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ŠUMARSKI LIST 1-2/1966 str. 135     <-- 135 -->        PDF

(Salix alba L.) AND CRACK WILLOW (Salix fragilis L.)

(Contributed paper)


Forestry Faculty, Zagreb, Yugoslavia.

During a three-year work on the selection of White Willow, we visited
a number of localities in Yugoslavia. According to A. Krstinić — M. Vidaković

(1) from the genetic point of view the populations of White Willow on the
surveyed localities distinguish themselves in a wide range of variability. This
variability does not manifest itself only in the essential characteristics of the
habit (straightness, branching), but also in the basic taxonomical characteristics
(leaf, buds, colour of shoots, etc.).
In the region of the Sava River the representatives of the population of
White Willow have to a great percentage bent and spirally grown stems,
thick branches which are relatively lowplaced on the stem, while the branch
angle is small. Along the Drava River we found a population of White Willow
whose representatives exhibit stems of long commercial lengths, with marked
staightness, free of spiral grain, and great growing power. In these populations
we also found the best specimens of plus trees. Several of these best
plus trees with respect to their taxonomic characteristics could not be determined
either as being typical individuals of Salix alba L. or Salix fragilis L.
Thus we were led to assume that in this case we had to deal with the interspecific
hybrids between these two species. After a detailed survey of a wider
area along the Sava and Drava Rivers we found that along the Sava River
Crack Willow (Salix fragilis L.) is very scarce and that it occurs only in
clearings and at the borders of stands. In the area of the Drava River Crack
Willow (Salix fragilis L.) occurs very frequently and not only that it appears
in clearings and at the stand borders but is largely interspersed within the
population of White Willow. In the area of the park forest of »Maksimir«,
Zagreb, along the brook of »Bliznec« there occurs also Crack Willow together
with White Willow, but in that locality too we found specimens of arborescent
Willows which respect to the taxonomic characteristics do not represent pure
species either. In order to verify our assumption that in this case we had
actually to deal with interspecific hybrids of White and Crack Willow we
collected during 1964/65 the seed from a number of female plus trees and
raised plants, while the male plus trees were crossed with pure species of
Salix alba L. and Salix fragilis L. On analysing the generative progenies we
found that also in that case we were considered with interspecific hybrids
of the mentioned two species because in the progeny there appear pure parent

ŠUMARSKI LIST 1-2/1966 str. 136     <-- 136 -->        PDF

species (Salix alba L. and Salix fragilis L.) as well as intermediate types
resembling the mother and father respectively.

Basic mensurational data concerning the mentioned hybrids from the
region of the Drava River and the park forest »Maksimir« are given in
Table 1.

No. Age; Height D. b. h. Volume annual
of Sex years m. cm. cu. m. increment Locality Remarks
tree cu. m.

15 39 28,0 47,0 1,961 0,0502 Crni Jarci
as: S. alba L.
x S. frag. L.
22 M 11 22,0 32,0 0,743 0,0675 Limbuš
S. frag. L.
S. alba L.
23 F 30 28,0 64,0 3,716 0,1242 Maksimir
S. alba L. x
S frag. L.
24 M 30 22,0 48,0 1,701 0,0568 Maksimir
S. frag. L.
S. alba L.

From the tree No. 24 was not raised a generative progeny but on the
basis of taxonomic characteristics we assume that it is also an interspecific

As can be seen from the enclosed table the interspecific hybrids between
White and Crack Willow and between Crack and White Willow distinguish
themselves by their vitality. E. Weber (4) states that between the above-
mentioned species could be found individuals of excellent qualities with regard
to the essential characteristics of habit, and in addition, with high growth

On the basis of observations made on the mentioned hybrids and on the
ground of results of the controlled hybridisation between these two species
it must be assumed that the reciprocal hybrids are not equal but resemble
to the one or other species in dependence on which species functions as the
female parent. We assume that in these cases we have the effects of matroclinal
inheritance. The species Salix alba L. and Salix fragilis L. are easy
to cross with one another. Fertile are also the interspecific hybrids of these
two species.

