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1978年,在田间研究了水稻(OryzaSativa L.)58个抗白叶枯病Xanthomonas campestris pv Oryzae(Ishi yama1972Dye)品种的遗传方式和基因的等位关系。由抗病品种和感病品种“TNI”杂交组合F_1和F_2群体的分析揭示了48个品种的抗性变由单一显性基因控制,其余的10个品种的抗性变单一隐性基因操纵。等位基因测验表明这48个品种具有Xa4抗性基因,8个品种的隐性抗性基因与Xa5等位。然而,“Khao Lay Nhay”和“Sateny”品种的隐性抗性基因彼此是等位的,与Xa3、Xa4、Xa5、Xa7和Xa8不等位且可独立分离。这个新的隐性基因同Xa6连锁,其同型染色体局部交换值为5.9％。因而,品种“Khao Lay Nhay”和“Sateng”有新的抗性基因,这种基因定名为Xag。水稻白叶枯病(Xanthomonasc ampestris pv.oryzae)是亚洲分布最广的一种水稻病害。早在1930年代,日本就开始系统研究寄主植物对白叶枯病的抗性并鉴定出许多抗日本菌系的品种(Mizukami1966,Ezuka和Horino1974)。研究了对日本菌系的抗性遗传并鉴定出三个抗性位点(Nishimura和Sakaguchi 1959,Sakaguchi 1967和Ezuka等1975)。把这三个位点叫做Xa1、Xa2、Xa3。在热带地区,早在1960年代,国际水稻研究所(IRRI)开始系统研究水稻白叶枯病并鉴定了3000多个抗病品种。近10年间,在进行遗传研究的基础上,鉴定出抗菲律宾菌系的另外5个抗性基因(Xa4、Xa5、Xa6、Xa7和Xa8)(Petpisit等1977;Olufowote等1977;Sidhu和Khushl978;Siolhu等1978)。其中,Xa4和Xa5分布最广。这两个基因彼此独立分离。Xa6与Xa4连锁(Sidhu和Khush 1978)。在IRRI和其它地方Xa4、Xa5和Xa6被广泛地用于育种计划,为了鉴定另外的抗性基因,进行了本研究。
In 1978, the genetic patterns and allelic relationships of 58 Xanthomonas campestris pv Oryzae (Ishi yama1972Dye) cultivars resistant to bacterial leaf blight in rice (OryzaSativa L.) were studied in the field. Analysis of F_1 and F_2 populations from the resistant and susceptible “TNI” crosses revealed that the resistance of 48 cultivars was controlled by a single dominant gene and that of the remaining 10 cultivars by a single recessive gene. Allele tests showed that these 48 cultivars had Xa4 resistance genes, and eight cultivars had recessive resistance genes with Xa5 alleles. However, the recessive resistance genes of “Khao Lay Nhay” and “Sateny” varieties are allelic to each other and are not separated from Xa3, Xa4, Xa5, Xa7 and Xa8 and can be isolated independently. This new recessive gene, linked to Xa6, has a 5.9% local exchange of its homologous chromosomes. Thus, the varieties “Khao Lay Nhay” and “Sateng” have new resistance genes, which are called Xag. Rice bacterial blight (Xanthomonas ampestris pv. Oryzae) is the most widely distributed rice disease in Asia. As early as the 1930s, Japan began a systematic study of host plant resistance to bacterial blight and identified many strains of anti-Japanese strains (Mizukami 1966, Ezuka and Horino 1974). Resistance inheritance to Japanese strains was studied and three resistance sites were identified (Nishimura and Sakaguchi 1959, Sakaguchi 1967 and Ezuka et al. 1975). Call these three sites Xa1, Xa2, Xa3. In the tropics, as early as the 1960s, the International Rice Research Institute (IRRI) began a systematic study of bacterial leaf blight and identified more than 3,000 resistant varieties. In the past 10 years, five additional resistance genes (Xa4, Xa5, Xa6, Xa7 and Xa8) against the Philippine strain have been identified based on genetic studies (Petpisit et al. 1977; Olufowote et al. 1977; Sidhu and Khushl 1977; Et al. 1978). Among them, Xa4 and Xa5 the most widely distributed. The two genes are separated from each other. Xa6 is linked to Xa4 (Sidhu and Khush 1978). In IRRI and elsewhere Xa4, Xa5 and Xa6 are widely used in breeding programs, and this study was conducted in order to identify additional resistance genes.