Sweetpotato, with a global annual planting area of approximately 9 million ha, is the second most important tropical root crop. It is widely adapted, being grown in more than 110 countries. Early maturing varieties grow in 3-4 months. It is hardy and has multiple uses. Both roots and foliage are edible and provide energy and nutrients in diets. Distinct quality types have different uses, with orange-fleshed sweetpotato being valued for its extremely high provitamin A content, and other types used in varied fresh and processed forms. Sweetpotato is easily bred, as true seed is easily obtained and generation cycles are short. There are five objectives of this review. The first objective is to briefly describe recent production and utilization trends by region; the second is to review knowledge about the origin and genetic nature of sweetpotato; the third is to review selected breeding objectives. The fourth objective is to review advances in understanding of breeding methods, including: (i) generation of seed through polycross nurseries and controlled cross breeding; (ii) a description of a new accelerated breeding approach; (iii) recent efforts to systematically exploit heterosis; and (iv) new approaches of genomic selection. The fifth objective is to provide information about variety releases during the past 20 years in West, East and Southern Africa, South Asia, East and South-east Asia, China and the Pacific.

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The existence of genetic diversity in germplasm collections is crucial for cultivar development. Genetic relationships among 105 Bambara groundnuts (Vigna subterranea (L) Verdc.) accessions from Kenya were evaluated using 12 microsatellite markers. The Bambara landraces were collected from farmers in the western region and the National Genebank of Kenya. A total number of 24 alleles were revealed with a mean of 2 alleles per locus. The polymorphic information content and gene diversity values averaged 0.28 and 0.35, respectively indicating low genetic diversity among the evaluated Bambara groundnut germplasm. Genetic distance based on Jaccard's similarity coefficient from the simple sequence repeat (SSR) marker analysis ranged from 0.08 to 1.16 among the landraces. Cluster analysis distinctly grouped the 105 accessions into three major clusters. The analysis of molecular variance (AMOVA) revealed that 98% of the total genetic variation was within accessions whereas the genetic variation among accessions accounted for 2% of the total genetic variation. The genetic diversity observed in this study provides the basis for selection of appropriate parental genotypes for breeding programmes and mapping populations to further broaden the genetic base of Bambara groundnut germplasm in Kenya.

Banana streak virus (BSV) is a significant constraint to banana production in Kenya. The ability to quickly and reliably detect BSV is important for the management of the virus. Hence, detection of the variability of BSV was necessary for the optimization of a suitable diagnostic protocol to be used for routine screening of tissue cultured material. In this study, 215 potentially infected banana plants from nine major banana growing regions in Kenya were tested for BSV using serological and molecular techniques. Virus particles were detected by immunosorbent electron microscopy (ISEM) in seven of the ten tested samples confirming the presence of BSV. Immuno-capturepolymerase chain reaction (IC-PCR) using a degenerate primer was used on extracted viral DNA and on immune-captured viral particles from 80 samples. Enzyme-linked immunosorbent assay (ELISA) confirmed the presence of BSV in 200 samples and IC-PCR in 38 of the 80 tested samples. A total of 33 sequences were obtained from eight samples by PCR (EMBL accession numbers AM 905900-AM905905) across the conserved reverse transcriptase ⁄ RNaseH region of the genome. Pairwise comparison of the sequences suggested that they represented seven different isolates with sequence identity thresholds of 90-100%. Southern blotting and hybridization with a radiolabelled probe of the Lisulya clone, confirmed that both integrated and episomally replicating viral DNA may be present in at least one of the Kenya samples. Therefore, the presence of BSV in Kenya and some diversity within the Kenyan population was confirmed. The diagnostic protocol was optimized for the confirmed isolates.