In order to verify our hypothesis that the interspecific hybrids between
White and Crack Willow are of greater vitality than pure parent species we
raised during 1964/65 the interspecific hybrids Salix fragilis L. x Salix alba

L. We also wanted to find out whether the populations along the Drava River
are actually of greater vitality than these along the Sava River, or whether
the differences in vitality are conditioned by more favourable environmental
conditions along the Drava River. Therefore we raised in 1964 a generative
progeny from one population occuring along the Drava River (Bakovci—
Đurđevac), and from one population inhabiting the area along the Sava River
(Osman Polje — Lipovljani). In the population »Bakovci« the seed was
collected from 4 trees, and in the population »Osman Polje« from 6 trees.

ŠUMARSKI LIST 1-2/1966 str. 137     <-- 137 -->        PDF

Data concerning heights of the interspecific hybrids (from 1964) and seedlings
of White Willow from the mentioned populations are presented in Table 2.*

Ser. Species Population No. of Heights
No. data cm »t« — value
1 Salix alba L. Bakovci 122 202,21 1:2 = 11,6047***
2 Salix alba L. Osman Polje 434 128,13 1:3 = 0,8514
3 Salix frag. L. x 9 186,22 3:2 = 3,2249**
Salix alba L.

In Table 2 is visible that the representatives of the population »Bakovcihave
greater heights than the representatives from the population »Osman
Polje«, and that they differ significantly at a level of 0,1%. Between the
hybrids and the population »Bakovci« there is no significant, difference,
while if compared with the population »Osman Polje« they are superior and
differ significantly at a level of 1%.

Between the population »Bakovci« and that of »Osman Polje« there exist
not only differences in the intensity of height and diameter growth but also
differences in the branch angle, colour of shoots and the time of flushing
and seed setting. The arithmetic mean of the branch angle is greater in oneyear-
old seedlings from the population »Bakovci« than of one-year-old
seedlings from the population »Osman Polje«. As to this characteristic a
significant difference at a level of 1% in the lower 1/3 of the seedling height
exists. The colour of shoots in seedlings from the population »Osman Polje«
does not show a greater variability and it is light-red in all representatives
of the population, while in the population »Bakovci« it ranges from yellow,
light-green, dark-green, light-red to chocolate brown. As regards the flushing
and seed setting it was found that the individual representatives from the
population »Bakovci« approach the interspecific hybrids Salix alba L. x Salix
fragilis L.

According to J. Wright (5) in the centre of occurence of two species of
the same genus between which a hybridisation is feasible there comes to s
migration of the genes from one species to another. Because on the locality
»Bakovci« there exists the possibility of the intergradation between the
species Salix alba L. and Salix fragilis L. It can be assumed that in this case
we are also concerned with introgression, i.e. that the representatives of these
populations contain also the genes of Salix fragilis L. The population »Osman
Polje« is small and relatively isolated and perhaps here we also have the
effects of inbreeding which brought this population to a greater

On the basis of what precedes it would seem that the representatives of
the population of White Willow posses a greater vitality and a more beautiful
habit on those locations where within the population of White Willow is
interspersed also Crack Willow, i.e. that probably also in these cases we are
concerned with introgression. Further, we assume that the interspecific
hybrids between these two species are more vital and of a more beautiful
habit than the pure species.

Works in this direction are in progress.

* Measurements were taken in the second half of August 1965, i.e. in the middle
of the second growing period.

ŠUMARSKI LIST 1-2/1966 str. 138     <-- 138 -->        PDF

Kratki sadržaj


Tokom trogodišnjeg rada, na selekciji bijele vrbe, obišli smo više lokaliteta na
području Jugoslavije. Predstavnici iz populacija bijele vrbe sa područja rijeke Savs,
imaju u velikom postotku kriva, usukana debla, debele grane, koje su smještene
srazmjerno nisko na deblu, a kut insercije im je malen. Uz rijeku Dravu našli smo
populacije bijele vrbe, čiji predstavnici imaju veliku tehničku dužinu debla, izrazito
pravna, neusukane žice, sa velikom sposobnošću prirašćivanja. U ovim populacijama
nalazili smo i najljepše egzemplare plus stabala. Neka od ovih najljepših
plus stabala po taksonomskim karakteristikama nisu se mogla determinirati kao tipične
vrste Salix alba L. niti kao Salix fragilis L. Ovo nas je navelo na predpostavku,
da se u ovom slučaju radi o međuvrsnim hibridima između ove dvije vrste. Detaljnijim
pregledom šireg područja uz rijeke Savu i Dravu, konstatirali smo, da je krta
vrba (Salix fragilis L.) uz rijeku Savu rijetka, da se javlja samo na rubovima sastojina,
a da je ona na području rijeke Drave vrlo česta i da se ne javlja samo na čistinama
već da dolazi uprskana unutar populacije bijele vrbe.

