Tschaplinski Timothy J, Tuskan Gerald A, Sewell Mitchell M, Gebre G Michael, Todd Donald E, Pendley Carrie D
Environmental Sciences Division, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, Tennessee 37831-6422, USA.
Tree Physiol. 2006 May;26(5):595-604. doi: 10.1093/treephys/26.5.595.
Elucidation of the mechanisms of dehydration tolerance in poplar (Populus sp.) trees will permit development of biochemical and molecular indicators to identify dehydration-tolerant genotypes during genetic selection. The objectives of this study were to characterize the degree of phenotypic variation in osmotic potential (a determinant of dehydration tolerance), determine the relationship between osmotic potential at full turgor and relative growth rate, and identify quantitative trait loci (QTL) for osmotic potential in an advanced-generation, interspecific poplar pedigree established in contrasting environments. A three-generation, sib-mated black cottonwood (Populus trichocarpa Torr. & Gray) and eastern cottonwood (P. deltoides Bartr.) segregating F(2) family (Family 331) was analyzed at a dry site east of the Cascade Mountain Range (Boardman, OR) and at a wet site west of the mountains (Clatskanie, OR). At the Boardman site, 2-year-old trees (59 clones) were either irrigated everyday (wet) or every other day (dry), whereas 3- and 4-year-old trees (58 clones) at the Clatskanie site were unirrigated. At the Boardman site, the typically narrow range of osmotic potentials exhibited by grandparents and parents was greatly expanded in the F(2) population, spanning from -1.38 to -2.35 MPa under wet conditions, with a similar range under dry conditions (-1.40 to -2.15 MPa). Clones that had osmotic potentials < or = -1.90 MPa generally displayed full maintenance of stem relative growth rates under dry conditions in contrast to clones with osmotic potentials that were < or = -1.60 MPa, in which stem relative growth rates were reduced by an average of 38% in the dry treatment relative to the wet treatment. Although osmotic adjustments of 0.13 to 0.36 MPa were observed in nine out of 59 clones, adjustment typically occurred from relatively high baseline osmotic potentials. The range in osmotic potential at the wetter Clatskanie site at age three was higher (-1.27 to -1.84 MPa) and was further expanded the following year (-1.14 to -1.94 MPa), which had a wetter spring than the previous year, followed by a typically dry July. Seven QTL for osmotic potential were identified that each explained > 7.5% of the variation in osmotic potential. Given that four clones (7%) had osmotic potentials of -2.00 MPa or less and that QTL for osmotic potential have been identified, we suggest that there are opportunities to extend the limit of dehydration tolerance in Populus.
阐明杨树（Populus sp.）的耐旱机制，将有助于开发生化和分子指标，以便在遗传选择过程中识别耐旱基因型。本研究的目的是表征渗透势（耐旱性的一个决定因素）的表型变异程度，确定完全膨压下的渗透势与相对生长速率之间的关系，并在不同环境中建立的一个高级代种间杨树谱系中，识别控制渗透势的数量性状位点（QTL）。对一个三代同堂、同胞交配的黑杨（Populus trichocarpa Torr. & Gray）和东部杨（P. deltoides Bartr.）分离的F(2)家系（家系331），在喀斯喀特山脉以东的干旱地点（俄勒冈州博德曼）和山脉以西的湿润地点（俄勒冈州克拉茨卡尼）进行了分析。在博德曼地点，对2年生树（59个无性系）要么每天灌溉（湿润），要么隔天灌溉（干旱），而在克拉茨卡尼地点，3年生和4年生树（58个无性系）不进行灌溉。在博德曼地点，祖父母和父母通常表现出的较窄的渗透势范围在F(2)群体中大幅扩大，在湿润条件下从-1.38到-2.35 MPa，在干旱条件下范围相似（-1.40到-2.15 MPa）。渗透势≤-1.90 MPa的无性系通常在干旱条件下茎相对生长速率能完全维持，而渗透势≤-1.60 MPa的无性系则不同，其茎相对生长速率在干旱处理中相对于湿润处理平均降低了38%。尽管在59个无性系中有9个观察到了0.13至0.36 MPa的渗透调节，但调节通常发生在相对较高的基线渗透势上。在更湿润的克拉茨卡尼地点，3岁时的渗透势范围更高（-1.27至-1.84 MPa），次年进一步扩大（-1.14至-1.94 MPa），该年春季比上一年更湿润，但随后的7月通常较为干旱。识别出了7个控制渗透势的QTL，每个QTL解释的渗透势变异均>7.5%。鉴于有4个无性系（7%）的渗透势≤-2.00 MPa，并且已经识别出了控制渗透势的QTL，我们认为有机会扩展杨树的耐旱极限。
