OFSP) was conducted at National Root Crops Research Institute, Umudike, Abia State and at, Igbariam, Anambra State. The experiment comprised three phases viz; field evaluation, crosses in crossing block and progeny evaluation. The field evaluation was conducted to assess the magnitude of variability within 47 genotypes and to estimate the yield and nutritional performance which was used to establish a crossing block. The results from root yield at Igbariam showed that K 003 produced the highest root yield (32.60t/ha), followed by Umuspo/3(28.89t/ha), A 079b (26.22t/ha) and Umuspo/1(24.45t/ha). In Umudike, Umuspo/3 produced the highest root yield (29.81t/ha), followed by Delvia (27.88t/ha), Umuspo/1(27.33t/ha) and A 097a (27.19t/ha). With respect to location, Umudike recorded highest root yield (10.09t/ha), compared to that of Igbariam 9.28t/ha). In Igbariam the highest beta carotene, which were 12.35, 12.34, 11.76 and 11.76mg/100g FW were recorded from A 089, A 010a , B 060 and Ex-Oyunga respectively. The results obtained from Umudike showed that highest beta carotene content, which were 11.03 and 11.02 mg/100g FW were recorded from A 080 and A 010a respectively. The result also revealed that in Igbariam, genotype with the highest dry matter content were Delvia(52.16%), A 099 (52.05%), Malawi II (50.76) and Amelia (49.82%). The least dry matter content was recorded from Umuspo/3(17.83). With respect to location, highest dry matter content of 40.23% was obtained in Igbriam compared to Umudike(34.38%). The cluster means showed that cluster I comprised of high yielding genotypes with very high dry matter content, lowest beta carotene content and lowest vitamin A content. The ranking of the 47 OFSP genotypes showed that Delvia had the best overall performance with a Rank Summation Index (RSI) value of 49. The correlation coefficients (r) indicated that root yield had highly positive and significant correlation with total root weight per plant(r = 0.696**, p = 0.01) and total number of root per plant(r = 0.770**, p = 0.01) and highly significant but negatively correlated with pest incidence(r = -0.394**, p = 0.01). Beta carotene had significant and negative correlation with dry matter(r = -0.503**, p = 0.01) and starch (r = -0.364**, p = 0.05). Path coefficient analysis using root yield as dependent variable and others as independent variables showed the highest positive direct effect on root yield (RY) were exhibited by number of roots per plant(NRPP)(0.65) and root weight per plant(RWPP) (0.31). The progeny evaluation was conducted in RCBD involving 59 genotypes (three testers, fourteen lines and forty two crosses) of OFSP. From the results, phenotypic coefficients of variation was higher in magnitude than the genotypic coefficients of variation for all the characters. The magnitude of additive variance (σ 2 A) was consistently larger than that of dominance variance (σ 2 D) for all traits studied. All the characters studied had high broad sense heritability (>60%). Lines L5 (A 106 -1) and L13(Solo Abuja -1) were best general combiner for root yield per hectare. Line L7 (A 141 - 1), L3 (A 089 -1) and L1(A 079b -1) were best general combiners for increased beta carotene content whereas, line, L12(Malinda -2), L11(Malinda -1) and L6(A 106 -2) were best general combiner for dry matter content.