The Cassava Genome: Current Progress, Future Directions

The starchy swollen roots of cassava provide an essential food source for nearly a billion people, as well as possibilities for bioenergy, yet improvements to nutritional content and resistance to threatening diseases are currently impeded. A 454-based whole genome shotgun sequence has been assembled, which covers 69% of the predicted genome size and 96% of protein-coding gene space, with genome finishing underway. The predicted 30,666 genes and 3,485 alternate splice forms are supported by 1.4 M expressed sequence tags (ESTs). Maps based on simple sequence repeat (SSR)-, and EST-derived single nucleotide polymorphisms (SNPs) already exist. Thanks to the genome sequence, a high-density linkage map is currently being developed from a cross between two diverse cassava cultivars: one susceptible to cassava brown streak disease; the other resistant. An efficient genotyping-by-sequencing (GBS) approach is being developed to catalog SNPs both within the mapping population and among diverse African farmer-preferred varieties of cassava. These resources will accelerate marker-assisted breeding programs, allowing improvements in disease-resistance and nutrition, and will help us understand the genetic basis for disease resistance

Farming for balanced nutrition: an agricultural approach to addressing micronutrient deficiency among the vulnerable poor in Africa

Concepts on malnutrition have evolved from an emphasis on protein deficiency through energy deficit, to the realization that food quality in general and an adequate supply of micronutrients in particular, is often more of a problem than food quantity. Throughout the developing world, micronutrient deficiency is one of the most important factors influencing human health, being directly responsible for conditions such as xeropthalmia, associated with vitamin A deficiency and anaemia, due to iron deficiency. In addition, micronutrient deficiency predisposes children to infection and retards recovery from common infections such as malaria, measles and diarrhoea. The groups most at risk from micronutrient deficiency are usually children and those for whom labour for food production is limited by ill health (HIV sufferers), advancedage or intense social commitments (single mothers, for example). There have been numerous health projects in sub-Saharan Africa and elsewhere in the developing world, to address micronutrient deficiency through the distribution of vitamin and mineral supplements, which usually have to be imported. An alternative (or complementary) approach is to promote the inclusion of high quality food crops in the farming system to enrich the diet with essential vitamins and minerals. This agricultural approach to the problem of micronutrient deficiency can provide sustainable solutions, which improve diet quality. An increase in the cultivation ofhigh quality foods such as legumes, fruits and green vegetables, may be able to deliver a balanced diet to households, without necessarily requiring additional land and labour. Agricultural approaches to enhance dietary intake of vitamins and minerals have the additional advantage that they foster community self-reliance, they are sustainable in the absence of external funding, and, offer the opportunity for enhanced income by marketing surplus production. Diet diversification through betteruse of existing biodiversity offers an immediate means to address poor diet quality and can also include the use of presently available nutritionally enhanced crops, such as orange-fleshed sweet potato

Distribution, incidence and management of Phaeoramularia fruit and leaf spot of citrus with special reference to western Kenya

No Abstract Available E. Afr. Agric. For. J Vol.68(2) 2002: 85-9

Phaseolus bean improvement in Tanzania, 1959-2005

Common bean is an important source of dietry protein and starch in Africa and a primary staple in parts of the Great Lakes Region. Tanzania remains one of the worlds' major bean producing countries although according to official statistics, production per capita has almost halved in the last 20 years. The main international bean improvement programmes are run by the Centro Internacional de Agricultura Tropical [CIAT] from Colombia and by the Collaborative Research Support Programme [CRSP] co-ordinated by the Land Grant Universities in the USA. CIAT also maintains the world's largest collection of Phaseolus germplasm. The National Bean Programme in Tanzania is supported by both CIAT and CRSP. Collaboration between these international programmes and the National Programme has resulted in the release of more than 20 improved bean varieties. The paper reviews the development of bean improvement programmes in Tanzania since 1959, the contribution made by the international programmes and the strategies used to develop high-yielding bean varieties with resistance to pests and diseases and tolerance to some edaphic stress factors

Screening common bean accessions for resistance to charcoal rot (Macrophomina phaseolina) in Eastern Kenya

Common bean (Phaseolus vulgaris L.) germplasm was screened for resistance to charcoal rot (Macrophomina phaseolina) under field conditions at Kiboko and Katumani, eastern Kenya. Of the 313 bean accessions evaluated, 50 lines were resistant and six were tolerant to M. phaseolina, the charcoal rot incidence was less than 25% and between 25% and 50% for the resistant and tolerant lines respectively. Yields ranged from 135 to 1051 kg ha?1 compared with 55 kg for the susceptible control A464. Time to maturity did not seem to influence or affect the susceptibility or resistance to M. phaseolina of the various bean accessions