二倍体及四倍体中抗叶锈病基因在双二倍体中的表达与抑制

 通过杂交将近缘植物中的抗病基因导入普通小麦是抗病育种的常用方法。在利用二倍体和四倍体杂交合成双二倍体小麦过程中, 二倍体或四倍体携带的抗叶锈病基因在双二倍体中大多数情况下可以完全表达或部分表达其固有的抗病性, 但部分抗叶锈病基因则不能表达。四倍体波斯小麦Ps5、Ps8和野生二粒小麦D s3含有相同的抗叶锈病基因LrPs (暂定名), 在双二倍体Am1、Am2、Am3、Am5和Am7中可以表达其抗病性, 但在Am4中不能表达;二倍体粗山羊草Ae37含有Lr41和未知基因, 但Lr41在双二倍体Am2中不能表达;四倍体硬粒小麦Dr147携带Lr23和未知基因, 在双二倍体Am6中不能充分表达。抑制基因的存在是导致抗病基因不能表达或部分表达的主要原因之-。抑制基因位于AB染色体组或D染色体组上, 其抑制作用对抗病基因和病菌致病类型具有专化性, 还可能受温度等环境条件和寄主遗传背景等因素的影响。遗传分析结果表明, 在常温下, 双二倍体Am1、Am2、Am3和Am5对叶锈菌致病类型DGS/HB的抗病性均由1对相同的隐性抗病基因LrPs (暂定名)控制, 与它们具有共同的四倍体亲本Ps5有关。Am4不具有苗期抗叶锈病基因, 但含有来自粗山羊草A e39的1对隐性抑制基因SuLrPs (暂定名), 可抑制Am1、Am2、Am3和Am5中隐性抗叶锈病基因的表达。对抗病抑制基因存在原因和遗传分析验证方法等进行了讨论。

Expression and suppression of leaf rust resistance genes in amphidiploids from crosses of diploids and tetraploids

A great deal of effort has been made on establishment of genetic diversity by seeking resistance genes from alien genetic materials of wheat and subsequently incorporating into cultivated wheat.Seven synthetic amphidiploids Am1-Am7,obtained from the crosses of four tetraploids,Ps5(Triticum carthlicum var.darginicum),Ps8(T.carthlicum var.fuligioscum),Ds3(T.diccoides var.fuligioscum),Dr147(T.durum Desf.) and five T.tauschii spp.,and their parents were tested with eighteen pathotypes of Puccinia triticina at seedling stage.The expression of leaf rust resistance genes in amphidiploids from diploids and tetraploids was investigated.As the results indicated,the level of leaf rust resistance based on the infection types could be expressed or partially expressed in the synthetic amphidiploids in most instance compared with that in one or both parents,respectively,but in some instance the level of leaf rust resistance was significantly reduced.The same leaf rust resistance gene(s) LrPs(temporary designation) were postulated in tetraploids Ps5,Ps8 and Ds3,and LrPs could express its(theirs) resistance in amphidiploids Am1,Am2,Am3,Am5 and Am7 except Am4.Lr23 and unknown leaf rust resistance gene(s),postulated in the durum wheat Dr147,were partially expressed in amphidiploid Am6.Diploid Ae37 possessed Lr41 and unknown gene(s),but Lr41 was completely unexpressed in amphidiploid Am2.It was the suppressor(s) in the synthetic amphidiploids when crossed tetraploids with diploids that leading to the unexpression or partially expression of resistance.The suppressor(s) for leaf rust resistance occurred in T.tauschii(Coss.) Schmal Ae39 or T.carthlicum var.darginicum Ps5.The suppressor(s) had a specific mode of action to the resistance genes from parents and the pathotypes of P.triticina,and the suppression could be affected by the background of host and/or environment factors,such as temperature.The results of genetic analysis also suggested that the resistance of Am1,Am2,Am3 and Am5 to DGS/HB of P.triticina was controlled by a same recessive resistance gene from parental Ps5 at room temperature,and that Am4,without any leaf rust genes,possessed a recessive suppressor SuLrPs(temporary designation),which could inhibit the expression of the recessive resistance gene in Am1,Am2,Am3 and Am5.The existence reasons of suppressor and the verification methods in genetic analysis were discussed in this paper.