BREEDING SYSTEMS IN ASCLEPIAS INCARNATA L., A. SYRIACA L., AND A. VERTICILLATA L.

A series of experimental pollinations involving three sympatric species provided strong evidence for physiological and/or genetic barriers to hybridization in Asclepias. Pollen tubes were observed to penetrate the style in some interspecific crosses of all species pairs. Aniline blue fluorescence microscopy also demonstrated pollen tube penetration of foreign ovules following pollinations between A. incarnata and A. verticillata. However, none of the 279 total pollinations attempted between species yielded mature seed, indicating the presence of late pre-fertilization or early post-fertilization incompatibility. Intraspecific pollinations in greenhouse and field populations revealed greater crossability between populations than within populations of a single species. Self-pollinations of A. verticillata were unsuccessful, while 29% and 4% of those of A. incarnata and A. syriaca, respectively, yielded mature follicles. It is suggested that the potential for autogamy, combined with floral mechanisms requiring pollination by insects, insure the advantages of both the genetic variability promoted by outcrossing and the reproductive assurance of uniparental reproduction. Strong reproductive barriers between species reduce the change of intergradation where species occur sympatrically.     

胡葱与洋葱、葱亲缘关系初探

Allium ascalonicum L,在我国的邦名比较混乱,而且它与洋葱、葱的亲缘关系不清。作者认为,它在我国的邦名应规范为胡葱,同时,从性状比较的角度研究胡葱与洋葱、葱之间的亲缘关系。结果表明,胡葱的植物学特征和生物学特性介于洋葱和葱之间。     

胡葱与洋葱、葱过氧化物酶同工酶研究及聚类分析

本文对胡葱与洋葱、葱的功能叶过氧化物酶同工酶电泳图谱分析和聚类分析表明：这三个种及葱的3个交种闻的亲缘关系被区分开来;胡葱与洋葱的亲缘关系比胡葱与大葱的亲缘关系更近。     

Bulb-type onion introgressants posessing Allium fistulosum L. genes recovered from interspecific hybrid backcrosses between A. cepa L. and A. fistulosum L.

Allium fistulosum possesses a number of traits which would be desirable in A. cepa. Thus far, no commercial A. cepa cultivars have been released which harbor Allium fistulosum traits. F₁BC₃ populations were generated for this study by backcrossing A. cepa to A. cepa×A. fistulosum hybrids. The F₁BC₃ plants were evaluated for plant morphology, floral characters, male- sterile cytoplasm, soluble solids and pungency, and isozymes. Overall growth habit and floral characters of the F₁BC₃ plants were much like A. cepa. We report here the recovery of recombinant, bulbing, and fertile A. cepa-type onions that exhibit A. fistulosum isozyme alleles and morphological markers. Recombination between A. cepa and A. fistulosum genomes was achieved using the introgression strategy of backcrossing A. fistulosum into A. cepa, thereby ameliorating the nuclear cytoplasmic barriers that occurred in previous less successful introgression attempts when plants were not in A. cepa cytoplasm. We believe this report to be the first demonstration of onion introgressants that are like A. cepa in appearance, are male- and female-fertile, and possess A. fistulosum genes. Received: 29 May 1999 / Accepted 22 June 1999     

THE BEHAVIOUR OF ADULT CLICK BEETLES OF THE GENUS AGRIOTES (A. OBSCURUS L., A. LINEATUS L., AND A. SPUTATOR L.)

Various methods of trapping click beetles were tried, the aim being to devise a method which could be used for population and movement studies in grass fields. It is shown that a trap consisting of a 3 in. thickness of hay over closely clipped grass is suitable for this purpose. Annual and daily activity are discussed. Maximum activity occurred in late May and early June, and during the afternoon and evening. The beetles showed a preference for the most humid sites during dry weather. Numbers fell as the hedge was approached and very few occurred under the hedge. Marked beetles were released, and the maximum distance at which they were recovered was 26 yards (23.8 m.). The majority moved in a very restricted area.     

A note on the genusTurritis L.

Conclusion The genusTurritis L. differs from the genusArabis L. by the arrangement of the myrosine cells and by the alignment of the seeds in the pods in two rows.The anatomical structure of the septum ist not a character differentiating the genusArabis from the genusTurritis. The author backs the view that it would be more correct to evaluate the genusTurritis only as an infrageneric taxon of the genusArabis.