Estimation of phenotypic variability in symbiotic nitrogen fixation ability of common bean under drought stress using 15N natural abundance in grain

Common bean (Phaseolus vulgaris L.) is the most important food legume, cultivated by small farmers and is usually exposed to unfavorable conditions with minimum use of inputs. Drought and low soil fertility, especially phosphorus and nitrogen (N) deficiencies, are major limitations to bean yield in smallholder systems. Beans can derive part of their required N from the atmosphere through symbiotic nitrogen fixation (SNF). Drought stress severely limits SNF ability of plants. The main objectives of this study were to: (i) test and validate the use of ¹⁵N natural abundance in grain to quantify phenotypic differences in SNF ability for its implementation in breeding programs of common bean with bush growth habit aiming to improve SNF, and (ii) quantify phenotypic differences in SNF under drought to identify superior genotypes that could serve as parents. Field studies were conducted at CIAT-Palmira, Colombia using a set of 36 bean genotypes belonging to the Middle American gene pool for evaluation in two seasons with two levels of water supply (irrigated and drought stress). We used ¹⁵N natural abundance method to compare SNF ability estimated from shoot tissue sampled at mid-pod filling growth stage vs. grain tissue sampled at harvest. Our results showed positive and significant correlation between nitrogen derived from the atmosphere (%Ndfa) estimated using shoot tissue at mid-pod filling and %Ndfa estimated using grain tissue at harvest. Both methods showed phenotypic variability in SNF ability under both drought and irrigated conditions and a significant reduction in SNF ability was observed under drought stress. We suggest that the method of estimating Ndfa using grain tissue (Ndfa-G) could be applied in bean breeding programs to improve SNF ability. Using this method of Ndfa-G, we identified four bean lines (RCB 593, SEA 15, NCB 226 and BFS 29) that combine greater SNF ability with greater grain yield under drought stress and these could serve as potential parents to further improve SNF ability of common bean.     

Effect of water deficiency on relationships between metabolism,physiology,biomass,and yield of upland cotton(Gossypium hirsutum L.)

Drought is a common abiotic stress that considerably limits crop production. The objective of this study is to explore the influence of water deficiency on the yield, physiologic and metabolomic attributes in upland cotton cultivars(Gossypium hirsutum L). Cotton cultivars, 'Ishonch' and 'Tashkent-6' were selected to study the relationships among their physiologic, metabolomic and yield attributes during water deficiency. Deficit irrigation was designed by modifying the traditional watering protocol to reduce water use. Results indicate that cotton cultivars respond differently to water deficit stress. Water deficit significantly influenced plant height, the number of internodes, and sympodial branches in both cultivars. However, yield components such as the number of bolls, boll seed, lint mass, and individual plant yield were significantly reduced only in 'Tashkent-6'. The leaf area decreased and the specific leaf weight increased in 'Ishonch' under deficit irrigation conditions. However, 'Tashkent-6' demonstrated significant water loss compared to 'Ishonch', and both cultivars showed reduced transpiration rates. Untargeted metabolite profiles of leaves showed clear separation in 'Ishonch', but not in 'Tashkent-6' under deficit irrigation compared to full irrigation. The individual metabolites such as proline and galactinol showed strong association with yield under water deficit stress. Moreover, this study indicates that leaf area and transpiration intensity influence yield during water deficiency. In summary, the correlation among morpho-physiologic, metabolic, and yield components significantly varied between the two cultivars under water deficiency. The flowering stage was sensitive to water stress for both cultivars. The direct relationship between physiology, metabolism, and yield may be a useful selection criterion for determining candidate parents for cotton drought tolerance breeding.     

紫花苜蓿形态和生理指标响应干旱胁迫的品种特异性

为研究紫花苜蓿在叶片和根系水平上响应干旱胁迫的形态和生理的品种特异性规律,在温室内分析了干旱胁迫下WL363HQ和巨能7紫花苜蓿株高、分枝数、生物量及叶片和根系中丙二醛（MDA）、脯氨酸、抗氧化酶类物质、C、N含量、C/N、稳定性C同位素（δ¹³C）和稳定性N同位素（δ¹⁵N）。结果表明：干旱胁迫显著降低了供试品种地上部分和根系的干重及分枝数（P<0.05）。干旱胁迫显著降低了巨能7的株高（P<0.05）,但增加了巨能7的根冠比,而WL363HQ的结果与之相反,这说明干旱胁迫下供试品种的株高和根冠比具有品种特异性的规律。干旱胁迫增加了WL363HQ和巨能7叶片和根系中MDA和脯氨酸的含量及抗氧化酶物质的活性,且在器官水平也具有品种特异性规律。干旱胁迫下巨能7叶片的MDA含量显著增加（P<0.05）,而在WL363HQ根系中的MDA含量也显著增加（P<0.05）。干旱胁迫下WL363HQ叶片脯氨酸含量、POD和SOD活性,及根系SOD的活性均显著增加（P<0.05）,而巨能7仅叶片SOD活性,根系脯氨酸含量、POD活性显著升高（P<0.05）。尽管干旱胁迫对供试品种叶片和根系C、N含量无显著影响（P>0.05）,但干旱胁迫显著提高了WL363HQ和巨能7紫花苜蓿根系的δ¹³C（P<0.05）,且WL363HQ叶片的δ¹⁵N均显著高于巨能7（P<0.05）。此外,干旱胁迫均显著提高了巨能7叶片和根系的C/N（P<0.05）。干旱胁迫下供试品种C、N代谢参数并没有在叶片和根系中表现出较为明显的品种特异性规律,深层次的机制还有待进一步研究。本研究结果将为进一步掌握紫花苜蓿叶片和根系协同抗旱机制及抗旱丰产紫花苜蓿新品种的选育提供理论依据。     

