Development of plant genotypes for multiple cropping systems

Thus concludes this paper, which was presented at a plant breeding symposium held at Iowa State University in 1979. Emphasis throughout is on intensive cropping systems that combine two or more crops in the field at the same time. Species choice and genetic selection are discussed first; attention is given to the interactions of genotypes in different cropping systems, and statistical alternatives for comparing these interactions. Steps in the practical screening and testing of new cultivars are then outlined: the decision to breed for intercropping systems; phenotypic traits desirable for intercropping (with respect to photoperiod, temperature sensitivity, plant morphology, rooting systems, planting density, and early seedling growth); insect and disease resistance; screening techniques for breeding; and on-farm testing and technology transfer. The potential productivity of multiple cropping systems is assessed in terms of competitive ability to use available resources. A multidisciplinary research focus and improved graduate study are recommended to provide the necessary expertise in genotype development. Comments by symposium panel members and a 136-item bibliography are appended.