REPRODUCTIVE-BIOLOGY OF VICIA-FABA - ROLE OF POLLINATION CONDITIONS

The effects of two different pollination conditions, self versus open, were studied in two consecutive years in 12 genotypes which showed wi de variation for some reproductive characters related to plant structu re, fertility and yield.Yield was not apparently limited by pollen ava ilability. However, the first node to bear pods was lower in open- tha n in self-pollinated plants, which developed more flowers into young p ods. The superabundance of flowers developed into young pods was compe nsated by adjustment of other yield components to achieve the physiolo gical maximum yield. Open pollination may also have increased both pod and seed set, but only to a lesser extent, and depended on year and g enotype. The results of these experiments also suggested that yield re gulation operated by different mechanisms for the various genotypes; p articularly, abortion of young pods, ovules and seeds, and seed-size a djustments. In some genotypes, many young pods were produced but few m atured. in others, few ovules develop into seeds, or seeds remained sm all. Theoretically, such alternative strategies, present in different genotypes, could be combined to produce new high-yielding cultivars, i n such a way that highly self-fertile genotypes respond optimally to t he presence of pollinators.