Résumé
► Durable resistance was identified in parents and introduced in progenies. ► Productive and resistant recombinant genotypes were selected. ► 13 high resistant and productive Hevea clones were selected in a rubber collection. ► Clone resistance was confirmed in an international network of clone trials. ► Three clones are currently recommended in Brazil for development.
The CIRAD-Michelin-Brazil (CMB) breeding program was set up in 1992 and has produced several genotypes as alternative varieties for growing in suboptimal regions and areas affected by South American Leaf Blight (SALB). From a large parent population of more than 113 clones, the program developed CMB genotypes evaluated in large-scale clone trials. Based on accurate knowledge of the parents’ agronomic potential, the CMB breeding program combined family and individual selection in the seedling evaluation trials. The segregation ratios of the SALB resistance traits in the progeny were used to identify and reject parents whose resistance was determined by a small number of genes, easily overcome by Microcyclus ulei strains. After evaluating the germplasm, 13 genotypes were selected for evaluation of their resistance, girth and rubber production in a trial network covering eight sites in Brazil and Ecuador. There were significant differences between clones, sites and clone-site interactions. The resistance of the clones to SALB was confirmed for all sites, both for conidial and sexual fungal stages. The growth rate in Ecuador was always higher than in Brazil with the exception of one clone. Data from previous years of production for a few clones was used to estimate the potential yield of these clones compared to clones usually planted in Latin America. Simultaneous selection for SALB resistance, yield and growth resulted in promising genotypes which need to be tested in areas with different environments.