将大赖草种质转移给普通小麦的研究Ⅳ．通过花药培养选育双重二体异附加系和代换-附加系

通过普通小麦“中国春”与抗赤霉病的亲缘物种大赖草杂种回交后代ＢＣ２Ｆ３和自交Ｆ４代的花药培养,获得了７２株花培植株,其中２８株结实。这些株系的株高、穗形和成熟期等性状在Ｈ２系间差异明显,但株系内整齐一致。对２８个Ｈ２代株系进行根尖细胞染色体计数,２５个２ｎ＝４２,１个２ｎ＝４４,２个２ｎ＝４６。通过花粉母细胞减数分裂中期Ⅰ染色体配对分析和染色体Ｃ－分带,在Ｈ２代中选育出一个异代换－附加系（２ｎ＝４４）Ｌ０７,两个双重二体异附加系（２ｎ＝４６）Ｌ０３－０５和Ｌ０６。     

Evidence that wheat cultivars differ in their ability to build up inoculum of the take‐all fungus,Gaeumannomyces graminis var. tritici,under a first wheat crop

The effect of wheat cultivar on the build‐up of take‐all inoculum during a first wheat crop was measured after harvest using a soil core bioassay in field experiments over five growing seasons (2003–2008). Cultivar differences in individual years were explored by analysis of variance and a cross‐season Residual Maximum Likelihood (REML) variance components analysis was used to compare differences in those cultivars present in all years. Differences between cultivars in the build‐up of inoculum were close to or at significance in two of the five trial years (2004 P < 0·05; 2006 P < 0·07), and current commercially listed cultivars were represented at both extremes of the range. In 2007 and 2008, when environmental conditions were most favourable for inoculum build‐up, differences were not significant (P < 0·3). In 2005 the presence of Phialophora spp. at the trial site restricted the build‐up of take‐all inoculum under all cultivars. The cross season REML variance components analysis detected significant differences (range: 3·4–47·8% roots infected in the soil core bioassay; P < 0·01) between the nine cultivars present in all years (excluding 2005). This is the first evidence of relatively consistent differences between hexaploid wheat cultivars in their interactions with the take‐all fungus, and this could give an indication of those cultivars that could be grown as a first wheat crop, in order to reduce the risk of damaging take‐all in a second wheat crop. This phenomenon has been named the take‐all inoculum build‐up (TAB) trait.     

Genotyping Cephalosporium gramineum and development of a marker for molecular diagnosis

This study investigated the genetic variation of 40 isolates of Cephalosporium gramineum, the causal agent of cephalosporium stripe disease of wheat, based on variations in internal transcribed spacers (ITS) and intergenic spacers (IGS) of rDNA. Of the isolates, 29 were from Japan and the rest from the USA and Europe. The ITS region was about 600 bp and almost identical among these isolates. In the IGS region (～5 kbp), restriction fragment length polymorphism analysis detected four genotypes among the 40 isolates. One representative isolate was selected from each of the four genotypes, and the IGS region was sequenced. Attempts to design a genotype‐specific marker based on the size of PCR products amplified with selected primers failed to differentiate among the four genotypes. Alternatively, a species‐specific primer set (CGIGS1 and CGIGS2) was developed that annealed within the conserved region, producing a DNA fragment of about 1·8 kbp. Tests of this primer set on a wide range of other fungi from 11 genera confirmed that it was specific to C. gramineum. This primer set could serve as an effective tool in the molecular diagnosis of C. gramineum and has the potential to assist in a better understanding of the host–pathogen interaction.     

Effects of 15N-labelled ammonium nitrate and urea on soil nitrogen during growth of wheat (Triticum aestivum L.) under field conditions

We studied the effects of ¹⁵N-labelled ammonium nitrate and urea on the yield and uptake of labelled and unlabelled N by wheat (Triticum aestivum L., cv. Mexi-Pak-65) in a field experiment. The dry matter and N yields were significantly increased with fertilizer N application compared to those from unfertilized soil. The wheat crop used 33.6–51.5 and 30.5–40.9% of the N from ammonium nitrate and urea, respectively. Splitting the fertilizer N application had a significant effect on the uptake of fertilizer N by the wheat. The fertilizer N uptake showed that ammonium nitrate was a more available source of N for wheat than urea. The effective use of fertilizer N (ratio of fertilizer N in grain to fertilizer N in whole plant) was statistically similar for the two N fertilizers. The application of fertilizer N increased the uptake of unlabelled soil N by wheat, a result attributed to a positive added N interaction, which varied according to the fertilizer N split; six split applications gave the highest added N interaction compared to a single application or two split applications for both fertilizers. Ammonium nitrate gave 90.5, 33.5, and 48.5% more added N interaction than urea with one, two, and six split N applications. A values were not significantly correlated with the added N interaction (r=0.557). The observed added N interaction may have been the result of pool substitution, whereby added labelled fertilizer N replaced unlabelled soil N.     

