Abstract:

The purpose of this study is to identify the pathogen types of citrus bacterial canker disease in Zhanjiang area and screen effective bactericides. Lemon leaves were used as materials, and the strains were isolated and identified by tissue separation. The indoor toxicity of five bactericides to this pathogen was determined by inhibition zone test. The colony morphology of classic strain zlm1908 on nutrient agar medium (NA) was wax yellow, circular, entire, glistening, convex and mucoid. Citrus canker disease symptoms appeared obviously after reinoculating healthy lemon leaves. The strain zlm1908 was identified as Xanthomonas citri subsp. citri (Xcc) by physiological and biochemical reaction, specific primer amplification and sequence analysis. The EC₅₀ of five bactericides was 18.45 g/L, 14.99 g/L, 5.28 g/L, 14.60 g/L and 32.81 g/L, respectively. According to the analysis of EC₅₀ value, the inhibiting effect of Bacillus subtilis is the strongest among the five bactericides, followed by zhongshengmycin, copper dihydroxosulphate, copper hydroxide, while chlorobromoisocyanurate has the least inhibiting effect.

Key words: Xanthomonas citri subsp. citri (Xcc), pathogen identification, bactericide, toxicity test