【作者】 Mohammed Shalim Uddin；

【导师】 徐云碧； 李文学；

【作者基本信息】 中国农业科学院 ， 作物遗传育种， 2014， 博士

【摘要】 玉米广泛种植于全球温热带地区,是一个具有广泛用途和丰富遗传多样性的物种。磷是对植物生长发育具有重要作用的大量元素,低磷胁迫影响植物的正常生长。为了适应低磷胁迫的土壤环境,植物进化出适应低磷环境的机制,帮助植物在缺磷的条件下搜寻、活化和吸收土壤中的磷并对体内的磷进行循环利用。土壤中缺磷是限制玉米产量的重要因素之一,这种情况在以低投入农业为主的发展中国家更为严重。本研究应用遗传育种学的方法和技术初步揭示了玉米耐低磷遗传变异的生理机理。我们利用室内水培培养的方法进行对550个玉米自交系(包括338份来自于两个RIL群体的材料,69份温带自交系和143份热带自交系)进行了耐低磷的表型鉴定。试验设置低磷和常磷两个处理。统计分析表明所测定的茎叶性状在玉米材料之间表现出较大的遗传变异性,遗传力在0.70到0.91之间。最佳线性无偏估计(BLUP)分析发现BLUP和平均值之间表现出较强的正相关。苗长和其他性状相关性极显著,表明通过对苗长进行选择,可以达到改良其他性状的目的。我们对所有性状进行主成分分析,前两个主成分可以解释81.27%的表型变异,其中第一个主成分可解释表型变异的59.35%,主要贡献来自于总干重、苗干重、根干重、苗鲜重、根鲜重、根长和苗长。通过主成分分析计算出一个综合选择指数,利用该选择指数对玉米的耐低磷能力进行筛选,共筛选出30个优良材料。这些材料可能对提高玉米的耐低磷能力有一定的应用价值。我们利用GiA Root软件对低磷和常磷处理下的220个玉米自交系的根系性状进行了测量。方差分析表明,这些根部性状的遗传变异较大,遗传力在0.59到0.95之间,不同性状的遗传方差在0.01到0.60之间。BLUP与平均值之间表现出较强的线性关系。Euclidean遗传距离在0.61到29.33之间,表明自交系之间的变异性较大。主成分分析表明,前三个主成分解释表型变异的79%,其中贡献最大的是根系总长、根系表面积、根系周长、根系面积、最大根数、根系体积、根系凸面面积、根长、根系深度、交叉根数和根系宽度。缺磷将激发植物许多转录水平、生化水平和生理水平的变化,这些变化能够帮助植物吸收土壤中的磷以及改善植物的磷利用效率。玉米遗传材料的磷利用效率变异很大。系统生物学结合高通量、多维度和高精度的表型鉴定将有助于培育耐低磷的玉米新品种。更多还原

【Abstract】 Maize (Zea mays L.) is a versatile cereal crop and can grow in tropical, subtropical and temperate agro-climatic conditions. Phosphorus (P) is a second most important macro-element that is essential for plant growth and development. Plants have developed complex responsive and adaptive mechanisms for foraging, remobilizing and recycling of phosphorus to retain P homeostasis. Low-phosphorus (LP) in the soil is a major yield-limiting factor in maize production, particularly in low-input agriculture and developing countries. The present studies experimental breeding approaches were applied to reveal morpho-physiological mechanisms underlying natural variation for LP tolerance in maize and to find ways to explore this variation.A total of550maize germplasm, including338from two RIL populations and69temperate and143tropical maize inbreds, were evaluated for seedling traits in hydroponic under LP (2.5×10-6mol L"-1of KH2PO4) and normal phosphorus (NP)(2.5×104mol L-1of KH2PO4) conditions. Descriptive statistics and analysis of variance revealed a wide range of variability for LP tolerance related traits. Estimated broad-sense heritability (h2) for all the measured traits ranged from70%to91%, indicating that all the traits were highly inheritable. Genetic variances were low to moderate (0.05-0.31) for most seedling traits, indicating strong treatment effects and/or complex genetic architecture. Best linear unbiased predictor (BLUP) analysis found a strong positive correlation between BLUPs and means of the traits. Shoot length was significantly correlated with other root traits, indicating that direct selection based on maximum shoot length (MSL) might be sufficient for improvement of other traits. The first two principal components (PCs) explained about81.27%of the total variation among lines for the eight maize seedling traits. The relative magnitudes of eigenvectors for the first principal component was59.35%, explained mostly by total dry matter (TDM), shoot dry weight (SDW), root dry weight (RDW) shoot fresh weight (SFW), root fresh weight (RFW), maximum root length (MRL) and MSL. Genotype by trait (GXT) biplot revealed superior genotypes with combinations of favorable traits. The average genetic distance was3.53, ranging from0.25to20.01, indicating high levels of variability among the germplasm. A multi-trait selection index was calculated based on principal component analysis (PCA) using all measured traits, and30accessions with tolerance to LP stress were selected. These lines could be of potential use for breeding LP tolerance maize.Root network system (RNS) traits were measured from images of220inbred lines using GiA Root software. The inbred lines grew up to15days under hydroponic conditions in the high lux plant growth room with LP and NP treatments. Analysis of variance revealed a wide range of variability among the inbred lines, and heritability estimates ranged from0.59to0.95for all RNS traits, indicating consistency across experiments. The proportions of genetic variance ranged from0.01-0.60in the maize RNS traits. There was a strong positive, linear relationship between best linear unbiased predictors and estimated means. The Euclidean genetic distances ranged from0.61to29.33, indicating high levels of variability among the inbred lines. The first three PCs explained more than79%of total genetic variation, which were mostly contributed by network length (NWL), network surface area (NWSA), network perimeter (NWP), network area (NWA), maximum number of roots (MANR), median number of roots (MENR), network volume (NWV), network convex area (NWCA), specific root length (SRL), network depth (NWD), number of connected components (NCC) and network width (NWW). The G×T biplot revealed superior genotypes with combinations of favorable traits. Some outstanding genotypes with higher values of most RNS traits were identified. These lines could be of potential use for breeding LP tolerance maize.P deficiency in plants triggers many transcriptional, biochemical, and physiological changes that ultimately help the plants absorb P from the soil or improve the P use efficiency. Substantial genetic variation in P efficiency exists among the maize genotypes. It is expected that integration of systems biology with high-throughput, high-dimensional and precision phenotyping will contribute to the development of maize varieties tolerant to LP stress.更多还原