, 2013). Furthermore, the establishment of new breeding populations and the need to enrich the VX-770 cell line genetic diversity of existing ones has maintained the demand for collecting seed from natural stands of acacias and eucalypts. There are, however, logistical difficulties in collecting from some locations, particularly for those species with natural distributions outside of Australia. Some important source populations have been lost due to deforestation and urban encroachment in recent decades. This has encouraged breeding programmes to exchange their
germplasm instead of investing in new seed collections from natural populations. Seed from Central American and Mexican pines are now largely obtained from seed stands and seed orchards. The seed of P. caribaea are produced in commercial seed stands and seed orchards in several countries (e.g., Australia, Brazil and Venezuela) and are sold on the world market. In the case of P. patula, large-scale seed producers include South
Africa and Zimbabwe, which have extensive breeding and planting programmes. However, the collection of pine seed from natural populations also continues, with Honduras, for example, selling large quantities of bulk seed of P. caribaea, P. maximinoi and P. tecunumanii. The demand and supply of Central American and Mexican pine seed have greatly fluctuated over the past 30 years, depending on the establishment rate of new plantations and
changes in seed production capacity, as new seed stands and seed Alpelisib in vitro orchards mature. Currently, the available world-wide seed production of P. caribaea, P. greggii, P. oocarpa and P. patula appears to be able to meet demand, but in the cases of P. maximinoi and P. tecunumanii demand exceeds supply. For high value tropical hardwoods, the picture is rather different. There are few improved seed sources many available and seed is mostly sourced from natural stands, plantations and even research trials. Usually, the available seed supply cannot meet the strong demand for plantation establishment. In the case of T. grandis, for example, Kjaer and Suangtho (1997) found that (fairly large) selected seed production areas in Thailand could only supply a small portion of the seed needed by nurseries, because of very low seed yield per tree. Low seed yield per tree is also a problem in clonal seed orchards of the species ( Kaosa-ard et al., 1998, Nagarajan et al., 1996, Palupi and Owens, 1996, Varghese et al., 2008 and Wellendorf and Kaosa-Ard, 1988). This problem, combined with the low and sporadic germination of T. grandis seed, leads to a low multiplication factor. To overcome these difficulties, vegetative propagation methods were developed for T. grandis in the 1980s (e.g., Guptha et al., 1980 and Kaosa-ard et al., 1987). These efforts have yielded positive results ( Kaosa-ard et al.