Genetic diversity of Pakistan wheat germplasm as revealed by RAPD markers

Wheat breeding in Pakistan started in 1930s before partition in the United India and so far has released more than 68 cultivars, but no systematic analyses of the genetic diversity of Pakistan wheat have been made. Twenty Pakistan wheat cultivars released from 1933 to 2002 were examined for genetic diversity and relationships using random amplified polymorphic DNA (RAPD) markers. Forty-two RAPD primers were applied and 184 polymorphic bands were generated for each cultivar. Most of the cultivars were genetically interrelated, although six of them displayed some genetic distinctness. The RAPD variation observed among these cultivars was low. Only 40.7% of the total scorable bands were polymorphic, and 26.1% of the polymorphic bands were observed most frequently (f = 0.95) among the 20 cultivars. The proportions of polymorphic bands for each cultivar ranged from 0.67 in ‘Yecora’ to 0.84 in ‘C-250’ with an average of 0.76. About 1.4% of the RAPD variation might have been fixed over the 69 years of wheat breeding, but such fixation was not statistically significant. These results are significant for future improvement and conservation of Pakistan wheat.     

Analysis of Genetic Variability in a Sample of the Durum Wheat (Triticum durum Desf.) Spanish Collection Based on Gliadin Markers

In this work gliadin proteins were used to analyse the genetic variability in a sample of the durum wheat Spanish collection conserved at the CRF-INIA. In total 38 different alleles were identified at the loci Gli-A1, Gli-A3, Gli-B5, Gli-B1, Gli-A2 and Gli-B2. All the gliadin loci were polymorphic, possessed large genetic diversity and small and large differentiation within and between varieties, respectively. The Gli-A2 and Gli-B2 loci were the most polymorphic, the most fixed within varieties and the most useful to distinguish among varieties. Alternatively, Gli-B1 locus presented the least genetic variability out of the four main loci Gli-A1, Gli-B1, Gli-A2 and Gli-B2. The Gli-B1 alleles coding for the gliadin γ-45, associated with good quality, had an accumulated frequency of 69.7%, showing that the Spanish germplasm could be a good source for breeding quality. The Spanish landraces studied showed new gliadin alleles not catalogued so far. These new alleles might be associated with specific Spanish environment factors. The large number of new alleles identified also indicates that durum wheat Spanish germplasm is rather unique.     

A reliable method for the selection of axenic seedlings

Summary Sterile seedlings are required for the investigation of interactions between microorganisms and plants. The present study was designed to develop a simple and reliable method for the selection of sterile seedlings by the use of liquid nutrient media, avoiding some of the disadvantages of solid media. The method of germinating surface-sterilized seedlings on solid water agar or nutrient media was compared with our method for sterility control in nutrient broth. Sterile plant selection in liquid media was the most sensitive method for detecting bacterial and fungal contaminants. Sterile plants grow with the same vigour as unsterilized plants and can be used for sterile plant experiments.     

Improvement of somatic embryogenesis and plant regeneration from durum wheat (Triticum turgidum var. durum Desf.) scutellum and inflorescence cultures

Scutellum and inflorescence explants of four genotypes of durum wheat(Triticum turgidum var. durum Desf.) were used to define culture conditions to obtain high frequencies of embryogenesis and plant regeneration in vitro. Under all conditions tested, scutellum cultures gave higher frequencies of embryogenesis and plant regeneration than inflorescence cultures. Two different auxins, 2,4-D(2,4-dichlorophenoxyacetic acid) and picloram(4-amino-3,5,6-trichloropicolinic acid), were compared for their effect on scutellum and inflorescence explant response in vitro. Picloram was found to significantly increase the frequency of plant regeneration from both explants. When cultures were grown on regeneration medium containing zeatin for two three-week passages, the frequency of plant regeneration increased by between 20–30% compared with cultures exposed to hormones for a single three-week passage. Finally, the addition of 1 mg/l 6-BAP (6-benzyl aminopurine) to the plantlet growth medium was found to enhance tiller production in regenerants. The optimized culture conditions were applicable to the four genotypes tested and frequencies of plant regeneration varied between 97% to 100% for scutellum cultures (2 mg/l picloram in induction medium) and between45% and 80% for inflorescence cultures (4 mg/l picloram in induction medium). The number of plants regenerated per explant was improved over previous procedures, with means of 34 plants per scutellum, and 16 plants per inflorescence explant. This revised version was published online in July 2006 with corrections to the Cover Date.     

Relationship between electrophoretic pattern of storage proteins and gluten strength in durum wheat landraces from Turkey

A collection of 180 Triticum durum lines from Turkey and 22 Italian cultivars were investigated by electrophoretic techniques and evaluated for grain parameters such as protein content and sodium dodecyl sulphate (SDS)-sedimentation test. A total of 14 different patterns were observed for high-molecular-weight (HMW) glutenin subunits resulting from the combination of three alleles from the A genome and seven from the B genome. Three new allelic variants, one at Glu-A1 and two at Glu-B1, were found. Five different alleles were detected at the Glu-B1 locus. Genotypes with the same allelic variant at Gli-B1 showed inconsistency of composition in B group of low-molecular-weight (LMW) glutenin subunits. A total of 11 different B-subunit patterns were identified in the material analysed. A substantial proportion (78%) of the variation in gluten properties could be explained in terms of protein composition, with the LMW glutenin subunits making the largest contribution (54%). Results indicate that, in addition to Glu-B3 encoded proteins, variation at other loci coding for some intermediate and fastest B subunits might also influence rheological properties.