Johannessen M M, Andersen B A, Jørgensen R B
Biosystems Department, Risø National Laboratory, Roskilde DK-4000, Denmark.
Heredity (Edinb). 2006 May;96(5):360-7. doi: 10.1038/sj.hdy.6800796.
Unlike most studies on hybridisation between oilseed rape and Brassica rapa, this study focused on hybridisation with oilseed rape as the maternal parent. This is a key cross because, assuming that plastids are inherited maternally, F(1)-hybrid production with maternal oilseed rape (B. napus) is the only transgene escape route from transplastomic oilseed rape. We investigated such F(1)-hybrid production in winter oilseed rape co-cultivated with weedy B. rapa at three plant densities each with two proportions of the different species. The paternity of the progeny produced on oilseed rape was assessed, and several fitness parameters were determined in oilseed rape mother plants in order to correlate hybridisation and plant competition. At higher density, the vegetative fitness per mother plant decreased significantly, but the density only affected the frequency of F(1)-hybrids significantly (a decrease) in the treatment with equal proportions of each species. As to the proportions, at higher B. napus frequencies, there were fewer F(1)-hybrids per mother plant and a significant increase in most biomass components. Thus, B. rapa was the stronger competitor in its effect on both the vegetative and reproductive fitness in B. napus, and the hybridisation frequency. In conclusion, the relative frequency of the two species was a more influential parameter than the density. Hybridisation with B. napus as the female will be most likely at current field densities of B. napus and when B. rapa is an abundant weed.
与大多数关于油菜和白菜型油菜杂交的研究不同，本研究聚焦于以油菜作为母本的杂交。这是一个关键的杂交组合，因为假设质体是母系遗传的，那么以母本油菜（甘蓝型油菜）进行F(1)杂种生产是转基因油菜中外源基因逃逸的唯一途径。我们研究了在三种种植密度下，冬油菜与杂草型白菜型油菜混种时的F(1)杂种生产情况，每种密度下两种物种的比例不同。对油菜上产生的子代的父本进行了评估，并测定了油菜母本植株的几个适合度参数，以便将杂交与植物竞争联系起来。在较高密度下，每个母本植株的营养适合度显著降低，但仅在每种物种比例相等的处理中，密度才对F(1)杂种的频率有显著影响（降低）。至于比例，在甘蓝型油菜频率较高时，每个母本植株产生的F(1)杂种较少，且大多数生物量组分显著增加。因此，白菜型油菜对甘蓝型油菜的营养和生殖适合度以及杂交频率的影响方面是更强的竞争者。总之，两种物种的相对频率是比密度更具影响力的参数。在甘蓝型油菜当前的田间种植密度下，当白菜型油菜是一种常见杂草时，以甘蓝型油菜作为母本的杂交最有可能发生。
