Genetic differentiation of watermelon landraces in Mozambique using microsatellite markers

Landraces of seed and dessert type watermelons from three provinces of Mozambique with distinct agro-ecological conditions, including humid and semi-dry areas from the north to the south of the country, were analysed to assess their genetic differentiation. Ninety-six accessions (269 plants) were tested with 24 microsatellite markers resulting in 110 alleles. Analysis of molecular variance showed that 63% of the total variation in the plant material could be explained among the accessions, while 37% of the variation was within accessions. Molecular variance between material used for seed extraction and dessert consumption explained 34% of the total variation whereas villages explained 27% of the molecular variation among the sampled locations. Structure analysis revealed that the material could be differentiated into three genetic groups. The seed types clustered in one genetic group, irrespective of provincial origin. Dessert type accessions from the semi-arid south and the central part were assigned to a second genetic group, while accessions from the northern more humid region of the country were assigned to a third genetic group. The observed genetic diversity may reflect farmer selection under different agro-ecological conditions or an introduction of material from different sources into the growing areas.Keywords: Citrullus lanatus, DNA fingerprinting, landraces, Mozambique, microsatellites, simple sequence repeats (SSR).African Journal of Biotechnology Vol. 12(36), pp. 5513-552

Occurrence and diversity of Xanthomonas campestris pv. campestris in vegetable brassica fields in Nepal

Black rot caused by Xanthomonas campestris pv. campestris was found in 28 sampled cabbage fields in five major cabbage-growing districts in Nepal in 2001 and in four cauliflower fields in two districts and a leaf mustard seed bed in 2003. Pathogenic X. campestris pv. campestris strains were obtained from 39 cabbage plants, 4 cauliflower plants, and 1 leaf mustard plant with typical lesions. Repetitive DNA polymerase chain reaction-based fingerprinting (rep-PCR) using repetitive extragenic palindromic, enterobacterial repetitive intergenic consensus, and BOX primers was used to assess the genetic diversity. Strains were also race typed using a differential series of Brassica spp. Cabbage strains belonged to five races (races 1, 4, 5, 6, and 7), with races 4, 1, and 6 the most common. All cauliflower strains were race 4 and the leaf mustard strain was race 6. A dendrogram derived from the combined rep-PCR profiles showed that the Nepalese X. campestris pv. campestris strains clustered separately from other Xanthomonas spp. and pathovars. Race 1 strains clustered together and strains of races 4, 5, and 6 were each split into at least two clusters. The presence of different races and the genetic variability of the pathogen should be considered when resistant cultivars are bred and introduced into regions in Nepal to control black rot of brassicas