Báo cáo khoa học: "Performance of vegetatively propagated Larix decidua, L kaempferi and L laricina hybrids"

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Original article Performance of vegetatively propagated Larix decidua, L kaempferi and L laricina hybrids LE Pâques INRA, Centre d’Orléans, Station d’Amélioration des Arbres Forestiers, 45160 Ardon, France 17 October 1991) (Received 25 January 1991; accepted Summary — Interspecific hybridization between the tamarack and the Japanese and European larches was attempted. Successful crosses between the tamarack and the Japanese larch as well as the 3-way hybrid (tamarack crossed to European x Japanese larches) were obtained for the first time in France but on a limited scale. Hybridization with tamarack seems possible but rather difficult due to differences in phenology and reproduction potential. Hybrid clones were successfully propa- gated by stem cuttings with high rates of rooting and a good quality of the root system, especially for the tamarack and its hybrids. Field performances at 8 years reveal that even if their initial growth is vigorous is absolute terms, neither the tamarack nor its hybrids could compete with the hybrid Larix decidua x L kaempferi for both growth and stem form. One exception is the 3-way hybrid L laricina x (L decidua x L kaempferi) which can be advantageously compared to the latter. An additional advan- tage could be its expected greater tolerance of wet soils. Nevertheless, its creation appeared to be difficult. So far, the hybrid L decidua x L kaempferi seems to be best for reforestation. I clonal test / interspecific hybridization / vegetative propagation Larix / larch / tamarack / cutting stem Résumé — Comparaison des performances de différents hybrides entre les mélèzes laricins d’Europe et du Japon multipliés végétatlvement. L’hybridization interspécifique offre à l’améliora- teur des perspectives intéressantes pour la création variétale, notamment pour la combinaison de caractères complémentaires favorables et par valorisation de l’hétérosis. Dans cette perspective, plusieurs croisements contrôlés entre le mélèze laricin (Larix laricina) - adapté aux sols hydro- morphes - et les mélèzes d’Europe (L decidua) et du Japon (L kaempferi) ont été tentés, certains succès tels le croisement entre le mélèze laricin et le mélèze du Japon et celui de l’hybride avec laricina x (L decidua x L kaempferi)). Bien que possible, l’hybridation avec le mélèze laricin triple (L est rendue difficile par de très nombreux problèmes de floraison, entre autres : décalage phénologi- que, virescence, absence de pollen. Les différents hybrides obtenus ont ensuite été multipliés par bouturage horticole avec des taux d’enracinement élevés et une bonne qualité du système racinaire. En particulier, le bouturage du mélèze laricin et de ses hybrides se révèle encore plus facile que celui des hybrides entre le mélèze d’Europe et du Japon. Les premiers résultats en forêt à 8 ans montrent que malgré une croissance initiale très vigoureuse en termes absolus, ni le mélèze laricin ni son hybride avec le mélèze du Japon ne supportent la comparaison avec l’hybride L decidua x L kaempferi. Seul l’hybride triple apparaît prometteur avec une vigueur et une qualité de forme du fût comparables. Néanmoins, la difficulté de son obtention limite son intérêt pratique à moins qu’il ne se révèle plus tolérant à l’hydromorphie du sol que son parent hybride. interspécifique / bouturage / test clonal Larix / mélèze / hybridation
INTRODUCTION mented for century (Henry and nearly a Flood, 1919). the Larix species, two are of com- Among Hybridization between tamarack and ei- for reforestation in western Eu- ther the European or the Japanese larches mon use rope, namely the European larch (Larix de- seems to be possible as reported by cidua Mill) and the Japanese larch (Larix Chowdbury (1931) and Syrack Larsen kaempferi (Lamb) Carr Larix leptolepis (1937) for Larix laricina and Larix decidua, = (Sieb and Zucc) Gord). A third one, ie the and by MacGillivray (1967) for Larix larici- tamarack, a species from North America na and Larix kaempferi. Nevertheless, as (Larix laricina (Du Roi) K Koch), has been suggested by MacGillivray’s (1967) obser- considered too as a potentially valuable vations, crossing between tamarack and species because of its tolerance to water- the Japanese larch was quite unsuccessful logged soils in its natural range. So far, its and seed could be obtained from reci- no plantation has been largely restricted in procal mating. Moreover, though Avrov Europe to botanical gardens and experi- (1982) characterizes