Figueroa-Castro Dulce M, Holtsford Timothy P
Division of Biological Sciences, University of Missouri, Columbia, MO 65211-7400, USA.
Sex Plant Reprod. 2009 Sep;22(3):187-96. doi: 10.1007/s00497-009-0103-6. Epub 2009 Jul 7.
In natural populations where interfertile species coexist, conspecific and heterospecific pollen can be delivered to the stigmas. Post-pollination mechanisms might determine the seed siring success of different pollen donors within species as well as the chances for hybridization between species. Nicotiana longiflora and N. plumbaginifolia occur in sympatry in Northwest Argentina, where they have overlapping flowering seasons and share floral visitors. We explored (1) pollen tube growth rates for outcross versus self pollen in single-donor pollinations; (2) siring success of self versus outcross pollen donors in competitive pollinations, and (3) possibilities for hybridization by performing two- (outcross conspecific vs. heterospecific) and three-pollen donor (self vs. outcross vs. heterospecific) crosses. In N. longiflora, both pollen tube growth rate and siring success favored outcross pollen over self pollen and strong rejection of heterospecific pollen. In N. plumbaginifolia, pollen tube growth rate was similar for self and outcross pollen, self pollen sired similar numbers of offspring than outcross pollen and heterospecific pollen sired roughly the same number of progeny than self pollen. Results suggest that in natural sympatric populations, interspecific crosses would likely lead to unidirectional hybridization with N. plumbaginifolia as the seed parent.
在可育物种共存的自然种群中，同种花粉和异种花粉都可能落在柱头上。授粉后机制可能决定物种内不同花粉供体产生种子的成功率以及物种间杂交的可能性。长花烟草和蓝花烟草在阿根廷西北部同域分布，它们花期重叠且共享访花者。我们探究了：（1）单供体授粉中异交花粉与自花花粉的花粉管生长速率；（2）竞争授粉中自花与异交花粉供体产生种子的成功率；以及（3）通过进行双花粉供体杂交（同种异交与异种杂交）和三花粉供体杂交（自花、异交与异种杂交）来研究杂交的可能性。在长花烟草中，花粉管生长速率和产生种子的成功率都表明异交花粉优于自花花粉，且对异种花粉有强烈排斥。在蓝花烟草中，自花花粉和异交花粉的花粉管生长速率相似，自花花粉产生的后代数量与异交花粉相似，而异种花粉产生的后代数量与自花花粉大致相同。结果表明，在自然同域种群中，种间杂交可能会导致以蓝花烟草为种子亲本的单向杂交。
