School of Plant Biology and Australian Herbicide Resistance Initiative, University of Western Australia, 35 Stirling Hwy, Crawley, WA 6009, Australia.
J Theor Biol. 2011 Aug 21;283(1):14-27. doi: 10.1016/j.jtbi.2011.05.010. Epub 2011 May 23.
Evolution of herbicide resistance in weeds is a growing problem across the world, and it has been suggested that low herbicide rates may be contributing to this problem. An individual-based simulation model that represents weed population dynamics and the evolution of polygenic herbicide resistance was constructed and used to investigate whether using lower herbicide rates or standard rates at reduced efficacy could reduce the sustainability of cropping systems by causing faster increases in weed population density as herbicide resistance develops. A number of different possible genetic bases for resistance were considered, including monogenic resistance and polygenic resistance conferred by several genes. The results show that cutting herbicide rates does not affect the rate at which weed densities reach critical levels when resistance is conferred exclusively by a single dominant gene. In some polygenic situations, cutting herbicide rates substantially reduces sustainability, due to a combination of faster increase in resistance gene frequency and reduced kill rates in all genotypes, while in other polygenic situations the effect is small. Differences in sustainability depend on combined strength of the resistance genes, variability in phenotypic susceptibility and rate delivered, level of control due to alternative measures, and degree of genetic dominance and epistasis. In the situation where resistance can be conferred by both a single dominant major gene or a number of co-dominant minor genes in combination, the difference made by low rates depends on the relative initial frequency of the major and minor genes. These results show that careful consideration of herbicide rate and understanding the genetic basis of resistance are important aspects of weed management.
杂草抗药性的进化是全球范围内一个日益严重的问题，有人认为低剂量的除草剂可能是导致这一问题的原因之一。本研究构建了一个基于个体的模拟模型，用于描述杂草种群动态和多基因除草剂抗性的进化，并用于研究使用较低的除草剂剂量或降低效果的标准剂量是否会通过加速杂草种群密度的增加，从而导致作物系统的可持续性降低，因为抗药性的发展。考虑了多种不同的可能遗传基础的抗性，包括单基因抗性和由多个基因赋予的多基因抗性。结果表明，当抗性仅由单个显性基因赋予时，降低除草剂的使用剂量不会影响杂草密度达到临界水平的速度。在某些多基因情况下，由于抗性基因频率的快速增加和所有基因型的杀伤率降低的综合作用，降低除草剂的使用剂量会极大地降低可持续性，而在其他多基因情况下，这种影响较小。可持续性的差异取决于抗性基因的综合强度、表型易感性和剂量的可变性、替代措施的控制水平以及遗传显性和上位性的程度。在抗性可以由单个显性主基因或多个共显性微基因的组合赋予的情况下，低剂量的差异取决于主基因和微基因的相对初始频率。这些结果表明，仔细考虑除草剂的使用剂量和理解抗性的遗传基础是杂草管理的重要方面。
