玉米种质保持中的适宜样本容量

A Suitable Sample Size in the Conservation of Corn Germplasm

用两个胚乳色基因型纯合的玉米品种不同比率的混合来模仿具有不同标记基因频率的玉米群体 ,通过田间试验、统计抽样以及MonteCarlo模拟研究玉米种质在繁殖前后标记基因频率的变化。两年田间试验和MonteCarlo模拟试验得到一致结论 ;在玉米群体田间植株中随机抽取 8株上的全部种子或 10株上每株 2 5粒种子作样本可使群体中频率大于 0 .0 5基因的丢失频率非常小 ,样本群体的基因频率相对稳定且基因频率的 95 %置信下限大于 0 ,达到保持较低频率基因的基本目的。在种质库中 ,一般可保存 30 0 0～ 5 0 0 0粒种子。为避免繁殖次数而增加的遗传漂变和漂移 ,要尽量减少繁殖次数。本研究结果可推广到其他异花授粉作物。

The corn populations prepared through mixing two maize cultivars, homozygous in endosperm color, Suyu 9 (yellow, YY) and Suyunuo 1 (white, yy) to form various marker (Y) frequencies, i.e. 0.01, 0.05, 0.10 and 0.30, were used to study suitable sample size in the conservation of corn germplasm. The changes of marker gene frequency after propagation were studied through field experiment combined with statistical sampling, as well as Monte Carlo simulation. The results from both field experiment and Monte Carlo simulation were basically the same and showed that a random sample of eight plants with all seeds or 10 plants with 25 seeds per plant could conserve the rare gene with 95% confidence. It was suggested that for germplasm storage, a sample with 3 000-5 000 seeds should be conserved. The variation of gene frequency after several times of reproduction was increased obviously and so was for the probability of losing a rare gene. The above conclusion might be applied to other cross-pollinated crops because the results from Monte Carlo simulation were (under) a general situation and were basically similar to those from the field experiments.