Genetic mapping provides evidence for the role of additive and non-additive QTLs in the response of inter-specific hybrids of Eucalyptus to Puccinia psidii rust infection

Abstract

Eucalypts are susceptible to a wide range of diseases. One of the most important diseases that affect Eucalyptus plantations worldwide is caused by the rust fungus Puccinia psidii. Here, we provide evidence on the complex genetic control of rust resistance in Eucalyptus inter-specific hybrids, by analyzing a number of full-sib families that display different patterns of segregation for rust resistance. These families are totally unrelated to those previously used in other inheritance studies of rust resistance. By using a full genome scan with 114 genetic markers (microsatellites and expressed sequence tag derived microsatellites) we also corroborated the existence and segregation of a resistance locus, explaining 11.5% of the phenotypic variation, on linkage group 3, corresponding to Ppr1. This find represents an additional validation of this locus in totally unrelated pedigree. We have also detected significant additive 9 additive digenic interactions with LOD [10.0 on several linkage groups. The additive and epistatic QTLs identified explain between 29.8 and 44.8% of the phenotypic variability for rust resistance. The recognition that both additive and non-additive genetic variation (epistasis) are important contributors to rust resistance in eucalypts reveals the complexity of this host-pathogen interaction and helps explain the success that breeding has achieved by selecting rust-resistant clones, where all the additive and nonadditive effects are readily captured. The positioning of epistatic QTLs also provides starting points to look for the underlying genes or genomic regions controlling this phenotype on the upcoming E. grandis genome sequence.

Genetic variability in progenies of Eucalyptus dunnii Maiden for resistance to Puccinia psidii

“…Miranda et al (2013) observed strong genetic control associated with rust resistance between provenances of E. grandis. For resistance in interspecific Eucalyptus hybrids to P. psidii, Alves et al (2012) observed that quantitative additive and epistatic trait loci explain between 29.8 and 44.8% of the phenotypic variation, respectively. This is evidence of a more complex inheritance pattern of the trait.…”

Forest tree genomics: 10 achievements from the past 10 years and future prospects

“…Mapping studies have revealed a major contribution of both additive and non-additive (epistasis) genetic variation to disease resistance, supporting the hypothesis of complex interaction and possible successful clonal selection in which all genetic effects can be readily captured (Jorge et al 2005;Alves et al 2012). Thanks to association genetics, La Mantia et al (2013) …”

Resistance of Eucalyptus pellita to rust (Puccinia psidii)

“…However, to ensure the long-term success and to simplify the selection of resistant progeny plants, the genetic control of the trait must be known for the transfer of resistance using controlled crosses. The inheritance of rust resistance in eucalypts, studied since the early 2000s (Junghans et al 2003a, Teixeira et al 2009, Rosado et al 2010, Alves et al 2011b, has shown different models to explain the segregation patterns. In the present study, we tested three models of the genetic control of resistance based on major-effect genes to explain the resistance segregation in progenies of E. pellita (Table 2).…”

“…Recently, the locus Ppr1 was placed on a genetic reference map of eucalypts in linkage group 3 and was validated in two unrelated families, confirming the hypothesis that Ppr1 controls a great portion of the variation in rust resistance (Mamani et al 2010). However, further studies, particularly in interspecific hybrids progenies indicated that the genetic control of rust resistance is complex (Teixeira et al 2009, Alves et al 2011b). …”