Studies on genetic variability, inheritance and heterosis in pepper (Capsicum annuum L.)

English: The knowledge of genetic similarity and dissimilarity among crop cultivars is of vital importance for the plant breeder. The genetic variability of 39 pepper (Capsicum annuum L.) genotypes of different varietal groups that were obtained from different geographical origins was studied using morphological traits and amplified fragment length polymorph isms (AFLP) markers. Both methods showed moderately high genetic distances among the different genotypes indicating genetic diversity among the total genotypes. However, when a comparison was made between the Ethiopian and the exotic genotypes, the mean genetic distance among Ethiopian genotypes was lower than that between the Ethiopian and the exotic ones. The dendrogram based on morphological data clustered the genotypes on the basis of fruit size and was generally consistent with different varietal groups. Similarly, with AFLP data, genotypes with similar fruit sizes clustered together. Combining ability and heterosis estimates are important to determine the direction and goals of a breeding program. Seven diverse parental lines were selected from the 39 genotypes and crossed in a half-diallel method. The parental lines and their 21 FI hybrids were evaluated to estimate the combining abilities and genetic effects determining the heritability of various characters, and to determine heterosis of hybrids over mid-parent, high-parent and standard checks for various characters. Generally, significant general (GCA) and specific (SCA) combining abilities were observed for all measured characters indicating the presence of both additive and non-additive gene actions. However, additive gene action is more important than non-additive gene action, as the magnitude of GCA effects was much higher than SCA effects. The estimates of predictability ratios for fruit length, fruit diameter, fruit weight, pericarp thickness and fruit number were closer to unity, suggesting the possibility of predicting progeny performance based on parental GCA alone. High heritability both in broad and narrow senses was also recorded for these characters indicating their inheritance is less influenced by the environment. Substantial heterosis over mid-parent, high-parent and the standard check was observed. Many crosses demonstrated high heterosis for fruit yield, fruit diameter, mean fruit weight and pericarp thickness over the standard check. For the traits of earliness (days to flowering, days to maturity and fruit maturation period), the overall mean mid-parent, high-parent and standard heterosis were negative. Thus, it can be suggested that with the proper choice of parents, pepper hybrids that have higher yield potential, good fruit characteristics and early maturity can be developed to increase pepper productivity in Ethiopia. Genetic diversity between parents may contribute positively to both heterosis and trangressive segregation. The relationship between genetic diversity of the seven parental lines, and heterosis and hybrid performance was assessed. The genetic diversity was measured using 15 morphological traits and six AFLP primer combinations. Cluster analysis using the two genetic distance measures generally grouped the seven parents differently. Morphological distance was negatively correlated only with mid-parent heterosis (MPH) for days to flowering and days to maturity. The correlations of AFLP measured genetic distances with mid-parent and high-parent heterosis were non significant for all characters with the exception of fruit diameter and proved to be of no predictive value. In addition to single crosses, three-way and double crosses can be used to overcome the low productivity of inbred lines. It is hypothesized that yield stability is high in three-way and double-cross hybrids owing to higher genetic heterogeneity as compared to single cross hybrids. Twenty-six genotypes, including six inbred lines, eight single, six threeway and six double crosses were evaluated for yield and other agronomic characters in two environments using a randomized complete block design with three replications. The three categories of hybrids performed differently across the environments and showed high variations for the majority of characters studied. Three-way crosses gave the highest mean fruit yield per plant followed by double crosses. The two types of hybrids were also more stable than the single crosses. In general, three-way crosses showed promising performance for the studied traits. The highest estimates of mid- and high-parent heterosis were also observed in the three-way and double cross hybrids. Therefore, the low productivity of local pepper cultivars in Ethiopia can be overcome through developing and utilizing three-way and double cross hybrids.