INFLUENCE OF ROOTSTOCK AND GRAFTING DATE ON THE SUCCESS AND GRAFTS GROWTH OF TWO CULTIVARS OF PINES
DOI:10.30825/5.EJPAU.165.2018.21.4

Sławomir Świerczyński¹, Marcin Kolasiński¹, Magdalena Urbaniak¹, Aleksander Stachowiak¹, Nikodem Nowaczyk^2
1 Department of Dendrology, Pomology and Nursery, Poznań University of Life Sciences, Poland
² Private Trees and Bushes Nursery in Kobylin, Poland

ABSTRACT

The experiment was conducted in Nowaczyk’s Private Trees and Bushes Nursery in Kobylin in the years 2013–2014. The purpose of the studies was comparison of the effectiveness of grafting of two pines cultivars Pinus densiflora(Japanese red pine)‘Golden Ghost’ and Pinus mugo (Mugo pine) ‘Golden Glow’. Three different rootstocks were used for grafting: Pinus mugo (Mugo pine) subsp. uncinata, Pinus sylvestris (Scots pine) and Pinus nigra (Black pine). Grafting was carried out in three different terms (the middle of February, the end of February and in the middle of March). The highest percentage of grafts success was obtained for two of the studied pine cultivars on Pinus mugo subsp. uncinata rootstock. The dates of grafting did not influence the process of pines grafts success. However the two earlier grafting dates increased the length of shoots. The shortest shoots and the smallest number of buds of 'Golden Glow' cultivar were obtained on Pinus nigrarootstock.

Key words: pine cultivars propagation, date of grafting, usefulness of rootstocks.

INTRODUCTION

There are very few available results of studies on the usefulness of individual rootstocks for grafting various pines species and cultivars [1]. However, numerous experiments [10, 14, 16, 17, 19] confirmed that the used rootstock influences the percentage of grafts success and the vigour of growth of the grafted cultivars of conifers. It was found that early-spring grafting gives the best grafts success and late-summer one the worst [11]. A grafting method varies grafts success and the growth of grafts as well [9]. Also the quality of scions, and especially the place they were taken from a mother plant [12, 25], the age of a mother plant [2, 20] and the period of storage of scions [5, 24] decides on grafts success and further growth of grafts. The course of weather conditions after the grafting process is also very important [18].

Recently, a lot of interesting pine trees cultivars have been introduced into the market. A very interesting cultivar of Japanese red pine(Pinus densiflora)is ‘Golden Ghost’, which has one of the most evident colour of ‘oculus draconis’ type among pine trees. It is a golden colour changing into white and golden, appearing in a form of stripes on dark green needles [3, 23] (Fig. 1). Another interesting cultivar of Mugo pine (Pinus mugo) is ‘Golden Glow’. This dwarf cultivar has golden-yellow colour in winter season, and it is green in summer [3, 23].

Fig. 1. Japanese red pine (Pinus densiflora) ‘Golden Ghost’ (phot. Nowaczyk)

MATERIALS AND METHODS

The experiment was conducted in Nowaczyk’s Private Trees and Bushes Nursery in Kobylin in southern part of Wielkopolska region in Poland, in the years 2013–2014. The plant material for the experiment were three-year-old rootstocks: Pinus nigra (J.F. Arnold), Pinus sylvestris (L.) and Pinus mugo subsp. uncinata (Ramond ex DC) cultivated in P9 containers and scions of two pines cultivars: Pinus densiflora (S. et Z.) of ‘Golden Ghost’ and Pinus mugo (Turra) of ‘Golden Glow’ cultivar. The rootstocks were grafted using side grafting method in three terms: in the middle of February, the end of February and in the middle of March. The experiment consisted of 18 combinations (2 cultivars, 3 rootstocks, 3 grafting dates). Each combination contained three repetitions, each having 20 grafted rootstocks. The rootstocks had a diameter of 7 mm at the place of grafting. On the day of grafting 15 cm long scions were taken from mother plants growing in the nursery.

The grafted plants were labeled (Fig. 2) and they were placed in heated 140 cm x 200 cm foil tunnels. After the period of 5 weeks the process of airing and weathering the grafts started. After two months from the grafting date the plants from each grafting date were taken out from the foil tunnel. Next, the pots were placed outside on the mat and sprinkled with peat (Fig. 3).

