1 Introduction

An attempt is made in this paper to review the status of genetic resources, tree improvement and breeding programmes and gene conservation of 5-needle pines in East Asia including China, Japan, the Democratic People' s Republic of Korea (DPRK), the Republic of Korea (ROK) and Far East.

The genus Pinus L. is generally divided into two subgenera, Subgen. Strobus (Sweet) Rehd., Haploxylon, and Subgen. Pinus, Diploxylon, they are commonly known as soft pines and hard pines. The species of Haploxylon are further classified into two sections, those with 5 needle leaves in a fascicle, are fallen into section Cembra Spach. usually called 5-needled pines. The species with 3 needles in a fascicle are arranged in other section, Sect. Parrya Mayr.(AASE, 1978; Zheng, 1983).

Among the 5-needle pines Pinus armandii Franch. and P. koraiensis Sieb. et Zucc. are very important in timber production as some hard pines, for example, P. massoniana Lamb. and P. yunnanensis Franch. in China and P. densiflora Seb. et Zucc. in Japan, the rest 5-needle pines are not so economically important due greatly to their restricted resources. More emphasis is placed in this paper on the research in the genetic resources, tree improvement and gene conservation of the two most important species, P. armandii and P. koraiensis, in fact, very little information but in the aspects of taxonomy and ecology is available for other species.

2 Genetic Resources

Of 24 species of Pinus in East Asia 13, with 3 varieties, are haploxylon (Wu, 1956; Mirov, 1967; AASE, 1978; Zheng, 1983; Price et al., 1998), they are here listed as follows:

2.1 5-needle pines

Pinus armandii Franch. var. armandii, widely distributed and planted in China;

P. armandii Franch. var. mastersiana (Hayata) Hayata in Taiwan Province, China;

P. armandii Franch. var. amamiana (Koidz.) Hatusima with isolated populations in Japan;

P. dabeshanensis Cheng et Law, very restricted in a small area in central south China;

P. fenzeliana Hand.-Mzt., in southern China;

P. griffithii McClelland, Himalayan chains;

P. koraiensis Sieb. et Zucc. naturally distributed in China, Japan, Korea Peninsula and Far East;

P. kwangtungensis Chun ex Tsiang, distributed in the central and southern China;

P. morrisonicola Hayata, in central Taiwan, China;

P. parviflora Sieb. et Zucc., native to Japan but exotic to China and ROK;

P. pumila (Pall.) Reget, naturally distributed in China, Japan, DPRK and Far East;

P. sibirica (Loud.) Mayr., northwestern China and Siberia, Russia;

P. wangii Hu et Cheng, scattered and limited populations in southwestern China.

Ecologically, 5-needle pines are, in contrast to hard pines, mostly adaptive to the cold or temperate and moist environment, there exist a latitudinal gradient and trend of species replacement from north to south within their natural occurrences in East Asia (Wu, 1956; 1980; Kuan, 1982; Ma, 1992). In the north, P. pumila and P. koraiensis occur on relatively lower elevations, southwards in the temperate and subtropical zones, they are replaced by P. armandii, P. fenzeliana and P. kwangtungensis occur discontinuously further southwards at higher elevations in subtropical and tropical areas. P. dabeshanensis and P. wangii, in relic status, only occupies difficult sites in central south and southwestern China, respectively, with restricted populations or scattered individuals.

All the 5-needle pines in East Asia are common in geography characterized by discontinuous distribution. P. armandii is a very typical example (Ma, 1992). This species is extensively distributed in the mainland of China from the temperate to subtropical regions, with its two varieties, P. armandii var. mastersiana extending to Taiwan and P. armandii var. amamiana appearing in Japan (Nakashima et al., 2000). The populations of P. kwangtungensis and P. fenzeliana are also geographically isolated from each other. The ecological and geographic patterns raise these 5-needle pines a great genetic variability and make some of them very difficult in taxonomy.

2.2 3-needle pines

P. bungeana Zucc. ex Endl., endemic species, discontinuously distributed in central and central north China, and widely planted as ornamental trees.

P. gerardiana Wall. distributed in western Tibet.

Tab. 1 gives more detailed information for each taxon.

3 Tree Breeding and Improvement

Tree improvement in East Asian countries is mainly focused on commercially important species, research activities are mostly undertaken with P. koraiensis and P. armandii among the 5-needle pines even though P. kwangtungensis, P. fenzeliana and P. dabeshanensis have been locally used in planting programmes.

3.1 Pinus koraiensis

This species is by far the most important in tree improvement of the coniferous in northeast China, DPRK and ROK.(Kim et al., 1994a) estimated that more than 250 000 hm² of plantations were established with this species in ROK by 1994.

In China, tree improvement and breeding research programmes were launched in early 1980's with emphases on provenance trial, plus tree selection and gene conservation.

A provenance trial was established in 1986 with 12 seedlots which were in range-wide collected and 1 seedlot of plantation, 10-year result showed that there were significant differences in growth rates between provenances, the seedlots collected from areas around Changbai Mountain performed best (Zhang et al., 2000).

Wang et al.(2000) reported 10-year results of progeny tests, which were established on 3 sites using open pollinated seeds of 557 families in the natural stands. It was found that there were significant differences in growth performance between individual families and provenance zones, and also great G ×E reactions existed. Based on the progeny testing, a genetically improved seed orchard was established through grafting (Wang et al., 2000). It was observed that an interval between every two good seed crops was 5 years; strobile abortion reached 46.5% in seed orchard, but cone yield could be increased by 20% through crown shaping and manipulated pollination (Wang et al., 1992).

Fertility variation and its effects on the relatedness of seed produced in the clonal seed orchards were verified that relative gene diversity, compared to the reference populations from which the plus trees were selected, is still high enough (Kang et al., 1998). Variation in effective number of clones in the seed orchards of P. koraiensis was examined, the mean census number of clones averaged around 70 in each orchard, but the average effective number (N_c) was 43 (Kang et al., 2001).

