География и биология / 4. Биогеография, биоресурсоведение, биоразнообразие

N.A. Slepchenko

All–Russian Scientific and Research Institute of Floriculture and Subtropical Crops of the Russian Academy of Agricultural Sciences, c. Sochi, Russia

Working out a rapid vegetative propagation method for rare endangered species of Amaryllidaceae as a strategic element in preserving them on the Black Sea coast of the Caucasus

The article offers a special strategy, uniting in situ and ex situ methods in order to preserve such species as Leucojum aestivum L., Galanthus woronowii Losinsk., Pancratium maritimum L. (Amaryllidaceae) on the Black Sea coast of the Caucasus. One of the main strategic elements is a method of vegetative propagation of L. aestivum and P. maritimum by bulbous grafts. An optimal term for cutting is August, optimal grafts sizes are the segments which are 1 cm wide, and half-segments. The grafts must be planted at the depth of two/three metres. The developed method of vegetative propagation allows to rise the propagation coefficient of Leucojum aestivum and Pancratium maritimum in 5-6 times in comparison with the method of natural propagation.

Key words: rare endangered species, Amaryllidaceae, strategy of preservation, vegetative propagation, cutting.

The natural flora of the Black Sea coast of the Caucasus is special for its diversity. There are a lot of precinctive, rare and endangered plant species here, the number of which is declining. Preserving the gene pool of endangered species is one of the main tasks on environmental protection. The solution to the problem of preserving our biodiversity can be based on comprehensive research of rare endangered plant species, their biologic and ecologic features as well as surviving strategy.

Three following species from Amaryllidaceae Jaume Saint-Hilaire grow in the given region and relate to the endangered ones: summer snowflake (Leucojum aestivum L.),Woronowii snowdrop (Galanthus woronowii Losinsk.) and maritime pancratium (Pancratium maritimum L.). (The Red Book of Krasnodar region, 2007). The given species grow on the Black Sea coast and in forests of low hills zone and have high ornamental qualities.

So we offer a strategy of preserving rare and endangered species of Amaryllidaceae on the Black Sea coast of the Caucasus, considering two following technical approaches: preservation of the species in natural (in situ)and artificial (ex situ) conditions; this strategy includes the following measures:

- organizing a system of continuous monitoring of Leucojum aestivum, Galanthus woronowii and Pancratium maritimum population level;

- constructing nature monuments in places of compact growing for Leucojum aestivum, Galanthus woronowii and Pancratium maritimum;

- stopping economical activity of people in places where the given species grow;

- developing regional programs of ecological education in order to change consumer's attitude of different population groups towards nature;

- ban on selling flowers, picked in natural conditions and controlling bulbs procurement as crude drugs;

- involving Leucojum aestivum, Galanthus woronowii and Pancratium maritimum to the introduction process;

- developing effective ways of plants reproduction;

- preserving Leucojum aestivum, Galanthus woronowii and Pancratium maritimum gene pool in genotypic banks;

- repatriation of Leucojum aestivum, Galanthus woronowii and Pancratium maritimum to natural habitats.

Adoption of various methods of their mass propagation plays one of the dominant roles in solving the problems of introducing rare species into the culture, developing ways of repatriation and preservation of genetic diversity. The methods of getting huge number of planting stock from limited stools for a short period is of a great value.

It should be noted that Amaryllidaceae have a low potential of vegetative propagation, which is typical for other bulb plants (Гартман, Кеслер, 1963; Удра, Батова, 1999). Development of daughter bulbs provides an easy and reliable, but still slow for many cultures method of vegetative propagation. As a result, daughter bulbs adapt in new places for quite a long time. In order to overcome this drawback our aim was to develop shortcut method of vegetative propagation for Leucojum aestivum and Pancratium maritimum.

To solve this problem, a method of propagation by bulbous grafts was taken as a principle (Гартман, Кеслер, 1963; МcMillan, Browse, 1985). This method has already been used for hybrid knight's-star (Recomendations…, 1983, 1987) and narcissus (Выхристова, 1986) in the All–Russian Scientific and Research Institute of Floriculture and Subtropical Crops. Applying to Leucojum aestivum and Pancratium maritimum the method was studied for the first time.

The method consists in using specific bulb grafts, obtained by dividing the bulbs of initial stools into parts with the help of a slit into 4 – 8 or more parts, which is made by a sharp knife from a top to an ending. During the carried experiments the obtained grafts – segments were cut into separate double scales, consisting of several scale layers, connected by a piece of fundus. Half-segments, consisted of 6 – 7 scales, were obtained after division of segments into two parts. Depending on the position of scales in each bulb “half-segments” consisted of scales, which were situated nearer to the growing point. The half-segments were named “inside ones”, and the others – “external ones”. The pair scales are known as two scales, connected by a piece of fundus. Then, the grafts were gently dried and thickly planted into a box with preliminarily stained moist substrate, which consisted of peat and pearlite in the ratio of 1:1 at the depth of 1/3 and 2/3 of the grafts height. The substratum was than provided with temperate watering and maintenance of temperature not less than of 18^o C above.

