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 Zea 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.

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La enfermedad Huanglongbing (HLB) de los cítricos aun no ha sido diagnosticada en Sonora. Actualmente se lleva a cabo un plan regional para el manejo del psílido asiático de los cítricos, Diaphorina citri. En áreas citrícolas con producción orgánica, el uso de insecticidas sintéticos se encuentra contemplado solo si la enfermedad del HLB es diagnosticada en ellas. Es por ello, que se planteó la búsqueda de productos alternativos efi caces para uso orgánico con diferentes mecanismos de acción. En árboles de naranja valencia en desarrollo se probaron 8 productos orgánicos, Acceem ® , Cassia ® , Java ® , Knockout ® , Mosei ® y Oroboost ® (1 mL/L), Gardytec ® +Agrosiamil ® (1,5:1,5 mL/L), PureSpray ® (2,5 mL/L) y un control, Muralla Max ® (0,25 mL/L). Aplicados por aspersión sobre ninfas y adultos de D. citri, con muestreos a los 5 y 10 días después de la aplicación (DDA). Los mejores resultados se observaron a los 5 DDA, con una efi cacia de 98,45%, 78,93% y 74,52%, para Oroboost, Mosei y Agro-siamil+Gardytec respectivamente. Los productos probados funcionaron solamente sobre estadios ninfales.

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 Zea plants spanning those processes: Balsas teosinte, Mexican landrace maize, US landrace maize, and US inbred maize. We measured 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.

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258 words) Plant physiological processes generally are regulated by phytohormones, including plant biochemical responses to herbivory. Here, we addressed whether a suite of maize (Zea mays mays) phytohormones, including some precursor and derivative metabolites, relevant to herbivory defence were mediated by the crop's domestication, northward spread, and modern breeding. For this, we compared phytohormone and metabolite levels among four plant types representing the evolutionary and agronomic transitions from maize's wild ancestor, Balsas teosinte (Zea mays parviglumis), to Mexican and US maize landraces, and to highly-bred US maize cultivars, as affected by root herbivory by Western corn rootworm (Diabrotica virgifera virgifera). Following ecological-evolutionary hypotheses, we expected to find changes in: (i) maize defence strategy, from reliance on induced to constitutive defences; (ii) levels of phytohormones relevant to herbivore resistance consistent with gradual weakening of defences, and; (iii) levels of a phytohormone relevant to herbivory tolerance because it positively affects plant growth. We found that with its domestication, maize seemed to have transitioned from reliance on induced defences in Balsas teosinte to reliance on constitutive defences in maize. Also, we found that while one subset of phytohormones relevant to herbivory was suppressed (13-oxylipins), another was enhanced (9-oxylipins) with domestication, and both subsets were variably affected by spread and breeding. Finally, an auxin phytohormone directly linked to growth (indole-3acetic acid), increased significantly with domestication, and seemingly with spread and breeding. We concluded that rootworm defences in maize were mediated by domestication and ensuing processes, such as spread and breeding, and argued that agricultural intensification mediated maize defence evolution in parallel with modern breeding.