National Plant Breeding Research Centre Njoro

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Date
2005
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Kenya Agricultural Research Institute
Abstract
Wheat improvement in Kenya is faced by a number of production problems. The climatic conditions are very variable and the rainfall is unreliable, even in conventional wheat growing areas. Most of the commercial varieties are susceptible to rust diseases especially stem rust and stripe rust. Insect pests such as the Russian Wheat Aphid (RWA) are a major problem to the wheat farmers. The land area suitable for production of wheat under rain conditions is very low at 0.4% (Kamindi, 1995). In these areas wheat has to compete with other enterprises such as maize, tea and coffee. Meanwhile the marginal areas remain agriculturally underutilized and can form very valuable land under which suitable varieties of wheat can be grown ( Kinyua, ef al., 2000). The introduction of wheat in the non-traditional areas has serious economic implications such as high cost of production and low yield (Blum, 1998). There is need for more breeding to improve the yield of the existing varieties for these regions and improve the quality of the varieties. There is little variation in the existing wheat lines being screened for drought and so there is need to develop more lines through crossing and mutation so as to create variability and select for drought tolerance and high yield (Njau, 2001). The development of varieties of wheat with resistance to destructive diseases has been among the foremost contributions in wheat breeding in Kenya. In breeding program, each disease is considered as a separate problem. With wheat, attention has been given to the breeding of varieties resistant to stem rust, yellow rust and other diseases. Yellow rust, caused by Puccinia sfriformis westend is at present one of the major threats to wheat production in Kenya (KARl, 1995). Serious attacks of the pathogen occur annually and its severity increases with the altitude. Stem rust (Puccinia graminis tritici) is one of the most destructive of plant disease. In wheat improvement, stem rust resistance is a major objective. Breeding stem rust resistant varieties is a continuing process because the rust race complex is always changing. The use of noval biotechnology such as molecular marker assisted selection will not only increase the efficiency of selection but will provide rapid development of new varieties In acid soils manganese and aluminum toxicity are important growth inhibiting factors for plants and grain yield production. One of the remedial measures is the application of lime. However this is not economically feasible, as large quantities have to be applied. Hence a reasonable approach is to select genotypes with greater tolerance to excess aluminum among released varieties or Introductions. In wheat, tolerance to acid soils is controlled by 2 or 3 dominant genes. This could be introduced into the existing wheat varieties through crosses of commercial varieties with the selected acid soil tolerant Introductions. Up to date no variety has been bred and released specifically for acid soil conditions. The main objective of the programme therefore has been to develop wheat varieties that are tolerant to acid soils, with higher yields and good baking quality.
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