Clonal Variation of Eucalypts in Susceptibility to Bacterial Wilt Detected by Using Different Inoculation Methods

Abstract

Summary Four inoculation methods were investigated for assessing the clonal variation of eucalypts in susceptibility to bacterial wilt (Ralstonia solanacearum). The results showed that these inoculation methods obviously differed in the disease infection process, clonal variation and clonal mean repeatability in susceptibility of stock materials inoculated. For each inoculation method, the clonal effect was consistently significant over the assessment period. Root-collar suspension injection method (RSI) yielded the highest relative clonal variation (0.67±0.086) and clonal mean repeatability (0.92±0.038) in both disease infected incidence and severity at the end of assessment, attributable to the enhanced genetic variation or low environment effect. For a given inoculation method, an early assessment time might exist for maximizing relative clonal variation or repeatability. It is desirable in breeding to adopt an inoculation method and/or efficient assessment time with high clonal variance component, which would in turn improve the efficiency of clonal screening.

Ralstonia solanacearum and R. pseudosolanacearum on Eucalyptus: Opportunists or Primary Pathogens?

“…An essential requirement for a screening program is a reliable and reproducible inoculation method. In the case of Ralstonia species, artificial inoculations on Eucalyptus are rarely successful, i.e., inoculations either fail or inconsistent results are obtained ( Cruz and Dianese, 1986 ; Dianese et al, 1990 ; Dianese and Dristig, 1993 ; Coutinho et al, 2000 ; Wei et al, 2014 ). Fonseca et al (2016) described what they termed an “efficient method” to test for resistance of Eucalyptus to R. solanacearum but when attempted elsewhere ( Carstensen et al, 2017 ), the method failed to produce symptoms in a susceptible clone.…”

Integrated management of eucalyptus bacterial wilt in Sumatra, Indonesia.

“…Besides signi cant economic losses that might arise from plant mortality in the nursery, those asymptomatic mini-cuttings may also face stressful conditions in the eld and eventually express the disease symptoms (Coutinho and Wing eld 2017). Nevertheless, differences in the susceptibility of eucalyptus clones to Ralstonia species has been demonstrated previously (Wu and Liang 1988;Dianese et al 1990;Gan et al 2004;Wang et al 2011;Wei et al 2014;Fonseca et al 2016), representing an additional alternative on managing bacterial wilt. Resistance to bacterial wilt is a highly desirable trait not always readily available in the breeding population but may be introduced via controlled crosses followed by screening for resistant genotypes.…”

“…Liang 1988;Dianese et al 1990;Gan et al 2004;Wang et al 2011;Wei et al 2014;Fonseca et al 2016). Screening for disease resistance is particularly di cult for the pathosystem Rasltonia × Eucalyptus due to inconsistent reproducibility of symptoms even under controlled conditions, however, e cient inoculation methods have been studied previously and provided reliable protocols(Wei et al 2014;Fonseca et al 2016). In our study, the inoculation protocol was successfully implemented and helped to properly screen eucalyptus genotypes for resistance to bacterial wilt.…”