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| ŠUMARSKI 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 1950—1957. 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 |
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between the hybrids and their parents being the result of age, and that the same trees after several years may present a different picture as regards the occurence of heterosis. A review of the hybrids presented in Table 1 according to their taxonomic groupings (after Dode 1905) permits to draw the following conclusions. I. Subgenus Leuce I. 1. Section Albidae — no data. 2. Section Albidae x Section Trepidae. The natural hybrid P. x canescens Sm. displays according to the general belief a heterosis with respect to both its parents. Satisfactory results were obtained from the crosses P. alba x P. tremula and the reciprocal, however, some authors criticize the view that these results indicate heterosis. 3. Section Trepidae The crossing of P. tremula with P. tremuloides and reciprocally is considered very promising with respect to the heterosis of growth and resistance to some diseases (e.g. Venturia tremulae Aderh.) Several breeders seek heterosis, with partial success, in the hybrids between the various different provenances of P. tremula. 71. Subgenus Eupopulus 1. Section Aigeiros. Hybrids carrying the general name of Euroamerican poplars originated from the cross between P. nigra and P. deltoides. Many of them show heterosis with respect to their parents. 2. Section Aigeiros x Section Tacamahaca. The hybrids P. pyramidalis x P. simonii, P. angulata x P. berolinensis and P. deltoides x P. trichocarpa gave good results as regards frost resistance and fast growth. 3. Section Tacamahaca x Section Aigeiros. Particularly the hybrids P. maximowiczii x P. pyramidalis, P. maximowiczii x P. nigra, P. simonii x P. pyramidalis as regards their luxurious growth, and P. suaveolens x P. pyramidalis as regards frost resistance, need to be mentioned. 4. Section Tacamahaca. The most successful and heterotic hybrids come from the breeding work done by Schreiner and Stout (P. maximowiczii x P. berolinensis, P. maximowiczii x P. trichocarpa). This same maternal tree yilds good results in crosses with P. laurifolia. There are many more successful hybrids within this section. This short review of the data presented in Table 1 should be supplemented with information about hybrids which do not show heterosis. Data on this subject are incomplete since the authors often publish only those results of their works which have yielded successful cultivars. However, as an example, some of the respective data are presented in Table 2. The crosses between P. maximowiczii and P. berolinensis mentioned in Table 2 were made in Körnik in 1950 and 1954, but gave poor results from the economic standpoint, whereas similar crosses made by Schreiner and Stout have produced some very valuable cultivars that are characterized by heterosis with respect to the both parents. It is also interesting that the hybrid P. angulata x P. laurifolia has produced no heterotic individuals, whereas the |
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hybrid P. angulata x P. berolinensis (hybrid between P. pyramidalis x P. laurifolia) is characterized by intensive growth. Table 2 could be further expanded by including several P. tremula x P. tremula hybrids many of which do not show any heterosis at all. A review of both these tables (1 and 2) leads to the conclusion that the phenomenon of heterosis occurs more commonly in hybrids whose parental species come from regions far removed from one another or from stands otherwise isolated from each other (e.g. the aspen of Dimpfelmeir comes from various altitudes of the same mountain region). When the crossing takes place between individuals of the same species or of closely related species, the phenomenon of heterosis can be observed only when the parental trees represent distant provenances. This does not explain the heterosis of P. canescens, since the species P. alba and P. tremula occur next to each other and their hybrid occurs in many regions where their ranges of distribution coincide. However, the heterosis may be the result of the parents being adapted to different ecological environments. OBSERVATIONS MADE IN KÖRNIK Let us compare the hybrids within the subgenus Leuce. In Table 3 are presented the parental trees, the mean heights of their 5-year-old progenies (from population samples numbering 30 trees), their standard deviations, and the standard deviations as percentages of the means. The lowest mean height was obtained from the cross P. alba from Körnik x P. tremula from Szczecinek, which can be regarded as an »unsuccessful cross«. It does not significantly differ from the not much better progeny of the cross P. tremula x P. tremula of local origin, which has the lowest variance. P. alba from Körnik which was pollinated