Enhancement of disease resistance and health-promoting properties of fresh fruits and vegetables by postharvest conditioning with controlled abiotic stresses

到目前为止，我们的目标一直是开发有效的新鲜水果和蔬菜的收获后保存方法。我们一直在积极寻求的一种方法是增强植物组织对疾病的自然防御能力，并通过适当剂量的UV-C来延缓衰老过程。其中一个令人感兴趣的防御机制是关于抗菌植物防御素对特定剂量的UV-C的反应。在拟议的计划中，我们采用了一种综合的方法，不仅可以诱导植物保护化合物和其他防御反应，而且还可以在新鲜农产品中积累有益于健康的化合物(营养食品)。由于植物次生代谢物的主要作用是保护植物免受生物和非生物胁迫，利用这一原理可以提高植物次生代谢物的水平。这种代谢产物的积累通常会导致植物暴露在非生物胁迫或信号分子中。因此，本研究的目的是通过在采后条件下用一定剂量的非生物胁迫和植物信号调节剂来提高植物防御和营养次生代谢物的水平，从而增强新鲜水果和蔬菜的抗病和促进健康的特性。首先将对胡萝卜进行研究，胡萝卜是一种长期储存的作物，但容易受到各种病原体的影响；胡萝卜含有植物防御素和抗癌化合物，其中一些化合物同时具有这两种活性。具体地说，这项研究涉及：(1)描述各种非生物胁迫的氧化胁迫强度，以及作为非生物胁迫诱导的次生代谢物基础的氧化还原信号和激素信号的分布，并确定选定作物的胁迫阈值；(2)筛选具有增强活性次生代谢物的潜在能力的应激和植物信号调节剂；(3)评估互补胁迫和/或胁迫与信号调节剂在增强理想次生代谢物方面的交叉作用；以及(4)评估在储存过程中响应于选定的胁迫而产生的活性化合物的抗病性和效价的动态，并探索保持其增强属性的方法。这种保存新鲜作物的新方法不仅有助于生鲜农产品行业延长作物的储存期，减少收获后的损失，而不需要诉诸化学程序，而且还有助于确保更健康的人口。

Our goal to date has been to develop effective post-harvest preservation methods for fresh fruits and vegetables. One approach that we have been actively pursuing is the intensification of the natural defenses of the plant tissue against diseases and delaying senescence process by hormetic doses of UV-C. One of the defense mechanisms of interest was on the elicitation of antimicrobial phytoalexins in response to hormetic doses of UV-C. In the proposed program, we entertain an integrated approach to elicit not only plant-protecting compounds and other defense reactions but also to accumulate health-beneficial compounds (nutraceuticals) in fresh produce. Since the major roles of plant secondary metabolites are to protect plants from biotic and abiotic stresses, it is conceivable that their levels can be enhanced using this principle. Accumulation of such metabolites often results in plants exposed to abiotic stresses or signal molecules. Thus the objective of this research is to enhance the disease resistance and health-promoting properties of fresh fruits and vegetables through elevating the levels of plant defense and nutraceutical secondary metabolites by post-harvest conditioning with hormetic doses of abiotic stresses and plant signal modulators in a controlled manner. Studies will be carried out initially with carrot which is a long-term storable crop but susceptible to various pathogens; and contains phytoalexins and anticancer compounds, some of which exhibit both activities. Specifically, the research involves: (1) characterization of various abiotic stresses for their oxidative stress intensity as well as profiles of redox signals and hormonal signals, that underlie abiotic stress-induced secondary metabolites, and the determination of the hormetic thresholds of the stresses in selected crops; (2) screening of hormetic doses of stresses and plant signal modulators for their potential to enhance active secondary metabolites; (3) evaluation of cross-interactions between complementary stresses and/or stresses and signal modulators in the enhancement of desirable secondary metabolites; and (4) evaluation of the dynamics of the disease resistance and titers of the active compounds elicited in response to selected stresses during storage and explore ways to maintain their enhanced attributes. Such a novel approach to the preservation of fresh crops will not only help the fresh produce industry to extend the storability of their crops and reduce post-harvest losses without resorting to chemical programs, but also help them to ensure a healthier population.