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.     

Ueber Astragalus monspessulanus L., A. Wulfeni Koch,A. incanus L. und A. incurvus Desf

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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。     

Somatic embryogenesis and shoot regeneration from intact seedlings of Phaseolus acutifolius A., P. aureus (L.) Wilczek,P. coccineus L., and P. wrightii L.

A rapid, one-step procedure has been developed for inducing direct organogenesis and somatic embryogenesis in cultures of Phaseolus coccineus L., P. acutifolius A., P. aureus L. [Vigna radiata L. Wilczek] and P. wrightii L. Development of somatic embryos and shoot buds occurred within 6–8 weeks of culture from intact seedlings raised on MS (Murashige and Skoog 1962) medium supplemented with N⁶-benzylaminopurine (BAP). Shoot buds or embryoids originated from subepidermal tissue of the regions adjacent to the shoot apex, hypocotyl and cotyledonary axils. While P. acutifolius and P. aureus were regenerated via shoot formation and P. wrightii by somatic embryogenesis, both embryogenesis and shoot regeneration were observed in P. coccineus. Relatively higher levels of BAP, 50–80 M, were found to be optimal for inducing regeneration while lower concentrations were ineffective. About 40–70 shoots and 70–250 somatic embryos were produced per responding seedling. Regenerated shoots and somatic embryos developed into whole plants on a basal medium or the one supplemented with 1 M naphthaleneacetic acid.