Rodriguez-Saona Cesar, Polashock James J, Kyryczenko-Roth Vera, Holdcraft Robert, Jimenez-Gonzalez Giovanna, De Moraes Consuelo M, Mescher Mark C
P.E. Marucci Center, Rutgers University, Lake Oswego, Chatsworth, NJ, United States.
Genetic Improvement of Fruits and Vegetables Lab, United States Department of Agriculture-Agricultural Research Service, Chatsworth, NJ, United States.
Front Plant Sci. 2021 Aug 12;12:700242. doi: 10.3389/fpls.2021.700242. eCollection 2021.
Synthetic elicitors of the salicylic acid (SA) and jasmonic acid (JA) plant defense pathways can be used to increase crop protection against herbivores and pathogens. In this study, we tested the hypothesis that elicitors of plant defenses interact with pathogen infection to influence crop resistance against vector and nonvector herbivores. To do so, we employed a trophic system comprising of cranberries (), the phytoplasma that causes false blossom disease, and two herbivores-the blunt-nosed leafhopper (), the vector of false blossom disease, and the nonvector gypsy moth (). We tested four commercial elicitors, including three that activate mainly SA-related plant defenses (Actigard, LifeGard, and Regalia) and one activator of JA-related defenses (Blush). A greenhouse experiment in which phytoplasma-infected and uninfected plants received repeated exposure to elicitors revealed that both phytoplasma infection and elicitor treatment individually improved and mass compared to uninfected, untreated controls; however, SA-based elicitor treatments reduced mass on infected plants. Regalia also improved survival. Phytoplasma infection reduced plant size and mass, increased levels of nitrogen (N) and SA, and lowered carbon/nitrogen (C/N) ratios compared to uninfected plants, irrespective of elicitor treatment. Although none of our elicitor treatments influenced transcript levels of a phytoplasma-specific marker gene, all of them increased N and reduced C/N levels; the three SA activators also reduced JA levels. Taken together, our findings reveal positive effects of both phytoplasma infection and elicitor treatment on the performance of and in cranberries, likely enhancement of plant nutrition and changes in phytohormone profiles, specifically increases in SA levels and corresponding decreases in levels of JA. Thus, we found no evidence that the tested elicitors of plant defenses increase resistance to insect herbivores or reduce disease incidence in cranberries.
水杨酸（SA）和茉莉酸（JA）植物防御途径的合成诱导子可用于增强作物对食草动物和病原体的抵抗力。在本研究中，我们检验了以下假设：植物防御诱导子与病原体感染相互作用，影响作物对传毒和非传毒食草动物的抗性。为此，我们采用了一个营养系统，该系统包括蔓越莓、导致假花病的植原体以及两种食草动物——钝鼻叶蝉（假花病的传毒媒介）和非传毒的舞毒蛾。我们测试了四种商业诱导子，包括三种主要激活与SA相关的植物防御的诱导子（阿砣、碧护和瑞加乐）和一种激活与JA相关防御的诱导子（布润仕）。在一个温室实验中，感染和未感染植原体的植物反复接受诱导子处理，结果表明，与未感染、未处理的对照相比，植原体感染和诱导子处理单独都提高了钝鼻叶蝉和舞毒蛾的体重；然而，基于SA的诱导子处理降低了感染植物上钝鼻叶蝉的体重。瑞加乐也提高了舞毒蛾的存活率。与未感染植物相比，无论诱导子处理如何，植原体感染都会使植物大小和重量减小，氮（N）水平和SA水平升高，碳/氮（C/N）比降低。尽管我们的诱导子处理均未影响植原体特异性标记基因的转录水平，但所有处理都提高了N含量并降低了C/N水平；三种SA激活剂还降低了JA水平。综上所述，我们的研究结果揭示了植原体感染和诱导子处理对蔓越莓中钝鼻叶蝉和舞毒蛾生长性能的积极影响，这可能是由于植物营养的增强和植物激素谱的变化，特别是SA水平的增加和JA水平的相应降低。因此，我们没有发现证据表明所测试的植物防御诱导子能增强蔓越莓对昆虫食草动物的抗性或降低疾病发生率。
