THE WILT DISEASE OF PIGEON-PEA. 59 
Pedigree breeding consists simply in separating out once for all 
the individual plants possessing the required character, and multi- 
plying rapidly, under isolation, their progeny. 
The first step in pedigree breeding for disease resistance is to 
choose a considerable number of plants which are both resistant 
to the disease, and possess otherwise desirable qualities, such as 
productiveness, etc. This is simple enough in the case of a disease 
which spreads rapidly by air-borne spores, since in any year of con- 
siderable disease the mdividual plants in a plot will be all equally 
exposed to infection. Jn a disease of the type of wilt, where spread 
occurs comparatively slowly through the soil, it is not possible to 
be sure, in an experiment lasting through one season only, 
that healthy plants are resistant to the disease or have merely ~ 
escaped infection through not coming into contact with the para- 
site. Hencein the experiments at Poona the seed of selected 
healthy plants was resown on the same plot for several seasons, 
until the whole of the soil was thoroughly infested and the pos- 
sibility of any plant not being reached by the parasite was reduced 
toa minimum. It was early apparent that there was little hope of 
any variety proving resistant, as the plots became a mass of mixed 
types, presumably through free intercrossing. In the last season or 
two the crossing, if effected between plants within the plot, has 
been probably in most cases between more or less resistant 
individuals, and the individual plants possessing the quality of 
resistance inherent in them are, it is hoped, now fairly numerous. 
The seed of the selected plants will be harvested separately 
and planted separately next season. The resulting growth and 
behaviour in regard to the disease will be critically examined. If 
the desired character of resistance appears definitely in any of the 
plots, combined with other desirable characters sufficiently to make 
the variety suitable for general cultivation, it will be rapidly mul- 
tiplied and tested on a large scale for distribution. Should the 
first selections not prove successful, they must be repeated. Ultim- 
ately, though experience is as yet comparatively limited with 
