Conferring drought-tolerant wheat genotypes through morpho-physiological and chlorophyll indices at seedling stage

The decrease in water resources due to the excessive use of water for irrigation purpose and climatic changes represents a serious world-wide threat to food security. In this regards, 50 wheat accessions were analyzed, using completely random factorial design at the seedlings stage under normal and drought stress conditions. Significant variation was detected among all accessions under both conditions. All characters studied showed variations in the mean values in water deficit environments in studied gemplasm at seedling stage. As seedling fresh weight, dry weight, relative water content, cell membrane thermo-stability, chlorophyll a & b were positively associated among themselves under drought conditions which showed the significance of these attribute for water deficit areas in future wheat breeding programs. Based on their performance, five accessions namely Aas-11, Chakwal-86, Pasban-90, Chakwal-97 and Kohistan-97 were selected as drought tolerant and three accessions namely Mairaj-08, Lasani-2008 and Gomal-2008 were selected as drought susceptible genotypes. The choice of wheat accessions based on the characteristics of the seedlings is informal, low-priced and less hassle. Likewise, the seedlings attributes exhibit moderate to high variation with an additive genetics effects on the environments. Best performance accessions under water deficit environment will be beneficial in future wheat breeding schemes and early screening for the attributes suggested in current experiment will be useful for producing best-yielded and drought-tolerance wheat genotypes to sustainable food security.     

Comparison of natural and artificial epidemics of take-all in sequences of winter wheat crops

Winter wheat was grown for six successive years (Expt 1) and for three successive years (Expt 2) in field experiments on different soil types. Artificial inoculum of the take-all fungus (Gaeumannomyces graminis var. tritici cultured on autoclaved oat grains) was incorporated in the soil of some of the plots just before, or at, sowing of the first winter wheat crop. Expt 1 tested the incorporation of similar amounts of inoculum (212 kg ha^-1) at different depths. Expt 2 tested different amounts of inoculum at the same, shallow depth. Early sowing (September), late sowing (October) and spring inoculation were additional treatments, applied to the first crop only, in Expt 2. Seasonal factors apart, the disease outcome in the first year after inoculation depended on amounts and placement of applied inoculum, as well as date of sowing. Deeper inoculum resulted in less disease (Expt 1). Severe take-all was produced in Expt 2 by incorporating inoculum shallowly in sufficient quantities (400 kg ha^-1 or more). Less inoculum (200 kg ha^-1) generated less disease, especially in earlier-sown plots. Differences in disease amongst inoculum treatments were greatest in the first year and diminished subsequently, particularly where sowing had been early in the first year. In Expt 1, where first crops exposed to artificial inoculum developed moderate-to-severe disease, disease in subsequent second and/or third crops was less. In the fourth crop a second peak of disease occurred, coinciding with a first peak in sequences without added inoculum. Take-all decline (TAD) appeared to be expressed in all sequences thereafter. In Expt 2 in sequences without added inoculum, TAD occurred after a peak of disease in the second crop. Where 400 kg ha^-1 or more of inoculum were added, disease was severe in the first year and decreased progressively in successive years. Disease was less patchy in plots that received artificial inoculum. However, it remains uncertain mat severe disease caused by artificial inoculation achieved an early onset of true TAD. The infectivity of the top 12 cm of soil in the first 3 yr of Expt 1, determined by bioassay, depended on the depth of added inoculum and amount of disease in subsequent crops. However, at the time of the naturally occurring peak of disease severity (in either inoculated or non-inoculated plots) it did not predict either disease or TAD. Differences and similarities amongst epidemics developing naturally and those developing from different amounts and placement of applied inoculum have been revealed. The epidemiological implications of adding inoculum and the potential value of artificially-created epidemics of take-all in field trials are discussed.     

