Division of Plant Industry, CSIRO, Canberra, Australia.
Theor Appl Genet. 1978 Jul;51(4):177-84. doi: 10.1007/BF00273143.
The effects of the widespread use of "dirty crop" or "partially resistant" multilines on the racial composition of a pathogen population were investigated using simple theoretical models. It was found that the evolutionary changes in the pathogen attacking multiline varieties depend critically on two factors - the level of selection against unnecessary genes for virulence(s) and the number of lines in the multiline (n): (i) If s>0.5, then multilines will stabilize the racial composition of the pathogen population and simple races, carrying a single gene for virulence, will be the predominant biotypes. (ii) If s< 1/2 (n - 1) when unnecessary genes for virulence are additive in their effects in reducing pathogen fitness, or s< 1/n when unnecessary virulence genes act multiplicatively to reduce pathogen fitness, then the use of a multiline will lead to the development of a superrace which can simultaneously attack all the component lines. (iii) If 1/2> s>1/2 (n-1) for the additive model, or 1/2> s>1/n for the multiplicative model, the use of multiline varieties will stabilize the pathogen population, but with complex races, carrying two or more virulence genes, predominant. These findings are discussed in relation to the potential of multiline varieties as a means of achieving stable, long-term control of plant diseases. It is concluded that "dirty crop" and "partially resistant" multilines will provide stable disease control in crop plants only in limited and relatively rare circumstances.
采用简单的理论模型研究了“脏种子”或“部分抗性”多系在病原菌群体的种族组成上的广泛应用的影响。研究发现，病原菌攻击多系品种的进化变化取决于两个因素：（i）如果 s>0.5，那么多系将稳定病原菌群体的种族组成，携带单一毒性基因的简单种系将成为主要生物型。（ii）如果 s<1/2(n-1)（毒性基因在降低病原菌适应度方面具有累加效应）或 s<1/n（毒性基因具有相乘效应以降低病原菌适应度），那么使用多系将导致超级种系的发展，该种系能够同时攻击所有的组成系。（iii）如果对于累加模型，1/2> s>1/2(n-1)，或者对于相乘模型，1/2> s>1/n，则多系品种的使用将稳定病原菌群体，但主要是携带两个或更多毒性基因的复杂种系。这些发现与多系品种作为实现植物病害长期稳定控制的手段的潜力有关。结论是，只有在有限的和相对罕见的情况下，“脏种子”和“部分抗性”多系才能在作物中提供稳定的病害控制。
