Genotype by environment effects and selection for drought tolerance in tropical maize. II. Three-mode pattern analysis

A selection program in three tropical maize populations aimed to improve tolerance of mid-season to late season drought environments while maintaining grain yield (GY) potential. The selection process employed other attributes that included maintaining a constant anthesis date (AD) and, under drought, shortening the anthesis-silking interval (ASI) and increasing ear number per plant (EPP). Three-mode (genotypes × environments × attributes) pattern analysis, which consists of clustering and ordination, should be able to collectively interpret these changes from ten evaluation trials. Mixture maximum likelihood clustering identified four groups that indicated the populations' performance had changed with selection. Groups containing the advanced cycles of selection were higher yielding in most environments and had lower ASI and higher EPP, particularly in drought environments. Check entries with no selection for drought tolerance remained grouped with the initial cycles of selection. A 3 × 2 × 3 (genotypes by environments by attributes) principal component model explained 70% of the variation. For the first environmental component, ASI was shown to be highly negatively correlated with both GY and EPP while anthesis date (AD) was virtually uncorrelated with other traits. The second environmental component (explaining 10% of the variation) contrasted droughted and well-watered environments and showed that EPP and GY were better indicators of this contrast (in terms of changes in population performance) than were AD or ASI. Three-mode analysis demonstrated that improvements with selection occurred in both droughted and well-watered environments and clearly summarised the overall success of the breeding program. This revised version was published online in July 2006 with corrections to the Cover Date.     

An evaluation of seed and seedling drought tolerance screening tests in wheat

Summary A series of experiments was performed in order to evaluate the significance of seed germination and seedling growth in osmotic media as screening methods for drought tolerance.Ten spring wheat (Triticum aestivum L. em Thell.) and one durum wheat (Triticum durum Desf.) were tested under controlled environments, using polyethylene glycol-6000 (PEG) solutions as the moisture stress inducing media.Tolerance in the rate of endosperm utilization, under stress, prior to the onset of germination varied among cultivars.Germination rate or injury to germination at various concentrations of PEG differed significantly among cultivars. Cultivar rating with respect to injury to germination changed with stress levels. Injury to germination did not correlate with endosperm utilization rate in PEG or in water.Germinating seedlings were tolerant to extreme desiccation up to the stage of emergence of the first leaf from the coleoptile.Growth of photosynthesizing seedlings was monitored as they were carried through an increasing concentration gradient of PEG solutions, ranging from –5.9 to –11.3 bars of water potential. Cultivars significantly differed in seedling growth tolerance to increasing levels of water stress. Seedling growth tolerance across cultivars was not correlated with their germination responses under srress.It is concluded that tolerance to water stress in growing seedlings can be screened for by using PEG-containing nutrient solutions. It can not be predicted from germination tests in osmotica.Work was done under a US-Israel Binational Science Foundation (BSF) Grant no. 1654/78.Contribution from Agricultural Research Organization, The Volcani Center, Bet Dagan, Israel, No. 192-E, 1979 series.     

Relationship between Carbon Isotope Discrimination, Ash Content and Grain Yield in Wheat in the Peninsular Zone of India

Carbon isotope discrimination (Δ) and ash content (m_a) have been proposed as indirect selection criteria for grain yield in wheat. The associations between Δ, m_a and grain yield were found, however, to depend highly on the environmental conditions, the organ sampled and the time of sampling. In this study, carried out in the warm conditions of the Peninsular Zone of India, the relationship between Δ, m_a and yield was studied in 30 bread and durum wheat cultivars under residual soil moisture stress (RSMS), post‐anthesis water stress (PAWS) and well‐watered (WW) conditions. Both Δ and m_a were analysed in young seedlings (four‐leaf stage), leaves at anthesis and grain at maturity. Ash content was also evaluated in leaves at booting stage and maturity. Grain Δ was lower under PAWS and RSMS than under WW, while seedling and leaf Δ did not significantly differ among water regimes. Grain yield was positively correlated to grain Δ under PAWS and negatively correlated to grain m_a under RSMS. A significant positive correlation was noted under RSMS and WW treatments between m_aL_m and grain yield. Ash content in leaf at maturity consequently appears to be a useful indirect selection criterion in environments where Δ does not show any correlation with yield. The results highlight the potential of Δ and m_a as indirect selection criteria for wheat yield in the conditions of the Peninsular Zone of India.     

苗期干旱和施肥对棉花生长发育的影响

以晋棉21号为试材,采用盆栽试验、大田仿真的方法,研究了棉花苗期水分干旱胁迫和施肥互作对棉花生长发育的影响。结果表明:①苗期干旱水分胁迫对控制棉花主茎生长速度、降低主茎高度、培育壮苗有明显作用;②棉花苗期水分干旱胁迫持续10~20 d,能有效减少6月份以前早期花蕾的脱落率,结果导致棉花群体吐絮高峰提前10 d左右,在施肥不足情况下,7月底以前形成的早期幼铃脱落率较高,但增加施肥具有降低脱落率的明显效果;③晋中为特早熟棉区,9月1-21日采收的棉花铃重、衣分和衣指相对较高,品质相对较好,通过苗期水分干旱胁迫与施肥技术的合理搭配,能使棉花吐絮高峰期集中在9月上、中旬,提高棉花优质铃比率,是晋中地区棉花高产优质栽培,充分发挥优质品种增产潜力的关键措施。     