crossability between tamarack and either the European or the ments. Japanese larches as ’partial’, he could get As a result of certain biological limita- filled seed from crosses between tama- no tions of each of these species (eg canker rack and the Japanese larch and no re- sensitivity of Larix decidua, poor stem form sults are presented from crosses including and summer drought sensitivity of Larix the European larch. kaempferi and poor growth and stem form of Larix laricina; Pâques, in preparation), Several matings including the European great emphasis has been put on interspe- and Japanese larches on the one hand cific hybridization in French tree improve- and the tamarack on the other were at- ment programs. tempted in this exploratory study. Objec- tives were to test their interspecific cross- Interspecific hybridization is used both ability and if positive, to study the respec- develop and combine favourable com- to tive hybrids for use in reforestation. In par- plementary traits from both parent species ticular, it was interesting to compare their as well as to take advantage of hybrid vi- performances with those of pure larch spe- heterosis. or gour cies. Hybridization between Larix species is documented by numerous natural and arti- ficial interspecific crosses (Bobrov, 1973, MATERIALS AND METHODS cited in Wright, 1976; Avrov, 1982). No in- compatibility barriers, more severe than those observed within a species (corres- Hybridization and material ponding to low filled seed sets (Kosinski, 1987)), seem to exist. Successful crosses included crosses between Larix Hybridization have been made even between geographi- decidua and L kaempferi (coded as ’dec x kae’) cally distant species as reported by Syrach and its reciprocal: L kaempferi x L decidua (’kae Larsen (1937) and Delevoy (1949). x dec’). F hybrids were also attempted by cros- 2 sing several F hybrid clones (’(dec x kae) X 1 Among the three Larix species mentio- (dec x kae)’). Tamarack was involved in three ned above, hybridization between the Eu- crossings: L laricina x L decidua (’lar x dec’), ropean and the Japanese larches is most L laricina x L kaempferi (’lar x kae’) and the 3- commonly used in tree breeding and its way hybrid: L laricina x (L decidua x L kaempfe- ri) (’lar X (dec x kae’). feasibility and interest have been docu-
Hybridization through controlled crossing Vegetative propagation place at the INRA Forest Tree Improve- took ment Research Station in Orléans in spring Prior to field plantation, part of the material 1979. Hybrids ’lar X (dec x kae)’ and ’(dec x kae) under study (ie larch hybrids and tamarack) was X (dec x kae)’ shared the same father hybrid vegetatively propagated by stem cuttings and clone. Different tamarack mother clones were part by seedlings (ie Japanese larch, Norway used for obtaining hybrids ’lar x kae’ and ’lar X spruce and Douglas fir). Vegetative propagation (dec x kae)’. had two objectives: first, to multiply poor repre- Successful hybrids were then field tested and sented hybrid material, and secondly, to study compared to one provenance of Larix kaempferi the feasibility of the technique. (coded as ’kae’) and to two provenances of Larix Ortets of the different larch hybrids and of ta- laricina (’lar’). No pure European larch was pre- marack were selected for total height at 2 years sent in the experiment. In addition, two more in a progeny test. The proportion of ortets species were also used as controls of traditional (clones) selected ranged from 1.5 to 35.0% of reforestation material, namely Norway spruce each family. Nevertheless, for hybrids ’lar x kae’, (Picea abies (L) Karst, represented by two pro- ’lar x ’(dec x kae)’ and ’(dec x kae) x (dec x of southern Poland origin) and Dou- venances kae)’, all the seedlings were used as stock glas fir (Pseudotsuga menziesii (Mirb) Franco, plants due to the low number of available seed- by one provenance from Arlington, Washington). lings. In total, 184 ortets were finally chosen. They will be referred to in tables and figures by Further details about the origin of the material ’P ab’ and’P menz’ respectively. Provenances of are given in table I. both species have been recommended for refo- restation in France because of their outstanding Ortets were potted in autumn 1981 and for- performances. Japanese larch, Norway spruce ced under greenhouse conditions before propa- and Douglas fir are represented by open pollina- gation. ted material collected in natural forest stands. An average of 30 softwood cuttings per clone A brief description of the material is given in (about 10 cm long) were taken in May 1982 and table I. It presents only successful hybrids. dipped in a 0.5% IBA solution including a fungi-