from an introduced tree of the same species has a significantly greater mean height, and its highest progeny as well as that with the greatest variance is the one which comes from the cross P. tremula from Körnik pollinated by an introduced P. alba. The probability of obtaining some individuals characterized by heterosis increases when the variance is greater. On the other hand, it can be seen from Table 3 that a greater variance occurs when the mean height is greater. In order to obtain an objective measure of the variability that would be comparable, the standard deviation expressed as a percentage of the mean value is to be used. In the mentioned groups of individuals the greatest variability was exhibited by the progeny of the cross between a Körnik P. tremula and an introduced P. alba. The lowest variability was found in the population of the indigenous aspens. A similar example for the sub-genus Eupopulus is shown in Table 4. As before the data refer to the heights of 5-year-old seedlings for 4 hybrid progenies with 30 sample trees per progeny. The tallest ones and also significantly differing from the other is the progeny of the cross P. angulata x P. laurifolia (an intersectional hybrid). The remaining hybrid progenies do not differ significantly as to their mean heights. However, the variance expressed as a percentage of the mean places the progenies in a different sequence (2-3-1-4-). The greatest variability is shown by the hybrid P. angulata x P. nigra (intrasectional!) which means 128 |
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that it is in this hybrid progeny that heterotic individuals are most likely to be found. The progeny which had the highest mean height (1) has a small variability and the hybrid progeny form the cross P. pyramidalis x P. nigra varied least. At the same time, however, within the same section Aigeiros a cross between the American P. angulata and European P. nigra offers the greatest chance of obtaining heterosis. When breeding for trees which will be later propagated vegetatively it is necessary to aim at producing a small number of heterotic individuals, which could be used as new cultivars. Under these conditions the widest possible variability in the characters of economic interest is desirable. The result obtained with P. angulata x P. nigra is all the more interesting since it appears to be analogous to the excellent results obtained with the Euroamerican poplars (P. deltoides x P. nigra). CONCLUSIONS 1. On the basis of the available data it is difficult as yet to establish a definite relation between the parental affinity and the heterosis of the progeny, however, it does appear that this relation has no simple dependence on the systematic position of the parents. 2. Within a systematic unit (species or section), heterosis among hybrids appears to be greater the greater the heterogeneity of the parental forms. 3. This heterogeneity is best explained by the geographic isolation of the parental sites of origin which presumably have different ecological conditions, and also — as can be seen from the literature — other isolating factors can play a role here. 4. In the subgenus Eupopulus a greater degree of heterosis can be obtained in the intrasectional hybrids between parents of distant provenances than in intersectional hybrids between sympatric parents. 5. In the subgenus Leuce the results are not as clear cut, since hybrids between the sections Albidao and Trepidae often show considerable heterosis in spite of the fact that the parents are sympatric. UTJECAJ RODITELJSKOG AFINITETA NA STUPANJ IIETEROZISA KOD HIBRIDA TOPOLA Zaključak 1. Na osnovi raspoloživih podataka teško je zasada utvrditi tačno određen odnos između roditeljskog srodstva i heterozisa potomstva. Međutim .izgleda da taj odnos nije u jednostavnoj ovisnosti o sistematskom položaju roditelja. 2. Unutar sistematske jedinice (vrsta ili skupina) izgleda da je heterozis između hibrida to veći što je veća heterogenost roditeljskih formi. 3. Ta heterogenost se može najbolje objasniti geografskom izolacijom roditeljskih staništa porijekla koja vjerojatno imaju različite ekološke prilike, a također — kao što je vidljivo iz literature — ovdje mogu igrati ulogu i različiti drugi izolirajući faktori. 4. Kod podroda Eupopulus veći stupanj heterozisa može se dobiti kod unutarskupinskih hibrida između roditelja udaljenih provenijencija, nego kod međuskupinskih hibrida između roditelja istog područja rasprostranjenja. 5. Kod podroda Leuce rezultati nisu tako jasni budući da hibridi između skupina Albidae i Trepidae često pokazuju heterozis usprkos činjenici da su im roditelji s istog područja rasprostranjenja. |