It is established that the optimal term of bulbs division of Leucojum aestivum, and Pancratium maritimum is in late August (the last ten days) – early September (the establishment of the both species was in general 69 %). The lowest characteristics were noted during July-term of cutting (establishment – 25 and 35 %).

The quality of initial material plays an important role. Bulbs of Leucojum aestivum must be big and strong and more than 3,0 cm in diameter. An optimal size of Pancratium maritimum bulbs is from 3,0 till 3,9 cm. Such bulbs provide a high quantity of double scales within the preparation.

Differences in adaptation of double scales are connected not with temperature differences, but with an endogenous state of double scales tissue. It obviously relates to the content of growth regulators on a concrete development stage of stools. So in early August growing point of Leucojum aestivum is on the 3d stage of organogenesis – formation of flower graft, and in the middle of August the plant goes to the 4th stage of organogenesis: rudimentary knolls of all inflorescence elements begin to appear (Слепченко, 2007). New inflorescence of Pancratium maritimum forms at the end of flowering, which is in late July, and there can be observed a flower stalk of the next and the following year in the reproduction bud.

Within the study of double scales size and its influence on establishment it was determined that the best segments of Leucojum aestivum and Pancratium maritimum were 1 cm wide (table). Half-segments also had high indicators, and external half-segments had rather higher rooting than the internal segments had. Double scales of 1/3 segments and pair scales had the lowest adaptation.

So one should give preference to half-segments practically, since the quality of the obtained Double scales will be higher in two times with cutting, than the their quality while applying segments cutting methods.

Table. Average rooting of various double scales types of Leucojum aestivum and Pancratium maritimum after four months since planting (cutting term – August)

Type of double scales	Average rooting of double scales by years, %					Smallest essential difference05
	2003	2004	2005	2006	average
	Leucojum aestivum
Segments in 1 cm	88±4,16	91±5,57	76±3,61	96±2,65	88±1,00	3,40
Segments in 0,5 cm	69±4,36	79±6,25	70±4,58	72±5,29	73±0,58	4,33
Internal half-segment	78±5,29	76±2,65	43±5,29	71±7,81	67±2,00	4,42
External half-segment	82±5,57	82±10,15	47±4,58	88±9,54	75±4,00	5,49
1/3 of segment	30±3,61	45±9,64	–	–	38±4,04	7,98
Smallest essential difference 05	2,66	6,80	3,53	7,44	2,00
	Pancratium maritimum
Segments in 1 cm	90±5,57	99±1,16	46±6,66	88±6,25	81±4,16	4,01
Segments in 0,5 cm	78±3,61	89±8,00	44±5,57	80±6,25	73±5,51	4,34
Internal half-segment	67±2,65	89±9,00	47±12,00	50±11,36	63±9,29	6,29
External half-segment	76±5,29	44±5,51	49±7,23	90±1,53	65±4,93	3,47
Smallest essential difference 05	4,00	4,30	7,20	6,23	6,58

Using pair scales is known as an unpromising method. Attempts of propagating Leucojum aestivum in 2001-2004 and Pancratium maritimum – in 2001-2002, using this method, had no positive effects. The reason is that the scales of this species are thin (0,5-2 mm) and they haven’t got enough nutrients, in contrast to the hybrid Hippeastrum.

After the experiments on defining the influence of double scales planting depth on their rooting, it was revealed that best results had been obtained with planting at two-thirds of the double scales height, though in some years the differences weren’t essential. The best results were obtained for the segments of 1 cm high. The rooting made up 90,7 % for L. аestivum and 79,0 % for P. maritimum.

After 2-3 leaves are formed on the double scales, they should be planted at a light soil for further growth; a proper planting term is May – June. One should also pay a lot of attention to watering at appropriate time. As the bulbs reach 2-3 cm in diameter they can be planted then at a constant place. These plants begin to flower on the 3d – 4th year.

Thus, the developed method of vegetative propagation allows to increase propagation factor of Leucojum aestivum and Pancratium maritimum up to 7,5–10,8. It is higher in 5-6 times in comparison with natural propagation factor.

Research results allow to solve the problems of introduction of the experimental species into a culture. This may partly stop the extermination of natural populations and favour the preservation of regional genotypes. The obtained bulbs can be used for repatriation and introduction in ornamental horticulture, including obtaining cut flowers.

Thus, there are some plants on further developing methods for vegetative propagation of Galanthus woronowii, including the methods of tissue culture since it is impossible to propagate the plants using the same method, developed for Leucojum aestivum and Pancratium maritimum because of small size of snowdrop bulbs.

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