cide. They were rooted in a medium mixture (2- In addition, the number of rooted cuttings per 1-3 in volume) of peat, compost and pouzzolane clone judged to be plantable was based on the (volcanic ash) under greenhouse conditions. An frequency of score 1 and 2 for the quality of the intermittent mist was used and alternating fungi- root system and on further survival of ramets in cide treatments were applied as necessary. the nursery. Rooted cuttings were then transferred to the First measurements in the field took place in INRA nursery in March 1983 for two years be- 1989, 8 years after propagation. They concern fore being field planted while the control species survival rate (%S), total height (H), the length of (’kae’, ’P ab’, and ’P menz’) were sown in the the 1989 height increment (HI) and height same nursery in May 1983. growth of the last 4 years, from 1986 to 1989 (HG4)-which corresponds to the growth in the forest after overcoming planting shock. Stem form quality was evaluated by the frequency of Field experimental design basal sweep (%BS) and a subjective assess- ment of stem straightness (SS) on a 5-point Three-year old rooted cuttings and two-year old scale: class 1 severe crookedness with more = seedlings were planted together in the Massif than two crooks per stem; class 2 same as 1 = Central Mountains during the winter of 1984. but no more than one or two crooks per stem; Two tests were established: the major one in class 3 light crookedness with more than two = the State Forest of Eclache (Puy de Dôme, crooks per stem; class 4 same as 3 but no = 2°41’E, 45°44’N, 1 000 m), and a minor one in more than one or two crooks per stem; and, Peyrat-Le-Château (Haute-Vienne, 1 °44’E, class 5 straight stem. The frequency of = 45°49’N, 450 m). Because of low representation straight stems (%SS) for each clone was then of certain hybrids in the latter, only the former estimated from frequency of ramets score for will be considered. stem straightness greater than 3. Description of Eclache is a good coniferous forest site with stem straightness follows Keiding and Olsen’s deep brown forest soil and high precipitation classification (1965) but in the reverse order. a well distributed throughout the year (average When possible, an analysis of variance was annual rainfall up to 1 000 mm). Nevertheless, conducted on individual data following the because of the rather short growing season and model: particularly windy conditions, the elevation of this site is the upper limit where larch be can planted. An balanced randomized block incomplete, where used with 9 blocks, 95 plants per design was Yl th observation of clonek of species ijkl = block and two-tree random non-contiguous plots (’species’ will be used in this paper as a generic (see Libby and Cockerham, 1980) per genetic term to design both pure larch species and inter- entry and per block. Spacing was 3 by 3 meters. specific hybrids) jin block i No soil preparation and fertilisation were applied μ = general mean prior to plantation. B = effect of block i (fixed effect), i S = effect of species j(fixed effect), j BS= block x species interaction, ij Measurements C = effect of clonek within species j(random k(j) effect), The percentage of rooted cuttings per clone ϵerror term. ijkl = estimated and the quality of the root sys- was Prior to analysis, homogeneity of the pheno- tem was assessed according to the following typic variance-covariance matrices of each ge- numerous roots well distributed scale: 1 = netic entry was tested according to Kullback’s intermediate; 3 around the stem base; 2 = = test (Legendre and Legendre, 1984) in order to poor root system with one or two roots and a verify whether data from the different genetic en- one-sided distribution; 4 no roots. =
tries could be included in the same analysis pean larch and must therefore be used as or should be analysed separately. female. Tamarack clones produced no a Species means were then compared follow- viable pollen and stored pollen of Euro- ing Bonferroni’s test after adjustment of data for pean larch was not available at that time. significant block (and interaction) effects if any, Because of a very low reproduction po- and a second analysis of variance on adjusted tential of tamarack under Orléans condi- data. For qualitative variables (eg %S, %SS), tions (absence of pollen, numerous prolife- comparisons between species were based on the original observations according to the 2I or rated strobili and high rates of empty G-test as defined by Sokal