Abstract

Plants were regenerated from leaf-derived callus cultures of the diploid species Stylosanthes guianensis (four genotypes), and the tetraploid species S. scabra (four genotypes), and S. hamata (one genotype). No morphological variation was observed in the 97 regenerated plants (SC1) of S. scabra, but 23 of the 104 SC1 plants of S. hamata were sterile dwarfs. In a field experiment with 42 SC2 families of S. scabra, four were low yielding and five segregated for late flowering. Dwarfs were again found in SC2 families of S. hamata, and both high and low yielding families were observed. Glasshouse inoculations with various pathogenic races of Colletotrichum gloeosporioides were performed to assess the reactions of 276 S. guianensis, 56 S. scabra and 62 S. hamata SC2 families. A major gene mutation from dominant to recessive appeared to confer increased susceptibility in S. hamata SC2 families. Eight of twelve tetraploid S. guianensis cv. Graham families exhibited partial resistance to Type B race 3 anthracnose. Two S. scabra cv. Fitzroy families segregated for reaction to Type A race 1 anthracnose. Selfed progenies (SC3 generation) of two of the three partially resistant SC2 individuals maintained their partial resistance, indicating stable inheritance. Segregation data suggested that changes in minor genes caused this variation.