ペチュニア属(ナス科)分類群における自家不和合性の分化 Differentiation in the Status of Self-incompatibility among All Natural Taxa of Petunia (Solanaceae)

ペチュニアなどナス科植物は配偶体型自家不和合性を示すことで知られる。本報では,自家受粉後の着果率を指標として,既知のペチュニア属全分類群(17分類群)を対象とし,86群落由来の1,201個体の自家(不)和合性を調査した。Petunia axillaris subsp. parodii(前報)に加え,subsp. subandina, P. exserta, P. occidentalisを自家和合,残りの全分類群を自家不和合と判断した。P. reitziiには,自家不和合個体のみで構成される群落に加え,自家不和合個体に自家和合個体が一部混ざる群落が認められたが,これはP. axillaris subsp. axillarisの場合と同様,自家不和合機構の破壊によるものと推定された。自家和合分類群はすべて果柄が内曲し,P. axillaris subsp. axillarisとP. integrifolia subsp. inflataを除く自家不和合分類群は果柄が外曲することから,自家不和合性と系統との関連が議論された。ペチュニアの分布域の年間降水量は,東の大西洋沿岸で多く,アンデス山脈に近い西で少ないが,降水量の少ない地域に自家和合分類群が広く分布することと,東部産ながら自家和合性のP. exsertaの特殊な生育環境から,自家和合性が受粉媒介者の機能しにくい環境下でのオプション機能として発達した可能性が議論された。

By monitoring capsule-set after self-pollination, we had previously determined that Petunia axillaris subsp. axillaris was self-incompatible and subsp. parodii was self-compatible. In this report, the self-incompatibility status of the other 17 known natural taxa of Petunia was determined using a total of 1201 individuals derived from 86 different native populations in Argentina, Brazil, and Uruguay. Three of the 17 taxa, P. exserta, P. occidentalis, and P. axillaris subsp. subandina, were found to be self-compatible and all the other 14 were found to be self-incompatible. For one of these self-incompatible taxa, P. reitzii, at least one of the five native populations studied was found to contain both self-incompatible and self-compatible individuals. However, the self-compatible individuals were likely to have been derived from self-incompatible progenitors through the breakdown of self-incompatibility. The status of self-incompatibility in these taxa, revealed from this study, is discussed in relation to taxonomy, distribution, and native habitat.