COMPONENTS OF QUANTITATIVE RESISTANCE TO ANTHRACNOSE (COLLETOTRICHUM-GLOEOSPORIOIDES) IN TETRAPLOID ACCESSIONS OF THE PASTURE LEGUME STYLOSANTHES-HAMATA

Partial resistance to the anthracnose pathogen Colletotrichum gloeospo rioides was characterised in 6 tetraploid accessions and cv. Verano of the tropical pasture legume Stylosanthes hamata. Four components of r esistance (incubation period, latent period, spore production, weighte d infection type) were determined and compared with those of the susce ptible S. scabra cv. Fitzroy. There were significant differences betwe en the accessions for all resistance components. The mechanisms of res istance in the 3 most resistant accessions appeared to be different, w ith accession 55830 having a longer incubation period but higher sporu lation per day than either 92715 or 92412. Spore production, weighted infection type, and latent period were significantly (P<0.05) correlat ed with resistance of adult plants in the field (ADPC). The weighted i nfection type was useful in discriminating between accessions that had similar disease severity scores. A quantitative relationship was esta blished between 2 components, latent period and spore production per d ay, and the ADPC, using a multiple regression analysis (r2 = 0.9). If verified using a large number of accessions, such analysis may be used to obtain an index of resistance that may predict resistance levels i n the field based on the components.