and Rohlf (1981). It seed), only one full-sib family per success- tests the complete independence between two ful tamarack hybrid type (’ x kae’ and ’lar lar descriptors. Based on contingency tables, 2I is X (dec x kae)’) could be produced on two computed following Arbonnier (1966): different mother clones. Moreover, the number of viable seedlings obtained up to the nursery stage was low (for ’ x kae’, 2 lar seedlings out of 623 seeds and 41 clones; where for ’ x (dec x kae)’, 13 seedlings out of lar number of observations for genetic entry i 56 seeds and 330 clones). This result ij x = and score j(0/1), confirms Avrov’s (1982) and MacGillivray’s X marginal sum of observations for species i . i (1967) observations on the low fertility of = this type of crossings. For example, Mac- X.= marginal sum of observations for score j, j Gillivray’s results on growth performances k = number of species in comparison, of tamarack x Japanese larch are based n= number of scores, only four viable seedlings. on N = total number of observations. 2I is then compared to Chi distribution values 2 with (k-1) (n-1) degrees of freedom. Used in an Rootability and quality of root system iterative way, it allows association of the diffe- rent species in homogeneous groups. More than 5 200 cuttings were struck in the rooting medium and nearly 82% roo- RESULTS ted. All 184 tested clones were successful- ly rooted, with rooting percentages ranging from 9 to 100. Hybridization success Rate of success was also very variable from hybrid to hybrid (table II) with the low- In addition to crosses between European est values for ’kae x dec’ and ’(dec x kae) and Japanese larches (88% of which gave X (dec x kae)’. 2I-test reveals a heteroge- filled seed with rates of filled seed ranging nous response of rooting ability between from 16 to 76%), those with tamarack were 228 01 > χ 15 df 25.0) 0.95, 2 species (21 = = also partly successful. These included hand ’dec x kae’, ’lar’ and ’ X lar with on one crosses between tamarack and the Japa- (dec x kae)’ associated with the highest nese larch (’lar x kae’) and between tama- rooting rates and on the other hand, ’ x lar rack and the F hybrid ’dec x kae’. 1 kae’, ’(dec x kae) X (dec x kae)’ and ’kae x dec’ with the lowest. The absence of hybrids between tama- rack and the European larch is explained As a whole, 62% of the rooted cuttings by the fact that under Orléans conditions, had an excellent root system and more tamarack flowers earlier than the Euro- than 88% were judged satisfactory (scores
clones had disappeared at that stage, six 1+2). Nevertheless, hybrids responded of which were from the hybrid ’kae x dec’. differently (21 471.2 > Chidf 0.95, 15 2). very = Hybrids ’ x kae’ and ’ X (dec x kae)’ lar lar with the best root system quality could be grouped together, followed then by 4 other Field performance dec’; and ’ groups: ’ ’dec x kae’; ’kae lar’; x Homogeneity of the phenotypic variance- (dec x kae) X (dec x kae)’. covariance matrices for the seven larch en- At 3 years, before outplanting, the total tries for total height and stem straightness proportion of plantable cuttings went down at 8 years was accepted: Chi = 4.315 < K 2 to 57% (or less than 47% of the initial total Chi df Data of all the larch species 0.95, 18 2 ). number of cuttings inserted). This severe were then included in the analysis of va- reduction due to absence of rooting or riance, except those of the Japanese larch poor root system and mortality in the nur- propagated by seedlings. sery affected all species; the worst results Survival rates at 8 years (or 7 for seed- (up to 80% loss) were observed for hy- lings) ranged from 69 and 97% for cuttings brids ’kae x dec’ and ’(dec x kae) X (dec x (table III) and reached nearly 92% for the kae)’. For the others, nearly 50% of the Japanese larch seedlings. 2I-test was sig- cuttings could be planted in the forest. nificant at α 0.05 (2I 85.2 > χ df 0.95,10 2 ). Three homogeneous groups were consti- = = Three homogeneous groups could be de- tuted: they included from best to worst ta- fined, with hybrid ’lar X (dec x kae)’ in the marack and its hybrids (’ X (dec x kae)’, lar first group; in the second, Japanese larch ’ and ’ x kae’); ’dec x kae’; and ’(dec x lar lar’ seedlings, ’(dec x kae) X (dec x kae)’, ’lar x kae) X (dec x kae)’ and ’kae x dec’. Ten