不同水分环境下玉米叶面积QTL定位及候选基因分析

玉米叶面积的大小及分布特征不仅影响其光合效率、蒸腾速率,而且与其耐旱性、耐密性、抗倒伏性及产量形成紧密相关。深入剖析不同水旱环境下玉米不同生育时期不同叶位叶面积的分子遗传机理对玉米耐旱高产新品种的选育具有重要意义。本研究以构建的2套F_2∶3群体为试材,在8种水分环境下,采用复合区间作图法（CIM）和基于混合线性模型的复合区间作图法（MCIM）对玉米相应叶（V₁₈时期第10片叶、R₁时期穗三叶）叶面积进行单环境和多环境联合QTL分析;参考玉米基因组B73 RefGen_v3挖掘稳定表达的QTLs （sQTLs）区间内的候选基因,并对其进行功能分析。结果表明,采用CIM法,单环境下2个生育时期2套F_2∶3群体间总共定位到了7个玉米相应叶叶面积QTLs,主要受显性（81.0%）、部分显性（14.3%）和超显性（4.7%）等遗传效应的调控,其中在干旱环境下定位到了5个QTLs。采用MCIM法,在2套F_2∶3群体间总共检测到6个相应叶叶面积的联合QTLs,其中1个表现为显著的QTL与环境的互作（QTL×E, Bin 2.08~2.09）,1对QTLs （Bin 1.08~1.10与 Bin 2.08~2.09）参与了显著的加性与加性（AA）上位性互作。结合CIM和MCIM法进一步分析在2套F_2∶3群体间检测到了6个sQTLs,其分别位于Bin 1.08~1.10、Bin 2.08~2.09、Bin 4.08~4.09、Bin 6.05、Bin 8.03和Bin 10.03处,并在这些sQTLs区间内确定了12个玉米叶发育相关候选基因。采用生物信息学,总共收集了75个玉米叶发育相关候选基因,通过系统进化树分析表明,这些候选基因划分为3大进化分支,且上述检测到的12个候选基因分布于这3大进化分支上。这些结果为系统地解析玉米不同生育时期不同水旱环境下相应叶叶面积的分子遗传机理提供理论依据,检测到的sQTLs可作为叶面积改良的重要染色体区段,检测到的候选基因为其进一步克隆、功能分析及育种应用提供了信息参考。     

抗旱、耐盐碱、矮秆陆地棉数量性状的遗传相关及主成份分析

对从国内外引进的抗旱、耐盐碱、矮杆棉花资源材料 ,经抗旱、耐盐碱、矮杆性鉴定和比较 ,选取了其中表现较好的 1 9份材料 ,进行了遗传相关和主成份分析 ,结果表明 :在 5 0 mmol· L- 1Na Cland1 0 0 mmol· L- 1Na Cl胁迫下的出苗率间呈正相关 ,抗盐性与产量间呈负相关 ;第一棉铃高度与纤维品质性状呈正相关。抗旱、耐盐碱、矮杆棉花材料的前 6个因子贡献率达 86.5 % ,其分别为第一棉铃高度因子、果枝数因子、单株结铃数因子、矮杆因子、单铃重因子等     

Urinary catecholamine and metanephrine to creatinine ratios in healthy dogs at home and in a hospital environment and in 2 dogs with pheochromocytoma

BACKGROUND: Measurement of high concentrations of urine catecholamines and metanephrines is useful in diagnosing pheochromocytoma in humans. Stress increases catecholamine excretion in urine. HYPOTHESIS: Stress of a hospital visit increases urinary catecholamine and metanephrine excretion in dogs. ANIMALS: Fourteen clinically normal dogs, 2 dogs with pheochromocytoma. METHODS: Voided urine samples were collected by the owners 7 days before (t-7), during the hospital visit immediately after diagnostic procedures (t0), as well as 1 (t1) and 7 days (t7) after the hospital visit. Urine catecholamine and metanephrine concentrations were measured using high-pressure liquid chromatography and expressed as ratios to urine creatinine concentration. RESULTS: In client-owned dogs epinephrine and norepinephrine ratios at t0 were significantly higher compared with ratios at t7. Metanephrine and normetanephrine ratios at t-7, t0, and t1 did not differ significantly from each other; however, at t7 they were significantly lower compared to values at t-7. In staff-owned dogs no significant differences were detected among the different collecting time points for any variable. Metanephrine and normetanephrine ratios were significantly higher in client-owned dogs compared to staff-owned dogs at t-7, t0, and t1 but not at t7. CONCLUSIONS AND CLINICAL IMPORTANCE: Stress associated with a hospital visit and with the sampling procedure causes increases in urine catecholamine and metanephrine excretion. Urine collection for the diagnosis of pheochromocytoma probably should take place at home after adaptation to the sampling procedure.     

