据一项估计表明，世界粮食产量增长额的40%来自于纯产量增长，而60%依靠占用更多土地实现。

By one estimate, only 40% of the increase in world grain output now comes from rises in yields and 60% comes from taking more land under cultivation.

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但因光a纯合态的低衣分，其亲本繁殖和杂交制种时皮棉产量降低，故光a不育系在杂种优势中的利用有优势又有劣势。

However, Guang a has disadvantages as well as advantages in the utilization of heterosis because of its low lint percentage in parent propagation and hybrid seed production.

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以此为基础对湖北省水稻区域产量保险纯费率进行厘定，得出在80%保障水平下，潜江，仙桃等高风险地区的水稻保险费率为7。

Then this paper used the zoning result to determine the rice GRP rate, the study shows that at 80% guarantee level, the pure rate of premium in highest risk zone is 7.

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