Southern Research Station

Title: Genetic transformation of Pinus palustris (longleaf pine)

Author: Diner, Alex M.

Date: 1999

Source: n: Bajaj, Y.P.S. Transgenic trees. Biotechnology in Agriculture and Forestry, vol. 44. Heidelberg: Springer-Verlag Berlin: 185-192.

Description: 

Longleaf pine (Pinus palustris Mill.) is an important softwood species in the Southeast United States. In presettlement times, this species occupied extensive, pure stands throughout the Atlantic and Gulf Coastal Plains from southeastern Virginia to eastern Texas, as well as south throughout the northern two-thirds of Florida. Its range also includes the Piedmont Ridge and Valley, and Mountain Provinces of Alabama and Georgia.

Historically, longleaf pine was the premier timber and naval stores tree, a fact which resulted in its virtual disappearance from extensive regions. Its value as a timber species remains high; it shows excellent form and good wood qualities, as well as resistance to fusiform rust, the most damaging disease of Southern US three-needle pines.

An aspect of longleaf pine which negatively affects its relative reforestation value is its grass stage, during which its first 5 years of growth remains essentially limited to root development. This stage is also characteristically expressed for several years by adventitious micropropagules generated in vitro, although a few genotypes have shown precocious and rapid shoot elongation. Notwithstanding the obstacles to seedling growth presented by the grass stage, however, the value of this tree has compelled widespread reforestation efforts.

Current perspectives for value-added longleaf pine genetic transformants relate to both disease resistance and early shoot growth. The major microbial disease of this species is brown-spot needle blight (Scirrhia acicola), which causes severe defoliation and death to grass-stage seedlings. Other commercially important microbial diseases include pitch canker (Fusarium moniliforme var. subglutans), annosus root rot

(Heterobasidion annosum), and cone rust (Cronartium strobilinum). Longleaf pine suffers attack by a variety of defoliating insects, including both adult (Colaspispini Barber) and larval [(Neodiprion lecontei (Fitch); Dendroctonus terebrans (Oliv.); Hylobius pales (Hbst.); Pachylobius picivorus (German); Dioryctria spp.; Laspeyresia spp.)] insect forms. Because vector systems exist for plant transformation to such as chitinase and BT toxin syntheses, opportunities for transformation of longleaf pine for pest resistance are potentially available. Indeed, the whole-tree Larix transformant has been regenerated expressing BT toxin synthesis, suggesting that Pinus may be similarly transformed. Moreover because shoot growth restriction in grass-stage plants is a probable result of endogenous plant growth regulator (PGR) control, transformation of tissues for modified PGR synthesis, followed by regeneration of the plant, may provide early shoot elongation in the whole-tree transformant.

Longleaf pine shows great genetic variation in those traits affecting survival, growth, and disease resistance, suggesting its useful candidacy for clonal propagation. Rooting of cuttings is possible, but unreliable. Grafting is now the most common method used to establish seed orchards. However, methods are available for longleaf pine somatic embryogenesis, which allow opportunity for genetic manipulation and regeneration of the transformed regenerant. Since tissues of several species of pines have been transformed using biolistics, and this author was successful in regenerating Larix whole trees from Agrobacterium-induced transformants, both procedures for genetic transformation were undertaken using longleaf pine.

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Citation

Diner, Alex M.  1999.  Genetic transformation of Pinus palustris (longleaf pine).   n: Bajaj, Y.P.S. Transgenic trees. Biotechnology in Agriculture and Forestry, vol. 44. Heidelberg: Springer-Verlag Berlin: 185-192.