ウルグアイ産Petunia axillaris(ナス科)における自家不和合性の分化 Differentiation in the Degree of Self-incompatibility in Petunia axillaris (Solanaceae) Occurring in Uruguay

ペチュニア品種の片親であるPetunia axillarisを自家和合種とする文献と,自家不和合性とする文献があり矛盾していた。自生地での観察から亜種axillarisは自家不和合,亜種parodiiは自家和合種と思われたので,両亜種の共存するウルグアイから採取されたP. axillarisにつき,その自家和合性・不和合性の程度を調査した。ウルグアイ中央を東西に流れるRio Negroより北に分布する亜種parodiiと,それに形態の近い中間型の群落はすべて自家和合であった。亜種axillarisに形態の近い中間型には自家和合群落が多く,亜種parodiiのもつ自家和合遺伝子の浸透が推察された。Rio Negroより南に分布する典型的な亜種axillarisの群落の多くは自家不和合であったが,少数の自家和合群落が北部内陸に散在し,また自家不和合個体に一部自家和合個体を混ぜる混在群落が,亜種axillarisの分布城全体に認められた。ペチュニァ品種のもつ自家不和合性は,他方の親で自家不和合のP.integrifoliaだけでなく,P. axillarisにも由来する可能性が議論された。

Petunia axillaris, one of the parents of garden petunias, has been contradictorily described as a self-compatible and self-incompatible species. Self-pollination of individuals derived from 106 native habitats in Uruguay revealed the following facts: most plants of the typical subsp. axillaris are self-incompatible except for those found in the area close to the border separating two subspecies (the Rio Negro river), but all typical subsp. parodii are self-compatible. All intermediate forms close to subsp. parodii and most of those close to subsp. axillaris are self-compatible, and so intergradation of genes in subsp. parodii controlling self-compatibility into subsp. axillaris was suggested. In the area in which typical subsp. axillaris exclusively occurs, mixed populations of self-incompatible and self-compatible individuals were also found. The origin of S-genes controlling self-incompatibility found in garden petunias was discussed.