Genetic control of Eucalyptus urophylla and E. grandis resistance to canker caused by Chrysoporthe cubensis.

Lúcio Mauro Da Silva Guimarães,Acelino Couto Alfenas,Leonardo Novaes Rosse,Alexandre Alonso Alves,Marcos Deon Vilela De Resende,Douglas Lau

doi:10.1590/s1415-47572010005000069

Abstract

Chrysophorte cubensis induced canker occurs in nearly all tropical and subtropical regions where eucalypts are planted, causing losses in both wood quality and volume productivity, especially so in the warmer and more humid regions of Brazil. The wide inter and intra-specific genetic variability of resistance to canker among Eucalyptus species facilitates the selection of resistant plants. In this study, we evaluated resistance to this pathogen in five Eucalyptus grandis (G) and 15 E. urophylla (U) trees, as well as in 495 individuals from 27 progenies derived from crosses between the trees. In the field, six-months-old test seedlings were inoculated with C. cubensis. Lesion length in the xylem and bark was measured eight months later. The results demonstrated that xylem lesions could preferentially be used for the selection of resistant clones. Eight trees (7 U and 1 G) were susceptible, and the remainder (8 U and 4 G) resistant. Individual narrow and broad sense heritability estimates were 17 and 81%, respectively, thereby suggesting that canker resistance is quantitative and highly dependent on dominance and epistasis.

Highlights

Chrysophorte cubensis induced eucalypt canker is one of the most destructive diseases among plantation-raised Eucalyptus trees (Van Heerden and Wingfield, 2001)
The colonization of C. cubensis in host tissues was confirmed by re-isolating the fungus on PDA
The remaining parent trees (U1316, U1286, U1455, U1183, U1310, G547, U1282 and U1305) were susceptible, and in the case of U1183, U1310, G547, U1282 and U1305, mean xylem lesion lengths even exceeding those of susceptible control (SC) (Figure 2)

Summary

Introduction

Chrysophorte cubensis induced eucalypt canker is one of the most destructive diseases among plantation-raised Eucalyptus trees (Van Heerden and Wingfield, 2001). The disease, first reported by Bruner (1917) in Cuba, was initially attributed to Diaporthe cubensis Bruner. After the 1970’s, occurrence was reported in various regions of the world, but mainly in South America (Hodges et al, 1979; Van der Merwe et al, 2001), Africa (Gibson, 1981; Wingfield et al, 1989; Nakabonge et al, 2006) and southeastern Asia (Sharma et al, 1985; Davison and Coates, 1991). Hodges (1980) proposed transferring the eucalypt canker fungus to Cryphonectria cubensis (Bruner) Hodges.

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