at 8 years (H). The hybrid ’dec x kae’ and ’dec x kae’; and in the third group, height clearly gave the best results. It sur- tamarack ’lar’, ’kae x dec’, Douglas fir and kae’ Norway spruce. Survival of Norway spruce passed Norway spruce (’P ab’) by 108%, tamarack (’ by 44%, Douglas fir (’P was particularly poor. lar’) menz’) by 39% and the Japanese larch As reported in table III, height growth in (’kae’) by 25%. It was significantly superior 1989 (HI) was vigorous for all entries. too over the other hybrids with values ran- Among them, hybrids ’dec x kae’, ’lar X ging from 48% over ’ x kae’ down to lar (dec x kae)’ and ’kae x dec’ were the most 14% over ’ X (dec x kae)’. Results are lar noticeable with a shoot length of 93.8, 78.6 mostly similar for HG4 but with superiority and 76.4 cm respectively. Analysis of va- of hybrid ’dec x kae’ over the other genetic riance of vigour traits (H and HG4) showed entries even more important. As a compa- highly significant effects (α 0.001) of the = rison, in the minor test of Peyrat-Le- three main factors: block, species and- Château, the hybrid ’dec x kae’ reached clone within species with no significant in- 413 cm for total height at the same age; it teraction between blocks and species surpassed by only 9% hybrid ’lar X (dec x (table IV). Data were adjusted for block ef- kae)’ and by 72% tamarack (’lar’). fects. Figure 1 summarizes results of Bonfer- Total height growth development over roni’s test of comparison of means for total time from 1986 to 1989 is presented in fi-
gure 2. Except for the Japanese larch (dec x kae)’; ’lar’, ’kae’, ’kae x dec’ and ’dec (’kae’) and the hybrids ’kae x dec’ and ’lar kae’ for basal sweep, with values ranging x x kae’, superiority of the hybrid ’dec x kae’ from no defect for the species used as over the other species tended to increase. control up to more than 42% for the hybrid According to their growth curve pattern, ’dec x kae’. For frequency of straight stems the species might be associated in three (%SS), group 1 included Norway spruce (P groups corresponding to fast, intermediate ab) and Douglas fir (P menz); group 2 ’kae and slow growing material. Respectively, x dec’, ’lar X (dec x kae)’ and ’dec x kae’; these would include ’dec x kae’; ’lar X (dec and group 3 ’kae’, ’(dec x kae) X (dec x x kae)’, ’kae x dec’, ’(dec x kae) X (dec x kae)’, ’lar’ and ’lar x kae’. %SS ranged from kae)’ and ’kae’; and finally ’lar’ and ’lar x no defect for the control species up to kae’. 100% for the hybrid ’lar x kae’. brid (’dec x kae’) was quite severely affected with differences (at α Highly significant = nearly two-thirds of crooked stems (table noted too between species for 0.001) are III). stem straightness (SS) at 8 years as well as between blocks (table IV). Two entries including the tamarack (’lar’) and its F hy- 1 DISCUSSION AND CONCLUSION brid with the Japanese larch (’lar x kae’) were characterized by severe crook (table III) and were significantly different (at α Hybridization including tamarack is repor- = 0.01) from the other entries. ted here for the first time in France and the test at Eclache is the first opportunity to As well, for the frequency of basal observe tamarack hybrids performance in sweep (%BS) and the rate of straight the field. stems (%SS), the material responded dif- ferently (2I= 95.8 > Chi for %BS 0.95, 10 df 2 Hybridization between European and and 2I 195.6 > Chi 10 df for %SS). 0.95, 2 Japanese larches does not raise any parti- = The material could be associated in three cular problems besides those well known homogeneous groups. They included from to larch breeders, namely the low set of best to worst: Norway spruce (P ab) and filled seed per cone which is observed in Douglas fir (P menz); ’lar x kae’ and ’lar X both natural and artificial crosses (Kosins-
phenology with other species (Japanese larch)). Vegetative propagation was successful for most of the hybrids but clonal variation was substantial. Such a high rate of root- ing with young plants is not unusual (Mason, 1989). The low performance du- ring the propagation phase of two hybrids ’kae x dec’ and ’(dec x kae) X (dec x kae)’ ki, 1987). Hybridization using tamarack for both rootability and their root system but difficult under Or- proved to be possible quality cannot be attributed to vigour of the léans climatic conditions. The limited suc- donor plants; they were as vigorous as cess noted in this study may mostly be due those of other species. Possible explana- problems connected with flower deve- to tions could be either the age of the donor lopment (proliferated female strobili, matu- plants for hybrid ’kae x dec’ (one year older ration failure of male strobili with resulting than other hybrid stocks) or the genetic na- lack of pollen production, non-matching
