稻瘟菌无毒基因AVR-Pikm的定位

 无毒基因是病原物中决定寄主抗病性表达与否的功能基因,其功能的丧失导致毒性小种的产生。在先前的研究中,本研究小组从稻瘟病菌中分离了与无毒基因AVR-Pik^m连锁的2个SCAR标记SCO12₉₄₆和SCE12₁₄₀₆。在本研究中,作者首先通过TAC克隆末端核苷酸序列的测定及其与70-15全基因组序列的比较,将这2个标记定位到稻瘟菌第1号染色体上;然后,利用稻瘟菌70-15全基因组草图序列和SSR技术,又分离了与无毒基因AVR-Pik^m连锁的4个SSR标记:SSR47T34、SSR50CA24、SSR52TAGG18和SSR56A28。进一步分析表明:上述4个SSR标记位于与SCO12₉₄₆和SCE12₁₄₀₆相反的一侧,与AVR-Pik^m位点的遗传距离分别为4.90、7.01、19.12和21.94cM,无毒基因AVR-Pik^m位于SCE12₁₄₀₆和SSRA7T34之间。本研究获得的稻瘟菌无毒基因AVR-Pik^m的精细定位为通过染色体步移克隆该基因奠定了基础。

Mapping of avirulence gene AVR-Pikm in Magnaporthe grisea

Avirulence genes,which determine if the specific resistance is expressed in host cultivars,are functional genes in pathogens.Lose of the gene function usually results in generation of virulent races in the pathogen population.In previous studies,two SCAR Sequence-characterized amplified region makers SCO12_ 946 and SCE12_ 1406 linked with avirulence gene AVR-Pik~m in M.grisea were isolated.In this investigation,the two SCAR markers were mapped on the chromosome I.On the basis of this result,four more DNA markers,SSR47T34,SSR50CA24,SSR52TAGG18 and SSR56A28 linked with AVR-Pik~m,were identified by utilizing the whole genome draft sequence of M.grisea 70-15 and SSR Simple sequence repeat technology.Further analysis indicated that the four SSR markers lay on the side opposite to the two SCAR markers;the genetic distance between the four SSR markers and AVR-Pik~m is 4.90,7.01,19.12,21.94 cM,respectively.This mapping will facilitate the isolation of AVR-Pik~m by chromosome walking.