Survey for genetic resources in tropical rootcrops in relation to drought resistance

本研究是与菲律宾莱特州立大学根茎作物研究和培训中心合作进行的，目的是评估木薯和甘薯耐旱性的基因型变异，并确定与耐旱性密切相关的性状。除了该中心的收集外，我们还从菲律宾几个干旱易发地区收集了一些基因型。对块根作物种植户的几项调查表明，农民对持续采用某一品种的决策策略问题不同于偏好种植某一品种的问题。前者涉及的不仅仅是性格偏好；并包括其他考虑因素，如资源、种植材料的可获得性、用途和市场、感知或实际的物理或环境限制等，这是一个需要进一步研究的主题。在水分胁迫下，干物质是水分利用（WU）和水分利用效率（WUE）的产物。的基础。在此基础上，通过盆栽试验研究了28个木薯基因型和18个甘薯基因型对水分胁迫的生长响应。相关分析结果表明，干物质对干旱响应的基因型变异更适合于水利用效率的基因型变异，而不是水利用效率的基因型变异。在甘薯中，干旱植株的干物质产量也显著减少。干旱处理显著降低了水分利用效率，但对水分利用效率几乎没有影响。这些事实清楚地表明，减少水分而不是减少水分利用效率导致干物质减少，这与木薯的情况相反。一系列田间试验的结果与盆栽试验的结果基本一致，为进一步研究中对基因型x环境互作的评价进行验证是必要的。

This research was conducted in collaboration with Philippine Root Crop Research and Training Center, Leyte State University to evaluate genotypic variation in cassava and sweetpotato in drought tolerance and to identify the traits that are closely related to the tolerance. In addition to the collection of the Center, we further collected a number of genotypes from several drought-prone areas m the Philippines.Sevearl surveys among the rootcrop growing Canners indicated that the question on decision-making strategies by farmers on sustained adoption of a variety is different from the question of preference to grow a certain variety. The former involves more than just traits preference ; and includes other considerations, such as resources, availability of planting materials, use and market, perceived or actual physical or environmental constraints, etc., which is a subject for futher study.Under water stress, dry matter is a product of water use (WU) and water use efficiency (WUE). Based. on this concept, the growth responses of 28 cassava genotypes and 18 sweelpotato genotypes to water stress were examined in a series of pot experimentsIn cassava, drought significantly reduced dry matter production. Results of a correlation analysis indicate that the genotypic variation in dry matter response to drought was better explained by that in WUE than in WU. In sweetpotato, dry matter production was also significantly reduced in droughted plants. The drought treatment significantly reduced WU, while it scarcely affected WUE. These facts clearly show that the reduction of WU but not WUE caused dry matter reduction, which is opposite to the case of cassava.The results of a series of field experiments generally support those obtained by the pot experiments, which are necessary to validated by the evaluation of Genotype x Environment Interaction in further study.