Evaluation on drought tolerance in sweet potato and cassava

本研究旨在研究甘薯和木薯的根系发育和可塑性与其抗旱性的关系。在迄今为止建立或收集的巨大遗传库中，每个物种都选择了几个基因类型用于本研究。具体地说，我们进行了一系列的盆栽和根箱试验，以评估在不同生长阶段、不同时期和不同程度的高根区温度胁迫和干旱胁迫下两种植物的根系发育。主要研究结果如下：1)高根区温度促进了地上部的生长，但总体上抑制了整个根系的发育，但促进了高分枝级(2级和3级)侧根的发育；2)两种树种对干旱胁迫都非常敏感，干旱胁迫一般会降低地上部和根系的生长。但旱后复水尤其促进了高分枝级侧根的发育；3)对干旱的反应也存在着基因差异。每种植物都有一种在干旱条件下维持或增加根系生长的基因(cv.甘薯和品种的VSP-2。木薯的PSR-74)。此外，我们还走访了菲律宾莱特的四块种植了不同甘薯品种的农民田地，调查了其根系发育和土壤理化条件，以验证盆栽试验的结果。此外，目前正在进行田间试验，以评估田间的耐旱性，包括水分关系和田间根系发育。为此，目前正在建造一个雨棚。因此，在这项研究中，我们展示了根系对土壤胁迫的发育和响应，土壤胁迫是根茎作物中研究最少的部分。仍在继续努力完成实验和调查，并组织数据以供发布。

This study aimed to examine the root system development and plasticity in sweetpotato and cassava in relation to their drought tolerance. Among the huge genetic stock developed or collected so far, several genotypes for each species were selected for this study. Specifically, we have conducted a series of pot and root box experiments to evaluate the root system development in both species under high root-zone temperature stress and drouht stress imposed at different growth stages, for various periods and degrees. Major findings were : 1) high root-zone temperature promoted the shoot growth, while it inhibited the whole root system development in general, but development in the lateral roots of high branching orders (2nd and 3rd) was promoted ; 2) both species were very sensitive to drought stress which generally reduced shoot and root growth. However, rewatering after drought promoted especially the development of lateral roots of high branching orders ; 3) genotypic differences were also noted in the responses to drought. There was a genotype in each species that maintained or increased root growth under drought (cv. VSP-2 for sweetpotato and cv. PSR-74 for cassava). Besides, four farmers' fields in Leyte, Philippines, planted with different sweetpotato varieties were visited, in which we surveyed the root system development and soil physical and chemical conditions so that the results of the pot experiments be verified. In addition, field experiments are now being attempted to evaluate the drought tolerance including water relations and the root system development in the field. For the purpose, a rain shelter is being constructed at the moment. As such, in this study, we showed the development and responses of the root system to the soil stresses which are the least-studied part of the root crops. Efforts still continue to complete the experiments and survey, and organize the data for publication.