Quantification of stress sensitive markers in single fecal samples do not accurately predict excretion of these in the pig

All feces produced during 24 h were collected from five pigs and cortisol and immunoreactive cortisol metabolites (CICM), and IgA were quantified. Within pigs, the concentrations of CICM and IgA varied extensively between random samples obtained from a single fecal dropping, and deviated in most cases significantly from the true concentration measured in total fecal output (CV 6.7-130%). The CICM and IgA contents varied considerably (CV 8.1-114%) within and between individual fecal droppings from the same pig compared to the total fecal excretion. In conclusion, single random samples could not be used to reliably quantify the total fecal concentration or excretion of CICM or IgA in pigs. Analyses of all feces collected during shorter periods than 24 h did not provide an accurate estimate of the daily excretion of CICM. Thus, the concentration of stress sensitive molecules in random single fecal samples as an indicator of animal welfare should be interpreted with prudence.     

不同基因型大麦苗期对干旱胁迫的响应及HvPIPs基因表达特征分析

为研究不同基因型大麦苗期对干旱胁迫的响应,挖掘优质抗旱的大麦种质资源,以4份不同基因型大麦(2个高抗品种ZDM5430和ZDM5458,2个干旱敏感型品种7DCADA和IL-12)为材料,利用聚乙二醇(PEG-6000)模拟干旱条件,综合分析不同品种大麦的苗期抗旱性差异;并通过对不同品种根系进行PIPs实时定量分析,研究水通道蛋白AQPs基因与干旱胁迫之间的应答关系。结果表明,持续干旱胁迫会使大麦生长变缓,各处理苗长、根长、叶含水量和根含水量都呈下降趋势,其中,4个品种的大麦叶含水量在干旱胁迫14 d时下降最为显著,与对照相比,其降幅分别为29.14%、52.64%、21.67%和72.15%。干旱胁迫对大麦苗期干物质积累量和根冠比的影响较小,各处理间差异不显著;但持续干旱后,抗旱品种ZDM5430的根冠比呈上升趋势,在胁迫7、14、21 d时较CK分别增加了4.92%、42.86%和21.05%。随着胁迫时间的延长,大麦旗叶叶绿素含量和根系活力也呈下降趋势,其中ZDM5430和ZDM5458较对照组降幅较小,说明抗旱品种的形态指标、叶绿素含量及根系活力受干旱胁迫的影响较小。通过PIP...     

基于AHP-EWM-TOPSIS的温室辣椒最佳调亏灌溉方案优化研究

辣椒对土壤水分非常敏感,传统的灌溉方式以单一追求高产为目的,对农作物进行大量灌溉,辣椒产量的提高往往伴随品质的下降。为选出能平衡产量和品质的最优调亏灌溉方案,本试验以辣椒为研究对象,以全生育期充分供水(75%～85%θ_f,θ_f为田间持水量)作为对照(CK),在3个调亏时期(苗期M、花期H和果期G)分别设置2种调亏程度(轻度水分调亏LS:65%～75%θ_f,重度水分调亏SS:55%～65%θ_f)和2种调亏历时(短期调亏：连续亏水4 d,长期调亏：连续亏水8 d),研究不同调亏处理对辣椒生长、产量和品质的影响。结果表明,在各生育期进行调亏灌溉均会减小辣椒株高、茎粗、叶面积及营养器官干物质。与花期和果期相比,苗期水分调亏对辣椒生长指标及营养器官干物质的抑制程度最大,尤其在苗期长期重度水分调亏(MSS-8)下,营养器官干物质最少,较CK下降27.85%。另外,苗期和花期适度的水分调亏有利于提高辣椒生殖器官干物质和产量,其中,苗期短期轻度(MLS-4)、苗期长期轻度(MLS-8)及花期短期轻度(HLS-4)水...     

测定应力集中系数的灰色建模方法

通过对带轴肩的扭转圆轴、带双凹槽的拉伸板条、带偏心孔的纯弯曲梁等几种典型构件在应力集中处进行应变电测，利用灰色系统理论对测试数据进行累加生成处理、模型识别，建立了应变分布的灰色模型，用该模型求出了应力集中处的应力集中系数。结果表明：与目前常用的数据处理方法比较，灰色建模方法具有所需测试数据少、预测精度高等优点，非常适用于构件应力集中系数的实时测定。