品种退化在自然界是普遍发生的现象。一个优良的品种如果不加选择、复壮,就会逐渐混杂、变劣,以至退化。黄麻品种退化具体表现为生育期缩短,植株变矮,分叉点变低,麻皮变薄,产量降低,抗病性减弱等。特别是外地引入的品种经种植几年后就逐渐退化,产量逐年减低。如本区从广东引入“粤园4号”、“粤园5号”品种,第三年就比第一年减产百 Variety degradation is a common phenomenon in nature. If an excellent breed does not have any choice or rejuvenation, it will gradually become mixed, degraded and even degenerated. Jute varieties degenerated specifically for shortened growth period, plants become shorter, the bifurcation point becomes lower, thinner, lower yield, weakened disease resistance and so on. In particular, the varieties introduced from the outside gradually degenerate after being planted for several years, and the output is decreasing year by year. If this area from Guangdong to introduce “Guangdong Garden 4 ”, “Yueyuan 5 ” varieties, the third year than the first year cut 100