Fontes-Puebla Ana A, Bernal Julio S
Department of Entomology, Texas A&M University, College Station, TX, United States.
Front Plant Sci. 2020 Feb 27;11:223. doi: 10.3389/fpls.2020.00223. eCollection 2020.
Plants may defend against herbivory and disease through various means. Plant defensive strategies against herbivores include resistance and tolerance, which may have metabolic costs that affect plant growth and reproduction. Thus, expression of these strategies may be mediated by a variety of factors, such as resource availability, herbivory pressure, and plant genetic variation, among others. Additionally, artificial selection by farmers and systematic breeding by scientists may mediate the expression of resistance and tolerance in crop plants. In this study, we tested whether maize defense against Western corn rootworm (WCR) was mediated by the crop's domestication, spread, and modern breeding. We expected to find a trend of decreasing resistance to WCR with maize domestication, spread, and breeding, and a trend of increasing tolerance with decreasing resistance. To test our expectations, we compared resistance and tolerance among four plants spanning those processes: Balsas teosinte, Mexican landrace maize, US landrace maize, and US inbred maize. We measured the performance of WCR larvae as a proxy for plant resistance, and plant growth as affected by WCR feeding as a proxy for plant tolerance. Our results showed that domestication and spread decreased maize resistance to WCR, as expected, whereas breeding increased maize resistance to WCR, contrary to expected. Our results also showed that maize resistance and tolerance to WCR are negatively correlated, as expected. We discussed our findings in relation to ecological-evolutionary hypotheses seeking to explain defense strategy evolution in the contexts of plant resistance-productivity trade-offs, plant tolerance-resistance trade-offs, and varying resource availability vis-à-vis plant physiological stress and herbivory pressure. Finally, we suggested that defense strategy evolution in maize, from domestication to the present, is predicted by those ecological-evolutionary hypotheses.
植物可以通过多种方式抵御食草动物和疾病。植物针对食草动物的防御策略包括抗性和耐受性，这可能会产生影响植物生长和繁殖的代谢成本。因此，这些策略的表达可能受到多种因素的介导，例如资源可用性、食草压力和植物遗传变异等。此外，农民的人工选择和科学家的系统育种可能会介导作物中抗性和耐受性的表达。在本研究中，我们测试了玉米对西部玉米根虫（WCR）的防御是否由作物的驯化、传播和现代育种所介导。我们预计会发现随着玉米的驯化、传播和育种，对WCR的抗性有下降趋势，以及随着抗性下降耐受性有上升趋势。为了检验我们的预期，我们比较了跨越这些过程的四种植物的抗性和耐受性：巴尔萨斯野生玉米、墨西哥地方品种玉米、美国地方品种玉米和美国自交系玉米。我们测量了WCR幼虫的表现作为植物抗性的指标，以及受WCR取食影响的植物生长作为植物耐受性的指标。我们的结果表明，如预期的那样，驯化和传播降低了玉米对WCR的抗性，而育种却增加了玉米对WCR的抗性，这与预期相反。我们的结果还表明，正如预期的那样，玉米对WCR的抗性和耐受性呈负相关。我们结合生态进化假说讨论了我们的发现，这些假说试图在植物抗性 - 生产力权衡、植物耐受性 - 抗性权衡以及相对于植物生理压力和食草压力的不同资源可用性的背景下解释防御策略的进化。最后，我们认为从驯化到现在，玉米防御策略的进化是由那些生态进化假说所预测的。
