同域分布的紫堇属三种植物的繁育系统和传粉差异

为研究近缘物种之间繁育系统分化对传粉环境的适应性意义,本文针对湖北地区的3种紫堇属植物（紫堇Corydalis edulis Maxim.、尖距紫堇C.shearer S.Moore.和小花黄堇C.racemosa（Thunb.） Pers.）进行了传粉生态学研究,对比分析了它们在花部特征、分布模式、花期、交配系统、传粉系统等方面的差异。3种紫堇属植物常见伴生现象,花期有一定重叠;花色、距长、花蜜量等方面均有显著差异;尖距紫堇交配系统为自交不亲和、依靠传粉者异花授粉;而紫堇和小花黄堇交配系统为自交亲和,兼有自交和异交的混合交配系统。3个物种均由蜂类传粉,且花部性器官与传粉者的接触部位一致,但访花频率差异较大。在混合群落中,传粉者访花具有较高的忠实性,花部特征差异可能是传粉者选择性访花的原因。对于紫堇属3个物种,花部特征和交配系统的分化有助于其避免传粉过程的相互干扰,交配系统与传粉环境具有一定相关性,混合交配系统可能有利于提高植物对不同生境和气候的适应性。     

Sequence and expression of endogenous S-locus glycoprotein genes in self-compatible Brassica napus

Brassica napus is an amphidiploid plant which is self-compatible even though it is derived from hybridisation of the self-incompatible species B. oleracea and B. campestris. Experiments were undertaken to establish if S-locus glycoprotein (SLG) genes exist in B. napus and whether these are expressed as in self-incompatible Brassica species. Two different stigma-specific cDNA sequences homologous to SLG genes were obtained from the B. napus cultivar Westar. One of these sequences, SLG _WS1, displayed highest homology to class I SLG alleles, whereas the other, SLG _WS2, showed greatest homology to class II SLG genes. Both were expressed at high levels in Westar stigmas following a developmental pattern typical of SLG genes in the self-incompatible diploids. We infer that they represent the endogenous SLG genes at the two homoeologous S-loci. The occurrence of normally expressed SLG genes and its relevance to the self-compatible phenotype of B. napus is discussed.     

Family outcrossing rates and neighborhood floral density in natural populations of swamp milkweed (Asclepias incarnata): potential statistical artifacts

 To evaluate how environmental and genetic factors influence mating-system evolution, accurate estimates of outcrossing rates of individual plants (families) are required. Using isozyme markers, we observed wide variation in family outcrossing rates in three natural populations of Asclepias incarnata using three statistical methods: (1) a multilocus maximum-likelihood procedure (t _m); (2) a multilocus method-of-moments procedure (t _a); and (3) a direct comparison of progeny phenotypes against maternal phenotypes (t _d). Neighborhood floral-display size was positively correlated with t _a in one population, but showed no relationship with any of the other estimates of outcrossing for any population. Monte-Carlo simulations revealed that statistical variation associated with these estimation procedures can be large enough to explain all of the observed variation in outcrossing. We also found that significant, spurious correlations with neighborhood floral display could arise, on average, 7% of the time by chance alone. Our observations suggest that it is difficult to obtain accurate estimates of outcrossing in naturally pollinated plants using the estimation procedures currently available. Moreover, we caution that attempts to interpret observed variation in family outcrossing estimates by observing variation in ecological parameters could be misleading. Received: 28 September 1998 / Accepted: 27 October 1998     