Adapting wheat cultivars to resource conserving farming practices and human nutritional needs

As farmers increasingly adopt resource conserving farming practices, there is a need for wheat cultivars that better adapt to the changing environment and the nutritional needs of people, particularly those living in developing countries. Improved adaptation to zero and minimum tillage, better water use efficiency, improved root health, durable resistance to foliar diseases and enhanced nutritional value of the grain are key selection criteria for plant breeders. Significant responses to selection for these constraints have been achieved at the International Maize and Wheat Improvement Center (CIMMYT), by selecting segregating populations and advanced lines in carefully managed tillage, moisture deficit and heat stressed environments, that correlate with key spring wheat growing environments globally. Root health has been improved through a combination of marker assisted selection and disease bioassays, and the nutritional value of wheat grain has been enhanced using genetic variation for high Fe and Zn grain content found among tetraploid wheat ancestral species.     

用ITS序列确定小麦B基因组的可能供体间的关系

对小麦B基因组的可能供体山羊草属Aegilops sect．Sitopsis的5个种的核糖体DNA的内部转 录区(ITS)进行了PCR扩增和克隆,井测定ITSl和ITS2的序列,用ITSl+ITS2的序列重建了 Aegilops sect．Sitopsis中5个种的系统发育关系。结果表明,斯卑尔脱山羊草Ae．speltoides是sect． Sitopsis中特殊的一个种,它与该组其余4种间的平均遗传距离是后者彼此间平均遗传距离的3倍,Ae． speltoides与同组其余4个种的分离要比后者相互间的分离早得多;在拟斯卑尔脱组Sect．Sitopsis的5 个种中,长柱山羊草Ae．longissima与沙融山羊草Ae．sharonensis的关系最近。ITS序列可以进一步用来作为确定B基因组起源的分子标记。     

由小麦×玉米获得的普通小麦加倍单倍体后代的RFLP变异

用小麦（Ｔｒｉｔｉｃｕｍ　ａｅｓｔｉｖｕｍＬ．）的ｒＤＮＡ克隆ｐＴａ７１和与小麦基因组有部分同源性的玉米（ＺｅａｍａｙｓＬ．）ＤＮＡ克隆作探针,对由小麦ｘ玉米获得的普通小麦加倍单倍体（ＤＨ）后代群体进行ＲＦＬＰ分析。结果发现,不但用ｐＴａ７１在这些ＤＨ后代中检测到ｒＤＮＡ所发生的明显的减少和扩增及非转录间隔区的限制性片段长度的变化,而且用与小麦基因组部分同源的玉米克隆ＭＲ１３和ＭＲ５０在一些ＤＨ后代中检测到缺失变异,特别是用ＭＲ１３在普通小麦ＤＨ系的１８号株的基因组中检测到大幅度的限制性片段长度的变化,即原来的４．３ｋｂ的强信号带消失,取而代之的是４０．０ｋｂ、２．５ｋｂ和２．０ｋｂ三条杂交带。这可能与小麦基因组ＤＮＡ较大的重排事件有关,也可能是由外源的玉米ＤＮＡ插入造成的。     

Effect of 2,4-dichlorophenoxyacetic acid on callus induction and plant regeneration in anther culture of wheat (Triticum aestivum L.)

 Anthers from a doubled-haploid line of spring wheat (Triticum aestivum L.) cv. Pavon 76 were plated in liquid P-4 medium supplemented with 2,4-dichlorophenoxyacetic acid (2,4-D) at four concentrations (0.5, 1.0, 2.0, 4.0 mg/l) for 5, 10, 15, and 25 days before being transferred to another medium with the same or reduced 2,4-D concentrations for the remainder of the induction phase for a total of 45 days. Incubation with 0.5 mg/l 2,4-D for 45 days produced lower callus yield and plant regeneration, indicative of insufficient auxin for callus induction. Callus yield and regeneration frequencies were higher with 1.0 mg/l 2,4-D. With 2.0 or 4.0 mg/l 2,4-D, an induction period of 10 or 15 days was sufficient for initiation of callus development. The extended presence of 2–4 mg/l 2,4-D in the medium beyond the initiation phase was detrimental to plant regeneration. Thus optimal callus induction and plant regeneration could be obtained through manipulating the 2,4-D concentration and the duration of its presence in the induction medium. Received: 1 December 1997 / Revision received: 15 February 1999 / Accepted: 26 February 1999     

