Comparison of growth, yield and related traits of resistant Hevea genotypes under high South American leaf blight pressure.

摘要

Most natural rubber (NR) comes from the cultivation of Hevea brasiliensis in tropical areas. However, South American leaf blight (SALB), caused by Microcyclus ulei (P. Henn.) Arx, is the main factor limiting Hevea cultivation in the American humid tropics. Based on a preliminary selection from among more than 960 accessions, the aim of this work was to propose new SALB-resistant genotypes for South American plantations. Agronomic traits (SALB resistance, growth, production) and characters related to latex production, such as sucrose and inorganic phosphorus, along with structural traits of the bark of nine Hevea genotypes resistant to SALB (TP875, FDR5788, MDX608, PMB1, CDC429, CDC312, FDR4461, MDF180, SIAL893) were evaluated during the course of a 12-year trial located in the Michelin plantation (Bahia, Brazil). These genotypes presented a quantitative resistance to SALB characterized by partially sporulating lesions (anomorph stage). No sexual form of M. ulei (stromata, teleomorph stage) was found in FDR5788, MDF180, CDC312, PMB1. Only FDR5788 genotypes presented a higher NR yield than genotype TP875 used as a control. For FDR5788, MDX608, CDC312 and PMB1, the estimated yields of 12-year-old trees were, respectively 2.6, 2.0, 1.8 and 1.2 t year-1 ha-1. In all genotypes, medium sucrose and inorganic phosphorus concentrations were related to intermediate metabolism for cis-polyisoprene synthesis. The low yield of genotypes SIAL893 and MDF180 is related to the limited number of vessel rings, limited translocation of sucrose in the latex, and a slow metabolism indicated by low average concentrations of inorganic phosphorus in the latex. For the south east of the Bahia state, FDR5788 and CDC312 are recommended for new planting areas because of their capacity to prevent teleomorph formation, combined with high NR yields.