Fig. 2. Graft of ‘Golden Glow’ grafted on Pinus nigra rootstock (phot. Nowaczyk)

Fig. 3. Grafted plants placed in peat (phot. Nowaczyk)

At the same time the rootstocks were pruned at the middle of their height and lower shoots of the rootstocks were eliminated to provide the scions with light. After following six weeks the rootstocks were pruned a few centimeters above the place of grafting, leaving a few shoots of the rootstock to keep the plant’s assimilation capability. In the middle of June a slowly realised compound fertilizer Osmocote Plus 5–6 M was used with a dosage of 2.5 g per plant. Measurements and observation of the plants and grafts success were carried out after six months from the beginning of the experiment. The length of shoots was measured and the number of buds was counted. To compare the obtained results two factor variant analysis was applied (rootstocks, grafting dates) individually for each cultivar. The significance of differences between cultivars was evaluated using Duncan test for a confidence level α=0.05. To calculate percentage values Bliss transformation was applied.

RESULTS

The rootstocks used in the experiment influence the percentage of grafts success very much. The best results were obtained for grafting ‘Golden Ghost’ and ‘Golden Glow’ on Pinus mugo subsp. uncinata rootstock. The lowest percentage of grafts success was found on Pinus nigra rootstock for both discussed cultivars, however in the case of the 'Golden Glow' cultivar it did not differ significantly from the Pinus sylvestris rootstock. The grafting date did not differentiate significantly the number of grafts success of the two studied pines cultivars. A higher percentage of grafts success was observed for ‘Golden Glow’ cultivar (Tab. 1).

Table 1. The percentage of grafts success of two pines cultivars

Rootstock	Date of grafting						Average for rootstock
	11.02.		25.02.		11.03.
	‘Golden Ghost’	‘Golden Glow’	‘Golden Ghost’	‘Golden Glow’	‘Golden Ghost’	‘Golden Glow’	‘Golden Ghost’	‘Golden Glow’
Pinus sylvestris	64.1 bc*	72.1 a	68.1 cd	78.2 a	62.0 bc	80.2 a	64.8 b	76.9 a
Pinus nigra	48.0 a	68.1 a	54.0 ab	74.2 a	58.1a-c	76.2 a	53.4 a	72.9 a
Pinus uncinata	78.2 de	92.8 b	80.2 e	92.8 b	76.1 de	96.0 b	78.2 c	94.0 b
Average for date grafting	63.9 a	79.0 a	67.9 a	82.6 a	65.6 a	85.5 a
*Means followed by the same letters separately for one cultivar are not significantly different at the level of alpha=0.05

On the basis of statistics analysis of the obtained results one could not find any significant differences in the influence of rootstocks and dates of grafting on the average number of shoots of grafted pine cultivars (Tab. 2).

Table 2. Average number of grafts shoots of two pines cultivars

Rootstock	Date of grafting						Average for rootstock
	11.02.		25.02.		11.03.
	‘Golden Ghost’	‘Golden Glow’	‘Golden Ghost’	‘Golden Glow’	‘Golden Ghost’	‘Golden Glow’	‘Golden Ghost’	‘Golden Glow’
Pinus sylvestris	3.3 a*	3.9 a	3.0 a	3.9 a	3.2 a	3.9 a	3.2 a	3.9 a
Pinus nigra	3.2 a	3.9 a	3.1 a	3.8 a	3.0 a	3.9 a	3.1 a	3.9 a
Pinus uncinata	3.2 a	3.9 a	3.3 a	3.7 a	3.1 a	3.8 a	3.2 a	3.8 a
Average for date grafting	3.2 a	3.9 a	3.1 a	3.8 a	3.1 a	3.9 a
* For explanation, see table 1

The date of grafting, however, influenced the differentiation of the length of shoots of the grafted cultivars. The length of shoots of ‘Golden Ghost’ cultivar for the first and the second grafting term was significantly higher than for the last one. For ‘Golden Glow’ cultivar much better result was obtained in the first term than in the third one. The used rootstocks did not differentiate the length of shoots of ‘Golden Ghost’ cultivar. Shoots of ‘Golden Glow’ on Pinus nigra rootstock were shorter in comparison with the two remaining rootstocks. From the two grafted cultivars the most intensive growth, measured with the length of shoots, was obtained for ‘Golden Glow’ cultivar (Tab. 3).