ture of the material or both. Hybrid ’kae x ceeded performances of better known hy- dec’ clones were in fact selected in a brids (’dec x kae’ or its reciprocal) with the single progeny from open pollinated hybri- exception of hybrid ’lar X (dec x kae)’. Ta- dization in a seed orchard while hybrid marack was very poor but in any case, its ’(dec x kae) X (dec x kae)’ clones were se- height growth was faster than that of Nor- lected in a single F full-sib family, the pa- 2 way spruce. The three-way hybrid ’lar X rents of which were full sibs. In both (dec x kae)’ was vigorous with perfor- cases, inbreeding may have taken place mances intermediate (and significantly dif- and this could have serious depression ef- ferent) to those of its parental species (’lar’ fects, as expected on larch (Dieckert, and ’dec x kae’): -13,7% compared to ’dec 1964). No abnormality of growth (growth x kae’, + 26.7% with respect to ’lar’ for total depression, abnormal branchiness) was height at 8 years. In contrast, the single hy- nevertheless detected at the time of ortet brid ’lar x kae’ performances were even selection. lower (but not significantly different at α = 0.01) than those of its poorer parent spe- Considering the traits related to vegeta- cies (’lar’). MacGillivray (1967) observed a tive propagation, tamarack as well as its much more favourable performance of that hybrids perform better than the other hy- hybrid in south-central New Brunswick brids, ’dec x kae’ included. This is particu- where it was 48.0% and 57.4% taller res- larly true for the quality of the root system pectively than L laricina and L kaempferi at (table II). 7 years. But his observations were based In the field test, no serious adaptation on only four seedlings. problems have been noted as survival up The hybrid between L decidua and to 8 years is judged satisfactory, except for L kaempferi is known for its remarkable vi- tamarack with nearly 30% mortality. Simi- gour (Pâques, 1989) which is confirmed by lar results were observed for seedlings of the present study in rather severe ecologi- the same two tamarack provenances used cal conditions. As a comparison, at two in this study (and others from the same la- other sites in somehow milder conditions titude) in an arboretum located in the Mas- of the western range of the Massif Central sif Central Mountains (Margeride, Lozère, Mountains, total height at the same age elevation: 1470 m) (Imbert, 1988). Al- and for a similar genetic material exceeded though the latitudes of origin of the tested by 76 and 27% respectively total height re- provenances are similar to those of the corded on the site of Eclache. test sites, the local weather conditions are The F hybrid ’(dec x kae) X (dec x kae)’ 2 severe (windy) and a better choice of pro- had an intermediate growth. Its success venances from higher latitudes and less seems highly dependent on the coancestry oceanic influenced zones might be recom- level of its F parent clones (Dietze, 1974). mended. In any case, larches showed a 1 much higher survival rate than Norway If tamarack and its hybrids presented spruce and Douglas fir. This is not surpri- few basal sweep defects as compared to sing for this Douglas fir provenance (Ar- L decidua x L kaempferi, they were on av- lington) which may be at its ecological limit erage affected by serious stem form prob- here. For Norway spruce which is traditio- lems with a much higher frequency of nally used in this region, no obvious expla- crooked stems and more severe defects. nation can be given. Hybrid ’lar X (dec x kae)’ was once again an exception as its stem form quality was With regard to growth and vigour (table very close to that of ’dec x kae’ (table III). III), neither tamarack nor its hybrids ex-
Stem form is nevertheless a general cidua x L kaempferi)) which combines ex- problem in larch breeding (Keiding and Ol- cellent adaptability, fast growth (second to sen, 1965) and as shown in table III, no hy- L decidua x L kaempferi) and good stem brid or pure species is really free from this form (% BS, SS, %SS). Similar observa- defect, the frequency of which goes up to tions both on the remaining trees in the mi- nor test site of Peyrat-Le-Château and in 50% even for the best tested material. This condition is not restricted to vegetatively Orléans clone collection confirm its quality. propagated material (Dietze, 1974). More- Due to the low number of entries (ram- over, straightness and vigour have been ob- ets, clones and families) for some hybrids, served in many of our experiments to be precise comparison of material was not al- negatively correlated and for certain hy- ways possible. In particular, it is difficult to brids, correlations significantly different detect whether