Langevin Susan A, Clay Keith, Grace James B
Department of Botany, Louisiana State University, Baton Rouge, LA, 70803, USA.
Department of Biology, Indiana University, Bloomington, IN, 47405, USA.
Evolution. 1990 Jul;44(4):1000-1008. doi: 10.1111/j.1558-5646.1990.tb03820.x.
The objectives of this study were (1) to determine if hybridization occurs naturally between cultivated rice and a closely related weed, red rice (both Oryza sativa L.) and (2) to determine the incidence of hybridization and possible convergence of red rice with cultivated rice. Both morphological and electrophoretic characters were used to confirm the existence of hybrids. A total of 12,000 seeds were collected from red rice plants from fields of six different rice cultivars and sown in a common garden. Hybrids were generally taller and had longer, wider flag leaves than either red rice or cultivated rice. In addition, hybrids produced more tillers than red rice. Overall, hybrids were vegetatively robust plants, demonstrating heterosis and expressing morphological characteristics of both parents. That these plants were hybrids was confirmed by the existence of electrophoretic banding patterns common to both synthetic and natural hybrids. The incidence of hybridization was estimated as the percentage of hybrids found in red rice populations while morphological characteristics were used to test for convergence. Percentage hybridization ranged from 1% in the Lemont cultivar to 52% in the Nortai variety. The greater number of hybrids found in the Nortai variety was attributed to a later flowering time of this variety and the overlap of its flowering time with that of the F hybrids. F hybrids were observed to flower later than either red rice or the early season varieties of cultivated rice. Thus, early season varieties have a temporal separation in flowering time from the F hybrids that prevents back crossing. Unlike the other hybrids that were vegetatively robust, Nortai hybrids were less robust and more similar to the cultivar. These results suggest that later season cultivars may have a higher incidence of hybridization and introgression with red rice and that this may lead to morphological convergence of the weed toward the crop. Convergents were observed in the Nortai variety. Hybridization between cultivated and red rice has the potential to increase the adaptability of red rice populations by promoting genetic diversity.
（1）确定栽培稻与近缘杂草红米（均为稻属）之间是否自然杂交；（2）确定杂交发生率以及红米与栽培稻可能的趋同情况。利用形态学和电泳特征来确认杂种的存在。从六个不同水稻品种田间的红米植株上共收集了12000粒种子，并在一个共同的园地里播种。杂种通常比红米或栽培稻更高，剑叶更长、更宽。此外，杂种比红米产生更多的分蘖。总体而言，杂种是营养生长健壮的植株，表现出杂种优势，并表达了双亲的形态特征。合成杂种和天然杂种共有的电泳条带模式证实了这些植株是杂种。杂交发生率以红米群体中发现的杂种百分比来估算，同时利用形态特征来检测趋同情况。杂交百分比从Lemont品种的1%到Nortai品种的52%不等。在Nortai品种中发现的杂种数量较多，这归因于该品种开花时间较晚，且其开花时间与F杂种的开花时间重叠。观察到F杂种比红米或栽培稻的早季品种开花更晚。因此，早季品种与F杂种在开花时间上有时间间隔，可防止回交。与其他营养生长健壮的杂种不同，Nortai杂种生长较弱，更类似于栽培品种。这些结果表明，晚季品种与红米杂交和渗入的发生率可能更高，这可能导致杂草在形态上向作物趋同。在Nortai品种中观察到了趋同现象。栽培稻与红米之间的杂交有可能通过促进遗传多样性来提高红米群体的适应性。