3.2 Pinus armandii

Of the 5-needle pines, P. armandii is mostly widely and discontinuously distributed in 12 provinces in China, with a latitudinal range 23°30′~36°31′N, a longitudinal 85°30′~ 113°E and altitudinaly ranged from 1 000~3 500 m, which suggests that a great deal of intraspecific variations exist geographically.

Range-wide provenance trials of P. armandii were established on 9 experimental sites in 1980, the trials were coordinated by Research Institute of Forestry, Chinese Academy of Forestry, using seeds collected from 30 provenances. Because the seedlings of southern seedlots were all killed by frost at northern experimental sites, successive trials were established on 12 sites in the following year using northern seedlots. The provenance trial results indicated that not only G×E interactions existed but the differences in morphological characteristics and growth rates among provenances were so significant that two provenance zones, southern and northern, could clearly be distinguished (Ma et al., 1992a, b; Cooperative, 1992). Moreover, Ma (1992)further argued that these two population groups should perhaps be recognized as 2 varieties, namely, P. armandii var. armandii and P. armandii var. yunnanensis. He pointed out strongly that plantations of P. armandii in large area were failed, in many cases in central China during 1960~1970's, due to the reason that wrong provenances were used in afforestation programmes. He cautioned that great attention must be paid by plantation forestry to provenance selection, and P. armandii should not be grown for commercial purposes in the north of 40°N and beyond its ranges of vertical distribution in the central subtropical China.

To establish clonal seed orchards by grafting, 850 superior trees were selected in the southern provenance zone covering Yunnan, Sichuan and Guizhou provinces. Research in reproductive biology showed that P. armandii starts flowering from age 5~7 years, but over 70% of female strobiles become abortion (Wu, 1992; Zhang et al., 1992). Generally, seed yielding of P. armandii is very low, 15 kg·hm^-2 in average for 133 hm^-2 of seed orchards of the whole country. In addition to much rain and wind during flowering in May, genetic variation in reproductive ability between clones was observed (Liao et al., 1998).

4 Genetic Diversity and Gene Conservation

In recent years, genetic diversity was detected using analysis of enzyme gene markers.Kim and Lee (1995) found that the overall mean proportions of polymorphic loci were 66.7% which showed the tendency of less genetic variation and more genetic differentiation compared with other two native pines, P. densiflora Sieb. et Zucc. and P. thunbergii Parl. They also stressed (1995) that although many populations of P. koraiensis were in small size distributed at high elevations and built up by closely related individuals, gene flow between those isolated populations still remained sufficiently high in this species. To study genetic variation, 8 populations of P. koraiensis were sampled within its range in ROK, the research result suggested that 7 of the 8 populations should, at least, be included in gene conservation programmes (Kim et al., 1994b; 1998).

Politov et al.(1999)reported that genetic evidence existed in natural hybridization and possible gene exchange between P. sibirica and P. pumila.

In northeastern China, the remained forest of P. koraiensis has been protected in the natural reserves with total area of 56 000 hm^-2 since the natural forest resources were over exploited in the last several decades. In addition, 88 natural stands, totally over 40 000 hm^-2, have been identified and conserved in situ as gene resources for sustainable forest management (Li, 1997). More plantations, however, are established with this species requiring for right seed sources, over 30 ha of gene banks were set up on several locations with about 1 000 selected individuals for ex situ gene conservation (Niu et al., 1992).

In ROK, 3 and 1 populations, with area of 55 hm^-2 and 2 hm^-2, have been identified for P. koraiensis and P. pumila, respectively, for in situ gene conservation; 91 hm^-2 of seed orchards have been established for P. koraiensis in the last 30 years, on the other hand, the seed orchards also served as ex situ gene conservation (Lee 1997).

5 Conclusions and Remarks

Of Haploxylon pines, P. koraiensis and P. armandii are most important forest species for wood and nut production. Traditional breeding programmes for advanced generations should be maintained and strengthened by using molecular genetic markers, especially for P. armandii which is naturally distributed in such a wide range that little understanding of population structure and genetic diversity was so far obtained. It is recommended that priority research programmes to study genetic variation be still critical for long term breeding and gene conservation of these two species. It should be recognized that priority research programmes to study genetic variation are still critical for long term breeding and gene conservation of these two species.

Molecular biology can also help with understanding of spatial patterns of occurrence of the less-known 5-needle pines and of evolutionary history and intraspecific variations, research in these aspects has not started yet in China since biochemical andmolecular genetic markers in biosystematic and biogeographic studies of forest trees have proven to be a powerful means (Adams, 1992; Straus et al., 1992). Conservation strategy can, otherwise, not be established at sound scientific bases.

The remained genetic resources of P. koraiensis are mostly protected in the nature reserves, whereas, the outstanding seed stands of P. armandii which had been identified in the previous provenance trials have not been integrated into activities of forest management, Gene management is a crucial component of sustainable forest management (Eriksson et al., 1993; Pamlberg-Lerch, 1999).

It must be noticed that no activities have so far been undertaken of research in resistance breeding for any species of 5-needle pines in East Asia, however, many studies have shown evidences that P. koraiensis and P. armandii are, in natural stands and plantations, suffering from diseases and insect attacks (Xue et al., 1995; Tang et al., 1999; Li et al., 2000).

Since the genetic resources are common heritage of the nature and shared among nations, a strategy for gene conservation and utilization of 5-needle pines should be developed and integrated into a regional action plan, as a whole, for the conservation of the forest genetic resources in East Asia as FAO and other concerned organizations have encouraged (Palmberg-Lerch, 2000; Sigaud et al., 2000).