| dc.description.abstract | African nightshade, Solanum nigrum L .is one of the most significant leafy vegetable
rich in nutritional and medicinal value, and can be used to feed people with human
immune deficiency virus, HIV/AIDS in Kenya. There is limited information available
of this species that hinders its sustainable conservation and development. Limited
information on the crop pests and diseases also present major challenges that limit
production of the African nightshade species since farmers are still using farm saved
seed which is a danger of inadvertently spreading quarantine pest and diseases like
Ralstonia solanacearum. The utilization of genetic diversity in breeding programs can
be employed to enhance the development of African nightshade accessions that
exhibit better yield potential for both leaf and fruit production, while also displaying
resistance to various biotic and abiotic challenges. The objective of this study was to
assess the presence of genetic diversity among African nightshade accessions by
conducting morphological and genotypic characterisation. Additionally, the study
aimed to determine the inherent resistance to bacterial wilt caused by Ralstonia
solanacearum by field and greenhouse screening experiments. A total of 30 samples
from three counties Bungoma, Kakamega and Trans Nzoia were evaluated. For
morphological characterization the African nightshade accessions were planted at
Kibabii University farm and scored for several agro morphological characters based
on National Bureau of Plant Genetic Resource NBPGR descriptors on following
qualitative traits; Leaf surface as Glaborous or pubscent, Colour of ripe fruit as
Orange or Dark purple or Black, Stem ridge as Smooth ridges or Dented, Leaf shape
as Lanceolate or Ovate or rhomboid, Leaf margin as Sinuate dented or Entire and
Inflorescence orientation as Simple or Forked the plant type was scored as Semi erect
or erect. Cluster analysis of morphological data was done using PASW Version 20
Statistical software. Results showed that there was phenotypic variation amongst
accessions of African nightshade collected from the three counties since they were
grouped into two major clusters A and B meaning that there is rich diversity both
within and among African nightshade accessions which can be used for the crop
breeding work. Molecular characterization was done using SSR markers on 30
African nightshade accessions. Each of the 6 SSR primers utilized produced a single
polymorphic band. The mean polymorphic information content was 0.5881, with
values ranging from 0.4215 to 0.8212. He=0.9111 is the mean heterozygosity for SSR
markers utilized. The dendrogram indicated that the accessions were categorized into
three primary clusters, each characterized by a high degree of diversity. Furthermore,
it disclosed that the coefficient distance separating the majority of the accessions was
below 79.56. These results indicate that cross-breeding was a possibility among the
accessions; genetic variation between regions was not apparent. Screening of the 30
African nightshade accessions, to Ralstonia solanacearum was done in the screen
house at Masinde Muliro University of science and Technology. Seedlings were
inoculated at four to six leaf stages with 30 ml of 108cfu/ml per seedling in the pot
and disease incidence was recorded. The different accessions of Solanum nigrumL,
Solanum villosum L from Trans Nzoia, Bungoma and Kakamega counties were
identified as susceptible. However, improved accessions of Solanum scabrum L
sampled from the African nightshade growing areas in Western Kenya were resistant
to bacterial wilt, the accessions that were found to be susceptible, symptoms appeared
4 days after inoculation, while the accessions that were found to be resistant/ tolerant
no symptoms were observed even after 14 days after inoculation. The resistant
accession of improved variety of Solanum scabrum L can be used in production and
also breeding programmes for developing new varieties of the African nightshade
crops. | en_US |
