Abstract:

Pepper {Capsicum spp.) production is constrained by poor quality cultivars and various biotic stresses, among which diseases are prominent. Lack of information on diversity, yield, disease resistance and a narrow genetic base for the existing Capsicum cultivars hinder pepper improvement in Uganda. The main objective of this study was to establish the performance and morphological characteristics among a diverse collection of hot pepper germplasm, as a basis for contributing towards the improvement of pepper production in Uganda. To achieve this, studies were carried out between April 2008 and October 2010 in Wakiso district to: a) characterize the morphological diversity of hot exotic and local Capsicum annuum genotypes, b) identify pepper genotypes with superior agronomic (growth), yield and quality traits for use in pepper cultivar improvement efforts in Uganda and/or for direct release to farmers, c) establish levels of disease resistance among various pepper genotypes and select parents for disease improvement efforts, d) analyze the nature of gene action among pepper genotypes through combining ability studies, in order to identify parents that produce offspring with superior fruit yield and associated traits. Thirty-seven local and introduced genotypes were characterized for morphological traits in a screen-house at the National Agricultural Research Laboratories (NARL), Kawanda. Thirty-five genotypes were evaluated for growth, yield, quality and disease resistance traits for two seasons in a high disease pressure site at the National Crops Resources Research Institute (NaCRRI), Namulonge. Detection and diagnosis of field disease causative organisms (viruses) was done in the Virology laboratory at the International Institute of Tropical Agriculture (IITA) in Namulonge, Uganda and in the Molecular Biology laboratory at the Department of Agricultural Production, Makerere University for fungal and bacterial diseases. Combining ability studies for yield and yield-contributing traits was done at NaCRRI. Findings indicated significant morphological differences among pepper germplasm for most characterized quantitative traits (P<0.001) and for days to fruit maturity (P=0.003) except in the case of primary branch numbers. Local genotypes were characterized by smaller fruits and later maturing types compared to exotic accessions, with the exception of local accessions CA-EASC 09-1 and CA-UGKA 09-3. However, local types performed better in plant height, width and fruit numbers per plant. On the other hand, very little diversity was detected among genotypes for qualitative traits (Diversity index, e" = 1.83). Higher diversity indices were observed for stem pubescence type (3.20), leaf pubescence type and density (2.77), anther colour (2.56), calyx margin and fruit surface (2.90), and immature fruit colour intensity (2.80). Cluster analyses using 20 quantitative and 28 qualitative traits showed diversity among the genotypes at phenotypic level but with some level of genotypic relatedness and closeness. Very highly significant differences were observed in all plant growth (P<0.001), most yield (P<0.001) and most quality (P<0.001) traits in the two seasons. The performance of pepper genotypes during season 2009B was far higher than in season 2009A for majority of the traits. Local genotypes performed better in season 2009A than in 2009B in number of fruits per plant, percentage of non-marketable fruits, number of seeds per fruit, fruit seed yield (t/ha) and 200 seed weight (g). A pooled analysis across seasons showed that local genotypes performed worse than exotic genotypes in all scored parameters except plant width. The commercial local check genotype CA-UGKA 09-3 performed better than all the local genotypes and most of the AVRDC genotypes in terms of fruit yield and early maturity. The local genotype CA-EASC-09-lfrom the East African Seed Company was the earliest maturing among all genotypes and could be used as a donor parent for earliness, even though it was also the poorest yielding type. An AVRDC check genotype PP97-7195-1 performed best of all the exotic genotypes in all traits except fruit size. With the exception of number of seeds per fruit, highly significant genotype by season (GxE) (P<0.001) interactions was observed in other traits, an indication of lack of trait stability among genotypes across seasons. Eight of the agronomic traits showed significant correlations between seasons indicating some degree of stability for these traits. Correlation analyses indicated that fruit size (weight and length) and numbers per plant were the most important determinants of total and marketable yield (t/ha) suggesting that selecting genotypes that produce many and/or bigger fruits during the hot pepper breeding programme can consequently lead to increased yields. However, fruit weight contributed more compared to number of fruits per plant.