The amount of genotypic and phenotypic variability that exists in a species is
important for selection and initiating breeding programs. Yam bean is grown locally in
tropical countries of the Americas and Asia for their tasty storage roots, which usually
have low dry matter content. The crop was recently introduced in Uganda and other East
and Central African countries to supplement iron (Fe) and protein content in diets. This
study aimed to estimate genetic variability for root yield and quality traits among 26 yam
bean accessions in Uganda. A randomized complete block design was used with two
replications across two ecogeographical locations and two seasons during 2012 and 2013.
Near-infrared reflectance spectroscopy (NIRS) was used to determine quality of storage
root samples. Significant differences among genotypes were observed for all traits except
root protein, zinc (Zn), and phosphorus contents. Genotypic variance components (s2
G)
were significant for storage root fresh yield (SRFY), storage root dry matter (SRDM),
storage root dry yield (SRDY), vine yield (VNY), fresh biomass yield (FBY), and storage
root starch (STA) and Fe contents. For traits with significant s2
G; the broad sense
heritability estimates ranged from 58.4% for SRDY to 83.6% for FBY; and phenotypic
coefficients of variation were high for SRFY (66%), SRDY (53.3%), VNY (60.5%), and
FBY (59%), but low to medium for SRDM (22.6%), STA (15.1%), and Fe (21.3%).
Similarly, the genotypic coefficients of variation were high for SRFY (56.7%), SRDY
(53.3%), VNY (55%), and FBY (53.9%); and low for SRDM (20%), STA (12.4%), and Fe
(17.8%). There were strong positive correlations between SRFY and both SRDY (r =
0.926) and FBY (r = 0.962), but low-to-moderate correlations among quality traits. It
should be possible to breed for high dry matter yam beans by using low dry matter
accessions due to the observed genetic variation (s2
G = 9.3%2), which is important if the
high dry matter Pachyrhizus tuberosus accessions (known as chuin) from Peru cannot be
accessed. This study indicated substantial genetic variation for yield and quality traits in
yam bean, demonstrating potential for adaptability to growing conditions and consumer
needs in East and Central Africa and for genetic improvement through selection.