Progeny test of tetraploid Betula platyphylla and preliminary selection of hybrid parents
Estimating genetic parameters of parental lines through progeny testing and choosing good hybrid parents are important for genetically improving seed orchard trees. In this study, 24 tetraploid progeny seedlings were used as experimental materials, which came from test cross design: six tetraploid Betula platyphylla lines (Q33, Q13, Q103, Q19, Q83 and Q14) as female parents and four individual B. platyphylla diploid lines (F3, F4, F9 and F11) as male parents were crossed. Variance analysis of height, diameter, height-to-diameter ratio, and internodal distance showed that the differences between hybrid combinations reached highly significant levels. Using multi-objective decisionmaking, we performed a comprehensive assessment of the various hybrid combinations. Using a selection rate of 20 % of the standard, five hybrids were selected; their genetic gains in average height, diameter, height-to-diameter ratio, and internodal distance were 20.95, 6.07, 13.07 and 8.96 %, respectively. We also analyzed the combining ability and genetic parameter effect values of parents and hybrid combinations. The combined analysis revealed that Q13, Q103, Q33 and Q83 were superior females; F3, F4, and F9 were superior males; and F3 × Q13, F4 × Q83 and F9 × Q33 were superior hybrid combinations. The heights and diameters of these progenies were 22.49 and 11.48 % greater than average, respectively.
Variation and growth adaptability analysis of transgenic Populus simonii×P. nigra lines carrying TaLEA gene
A totlal of 12 Populus simonii×P. nigra lines (11 transgenic Populus lines and one control line) in 2 years old were used to study the phenotypic variation of tree height(H) and basic diameter(BD) in 6 different sites. The analysis of variance showed that there was a remarkable difference in H and BD among sites (P0.01), lines (P0.01), and sites×lines (P0.05). The average H and BD of transgenic poplar lines ranged in 128- - 235 cm and 13- - 24 mm in different sites respectively. The coefficients of H and BD of transgenic poplar lines changed in 19.84%- - 33.38% and 24.21%- - 49.16% and repeatabilities ranged in 0.497- - 0.952,indicating that the variation of poplar transgenic lines was strongly controlled by genetic factors,which were in favor of line selection. Tai model was introduced to analyse the genetic adaptability of poplar lines in different sites. The results showed that except line XL11, other lines grew steady in different sites. Based on the genetic adaptability parameter and the domino effect values of interaction between H and environment, the most adapted site of each line was predicted. Lines XL9, XL1 and XL14 are high biomass and strong stability, which are suitable generalized in 6 different sites.
Inhibition of Root Growth and Polyamine Metabolism in Sunflower (Helianthus annuus) Seedlings Under Cadmium and Copper Stress
Although sunflower is usually regarded as a highly tolerant crop, impairment of root growth at initial stages of plant development may result in poor crop establishment and higher susceptibility to pathogen attack. In order to evaluate if Cd2+ and Cu2+ may impact on sunflower germination and initial root development, a pot experiment under controlled conditions was carried out. Possible involvement of polyamine metabolism in sunflower response to these stressors was also investigated. Although Cd2+ and Cu2+ treatments affect neither seed germination nor radicle emergence, sunflower seedlings grown in the presence of these heavy metals showed significant inhibition of root growth, being this inhibition greater for Cd2+. Both metals caused significant increases in proline contents at the highest concentrations tested (0.5 and 1 mM), and these increments were more pronounced for Cd2+ treatments, especially between days 3 and 10. Metals also increased putrescine (Put) contents at all concentrations assayed from the seventh day onward, causing no variations on this polyamine time-course pattern. Spermine and spermidine contents, however, were increased only by 1 mM Cd2+. Arginine decarboxylase seems to have been the enzyme responsible for Put increases under both metal treatments. This work demonstrates that initial root growth of sunflower seedlings may be significantly impaired in Cd2+ or Cu2+ contaminated soils. It also shows that polyamines are key biological compounds, which are probably involved in signaling pathways triggered under stress environmental conditions.