Analysis of wheat mitochondrially encoded polypeptides by in organello labelling

 The in organello labeling pattern in wheat (Triticum aestivum) mitochondria isolated from imbibed embryos were compared with those from the commonly used starting material, etiolated seedlings. Mitochondria from imbibed embryos proved to be metabolically more active than those from etiolated seedlings and produced a large number of strongly in organello-labeled polypeptides. Immunoprecipitation of the labeled proteins enabled the identification of mitochondrially encoded subunits of the respiratory chain complex I, some of which could not be detected by conventional Western blotting due to their high hydrophobicity. A method for mass isolation of wheat embryos is also presented which allows easy preparation of large amounts of intact and highly active mitochondria suitable for biochemical studies. Received: 9 November 1998 / Revision received: 10 March 1999 / Accepted: 1 April 1999     

小麦根质膜H^＋—ATPase的部分纯化

以小麦（ＴｒｉｔｉｃｕｍａｅｓｔｉｖｕｍＬ．）根为材料,采用不连续蔗糖密度梯度离心法制备高纯度质膜微囊。质膜经ＴｒｉｔｏｎＸ１００和ＫＣｌ处理后,再用Ｚｗｉｔｅｒｇｅｎｔ３１４增溶Ｈ＋ＡＴＰａｓｅ,最后用硫酸铵沉淀得到部分纯化的质膜Ｈ＋ＡＴＰａｓｅ。ＳＤＳＰＡＧＥ结果表明,经过上述步骤纯化,分子量为９４ｋＤ的膜蛋白组分得到富集;与质膜相比,其含量提高１５．７倍。部分纯化的质膜Ｈ＋ＡＴＰａｓｅ可以水解ＡＴＰ,受Ｋ＋刺激,并被Ｎ,Ｎ′ｄｉｃｙｃｌｏｈｅｘｙｌｃａｒｂｏｄｉｍｉｄｅ（ＤＣＣＤ）抑制;ＡＴＰ水解活力被Ｎａ３ＶＯ４抑制９５％,但不被ＮａＮ３、ＮａＮＯ３和Ｎａ２ＭｏＯ４抑制。     

甜菜碱对NaCl胁迫下小麦细胞保护酶活性的影响

本文以小麦为材料,研究甜菜碱对ＮａＣｌ胁迫下小麦幼苗细胞保护酶系统的影响。结果表明,外源甜菜碱能够提高ＮａＣｌ胁迫下小麦幼苗超氧化物歧化酶、过氧化物酶等细胞保护酶的活性,抑制过氧化作用产物丙二醛的积累,降低叶片质膜透性和盐害对细胞膜的伤害。所有这些变化都有利于提高ＮａＣｌ胁迫下小麦幼苗细胞膜的稳定性、完整性和对ＮａＣｌ胁迫的适应性     

He-Ne激光对小麦属间杂交影响的研究

1988年以来,作者采用He-Ne激光辐照黑麦花粉与杂交相结合的新方法,对小麦属间杂交(普通小麦×黑麦)进行了研究,获得了较好的效应.试验采用随机区组排列,重复三次,单粒条播.辐照方法,采用He-Ne激光分别以100秒、200秒、300秒辐照三个黑麦品种的花粉,与普通小麦授粉,配制成9个(普通小麦×黑麦)属间杂交组合.所得结果,采用方差分析、新复极差测验法,测定了组合与对照组合相比的差异显著性,也测定了各组合间相互比较的差异显著性.激光辐照小麦属间杂交所获种子的结实率极显著高于对照,为113.52～341.60%.籽粒千粒重和饱满度均超过对照,分别为84.07～295.43%、30.30～127.27%,差异均极显著.L1代籽粒出苗率和植株成活率分别比对照提高58.18～83.06%、41.35～87.78%,差异达到极显著水平.He-Ne激光的诱变作用,在于促进了小麦属间杂交的可交配性,提高了杂交籽粒的结实率,改善了籽粒的饱满度,提高了籽粒的千粒重,因而促进了杂种种子的出苗率和成活率.并且,在L1代植株中均获得了染色体自然加倍的双二倍体即小黑麦种子.现已获得L1～L8代的小黑麦后代材料和稳定株系.高科技的激光诱变育种,为小麦属间杂交育种工作开辟了新的简便途径.