Abstract:

EASC
{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-EASCPepper
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.
Disease assessment confirmed field infection with viral diseases, wilts, Phytophlhora blight,
Cercospora leaf spot, anthracnose and bacterial spot. Viral diseases and Cercospora leaf spot
were the most predominant and severe diseases, followed in descending order by anthracnose,
Phytophlhora blight and wilt diseases. Results showed highly significant genotypic differences
(P<0.001) for most scored diseases. No genotype was found to be resistant to all observed field
diseases apart from the AVRDC genotype PP97-7195-1, which was resistant to fungal and
bacterial diseases, and only moderately resistant to viral diseases. Field disease correlation
analysis across seasons indicated significant severity indices for viral disease and Phytophthora
blight implying some stability in these scores across seasons with the viral disease severity index
being the most consistently scored disease. In 2009A, all disease incidences and severities
correlated negatively with both total and marketable fruit yields except for the viral disease
severity index, implying that all except viral diseases contributed to the loss of both total and
marketable fruit yields. Anthracnose contributed most to the loss in yield. Cercospora leaf spot
contributed more to total fruit yield loss in 2009B.
Laboratory analysis found Phytophlhora capsici, Fusarium oxysporum f.sp. capsici and
Ralstonia solanacearum associated with wilt disease. Colletotrichum sp. was associated with
anthracnose diseases on stems while Xanthomonas campestris pv. vesicatoria caused bacterial
spot on leaves. Species confirmed to cause viral diseases included: Tomato spotted wilt virus
(TSWV), Chilli veinal mottle virus (ChiVMV), Tobacco mosaic virus (TMV), Potato virus Y
(PVY), Pepper mottle virus (PepMoV), Pepper veinal mottle virus (PVMV), Alfalfa mosaic
virus (AMV) and Cucumber mosaic virus (CMV). Of these PVY, ChiVMV and CMV were the
most prevalent.
Evaluation of Fl hybrids and their parents indicated significant differences in heterotic, general
combining ability (GCA) and specific combining ability (SCA) effects among the studied traits.
Additive gene action was predominant in viral and wilt disease incidences and a few quantitative
traits. The AVRDC genotype PP9852-115 and local genotype CA-UGKI 09-4, demonstrated
highly significant and desirable GCA effects for most of the studied traits. These were followed
by local parents CA-UGKI 09-6 and CA-UGCE 09-3 that were thus considered good combiners.
However, for wilt disease, only the AVRDC parent PP0537-7504 showed significant desirable
GCA. Three hybrids; CA-UGCE 09-3 x CA-UGKI 09-6, CA-UGKI 09-6 x PP9852-1 15 and CAUGCE
09-3 x PP0337-7562 were the top-most performers among all crosses with several
significant best SCAs for measured traits. Two hybrids; CA-UGCE 09-3 x PP9852-1 15 and CAUGKI
09-6 x PP9852-115 were better performers for Cercospora leaf spot resistance while
PP9852-115 x PP0537-7504 was the best for viral disease resistance. Some of these hybrids
performed well compared to their best parent for various traits, suggesting that obtaining
transgressive segregants should be possible in later generations.
The introduction of exotic pepper genotypes has the potential to diversify the existing Capsicum
genetic base in Uganda. Sources of improved traits have been identified that can be used in the
pepper breeding program. In order to enhance Capsicum improvement and production in
Uganda, the identified genotypes should be further evaluated and then released to farmers.
Alternatively, these genotypes could be used by breeders to introgress superior traits into
cultivars being grown by farmers and therefore improve specific traits for enhanced productivity.