蔊菜杂草性的研究

本文通过对十字花科常见杂草芹菜[Rorippa in lica(L.)Hiern]在南京地区的自然群体的周期性观察,以了解其在不同生态环境下的生活周期。本文还通过一系列实验来观察其繁育系统、种子传播的动因、结实力、种子发芽率和植物抗人为干扰的耐受性。花蕾套袋试验证明蔊菜主要是自交可亲和的,即使存在异型杂交也是微不足道的。种子传播效应试验揭示水和风都是种子传播的自然力。该种具有范围很广的耐受性,踏践和刈割试验证明在严重的人为于扰下仍能完成其生活周期。蔊菜尽管本质上属于多年生草本,能产生大量的种子,在很大程度上靠种子繁殖。种子萌芽试验证明它的种子萌发参差不齐。总之,蔊菜具有典型杂草的许多特性,而这些特性给它以适合在多种自然的和人为干扰的环境中正常地生长的能力。     

Pollination in vitro: effects on the growth of pollen tubes,seed set and gametophytic self-incompatibility in Trifolium pratense L. and T. repens L.

Summary Growth of pollen tubes and seed set were compared after hand pollination in situ and in vitro in two self-incompatible species, Trifolium pratense and Trifolium repens. Adhesion of pollen grains to the stigma was greater in vitro for both species. After cross-pollination, in vitro culture gave a significant increase in the cumulative growth of pollen tubes in pistils of T. pratense compared to in situ conditions. After selfing in T. repens, pollen tube growth was significantly increased by in vitro culture of florets. Seed set after crossing in situ and in vitro was similar for both species. Seed set after selfing in vitro was not increased in T. pratense. Several genotypes of T. repens were classified as very good, good and poor selfers based on their capacity for seed set following selfing in situ. In vitro pollination increased self seed formation by 1.7-, 18.0- and 31.0-fold for each class, respectively. Ovules located nearest to the style were fertilized more often after selfing than after crossing.     

Competitive interaction between two functional S-haplotypes confer self-compatibility on tetraploid Chinese cherry (Prunus pseudocerasus Lindl. CV. Nanjing Chuisi)

Self-incompatibility (SI) has been studied extensively at the molecular level in Solanaceae, Rosaceae and Scrophulariaceae, all of which exhibit gametophytic self-incompatibility (GSI). In the present study, four PpsS-haplotypes (Prunus pseudocerasus S-haplotypes) comprising at least two genes, i.e., PpsS-RNase (P. pseudocerasus S-RNase) and PpsSFB (P. pseudocerasus S-haplotype-specific F-box) have been successfully isolated in tetraploid P. pseudocerasus Lindl. CV. Nanjing Chuisi ("NC") which exhibited self-compatibility (SC), and its S-genotype was determined as S-1/S-3'/S-5/S-7. These PpsS-RNases, which were expressed exclusively in style, shared the typical structural features with S-RNases from other Prunus species exhibiting GSI. All PpsSFBs showed similar structure characteristics of SFBs from other Prunus species, and matched with the necessary conditions for pollen S-determinant. No mutations leading to dysfunction of S-haplotype were found in their full-length c-DNA sequences, except for PpsS-3'-haplotype which was not amplified by PCR. These four S-haplotypes complied with tetrasomic inheritance. Diploid pollen grains with S-genotypes S-7/S-1, S-7/S-5 and S-1/S-5 can grow the full length of the style after self-pollination, while pollen grains with S-3'/S-7, S-3'/S-1 and S-3'/S-5 cannot. These results suggest that PpsS-haplotypes-1, -5 and -7 are functional, and that competitive interaction between two of them confer self-compatibility on cultivar "NC". Furthermore, in terms of recognition specificity, diploid pollen grains carrying PpsS-3'-haplotype are equal to monoploid pollen grains carrying the other functional S-haplotype.     

Is self-compatibility the main breeding system in borage (Borago officinalis L.)?

The polygenic postzygotic self-incompatible system reported in borage (Borago officinalis L.) is refuted. The behaviour of pollen tubes after self- and cross-pollination, analysis of the crossability coefficient, seed set after continuous generations of self-pollination and the effects of inbreeding depression in borage were studied. Evidence of self-compatibility was established. The influence of protandry in a self-compatible system is also discussed. Received: 15 July 1999 / Accepted: 3 November 1999