DIGITALNA ARHIVA UMARSKOG LISTA
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| UMARSKI LIST 1-2/1966 str. 128 <-- 128 --> PDF |
THE INFLUENCE OF PARENTAL AFFINITY ON THE DEGREE OF HETEROSIS IN POPLAR HYBRIDS (Contributed paper) by ZBIGNIEW STECKI Institute of Dendrology and Körnik Arboretum, Polish Academy of Science, Poland. The term »heterosis« has been variously defined by different authors and referred to different phenomena. The dominating view seems to be that heterosis is the occurrence in Fi hybrids of quantitative characters that surpass in magnitude the parents. In this sense heterosis is synonymous with »hybrid vigour« or the German »Luxurienz«, particularily when referred to growth in height or similar characters. Some authors (e.g. Schönbach) make s clear distinction between luxurience and heterosis. In the hybrids of cultivated plants we expect to find heterosis in respect of characters that are economically of interest. Thus breeding work is aimed at obtaining heterosis. However, not all hybrids display it. The present paper attempts to present the problem of heterosis in poplars in the light of available literature and observations made on hybrids obtained in Körnik during the years 19501957. 1. A REVIEW OF INFORMATION ON THE HETEROSIS OF POPLAR HYBRIDS. Much breeding work has been done on poplars in the various parts of the world, and as a result many hybrids were obtained that are characterized by fast growth, or the intensification of other characters of economic interest Many breeders describe these results as heterosis. In Table I are presented parental combinations that have yielded heterotic progeny. In column 4 the date of publication of the information and in colum 5 the author or an other source is presented. It is not sufficiently clear when the results obtained can be considered as heterosis in the true sense. Some authors consider the results that are better than the mean for the two parents as indicating heterosis (hypothetical heterosis). Others reserve the term heterosis only for such results that are better than in both the parents (true heterosis). Le and Sekawin present their results in percentages of the parental performance. Bialobok and Pohl characterize the hybrid populations by dividing them into performance groups. Stecki compares the new hybrids with the cultivar P. robusta. Similar comparisons are made by Larsen. All the data collected refer to a young material. The authors usually do not bother to comment on the possibility of differences in growth rhythm |