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

Abstract

ResumoPopulações de Eucalyptus grandis foram introduzidas no Brasil a partir de Queensland e New South Wales, Austrália. No entanto, no Brasil, estas plantas têm sido severamente prejudicadas pela ferrugem (Puccinia psidii Winter). Portanto, objetivamos estimar os parâmetros do sistema de reprodução e a herdabilidade para resistência a ferrugem em E. grandis por meio de um teste de progênies. Nós avaliamos a resistência a ferrugem em vinte e cinco progênies de polinização aberta, que foram severamente afetadas por P. psidii, utilizando quatro marcadores de microssatélites. A taxa de cruzamento foi significativamente menor do que a unidade ( = 0.782) e a diferença entre as taxas multilocus e unilocus foi significativamente maior do que zero ( = 0.077). Esses resultados mostram que algumas sementes eram endogâmicas como confirmado pelo índice de fixação ( = 0,144, P< 0,05). Além disso, a correlação de paternidade ( = 0,102) indicou um pequeno número de irmãos-completos dentro de progênies. O coeficiente de parentesco estimado dentro de progênies ( ) foi significativamente maior (0,421) do que o esperado para meios--irmãos (0,25). O coeficiente de herdabilidade entre progênies ( = 0,956), bem como em nível individual ( = 0,634) e dentro de progênies ( = 0,515) foram elevados. Nossos resultados evidenciaram forte controle genético para o caráter resistência à ferrugem, indicando que o melhoramento dessas populações pode ser feito pela seleção massal ou pela seleção simultânea entre e dentro de progênies.Palavras-chave: Parâmetros genéticos; teste de progênie; Puccinia psidii; sistema de reprodução. AbstractPopulations 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 ( = 0.782), and the difference between multilocus and single-locus was significantly higher than zero ( = 0.077). These findings highlight that a few seeds are inbred lines as confirmed by the fixation index ( = 0.144, P< 0.05). Furthermore, the paternity correlation ( = 0.102) indicated a small number of full-sibs within progenies. The estimated relatedness coefficient within progenies ( ) was significantly higher (0.421) than that expected for half-sibs (0.25). The mean heritability coefficient among progenies ( = 0.956), as well as at the individual level ( = 0.634) and within a progeny ( = 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.

Maintenance of genetic diversity in Eucalyptus urophylla S. T. Blake populations with restriction of the number of trees per family

“…As N e is determined by the co-ancestry among individuals and inbreeding within individuals; and since without restriction some related individuals were selected, this resulted in a higher group of co-ancestry and lower N e than when selecting one tree per family. Maintenance of a high N e is important to avoid the loss of genetic diversity and allele fixation, which permits advancing genetic gain and is a buffer against stress (Lande and Barrowclough, 1987;Jurskis, 2005;Brawner et al, 2013;Bertoncini et al, 2017).…”

“…This result indicates also that some inbred individuals do not present inbreeding depression in the present population up to 3 years of age. Inbreeding has been observed in progeny trials of E. grandis open-pollinated seeds from two landraces in Brazil (Bertoncini et al, 2017), and in Eucalyptus globulus the effect of self-pollination was observed under field conditions months after planting (Hardner and Potts, 1994).…”