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Pyrus spinosa und ihre Hybriden in Südwestbulgarien

Jiří Dostálek
Folia Geobotanica & Phytotaxonomica
Vol. 15, No. 1 (1980), pp. 59-73
Published by: Springer
Stable URL: http://www.jstor.org/stable/4180153
Page Count: 15
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Pyrus spinosa und ihre Hybriden in Südwestbulgarien
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Abstract

Pyrus spinosa Forsk. (= P. amygdaliformis Vill.) kreuzt sich in beträchtlichem Masse mit P. pyraster Burgsd. und mit P. communis L. Es wurden drei Hybriden beschrieben, die zwar weniger, aber gut keimende Samen haben. Potentiell sind in der bulgarischen Population von P. spinosa Merkmale aller infraspezifischen Taxa vertreten, doch nur zwei von ihnen kommen in grösserem Masse vor, das Vorkommen der weiteren drei ist nur gering. Merkmale des übrigen infraspezifischen Taxon kommen nur in Kombination mit Merkmalen anderer Taxa bei Übergangsformen vor. Vorläufig ist auch die Verbreitung von P. spinosa und ihrer Hybriden in Bulgarien angegeben. /// Pyrus spinosa Forsk. (= P. amygdaliformis Vill.) hybridizes to a great extent with P. pyraster Burgsd. and with P. communis L. For example, in southwestern Bulgaria near the village Lozenica 13,6% hybrids of the total number of pear- trees were ascertained. The hybrids in most cases are more or less intermediary. In questionable cases the papillae on the epidermis of the lower leaf side can be used as a good diacritical character for verification of the hybrid origin, and the accessory cells surrounding the quard cells of stomata as well. The number of seeds in the fruits of hybrid plants is a little lower than in the fruits of P. spinosa. Also the differences between individual hybrid trees are more distinct than in trees of P. spinosa. The seeds of hybrid plants mostly germinate very well; however, hybrids with worse germinating seeds also occur. An analysis of descendants has proved a great extent of hybridization. The descendants of all plants of P. spinosa evaluated in detail were coincidentally hybrid, showing that the trees were pollinated with the pollen of P. pyraster or P. communis, or that these plants owing to repeated reciprocal pollination were very similar to P. spinosa. However, they were not homozygous, and an introgression difficult to distinguish was therefore the case here. In other cases, of course, descendants of P. spinosa were found, which did not split. The descendants of hybrids split in all cases, proving the correctness of determination of hybrid plants. Three hybrids have been described in German: P. pyraster Burgsd. × P. spinosa Forks., P. communis L. × P. spinosa Forsk. and P. communis L. × P. pyraster Burgsd. × P. spinosa Forsk. In the population of P. spinosa in southwestern Bulgaria the characters of all infraspecific taxa are potentially represented. However, only two of them, viz. var. spinosa and var. microphylla f. microphylla, occur more frequently. The next three of them (var. diapulidis, var. oblongifolia and var. microphylla f. lobata) are only slightly represented. In the other plants two or even more infraspecific characters occur; they are therefore the transitional forms. Not only in the whole territory under investigation, but also at one locality near the village of Lozenica some infraspecific taxa and the transitional forms grow together, so that panmixis must inevitably take place. However, the whole distribution area of P. spinosa is relatively extensive, and it is not known for certain whether a stronger differentiation of infraspecific taxa has not already taken place in other parts of the distribution area. The preliminary data on distribution of P. spinosa and of its hybrids in Bulgaria is also mentioned here.

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