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农作物的品种改良,在推动世界食品生产已经取得了引人注目的成效。但在广泛采用现代良种的同时,由于传统农家品种的渐趋减少以及多样性种质的严重丧失,已使许多栽培作物的遗传变异性明显减少,出现了作物遗传性相近的现象而带来易受病虫流行的威胁。美国南方玉米小斑病的流行,爱尔兰马铃薯疫病的侵袭,都是近代的典型例子。还有斯里兰卡的咖啡,法国的葡萄,美国的小麦和燕麦,孟加拉和印度的水稻,都曾受到流行病的严重祸害。虽然不能认为所有这些流行病都是由遗传因素造成的,但也不能否认许多病害的流行确实与遗传种质单一化有关。早年爱尔兰马铃薯疫病流行,近代巴拿马香蕉和小麦
Improvements in crop varieties have yielded remarkable results in promoting world food production. However, at the same time that modern varieties are widely used, the genetic variability of many cultivated crops has been significantly reduced due to the gradual reduction of traditional farm varieties and the serious loss of diverse germplasms, leading to similar phenomena in crop geneticities By pest epidemic threat. The prevalence of southern corn spot blight in the United States and the invasion of Irish potato blight are all typical examples of modern times. There are also Sri Lanka coffee, grapes in France, wheat and oats in the United States, rice in Bangladesh and India, which have all suffered the scourge of the epidemic. Although it is not believed that all of these epidemics are caused by genetic factors, it can not be denied that the prevalence of many diseases is indeed linked to the simplification of genetic germplasm. The early Irish potato epidemics, modern Panama bananas and wheat