过饱和持水时间和温度对固形基质浸液成分的影响

将木屑、砻糠、草屑、泥炭、风化煤和鸡粪6种不同物料置于不同温度下浸水后取其滤液,分析其铵态氮、硝态氮、速效磷以及可溶性的5种金属元素(钾、钙、镁、钠、铁)的含量,为调整营养液配方提供依据。几种物料浸液中的矿质元素在108 h以后基本趋于稳定。高温利于氮素释放,使有效氮含量峰值出现提早;在氮素形态上,木屑等5种物料主要以铵态氮的形式释放,而泥炭则主要以硝态氮的形式释放。浸液中有效磷含量的相对稳定值有所不同,在不同物料上表现为:鸡粪>木屑>砻糠>草屑>泥炭>风化煤;浸液中不同温度、不同时间下的有效金属元素含量基本保持稳定,只有K 含量随温度的升高变化较为明显。根据研究结果,在忽略复合后基质间影响的情况下,建议复合基质浸水7 d后待浸液中各矿质养分含量稳定,初步按下列公式调整营养液,C调=C理-C浸液使基质内各成分含量稳定在理想状态,以后营养液管理仍按原配方添加营养液。     

土壤水分对谷子(粟)结实的影响及其生理效应

土壤水分对谷子结实的影响主要在结实阶段.土壤水分过少或过多,都能显著降低结实率、成粒数和产量.这一时期以保持土壤毛管持水量的70%左右对结实最为有利.供水不足,首先影响根系活性和体内水分状况,从而影响体内外气体交换,降低光合速率和呼吸强度,同时影响细胞膜透性,导致体内物质代谢过程改变,降低有机物质的积累,造成穗部营养贫乏,形成秕谷.土壤水分过多,通气不良,影响根系活性,降低伤流量,抑制体内代谢过程及物质运转,造成穗部营养不足,形成秕谷.     

施用膨润土对土壤含水量和有机质含量的影响

通过田间条件下砂滤管试验，研究了不同膨润土施用量及有机物料对砂土土壤含水量和有机质含量的影响。结果表明，施用膨润土和有机物料能显著地提高砂土土壤含水量和有机质含量，且二者存在明显的交互作用，差异达极显著水平，施用膨润土能明显增加土壤有机质的累积是，说明在施用同样有机物料的前提下，施用膨润土可有显著提高砂土土壤有机含量。     

Thermal Infrared Radiation for Assessing Crop Water Stress in Wheat

Field studies on differentially irrigated wheat ( Triticum aestivum L.) crops were conducted at Pantnagar for two years to evaluate the use of thermal infrared radiation to detect crop water stress. Data show that the stress-degree-day index (mid day canopy-air temperature difference) is influenced by environmental variability other than soil moisture. Improvement in the stress-degree-day (SDD) index was achieved by including the measurements of vapor pressure deficit and approach was termed as plant water stress index (PWSI). Observations indicated that daily variation in SDD values due to meteorological changes was removed through PWSI. Better correlation was found between soil-induced leaf water potential and plant water stress index than between total leaf water potential and plant water stress index. It is concluded that remote sensing of thermal infrared radiation offers a promising technique which can be incorporated into irrigation management programme.     

2种熟型玉米籽粒灌浆特性及其与产量关系的比较研究

为了明确不同熟型玉米籽粒灌浆特性及其对产量的影响,比较研究了中晚熟品种农大108和中早熟品种石玉7号籽粒灌浆动态与产量表现,并对籽粒灌浆特性与籽粒水分的关系进行了分析。结果表明,石玉7号与农大108产量差异显著,百粒重是两品种产量差异的主要原因;石玉7号具有籽粒发育速度快、体积大等特点,前中期（0-45d）灌浆速率始终快于农大108,生育后期（45 d以后）急剧下降。农大108后期灌浆速率则下降缓慢。籽粒发育速度快,灌浆盛期灌浆速度快、强度大是石玉7号百粒重高的主要原因;籽粒水分状况与籽粒灌浆速率关系密切。回归分析表明,籽粒含水百分率在59.47%左右时,石玉7号灌浆速率达到最大值,为9.28 mg/（粒.d）;农大108则在57.92%左右时,灌浆速率达到最大值,为8.23 mg/（粒.d）。当籽粒含水百分率下降到某一临界值时,籽粒灌浆停止。两品种收获时,籽粒含水百分率尚远在籽粒灌浆终止临界值以上。     

覆盖措施对咸水结冰灌溉后土壤水盐动态和棉花生产的影响

对咸水结冰灌溉融冰后不同防止返盐措施处理的土壤水盐动态以及棉花的出苗、生长特征和产量进行了研究。结果表明,不同的覆盖措施对抑制土壤表层水分蒸发的效果有显著差异,3月和4月份表层土壤含水量影响5月份的含盐量,而5月份表层土壤的含盐量直接决定棉花出苗率。地膜覆盖和保留前茬旧膜的处理保墒抑盐效果最好,棉花出苗率和产量也最高;秸秆覆盖也有一定的抑盐效果;而翻耕和中耕对土壤保墒抑盐的作用较差;液态膜处理的抑盐效果最差,棉花的出苗率和产量最低。可见保留前茬旧膜是简便有效的保墒抑盐途径。