Heritability estimates and progeny testing of phenotypic selections for soluble solids content in dehydrator onion

Soluble solids comprise most of onion bulb dry mass, and dehydrator onion cultivars are developed from breeding populations that have high dry mass content. Realized and narrow-sense heritability estimates were obtained for the soluble solids content (SSC) trait in two open-pollinated dehydrator onion breeding populations (BP) using response to selection and half-sib family analysis. Parental populations, designated as BP9335-U and BP9243-U, were derived from two-way crosses of lines advanced as open- pollinated (OP) populations to the F7 or F_6 generation, respectively. BP9335-U had one previous selection cycle for increased SSC and BP9243-U had three SSC selection cycles. In these experiments, parental populations were screened again for high SSC, and selected bulbs were intermated to form half-sib progeny groups, designated as BP9335-S and BP9243-S. Mean SSC was increased by 6.6% and a realized heritability estimate of 0.64 was obtained for BP9335-S. Mean SSC was increased by 6.3% and a realized heritability estimate of 0.36 was obtained for BP9243-S. Narrow-sense heritability estimates of 0.58 ±0.05 and 0.30 ±0.03 were obtained for parental populations BP9335-U and BP9243-U, respectively. Narrow-sense heritability estimates of 0.40 ± 0.03 and 0.63 ± 0.23 were obtained for progeny populations derived from selected high-SSC bulbs of these lines (BP9335-S and BP9243-S), respectively, indicating that there is significant additive genetic control of the SSC trait in these populations. Significant differences in half-sib family performance in the advanced groups BP9335-S and BP9243-S demonstrate that progeny testing was effective for evaluating phenotypic selections. This revised version was published online in July 2006 with corrections to the Cover Date.     

Length of cuttings in establishment and production of short-rotation plantations of Salix ‘Aquatica’

The effect of length of cuttings, 10 to 50 cm long, on establishment and productivity of short-rotation plantations was investigated in five trials, for periods of 2 to 9 years. The trials were established on abandoned agricultural fields planted with unrooted Salix Aquatica cuttings. The effect of cutting length was very similar in all five trials: the longer the cuttings (up to 30–50 cm), the better the survival and growth. In most trials the greatest difference in survival was between cutting lengths of 10 and 20 cm, especially in unfavorable growing conditions. In an annually harvested trial during the 9-year test period, a cutting length up to 30 cm affected biomass production per stool positively. In two trials grown with 5-year rotation, the longest cuttings produced 7 times the above-ground biomass of the shortest ones. Results of these trials also emphasize the importance of establishment for the future success of willow plantations.     

2025杨及其3种芽变红叶杨光合生理和生态适应性研究

红叶杨系列品种是我国典型的彩叶乔木。为进一步明确红叶杨树在叶片光合生理及干物质分配的适应特征，以2025杨及其3个连续芽变品种中红杨、全红杨和金红杨的1年生扦插苗为试验材料，研究其在功能叶光合特性、器官间生物量分配等方面的种间差异。结果表明，随着对2025杨芽变的连续人工选择，其当年生长量显著降低，功能叶光合能力也呈降低趋势，但金红杨略高于全红杨；功能叶的瞬时水分利用效率（WUE）依次显著降低，中红杨和全红杨的光合氮利用效率（PNUE）显著低于2025杨，而金红杨的PNUE无显著差异。单叶面积、净光合速率、羧化速率（CE）及光合氮利用效率（PNUE）等指标显著降低可能是中红杨和全红杨生长量显著低于2025杨的原因，而非叶绿素含量。叶绿素a含量大幅度减少是金红杨功能叶光合能力低的重要原因。与2025杨相比，3种红叶杨的地上部干物质积累显著降低，叶器官分配比例逐渐增加而茎中干物质投资逐渐降低，这可能是对叶片光合能力降低的一种适应，但秋季落叶造成碳资源损失过大而对个体生长不利。