RAPD analysis of white clover cultivars and clones for swards with intensive grazing and those with low-input

这项研究的目的是(1)开发一种利用白三叶品种和无性系进行鉴定的技术；(2)检验放牧草地中的有利构型。这些技术和信息对于理解密集放牧沼泽地和可持续沼泽地白三叶的共存策略是非常有用的。首先，我研究了鉴定两个品种(大叶品种)的可能性。Kopu和小叶cv.Tahora)及其无性系。筛选结果表明，共有10个有效的引物，各引物的组合鉴定效果较好。同时利用随机扩增多态性DNA和同工酶标记，以相对较低的成本对白三叶进行了鉴定。其次，对结缕草型和黑麦草型白三叶的优势构型进行了评价。它们分别被视为可持续利用和集约利用的典型系统。我采用的研究方法是(1)在实验建立的小型沼泽中进行详细的观测和测量，以及(2)在野外进行观测。在黑麦草草地上的观察和测量表明，大叶型具有更大的存活和生长性能，而集约型草地则相反。他们还提出，由于大叶类型的可塑性较大，两种类型之间的这两种属性的差异可能在集约型牧场中较小。对于结缕草，检验了以下假设：如果新形成的斑块涉及大叶无性系，它会迅速生长，在斑块寿命结束时占据斑块面积。小型草地试验和野外观测的结果有力地支持了这一假说。他们还表示，气候条件对这一趋势有很大影响。

The aims of this research are (1) to develop a technique for identifying cultivars and clones of white clover using and (2) to examine the advantageous architecure in grazed swards. The technique and information are much useful in understanding the coexistence strategy of white clover inhabiting intensively grazed swards and sustainable swards. Firstly, I examined the possibility of identifying two cultivars (large-leaved cv. Kopu and small-leaved cv. Tahora) and their clones using RAPD markers. A screen-test showed that ten primers were useful and the combination of the performance from the primers gave well results in the identification. Use of both RAPD and isozyme markers provides well identification with relatively low cost.Secondly, I assessed the advantageous architecture of white clover in two grazed swards (zoysia-typed and ryegrass-typed). They are considered as a typical system for sustainable use and for intensive use, respectively. I used the studying approach combined (1) detailed observations and measurements in mini-swards experimentally set up and (2) observations in fields. Obserations and measurements in a ryegrass-sward showed that large-leaved type showed larger survival and growth performance, whereas the revearse was true in intensive swards. They also suggested that differences in both attributes between two types may be small in intensive swards due to larger plasticity of larger-leaved type. For a zoysia-sward, a following hypothesis was tested : If a newly forming patch involves a large-leaved clone, it grows rapidly to occupy the patch area by the end of the patch longevity. Results of the mini-sward experiment and observations in a field supported this hypothesis strongly. They also suggested that climatic conditions affected this trend strongly.