Da bi provjerili našu predpostavku, da se u ovom području zaista radi o međuvrsnim
hibridima između bijele i krte vrbe, tokom 1964/65 godine sa nekih ženskih
plus stabala sakupili smo sjeme i uzgojili biljke, a muška plus stabla smo križali sa
čistim vrstama Salix alba L. i Salix fragilis L. Nakon analize generativnog potomstva
ustanovili smo, da se u ovom slučaju stvarno radi o međuvrsnim hibridima spomenute
dvije vrste, pošto se u potomstvu javljaju čiste roditeljske vrste (Salix alba

i Salix fragilis L.), kao i intermedijarni tipovi, slični majci, odnosno ocu (hibridu).
Iz tabele 1 na temelju prosječnog godišnjeg prirasta vidimo, da se međuvrsni
hibridi bijele i krte vrbe odlikuju visokom vitalnošću.
Na temelju opažanja vršenih na spomenutim hibridima, te na temelju rezultata
kontrolirane hibridizacije između ove dvije vrste konstatiramo, da recipročni
hibridi nisu jednaki, već da su slični jednoj ili drugoj vrsti, ovisno o tome, koja
vrsta fungira kao ženski roditelj. Predpostavljamo, da se u ovim slučajevima radi o
efektima matroklinog nasljeđivanja.

Iz tabele 2 se vidi, da je i generativno potomstvo od matičnih stabala iz populacija
sa područja rijeke Drave veće vitalnosti od generativnog potomstva koje potječe
od matičnih stabala iz populacija sa područja rijeke Save. Također je iz iste
tabele vidljivo, da umjetno proizveden međuvrsni hibrid između krte i bijele vrbe
ne zaostaje po visinskom prirastu za najboljim generativnim potomstvom bijele vrbe
sa područja rijeke Drave, a da je bolji od generativnog potomstva sa područja rijeke

Populacije bijele vrbe sa područja rijeka Drave i Save ne razlikuju se samo u
visinskom prirašćivanju, već također posloje razlike i u kutu insercije grana, u boji
izbojaka te u vremenu listanja i plodonošenja. Kako je varijabilnost spomenutih karakteristika
veća kod predstavnika iz populacija sa područja rijeke Drave, a prije
smo spomenuli, da je u ovim populacijama uprskana i krta vrba, to smo predpostavili
da se u ovom slučaju radi o introgresiji, tj. da predstavnici iz ove populacije
sadrže i gene od Salix fragilis L.


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bijele vrbe. (A contribution to the solution of the problem of cultivation of White
Willow — Salix alba L.). Topola, 8/44, pp. 10—17.
LeClergE. L. — W. H. Leonard — A. G. Clark (1962): Field Plot Technique.
Burges Publishing Company, Minneapolis, 373 pp.
Tavča r Aloi s (1952): Osnove genetike. (Elements of Genetics). Škol. knjiga,
Zagreb, 493 pp.
Webe r E. (1963): Genetische, planzenzüchterische und baumschultechnischc
Untersuchungen an Baumweiden, München, 144 pp. q
Wrigh t J. W. (1962): Genetics of Forest Tree Improvement. FAO, Rome, 399pp.
Wrigh t J. W. (1963): Hybridization between Species and Races. World Consultation
on Forest Genetics and Tree Improvement, 2 b, Stockholm.
2 ufa L. (1958): Tablice drvnih masa vrbe (Salix alba L.). (Volume Tables for
White Willow — Salix alba L). Šum. Društvo A. P. Vojvodine, Novi Sad, 29 pp.