Early assessing performance and resistance of Colombian rubber tree genotypes under high South American Leaf Blight pressure in Amazon

摘要

In Latin America, natural rubber production is limited by an endemic disease known as South American Leaf Blight (SALB), caused by a leaf plant pathogen fungus, Microcyclus ulei, recently renamed Pseudocercospora ulei The main strategies for managing the disease are using genotypes with SALB resistance and identifying escape zones. The objetive of this study was to assess early performance (four growth parameters) and reaction to SALB (four variables of the disease) of nine Colombian rubber tree genotypes and clone IAN 873 (susceptible control) during the immature phase (an annual cycle analyzed by three climatic periods) in large-scale clone trials under SALB non-escape conditions in the Colombian Amazon. It was evident that most of the genotypes demonstrated optimal early growth, and severity and sporulation significantly increased in the genotypes most susceptible to SALB (ECC 35, ECC 83, ECC 60 and IAN 873), especially in the time between the transition into the dry period, and the consolidation of the dry period. The highest SALB scores were present in the latter. Genotypes with higher resistance to SALB generally demonstrated lower growth indices compared with more the susceptible genotypes. Genotypes ECC 29, ECC 64 and ECC 90 bring together optimal growth and partial SALB resistance characteristics and constitute a promising gene pool of evidence for expanding the genetic resource of rubber tree in the Colombian Amazon region.