Abstract:

Stylosanthes guianensis Swartz, one of the most important tropical forage legumes, is native to South and Central America and Africa. Anthracnose, caused by the fungus Colletotrichum gloeosporioides (Penz.) Sacc., is a major constraint to the extensive use of Stylosanthes as tropical forage. Forty-two accessions of S. guianensis were assessed by amplified fragment length polymorphism (AFLP) for genetic diversity and for resistance to anthracnose. In AFLP analysis, four selective primer combinations screened from 96 primer combinations were used to analyze these accessions, which showed a 95.5% level of polymorphism on average. Genetic similarity from 31.0% to 95.0% among the accessions was calculated with NTSYS-pc software. The dendrogram was constructed with unweighted pair group method of averages (UPGMA) based on the AFLP data, and five clusters were defined at 48% genetic similarity. Principal coordinates analysis showed that the contribution of the first principal coordinate and the second one to the genetic variation of 42 accessions is 56.04% and 6.40%, respectively. Two typical strains of C. gloeosporioides from Stylosanthes in China were used for anthracnose resistance screening. All plant accessions showed variation in the reaction to two strains, and the correlation of resistance had a value of 0.904 (P ＜0.01), suggesting the common resistance to the two strains. The resistant accessions were randomly distributed in the different groups of UPGMA clustering. Also, these results demonstrate that AFLP analysis is an efficient method for evaluating the genetic diversity among S. guianensis accessions.

Key words: Stylosanthes guianensis, AFLP, genetic variation, cluster analysis, resistance to Anthracnose