Table 3. Average shoots length of grafts of two pines cultivars (cm)

Rootstock	Date of grafting						Average for rootstock
	11.02.		25.02.		11.03.
	‘Golden Ghost’	‘Golden Glow’	‘Golden Ghost’	‘Golden Glow’	‘Golden Ghost’	‘Golden Glow’	‘Golden Ghost’	‘Golden Glow’
Pinus sylvestris	4.8 bc*	11.6 bc	4.7 bc	11.0 bc	4.2 ab	10.9 bc	4.6 a	11.2 b
Pinus nigra	4.6 abc	10.9 ab	4.3 abc	10.5 ab	4.0 a	9.4 a	4.3 a	10.2 a
Pinus uncinata	4.9 c	12.5 c	4.6 abc	11.7 bc	4.2 ab	10.9 bc	4.6 a	11.7 b
Average for date grafting	4.7 b	11.6 b	4.5 b	11.0 ab	4.2 a	10.4 a
* For explanation, see table 1

One could not observe any significant influence of the rootstock and the date of grafting on the number of buds on the grafted plants. Only grafts of ‘Golden Glow’ on Pinus nigra had fewer buds than those on Pinus sylvestris one. More buds were found for ‘Golden Glow’ cultivar than on ‘Golden Ghost’ (Tab. 4).

Table 4. Number of grafts buds on shoots of two pines cultivars

Rootstock	Date of grafting						Average for rootstock
	11.02.		25.02.		11.03.
	‘Golden Ghost’	‘Golden Glow’	‘Golden Ghost’	‘Golden Glow’	‘Golden Ghost’	‘Golden Glow’	‘Golden Ghost’	‘Golden Glow’
Pinus sylvestris	4.0 a *	5.3 a *	3.7 a	5.6 a	3.5 a	5.3 a	3.8 a	5.4 b
Pinus nigra	3.7 a	5.0 a	3.8 a	5.1 a	4.0 a	4.8 a	3.8 a	4.9 a
Pinus uncinata	3.8 a	5.2 a	3.9 a	5.3 a	3.9 a	5.2 a	3.9 a	5.2 ab
Average for date grafting	3.8 a	5.2 a	3.8 a	5.3 a	3.8 a	5.1 a
* For explanation, see table 1

DISCUSSION

Most of available publications [6, 15, 22] recommend grafting conifers in winter season. Also Pinus sylvestris and Pinus nigra are recommended rootstocks for two and three-needle pine trees [6, 15]. In the discussed experiment three different dates of winter grafting were kept, as well as three rootstocks recommended by the above mentioned authors were used.

Numerous studies proved [7, 8, 11, 13] that the date of grafting influences the percentage of grafts success in case of conifers. In the experiment the date of grafting did not differentiate significantly the results of grafts success. However, Frey et al. [11] observed differences in grafts success of Abies fraseri depending on the date of grafting, but the dates chosen in their experiment were much differentiated and they were mainly from summer months. Only one date was an early-spring one (6 April) and just in this term the best results of grafts success were observed (95%). Also Beenson and Proebsting [7] grafted plants grown under long days showed no greater graft success than those grown under normal short days in January. This fact confirms a bigger usefulness of late-winter and early-spring dates for grafting pine trees. In the discussed experiment lack of differences in the number of grafts success in individual terms could result from small time differentiation, as all the grafting dates were located within the period of one month.

Observations of the nurseryman in whose nursery the experiment was carried out (Nowaczyk, information not published), show that pine trees which discolour into yellow colour in winter season have a better percentage of grafts success in a later term of grafting (the middle and end of March). In the discussed experiment this rule was fully true for ‘Golden Glow’ cultivar; for the second cultivar the second date was the best.

The date of grafting also did not differentiate much the growth of grafts in the first year of cultivation. Longer shoots were observed only for the first date of grafting. A completely opposite dependence was observed by Frey et al. [11] for summer grafting dates of Abies fraseri, who obtained stronger growth of grafts in later terms of grafting. As the authors concluded it could have resulted from a better development of scions at the moment of their collection and grafting in a later term, which caused a stronger growth in the following year. In the discussed experiment the scions were taken during plant’s resting period, they did not differ in their growth advancement, and their further growth was observed only in the year of grafting. According to Tong-Sen [21] a good grafting term for pines are months from February till April. In the experiment with Picea sitchensis [4] the vigour of graft growth depended on how late in the winter the graft had been prepared, with least growth by grafts made in October, and most by grafts made in March. From the results of the conducted experiment one can conclude that earlier dates of pine trees winter grafting didn’t have a significant advantage over a later term. However, a spread of these dates was too small to draw far-reaching conclusions.

