Rust resistance and mating system in Eucalyptus grandis Hill ex Maiden progenies

Abstract

Populations of Eucalyptus grandis were introduced into Brazil from Queensland and New South Wales, Australia. However, in Brazil, these plants have been severely injured by rust (Puccinia psidii Winter). Therefore, we aimed at estimating mating system parameters and heritability of rust resistance in E. grandis through progeny testing. We evaluated rust resistance in twenty-five open-pollinated progenies severely affected by P psidii using four microsatellite markers. Outcrossing rate was significantly lower than unity (t(m) = 0.782), and the difference between multilocus and single-locus was significantly higher than zero (t(m)- t(s); = 0.077). These findings highlight that a few seeds are inbred lines as confirmed by the fixation index (F-o = 0.144, P<0.05). Furthermore, the paternity correlation (r(p), = 0.102) indicated a small number of full-sibs within progenies. The estimated relatedness coefficient within progenies (rho) was significantly higher (0.421) than that expected for half-sibs (0.25). The mean heritability coefficient among progenies (h(f)(2) = 0.956), as well as at the individual level (h(i)(2)=0.634) and within a progeny (h(rf)(2)=0.515) were high. Given that, our results indicated a strong genetic control on rust resistance and the feasibility in improving the populations by mass selection for both among and within progenies.