Labour efficiency

Labour-saving procedures are important. This is not because of laziness, but in order to increase labour efficiency. However much labour may be available, it is a fixed amount. The more efficient that labour is, the more plants can be screened. Conversely, the less efficient that labour, the fewer the plants that can be screened. The holistic approach is important here. Detailed work is labour-consuming, and it should be sacrificed to the two broad objectives of a large screening population and strong selection pressures.

Two examples will illustrate this point. If, as happens with pedigree breeding, every cross-pollination is made by hand, and every pollinated plant is labelled with a tie-on label that records many details, the number of cross-pollinations that can be made is strictly limited. Conversely, if a male gametocide is used to achieve a random cross-pollination, a virtually unlimited number of unrecorded crosses can be made with very little labour. All that is lost is a detailed knowledge of the parentage, but this is unimportant in recurrent mass selection.

Second, it is possible to examine every plant in the screening population repeatedly, and to keep detailed records in field notebooks. This could be described as being methodical, thorough, and truly 'scientific'. However, it is much more labour-efficient to keep no field records, and to let the parasites kill all the susceptible plants. At the appropriate time, a single screening operation is then made on the relatively few survivors in order to select the parents of the next breeding cycle. In this way, a far larger screening population can be monitored.

If large numbers of plants must be screened a useful rule is to employ the most simple tests first (e.g., eye-scores) when there are many plants to be examined, and the most elaborate tests (e.g., laboratory measurements) last, when there are only a few plants remaining.

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