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(接上期)17.什么叫原种?概括一句话:某一品种最好的种子。包括两个含义:(1)刚培育成功性状稳定的一代种子;(2)推广良种经提纯复壮而保持原品种典型性状的优良种子。18.杂种二代为什么不能做种用?杂种一代优势产生的原因,是因为它们来源于不同遗传基因的两个亲本,通过受精形成双重遗传性合子,这种子能使杂种一代表现出强大的杂种优势。杂种第二代要产生分离现象,产量显著下降,降幅一般为20%~30%,有的杂种二代减产会更
(Connected) 17. What is the original species? Summarized sentence: a variety of the best seeds. It includes two meanings: (1) just cultivating a stable generation of seeds with successful traits; (2) promoting good seeds that are purified and rejuvenated to maintain the typical characters of the original varieties. 18. Why hybrids can not be used for breeding? The reason for the heterosis generation is that they originate from two parents of different genes and form double hereditary zygotes through fertilization that give hybrids a powerful hybrid Advantage. Hybrid second generation to produce separation phenomenon, the yield dropped significantly, the decline is generally 20% to 30%, some hybrids will be more than the second cut