College of Landscape Architecture, Sichuan Agricultural University, Chengdu, China.
Heredity (Edinb). 2023 Apr;130(4):259-268. doi: 10.1038/s41437-023-00598-6. Epub 2023 Feb 14.
The evolutionary transition from self-incompatible distyly to self-compatible homostyly frequently occurs in heterostylous taxa. Although the inheritance of distyly and homostyly has been deeply studied, our understanding on modifications of the classical simple Mendelian model is still lacking. Primula forbesii, a biennial herb native to southwest China, is a typical distylous species, but after about 20 years of cultivation with open pollination, self-compatible homostyly appeared, providing ideal material for the study of the inheritance of distyly and homostyly. In this study, exogenous homobrassinolide was used to break the heteromorphic incompatibility of P. forbesii. Furthermore, we performed artificial pollination and open-pollination experiments to observe the distribution of floral morphs in progeny produced by different crosses. The viability of seeds from self-pollination was always the lowest among all crosses, and the homozygous S-morph plants (S/S) occurred in artificial pollination experiments but may experience viability selection. The distyly of P. forbesii is governed by a single S-locus, with S-morph dominant hemizygotes (S/-) and L-morph recessive homozygotes (-/-). Homostylous plants have a genotype similar to L-morph plants, and homostyly may be caused by one or more unlinked modifier genes outside the S-locus. Open pollinations confirm that autonomous self-pollination occurs frequently in L-morphs and homostylous plants. This study deepens the understanding of the inheritance of distyly and details a case of homostyly that likely originated from one or more modifier genes.
自交不亲和的异型花柱结构向自交亲和的同型花柱结构的进化转变经常发生在异型花柱类群中。尽管异型花柱和同型花柱的遗传已经得到了深入研究，但我们对经典简单孟德尔模型的修饰的理解仍然不足。报春花属植物是中国西南地区的一种二年生草本植物，是一种典型的异型花柱物种，但经过大约 20 年的开放授粉栽培，自交亲和的同型花柱结构出现了，为异型花柱和同型花柱的遗传研究提供了理想的材料。在这项研究中，外源油菜素内酯被用来打破报春花异型花柱结构的异型不亲和性。此外，我们进行了人工授粉和开放授粉实验，以观察不同杂交后代中花型的分布。自交产生的种子活力总是所有杂交中最低的，并且在人工授粉实验中出现了纯合 S 型（S/S）植株，但可能经历了活力选择。报春花的异型花柱结构由单个 S 座位控制，其中 S 型显性半合子（S/-）和 L 型隐性纯合子（-/-）。同型花柱植物的基因型与 L 型植物相似，同型花柱可能是由 S 座位外的一个或多个不连锁的修饰基因引起的。开放授粉实验证实，L 型和同型花柱植物中经常发生自主自交。这项研究加深了对异型花柱遗传的理解，并详细描述了一个可能起源于一个或多个修饰基因的同型花柱的案例。
