| Two other breeding approaches are mentioned. The possibility of building
up mechanical resistances has recently been re-advocated by Dr. Stakman
and may prove useful. Secondly, the search for higher levels of resistance
in inter-specific and inter-generic derivatives is considered important.
A number of such lines so far examined is listed, the main interest being
centred on derivatives of Triticum Timopheevi. Attention is being given to work on Kenya wheats in other countries. A considerable body of information is now available in the literature and this is being summarised, both for race resistances and for genes. The frequency of temperature effects is notable, but special value is being obtained from the realisation that certain Kenya wheats once discarded on local, limited susceptibilities nevertheless have marked general levels of resistance when viewred internationally and therefore merit renewed interest in Kenya. Much the same remarks apply to the data available on specific genes for rust resistance, and the value of Kenya Farmer is specially noted in this respect. Such research must proceed continually, but is essential to the best furtherance of the practical programme. For the future, two matters receive special attention. Speed of working can be increased in the multiplication stages by the use of an area near Mount Kenya where two crops can be grown each year. Irrigation can also be used. But on the breeding side, speed is more difficult to obtain successfully. Out-of-season crops upset selection for rust resistance and can cause unusual behaviour; they therefore need careful planning if they are to be effective. The use of growth chambers and other artificial devices carries similar reservations, but an investigation has been in progress to see to what extent supplemental lighting can be useful. Results have been disappointing and point to greater value being obtainable from extra generations out-of-doors. The risk of insufficient testing is also stressed where speed is the aim, for a fair balance must be struck between haste and caution if the new products are to have lasting value. The other line of thought for the future is the "composite variety" idea. This scheme, by relying on a number of components differing in their rust resistance, aims at offering greater breadth of resistance to infection and greater insurance against loss than pure-line varieties. There is clearly considerable value in this concept, though the practical implications are still being studied. The large backcrossing programme of 1958 is however suited to providing material for use in composites in due course. The final point to be made is that throughout the foregoing the need for genetic breadth has been stressed as the lesson of previous years. Intenrational co-operation in the Nurseries is shown as of the greatest importance in achieving this aim, and has already had a profound influence on wheat breeding progress in Kenya. |
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