the observed performance are from 0.05) (table V). Fortu- (for differences are the result either of clone zero α = nately, a rather broad variability exists for sampling or of the species themselves. this trait at the various levels (ramet (table Testing on more sites and of other clones III), clone, family and population). There- from a wider range of hybrid families fore, further selection will certainly improve should be undertaken to confirm these ear- this trait. ly results and to give indications about the interest of tamarack hybrids over L decid- Tamarack is a poorly known species in L kaempferi. France. These first results from experi- ua x ments indicate that choice of provenances But in any case, the difficulty - con- and proper sites for reforestation under firmed by later attempts - to obtain hybrids French conditions is important (Imbert, using tamarack either as female or as 1988; Pâques, in preparation). Although male under Orléans conditions is a major vegetative propagation and adaptation do limiting factor whatever the interest of not seem to be serious problems in this ex- some of its hybrids. periment, field performance for the most Transfer of favourable traits from one important traits (vigour and stem form) of species to another through interspecific hy- both tamarack and its hybrids was never bridization is of major interest in larch superior to better known hybrids between breeding as the species commonly used, the European and Japanese larches (even seem complementary for a number of to the second generation hybrid ’(dec x characteristics (eg canker resistance, stem kae) X (dec x kae)’). One major exception form). In particular, it is important to check is for the 3-way hybrid (L laricina X (L de- if the tamarack tolerance to waterlogged
soils Henry A, Flood MG (1919) The history transferred to other larch of the might be Dunkeld larch. Proc R Ir Acad Sec B 35 species through hybridization. Further re- Keiding H, Olsen HC (1965) Assessment of search work with tamarack will be oriented stem form in clones and progenies of larch. in this direction. Silvae Genet 14, 115-122 Kosinski G (1987) Empty seed production in Eu- ropean larch (Larix decidua). For Ecol Manag ACKNOWLEDGMENTS 19, 241-246 Imbert P (1988) Choix des Espèces de Reboise- The technical assistance of P Legroux and Haute-Margeride. Premier bilan de ment en M Faucher for data collection and the help of l’Arboretum Curie (Lozère-Col des 3 S&oelig;urs, CH Schneider for statistical analysis were great- Alt 1470 m). INRA-Orléans, document n° 397 ly appreciated. Legendre L, Legendre P (1984) Écologie Numé- rique. 2. La Structure des Données Écologi- ques. Masson, Québec, 182-183, 2nd edn REFERENCES Libby WJ, Cockerham CC (1980) Random non- contiguous plots in interlocking field layouts. Silvae Genet 29, 183-190 Arbonnier P (1966) L’analyse de l’information. applicationà la loi multi- MacGillivray HG (1967) Hybrid between tama- Aperçu théorique et nomiale. Ann Sci For 23, 950-1017 rack and Japanese larch appears promising in south central New Brunswick. Res Notes Avrov FD (1982) Crossability of various larch Dep For Can 23, 2-3 in collection-parent plantation at species a southern Siberia. Lesovedenie 5, 23-29 Mason WL (1989) Vegetative propagation of hy- (in brid larch (Larix x eurolepis Henry) using win- Russian) ter cuttings. Forestry 62 (suppl), 189-198 Bobrov EG (1973) Introgressive Hybridisation. LE (1989) A critical review of larch hy- Sippenbildung und Vegetationsänderung. Pâques Fed Rep 84, 273-294 bridization and its incidence on breeding stra- tegies. Ann Sci For 46, 141-153 Chowdbury KA (1931) Anatomical studies of the wood of Larix eurolepis. J For 29, 797 Pâques LE, Cornu D (1991) Effect of vegetative propagation on field performance up to age 8 Delevoy G (1949) Larix eurolepis (Henry A, of hybrid larch (Larix x eurolepis) clones. Ann Flood M, eds). Bull Soc Centr For Belg 1949, Sci For 48, 469-482 178-194 Sokal RR, Rohlf FJ (1981) Biometry - The Prin- Dieckert H (1964) Einige Untersuchungen zur ciples and Practice of Statistics in Biological Selbsterilität Und Inzucht bei Fichte und Research. Freeman, San Francisco, 859, Lärche. Silvae Genet 13, 77-86 2nd edn Dietze W (1974) Beurteilung von züchterischen Syrach Larsen C (1937) The Employment of Möglichkeiten zur Verbesserung quantitati- Species, Types and Individuals in Forestry. ver und qualitativer Eigenschaften bei euro- Copenhagen,1937 paischer Lärche (Larix decidua Mill). Disser- Wright JW (1976) Introduction to Forest Gene- Forstwissensschftl. Univ tation, Fakultät, tics. Academic Press, New York, 322-323 Munich