Ecological-Genetic Studies on Rice Germplasm in Tropical Asia (3rd Survey)

本文从遗传学和生态学的角度对普通栽培水稻（Oryza sativa）及其野生祖先（O. rufipogon）进行了变异调查。1989年，我们到不丹和孟加拉国游学。在1989年和1990年，我们三次访问了位于泰国中部平原的野生水稻永久研究地点。不丹——在不丹西部，我们观察了分布在三个山谷中的22块稻田，收集了158个种子样本。我们参观的海拔最高的稻田（可能是世界上海拔最高的稻田）在海拔2700米的地方。稻田在群体内具有不同程度的异质性，包括高碎粒率和半不育性的变异。这种“杂草”类型的起源仍未解决。种子性状调查表明，高海拔地区以粳稻型为主，低海拔地区以籼稻型为主。孟加拉国的稻田大部分分布在低洼地区，这些地区在雨季会被严重淹没。我们走访了三个种植深水稻和野生稻的地区。在14个地点采集了66份栽培稻和30份野生稻样本。传统的混作方法（两个生育期不同的品种的混作）提出了一个有趣的生态遗传学问题。一些品种被发现携带日本特有的同工酶等位基因，尽管热带低地品种被认为是印度品种。在野生稻中，大部分野生稻居群分布在靠近稻田的区域，并被栽培型基因渗入。幸运的是，我们发现真正的野生种群分散在一个由datura主导的巨大沼泽地区形成小种群。泰国的种群研究——自1983年以来，在我们监测的8个永久研究地点中，有4个野生种群已经灭绝或接近灭绝。它们都是一年生型的。其余4种为多年生或中多年生类型，在相对稳定的生境中持续存在。因此，自然人口的破坏或城市化。少

We have carried out the variation survey of the common cultivated rice (Oryza sativa) and its wild progenitor (O. rufipogon) from the viewpoint of genetics and ecology. In 1989, we made study-tours in Bhutan and Bangladesh. In 1989 and 1990, we visited three times our permanent study sites of wild rice which are located in the Central Plains of Thailand.1. Bhutan --- In West Bhutan we made observation of 22 rice fields distributed along three valleys and collected 158 seed samples. The field of the highest altitude we visited (probably the highest rice field in the world) was in 2700 m MSL. Rice fields were heterogeneous in varying degrees within population including variants which showed high seed shattering and semisterility. The origin of such "weedy" type remains unsolved. Character investigation of seed samples revealed that samples collected in higher altitude were mostly Japonica type, while those collected in lower altitudes were mostly Indica type.2. Bangladesh --- Rice fields … More in Bangladesh are distributed mostly in low-lying areas which are deeply flooded in the rainy season. We traveled three districts which are planted to deepwater rice and inhabited by wild rice. 66 cultivated and 30 wild rice samples were collected on 14 sites. Traditional methods of mix-cropping (mixture of two varieties having different growth duration) suggested an interesting problem of ecological genetics. Some of the accessions of cultivars were found to carry Japonica-specific isozyme alleles, although lowland cultivars in tropics have been believed as Indicas. In regards to wild rice, most of wild rice populations were found to be in close proximity to rice fields, and to be introgressed by genes of cultivated type. Fortunately, we found truly wild populations scattered forming small populations in a huge marsh places which were dominated by Datura.3. Population study in Thailand --- Among eight permanent studysites which we are monitoring since 1983, four wild populations became extinct or nearly extinct. They are all annual type. The remaining four are perennial or intermediate perennial-annual type, and persist in relatively stable habitats. Thus, natural populations destruction or urbanization. Less