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Abstract：
Water scarcity negatively impacts global crop yields and climate change is expected to greatly increase the severity of future droughts. The use of arbuscular mycorrhizal fungi (AMF) can potentially mitigate the effects of water stress in plants. Cassava is a crop that feeds approximately 800 million people daily. Genetically different isolates of the AMF R. irregularis as well as their clonal progeny have both been shown to greatly alter cassava growth in field conditions. Given that cassava experiences seasonal drought in many of the regions in which it is cultivated, we evaluated whether intraspecific variation in R. irregularis differentially alters physiological responses of cassava to water stress. In a first experiment, conducted in field conditions in Western Kenya, cassava was inoculated with two genetically different R. irregularis isolates and their clonal progeny. All cassava plants exhibited physiological signs of stress during the dry period, but the largest differences occurred among plants inoculated with clonal progeny of each of the two parental fungal isolates. Because drought had not been experimentally manipulated in the field, we conducted a second experiment in the greenhouse where cassava was inoculated with two genetically different R. irregularis isolates and subjected to drought, followed by re-watering, to allow recovery. Physiological stress responses of cassava to drought differed significantly between plants inoculated with the two different fungi. However, plants that experienced higher drought stress also recovered at a faster rate following re-watering. We conclude that intraspecific genetic variability in AMF significantly influences cassava physiological responses during water stress. This highlights the potential of using naturally existing variation in AMF to improve cassava tolerance undergoing water stress. However, the fact that clonal progeny of an AMF isolate can differentially affect how cassava copes with natural drought stress in field conditions, highlights the necessity to understand additional factors, beyond genetic variation, which can account for such large differences in cassava responses to drought.
摘要：
水资源短缺对全球作物产量产生负面影响，预计气候变化将大大增加未来干旱的严重程度。使用丛枝菌根真菌（AMF）可以潜在地减轻植物水分胁迫的影响。木薯是一种每天养活约8亿人的作物。AMFR的遗传上不同的分离株及其克隆后代均已被证明在田间条件下极大地改变了木薯的生长。鉴于木薯在许多种植地区经历季节性干旱，我们评估了不规则R.的种内变异是否差异改变了木薯对水分胁迫的生理反应。在第一个实验中，在肯尼亚西部的野外条件下进行，木薯接种了两种遗传上不同的不规则R。分离株及其克隆后代。所有木薯植物在干旱期间都表现出生理胁迫迹象，但是最大的差异发生在接种了两个亲本真菌分离株的克隆后代的植物之间。因为干旱没有在田间进行实验处理，我们在温室中进行了第二个实验，其中木薯接种了两种遗传上不同的R.regularis分离株并遭受干旱，然后重新浇水,允许恢复。木薯对干旱的生理胁迫反应在接种两种不同真菌的植物之间存在显着差异。然而,经历较高干旱胁迫的植物在重新浇水后也以更快的速度恢复。我们得出的结论是，AMF中的种内遗传变异性显着影响水分胁迫期间木薯的生理反应。这凸显了使用AMF中天然存在的变异来改善木薯在水分胁迫下的耐受性的潜力。然而,AMF分离株的克隆后代可以不同地影响木薯在田间条件下应对自然干旱胁迫的方式，强调了了解其他因素的必要性，超越遗传变异，这可以解释木薯对干旱反应的巨大差异。
