Am J Bot. 1998 Feb;85(2):168.
Twenty-one native populations (1120 individuals) of maize from Northern Argentina were studied. These populations, which belong to 13 native races, were cultivated at different altitudes (80-3620 m). Nineteen of the populations analyzed showed B chromosome (Bs) numerical polymorphism. The frequency of individuals with Bs varied from 0 to 94%. The number of Bs per plant varied from 0 to 8 Bs, with the predominant doses being 0, 1, 2, and 3. Those populations with varying number of Bs showed a positive and statistically significant correlation of mean number of Bs with altitude. The DNA content, in plants without Bs (A-DNA)(2n = 20), of 17 populations of the 21 studied was determined. A 36% variation (5.0-6.8 pg) in A-DNA content was found. A significant negative correlation between A-DNA content and altitude of cultivation and between A-DNA content and mean number of Bs was found. This indicates that there is a close interrelationship between the DNA content of A chromosomes and doses of Bs. These results suggest that there is a maximum limit to the mass of nuclear DNA so that Bs are tolerated as long as this maximum limit is not exceeded.
对来自阿根廷北部的 21 个本地玉米群体（1120 个人）进行了研究。这些群体属于 13 个本地品种，在不同的海拔高度（80-3620 米）进行了种植。分析的 19 个群体显示出 B 染色体（Bs）的数量多态性。带有 Bs 的个体的频率从 0 到 94%不等。每个植物的 Bs 数量从 0 到 8 个不等，主要剂量为 0、1、2 和 3。那些具有不同 Bs 数量的群体显示出 Bs 数量与海拔高度之间存在正相关且具有统计学意义。在没有 Bs（A-DNA）（2n = 20）的 17 个研究群体的植物中，确定了 DNA 含量。发现 A-DNA 含量有 36%的变化（5.0-6.8 pg）。在 A-DNA 含量与种植海拔高度之间以及在 A-DNA 含量与 Bs 的平均数量之间发现了显著的负相关。这表明 A 染色体的 DNA 含量与 Bs 剂量之间存在密切的相互关系。这些结果表明，核 DNA 的质量存在一个最大极限，只要不超过这个最大极限，Bs 就可以被容忍。
