Genetic mapping and validation of QTLs associated with resistance to Calonectria leaf blight caused by Calonectria pteridis in Eucalyptus

Abstract

Calonectria leaf blight (CLB) caused byCalonectria pteridis is one of the main leaf diseases in Brazilian Eucalyptus plantations in warm climates with prolonged periods of rain. The main symptoms are leaf spots followed by intense defoliation in highly susceptible plants.Exploiting the existing inter-and intraspecific variability for defoliation is the best option to control this disease. Nevertheless, nothing is known about the genetic architecture of resistance to CLB in Eucalyptus. We built microsatellitebased genetic maps for E. urophylla × E. camaldulensis (EU11×EC06) F1 family of 89 plants. Four or five clonal replicates per individual offspring were clonally propagated, totalling 445 plants which were phenotyped for defoliation in the basal third of the branches at 30 days following controlled inoculation with a single-spore isolate. Genetic mapping was performed using a pseudo-testcross, and QTLs detected using composite interval mapping. Five QTLs were detected for resistance to CLB; of them, only one could be validated in two unrelated pedigrees, and its effect was conservatively estimated as controlling between 5 and 10 % of the phenotypic variation when the bias derived from the limited size of the mapping population was taken into account. This work provides a starting point for future studies of the genetics of resistance to CLB, and adds further evidence to the challenge of ascertaining the effects of QTLs detected in a single biparental background across unrelated families.

Phosphorus, nitrogen and potassium nutrition on Calonectria leaf blight in eucalypt plants

“…This isolate is highly aggressive to eucalypt and has been used in the evaluation of resistance of Corymbia, Eucalyptus species and hybrids (Alfenas et al, 2016;Zarpelon et al, 2015). Disks from the monospore culture of the fungus were transferred to Petri dishes containing ODA medium (7% oat, 2% dextrose and 2% agar).…”

“…Dissemination of fungal spores is mainly by wind (Mohanty, Pandey, Arya, & Harsh, 2012). The planting of resistant clones is the most efficient and economical method for CLB control in eucalypt plantations Crous, 2002;Zarpelon et al, 2015). The planting of resistant clones is the most efficient and economical method for CLB control in eucalypt plantations Crous, 2002;Zarpelon et al, 2015).…”

Brief history of Eucalyptus breeding in Brazil under perspective of biometric advances

“…Authors identified QTLs for Eucalyptus traits, such as growth, disease resistance and wood properties (GRATTAPAGLIA et al, 1996;THAMARUS et al, 2004;THUMMA et al, 2010;ZARPELON et al, 2015). However, for selection purposes, QTLs have not shown good results for traits with low h² (RESENDE et al, 2008).…”

Screening of Corymbia and Eucalyptus species for resistance to Calonectria pteridis leaf blight

“…Recently, five Quantitative Trait Loci associated with resistance to CLB in Eucalyptus urophylla x E. camaldulensis (EU11 × EC06) were detected by Zarpelon et al. () providing a starting point for future studies of the genetics of resistance to CLB.…”

“…The use of resistant genotypes is the best method for CLB control, because observations in the field under natural infection and results of inoculations under controlled conditions indicate the existence of inter-and intraspecific variability for resistance in eucalypt Fonseca et al 2010). Recently, five Quantitative Trait Loci associated with resistance to CLB in Eucalyptus urophylla x E. camaldulensis (EU11 9 EC06) were detected by Zarpelon et al (2015) providing a starting point for future studies of the genetics of resistance to CLB.…”