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Heterosis mentioned Table 1. Female tree Male tree P. tremula P. tremula P. tremula P. tremula gigas P. alba P. tremuloides P. tremula P. tremula P. pyramidalis P. simonii P. laurifolia P. suaveolens P. pyramidalis P. yunnanensis P. deltoides v. virginiana P. balsamifera (tetraploidal pollen used) P. pyramidalis P. laurifolia P. berolinensis P. trichocarpa P. nigra P. I-438p (tetraploid clone) P. nigra plantierensis P. trichocarpa P. berolinensis Kind of heterosis Growth vigour Growth vigour Growth vigour Growth vigour Growth vigour Growth vigour and resistance against diseases Growth vigour Frost resistance Frost resistance Growth vigour Growth vigour Growth vigour Growth vigour Growth vigour Growth vigour Growth vigour Growth vigour Growth vigour Growth vigour Growth vigour %> rooted Growth vigour Growth vigour and resistance Growth vigour and resistance P. P. P. P. P. P. P. P. P. P. P. P. P. P. P. P. P. P. P. P. P. tremula tremula alba alba tremula tremula tremuloides alba suaveolens pyramidalis balsamifera balsamifera simonii simonii yunnanensis balsamifera maximowiczii maximowiczii angulata deltoides deltoides Several black poplars P. maximowiczii P. maximowiczii P. maximowiczii Date of publica tion 1956 1963 1961 1961 1956 1961 1961 1961 1961 1959 1959 1958/59 1960 1962 1962 1963 1960 1963 Breeder´s (author´s) name, country H. Johnson, Sweden R. Dimpfelmeier, Germany A. V. Albienskij, U. S. S. R. A. V. Albienskij, U. S. S. R. :S. Bialobok, Poland Several authors Natural hybrid — P. canescens A. V. Albienskij, U. S. S. R. A. V. Albienskij, U. S. S. R. A. V. Albienskij, U. S. S. R. A. V. Albienskij, U. S. S. R. Le T.-Y. China Le T.-Y. China Official report, New Zeland Manzos A. M., U. S, S. R. Z. Pohl, Poland Z. Pohl, Poland Z. Stecki, Poland C. M. Larsen, Belgium Many cultivars called P. x euramericana cv. M. Sekawin, Italy Many well konwn cultivars from Schreiner´s and Stout´s breeding works. |
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No heterosis Table 2. Date of Breeder´s (author´s) Female tree Male tre publication name, country P. balsamifera diploid P. balsamifera 1960 A. M. Manzos, U.S.S.R. diploid p. nigra P. pyramidalis 1961 A. V. Albienskij, U.S.S.R. p. maximowiczii P. berolinensis 1962 Z. Pohl, Poland p. angulata P. laurifolia 1963 Z. Stecki, Poland p. deltoides P. deltoides 1964 C. M. Larsen, Belgium p. trichocarpa P. trichocarpa 1964 C. M. Larsen, Belgium Crosses in the subgenus Leuce (5-year-old) Table 3. No. Female tree, origin Male tree, originMean height x Standard deviation 1 P. tremula, Körnik P. tremula, Körnik 476,0 66,6 2 IP. tremula, Körnik P. alba, Fredrowo 678,0 158,1 3 P. alba, Körnik P. alba, Fredrowo 545,0 107,4 4 P. alba, Körnik P. tremula, Szczecinek 436,2 89,5 Crosses in the subgenus Eupopulus (5-year-old) Table 4. No. Female tree Male tree Mean height Standard deviation 1 P. angulata P. laurifolia 515,5 79,7 2 P. angulata Pnigra 466,5 114,9 3 P. pyramidalis P. laurifolia 466,5 99,0 4 P. pyramidalis P. nigra 431,7 61,7 REFERENCES 1. Aldhou s L. R. 1957. Provenance studies. For. Res. For. Comm., London 1956/57. 2. Albienski j A. V. 1961. Dostignuća u selekciji šumskih vrsta u SSSR-u. Topola, 5, Beograd. 3. Anony m 1959. Poplar investigation. Report Soil Conservation and Rivers Control. Council, Wellington 1958/59. 4. Bialobo k S. 1965. Wstepne wyniki hodowli topoli w Zakladzie Dendrologii i Pomologii w Korniku. Arboretum Körnickie roezn. II, (175—193). 5. DimpfelmeierR . 1963. Ergebnisse fünfjähriger Kombinationszüchtungsversuche mit Populus tremula L. Forstwiss. Cbl., 72, (9) 10. |
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6. Dođ e L. A. 1905. Extraits d une monographic medite, seerie »Populus«. Societe d´ histoire naturelle d´ Antron, Buli. XVIII. 7. JohnssonH . 1956. Heterosiserscheinungen bei Hybriden zwischen Breitegradrassen v. Populus tremula. Z. Forstgen., (6). 8. Manzo s A. M. 1960. Bystrorastuszczaja forma Populus balsamifera L. poiuczonnaja ot opylenja ženskich cwetkow Populus balsamifera, L. frakcionirowanoj pylcoj etogo wida. Dokl. Akad. Nauk SSSR, 131. 9. Larse n C. S. 1958. Angewandte Genetik im Waldbau. Schweiz. Z. Forst., 109, (8/9). 10. Larse n Mühle . 1960. L amelioration du peuplier par voie genetique. Bull. Soc. for. Belg. 11. Le T. Y. 1959. New achievements in producing faster growing new hybrids through applying Mičurin´s genetic principles. For. Sei., Peking, 1959 (3). 12. Ljunge r Ake. 1959. AI och Alförädling. Skogen, 46 (5). 13. Ma 1 i no w sk i E. 1952. The problem of heterosis. VI. Bull. Acad. Polon. Sci., 41. 14. P o h 1 Z. 1962. Studia nad wzrostem i morfologia körnickich mieszancow Populus Maximowiczii Henry. Arboretum Körnickie, t. VII (115) 184. 15. S c h r e i n e r E. J. 1934. Description of the new Hybrids Poplars. Bull, Torrey bot. Club, 61. 16. Sekawi n M. 1963. Etude d´ un peuplier tetraploide obtenu artificiellement et sa descendance. World Consultation on forest genetics and tree improvement. Stockholm. 17. S t e c k i Z. 1963. Badania nad wzrostem mieszancow topoli w zastosowaniu do ich selekcji. Arboretum Kćrnickie, t. VIII. (155—218). 13i |