In the discussed experiment the number of buds on grafted plants did not differ depending on a grafting date. Such a difference, however, was noted by Frey et al. [11]. These authors observed that more developed scions collected in a later stage of growth increased the number of buds in the following year of shoots’ growth.

In the discussed experiment the used rootstocks did influence the studied growth parameters of grafts and their success. It is confirmed by studies of Ahlgren and Wilderness [1] in which different rootstocks used for pine trees differentiated grafts success and a further growth of grafts. In their experiment Pinus sylvestris rootstock did not stimulate a stronger growth of five-needle pines grafted on it, and Pinus strobus (L.)turned out to be the best one. In the discussed experiment the best grafts success was obtained on Pinus mugo subsp. uncinata, and worse ones on Pinus sylvestris and Pinus nigra. Also in grafting fir trees the influence of rootstock on grafts success and further growth of grafts was confirmed [13].

The two studied cultivars of pine trees differed in the percentage of grafts success and their further growth. Some specific cultivar differences could be observed analyzing the mean number of shoots. ‘Golden Ghost’ cultivar had more shoots than ‘Golden Glow’. It could be caused by the fact that the first of the mentioned cultivars is characterized by a stronger growth in comparison with the second one. Also Haines and Simpson [10] observed different grafts elongation depending on the vigour of growth of the grafted pine cultivar. In the discussed experiment Pinus mugo subsp. uncinata turned out to be the most useful rootstock giving the best result both for ‘Golden Ghost’ and ‘Golden Glow’, as far as the grafts success is concerned. What is more, the needles of ‘Golden Glow’ coloured better on Pinus mugo subsp. uncinata than on Pinus sylvestris and Pinus nigra. Also the strongest shoots growth of ‘Golden Glow’ were obtained on Pinus mugo subsp. uncinata rootstock.

It is commonly thought that Pinus sylvestris and Pinus nigra are the best two-needle rootstocks. On the other hand, the results of the discussed experiment, as well as earlier observations in the nursery where the experiment was conducted show that the best rootstock is Pinus mugo subsp. uncinata. Despite smaller percentage of grafts success, however, Pinus sylvestris and Pinus nigra can also be used for grafting the discussed cultivars of pine trees when the better one rootstock is not available.

To confirm these results another experiment is being conducted. It takes into account a broader span of grafting dates and different rootstocks for two-needle pines including Pinus contorta, suggested by Bärtels [6].

CONCLUSIONS

1. The highest percentage of grafts success of the two studied pines cultivars was obtained on Pinus mugo subsp. uncinata. The dates of grafting did not influence the differentiation of grafts success.
2. Earlier grafting dates stimulated the growth of longer shoots on grafts. The rootstocks did not have any influence on the intensity of the growth of grafts. Only for 'Golden Glow' on Pinus sylvestris the grafts had sorter shoots and a smaller number of buds in comparison with the other two rootstocks.
3. The grafts of ‘Golden Ghost’ had better grafts success, they were longer, had a bigger number of buds and a smaller number of shoots in comparison with ‘Golden Glow’.

REFERENCES

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12. Frey H.H., Frampton J., Blazich F.A., Hundley D., Hinesley L.E., 2011. Grafting fraser fir (Abies fraseri): effect of scion origin (crown position and branch order). HortScience, 46(1), 91–94.
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19. Schmidtling R.C., 1983. Rootstock influences flowering, growth and survival of loblolly pine grafts. Journal of Forest Science, 29(1), 117–124.
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Accepted for print: 19.12.2018

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Sławomir Świerczyński
Department of Dendrology, Pomology and Nursery, Poznań University of Life Sciences, Poland
Dąbrowskiego 159
60-594 Poznań
Poland

Marcin Kolasiński
Department of Dendrology, Pomology and Nursery, Poznań University of Life Sciences, Poland
Dąbrowskiego 159
60-594 Poznań
Poland
email: marcin.kolasinski@up.poznan.pl

Magdalena Urbaniak
Department of Dendrology, Pomology and Nursery, Poznań University of Life Sciences, Poland
Dąbrowskiego 159
60-594 Poznań
Poland

Aleksander Stachowiak
Department of Dendrology, Pomology and Nursery, Poznań University of Life Sciences, Poland
Dąbrowskiego 159
60-594 Poznań
Poland

Nikodem Nowaczyk
Private Trees and Bushes Nursery in Kobylin, Poland
63-740 Kobylin
Wyganów 1
Poland

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