Abstract: Eighty plants from the F₁ population of Ichang Papeda 2586 (resistant genotype) × Lingnan Shatian Pummelo (susceptible genotype) were inoculated with citrus canker [Xanthomonas axonopodis pv.citri (Xac)] for resistance evaluation in field. The results revealed that resistance segregation in the F₁
progenies was significant, and the ratio of resistant and susceptible plants was close to 1︰1. If immune and highly resistant types were regarded as disease resistance and moderate resistance, moderate susceptible and susceptible were regarded as susceptible types. A SSR molecular marker CCR-110
putatively related with resistance of citrus canker was obtained based on BSA(Bulked Segregant Analysis).Validation analysis of the marker was performed using F1 segregation population tested and resistant and susceptible genotypes generally known. Marker CCR-110 was found to show good resistance relevancy. Co-segregation analysis showed that correlation coefficient between the marker and citrus canker resistance was 0.79. The recombination frequency was calculated with maximum likelihood method
and transformed into centimorgans(cM) according to the Kosambi function. The recombination frequency is 9.38%±3.5% and genetic distance is 9.11 cM. The marker was not found in susceptible genotypes (sweet orange, pummelo and trifoliate orange), but it was observed in most resistant ones (Kumquat,
Ichang Papeda, Yuzu, and mandarin).

Key words: Citrus, citrus canker, resistance test, molecular marker