【作者】 张瑜；

【导师】 李春俭；

【作者基本信息】 中国农业大学 ， 植物营养学， 2014， 博士

【摘要】 充分发掘作物自身对养分吸收利用的潜力,是作物高产和养分高效的基础。这就要求能够选育出高产高效的作物品种。分子数量遗传学的发展为作物育种学家应用分子标记辅助选择技术(MAS)进行定向选育新品种提供了可能。本研究以玉米改良自交系224及其供体亲本478和轮回亲本312为试验材料,通过连续两年的田间和温室试验,系统比较了三个自交系玉米在不同供磷水平下在叶面积、植株生物量、穗部性状、产量、吸磷量及根系形态等方面的差异。为了验证玉米主要通过根系形态变化增加磷素吸收来适应低磷胁迫的假设,通过两年不同供磷水平的田间试验,比较了玉米和蚕豆在植株根冠比、根系形态和生理变化上的差异。主要结果如下：1.不同供磷水平(低磷5μmol/L和高磷250μmol/L)和限制种子根及节根生长(限根)的温室营养液培养试验中,在苗期根系对低磷的形态可塑性变化、限根后的补偿性生长、以及植株生长和磷素吸收等方面,玉米改良自交系224与轮回亲本312的表现相同,并显著低于供体亲本478。说明插入的DNA片段未能影响224在苗期的营养生长和磷素吸收。2.与营养液培养中对根系生长的影响类似,在两年不同供磷水平的田间试验中,吐丝期和成熟期时224的总根长、侧根长及其在0-40cm土层中的垂直分布与312相比无显著差异,并显著低于478。但224的总叶面积、整株生物量、产量和吸磷量都高于312,在低磷条件下尤为明显,说明插入的相关DNA片段影响了224在田间苗期之后的生长和磷素吸收。与供体亲本478类似,在两年田间试验中224的花后吸磷量均显著高于312,说明可能存在未鉴定的控制花后吸磷量的DNA插入片段发挥了作用。两年不同供磷水平的田间试验结果显示,在吐丝期和成熟期,相同供磷水平下三种自交系生长的不同土层土壤的速效磷(Olsen-P)浓度无显著差异；各自交系的根际与非根际土壤的速效磷浓度差异无规律。3.在田间对不同供磷水平下玉米自交系478根系在0-60cm土层中分布的研究结果表明,低磷水平下,拔节期和吐丝期时,自交系478在40-50cm土层中的细根量显著增加,但根际与非根际土壤的无机磷分级结果无显著差异。4.两年田间试验证明玉米和蚕豆根系对低磷胁迫的适应性反应不同。与蚕豆相比,低磷胁迫下玉米植株的根冠比净增量及其根系在浅层土壤(0-20cm)中的总根长都显著高于蚕豆。相反,与玉米相比,蚕豆的根际酸性磷酸酶活性显著升高,根际土壤pH值显著下降。综上,本论文的研究结果为通过遗传育种方法培育在适量供磷条件下高产和磷高效的作物品种提供了证据。虽然在改良自交系224染色体上检测到了来自供体亲本478控制根系性状的DNA片段,但是田间整个生育期试验以及水培苗期试验结果都无表型；而试验结果显示改良自交系224花后的吸磷量显著高于其轮回亲本312,但未见有在224染色体上插入了供体相关DNA片段的报道。通过与蚕豆的比较,验证了玉米主要通过根系形态变化适应低磷胁迫,以增加磷素吸收。在玉米生产中,应更加注重通过施肥和根际调控措施促进根系的生长,提高磷肥利用率。更多还原

【Abstract】 The physiological and biological potential of crops to take up and utilize nutrients underlies efficient nutrient utilization and high grain yield in crop production. A critical step is to breed crop varieties with high yield and high nutrient use efficiency. Molecular marker assisted breeding paves the way for modern crop breeders. Here, we carried out comparative studies of improved inbred line224, donor parent478, and recurrent parent312, in terms of leaf area, biomass, ear traits, grain yield, phosphorus (P) uptake, and root morphology via two consecutive year’s greenhouse and field experiments under different P regimes. Additionally, we hypothesized that maize responds to low P stress via root morphological adaptation that enhances P uptake. To test this hypothesis, we compared the root/shoot ratio, root morphological traits, and related physiological parameters between maize and faba bean under different P levels in a two-year filed experiment. The main results were as follows:(1) The improved inbred line224, similar to its recurrent parent312, was inferior to donor parent478at the seedling stage in terms of root morphological adaptation, compensatory root growth, biomass accumulation, and P uptake in hydroponic experiments under low P (5μmol/L) and high P (250μmol/L) conditions and after root-restriction treaement (removing seminal roots and brace roots), suggesting that introgressed DNA segments in line224had no detectable effects on plant growth and P uptake at seedling stages.(2) Similar to the results derived from the hydroponic experiments, the total root length, lateral root length, and vertical distribution of roots along the0-40cm soil profile of line224were statistically similar to those of its recurrent parent312at silking and maturity under different P conditions in a two-year field experiment, but lower or less than those of donor parent478. However, the total leaf area, the whole plant dry weight, grain yield and P uptake of line224were significantly higher than its recurrent parent312, especially under the low P condition, indicating that the introgressed DNA segment in224enhances post-seedling growth and P uptake in the field. Also, P uptake after silking in line224, similar to the donor parent478, is significantly higher than that of line312according to two year’s results, suggesting that certain unknown DNA segments mediating P uptake after silking may be introgressed into line224. In addition, there was no significant difference in the Olsen-P concentration in the0-40cm soil profile at silking and maturity among three inbred lines grown under the same P level; we also found no distinctive patterns of Olsen-P variation in the rhizospheric and bulk soil of each of the three lines.(3) We analyzed root distribution patterns along the0-60cm soil profile and found that the fine root of inbred line478increased in length in the40-50cm soil profile at jointing and silking stages. There was no significant difference in the inorganic P fraction between the rhizospheric and bulk soil.(4) Maize and faba bean root systems had different adaptive responses to low P according to two year’s field experiments. There was a significantly increase in the root/shoot ratio in maize and maize had larger total root length in the0-20cm soil profile under low P, in comparison with faba bean. On the contrary, the activity of acid phosphatase significantly increased and the pH had a significant decrease in the rhizosphere of faba bean.In conclusion, our results provided theoretical basis for P efficient high-yield crop breeding with appropriate P supplies. However, there were no obvious difference between224and312in either total root length or root vertical distribution within0-40cm soil profile at field and hydroponic experiments, although some important QTLs associated with root traits have been introgressed from the donor parent478into224; the results implied that DNA segment controlling post-silking P uptake was introgressed from the donor parent478into224, which had not been identified yet. In addition, maize, in contrast to faba bean, increased P uptake mainly via root morphological adaptation upon low P stress. The results suggest that it is more important in maize production to increase root growth by P fertilizer application and rhizospheric management, and thus to increase P use efficiency.更多还原