辣椒疫霉对烯酰吗啉的敏感性基线及室内抗药突变体研究

 采用菌丝生长速率法测定了125株采自河北、内蒙古、陕西、安徽和北京等地区的辣椒疫霉病菌对烯酰吗啉的敏感性,结果表明,其EC₅₀值分布于0.126~0.318μg/mL之间,最不敏感菌株是最敏感菌株的2.5倍,平均EC₅₀=(0.218±0.0368)μg/mL。125个菌株对烯酰吗啉的敏感性分布呈单峰曲线,未出现抗性的病原菌亚群体,可将该单峰曲线作为辣椒疫霉对烯酰吗啉的敏感性基线,将烯酰吗啉对该病原群体的平均EC₅₀值作为田间抗药性监测的参考标准。通过紫外诱变敏感菌株N-7的菌丝获得了12株抗烯酰吗啉的突变体,抗性指数在16.38~132.15之间;通过紫外诱变敏感菌株DZ-16的游动孢子获得1株抗性指数为680倍的高抗药水平的突变体。突变体的部分生物学性状研究表明,其致病力与敏感菌株相当;大部分突变体产生孢子囊的能力与亲本菌株相比均有不同程度的提高;离体条件下,突变体和亲本菌株释放游动孢子的能力相当;突变体的菌丝生长速率与亲本菌株相比具有不同程度的差异。测定了敏感亲本菌株和突变体的交配型,均为A1型菌株,经紫外诱变后交配型没有发生改变。综合分析表明,抗性突变体的产生有利于抗药性群体的发展。为避免和延缓抗药性的产生,生产上应将烯酰吗啉与其它无交互抗药性的杀菌剂交替使用。

Baseline sensitivity and laboratory mutants of Phytophthora capsici resistant to dimethomorph

The sensitivity to dimethomorph of 125 Phytophthora capsici strains collected from Hebei, Mongolia, Shannxi, Anhui and Beijing were determined by mycelia growth inhibition method. The results showed that EC_(50) values ranged from 0.126 -0.318 μg/mL. EC_(50) of the most insensitive strains was 2. 5 folds of the most sensitive ones with a mean of 0.218 0.0368 μg/mL . The sensitivity frequency of P. capsici to dimethomorph distributed as a unimodel curve, which showed there was no resistant subpopulation among these isolates , so this sensitivity baseline was suitable for resistance monitoring of P. capsici to dimethomorph. 12 resistant mutants to dimethomorph were obtained from N-7 parental strain in vitro by UV- irradiating,and the resistant factors ranged from 16.38-132.15 folds. One very high resistant mutant with 680 folds resistance factor was also selected from DZ-16 strain. The parental strains and their mutants were investigated for mating type. Some biological characteristics of mutants were studied in laboratory. The results indicated that the mutants possessed consistent pathogenicity with their parental strains. As compared to their original strain, sporulation ability of resistant mutants were increased in vivo, the quantity of asexual spores corresponded to that of sensitive strains in vitro and the resistant mutants exhibited diversity in mycelial growth rate. All the strains were A_1 mating type. Based on the above, the resistant mutants would favor the development of dimethomorph resistant population. It was suggested that the dimethomorph should be used alternately with other no cross-resistant fungicides to avoid or delay the development of resistance.