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

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.