柑桔溃疡病菌抗药突变体的生理特性研究

 经药剂驯化和紫外光诱导双重作用可获得柑桔溃疡病菌抗拌种灵突变体(XcR),病原菌抗药突变频率低于10-6。Xc R的生长速率与敏感菌株基本一致,对萎锈灵和叶枯唑具有潜在的正交互抗性,与浸种灵没有交互抗性。XcR胞外产物和胞外水解酶活性一般多于或高于敏感菌株,其中以淀粉酶活性变化最为明显。Xc R琥珀酸脱氢酶活性显著降低,并对拌种灵的敏感性亦降低。XcR能够引起烟草的过敏性反应,但失去对寄主的致病性。Xc R的性质表明,柑桔溃疡病菌对拌种灵产生抗药性的风险较低,病原菌获得抗药性状的同时可能导致其在田间的适合度下降。琥珀酸脱氢酶的活性可作为柑桔溃疡病菌抗药性的标记。

Physiological characters of the resistant mutant of Xanthomonas citri to amicarthiazol

The resistant mutant of X. citri (XcR) to amicarthiazol was obtained by dual treatments with amicarthiazol ta- ming and ultraviolet irradiation with a frequency lower than 10 -6. XcR possessed the similar growth velocity as the sensitive isolate (XcS), and had positive cross resistance to carboxin and bismerthiazol fungicides, but not to diisothiocyanatomethane. Investigation on physiological characters showed that XcR could secrete extracellular enzymes, such as amylase, pectase, cellulosase, proteinase and lipase. The bioactivities of these enzymes were usually higher than that of XcS, especially for amylase. The activity of succinate dehydrogenase of XcR was obviously reduced and not sensitive to the inhibition of amicarthiazol. Moreover, XcR could induce the hypersensitive reaction of tobacco leaves but lost the pathogenicity to ci- trus leaves. The characters of XcR indicated that the resistance of X. citri to amicarthiazol occurred with low frequency and accompanied with reduced fitness of XcR in field. The activity changes of succinate dehydrogenase could be used to tag the occurrence of resistance of X. citri to amicarthiazol fungicide.