青蒿素对小麦种子萌发及幼苗生长的影响

为了解青蒿素对小麦种子萌发和幼苗生长的影响,运用室内培养皿法,分析了不同浓度的青蒿素溶液浸种后小麦种子发芽率及幼苗高度、根长、整株鲜重、根和茎鲜重及干重、根系活力等指标的变化。结果表明,青蒿素对小麦种子萌发及幼苗生长有抑制作用,且浓度越高,抑制作用越显著。与无菌水对照相比,青蒿素浸种处理显著降低了小麦的种子发芽率、苗高、根长、根鲜重和茎的鲜、干重,增加了根干重和根冠比。小麦的根系活力和可溶性蛋白含量随青蒿素浓度的增加而递减,可溶性糖含量则随之递增,叶绿素含量则呈先升高后降低的趋势,以20mg·L-1处理含量最高。此外,青蒿素浸种处理对小麦幼苗各项指标的影响与15mg·L-1多效唑相似。     

小麦内生细菌分离培养基的选择

分别利用肉汁胨琼脂、营养琼脂、胰酶大豆琼脂、马铃薯葡萄糖琼脂、脑心浸液琼脂、金氏培养基B、LB营养琼脂和酵母膏蛋白胨琼脂8种常用的细菌分离培养基来分离小麦内生细菌,以选择适宜的分离培养基,结果显示,胰酶大豆琼脂和金氏培养基B的分离效果显著优于其他培养基,马铃薯葡萄糖琼脂和脑心浸液琼脂的分离效果较差。利用选择出的金氏培养基B和胰酶大豆琼脂分别对豫东麦区的7个小麦品种的内生细菌进行分离,进一步确认了胰酶大豆琼脂和金氏培养基B为分离小麦内生细菌的适宜培养基。     

夏玉米施氮量对后茬冬小麦土壤氮素供应与利用的影响

在冬小麦施氮144 kg/hm2的基础上,研究了夏玉米4个施氮量(0,90,180,270和360 kg/hm2)对后茬冬小麦生长期间土壤硝态氮含量变化、无机氮供应以及小麦氮素吸收与利用的影响。结果表明:与玉米不施氮(简称不施氮)相比,玉米施氮(简称施氮)0~200 cm土壤硝态氮含量在冬小麦生长期间显著增加,自冬小麦拔节起,0~40,0~130和0~200 cm 3层深的土壤硝态氮含量均随着玉米施氮量(简称施氮量)的增加而明显递增;与冬小麦播种时相比,不施氮0~130 cm土壤无机氮减少156 kg/hm2,施氮90 kg/hm2该层土壤无机氮富积41 kg/hm2,且富积量随着施氮量继续增加而递增;随着施氮量增加,冬小麦收获时的植株吸氮量和子粒氮素积累量均增加;当施氮量低于180 kg/hm2时,植物氮素积累量在不同施氮量之间无显著差异;当施氮量低于270 kg/hm2时,不同施氮量的子粒氮素积累量差异不明显。在本试验条件下,冬小麦子粒氮肥利用率随着施氮量增加而递增,但差异不显著。     

Effect of mannitol pretreatment to improve green plant regeneration on isolated microspore culture in Triticum turgidum ssp. durum cv. 'Jennah Khetifa'

The use of doubled haploids improves the efficiency of cultivar development in many crops and can be helpful in genetic and molecular studies. The major problem with this approach is the low efficiency of green plant regeneration. We describe here an efficient method for inducing embryos and regenerating green plants directly from isolated microspores of durum wheat cv. ‘Jennah Khetifa’. Tillers from donor plants were pretreated in 0.3 m mannitol and were stored at 4°C at various times: 3, 5, 6, 7, 8, 10 and 12 days. Our results showed clearly that the novel pretreatment combined mannitol 0.3 m and cold for 7 days had a strong effect on the number of embryos produced and regenerated green plants. Under this condition 13 475 mature embryos were produced from 2 693 500 microspores. Moreover, 85 green plants were obtained. High green plants regeneration frequency was recorded. As an average 11.55 green plants were produced per 100 000 microspores (about the equivalent of six plants per spike). Therefore, this study showed clearly that our results are the best ones published until now in durum wheat.     

小麦籽粒淀粉分支酶同工酶基因型与酶活性关系研究

测定了71个小麦品种的籽粒淀粉分支酶活性,并采用非变性聚丙烯酰胺凝胶电泳（Native-PAGE）,鉴定了分支酶同工酶的基因型,以明确小麦籽粒淀粉分支酶（SBE）各同工型等位基因的分布特点和基因型组成,阐明分支酶活性与分支酶同工酶基因型的相关性。结果表明,分支酶有SBEⅠ和SBEⅡ两个基因位点,SBEⅡ位点未显现多态性,SBEⅠ位点存在多样性。在SBEⅠ位点鉴定出A、B、D_ⅰ和D_ⅱ共4个等位基因位点,各等位基因位点出现频率分别为9.9%、76.1%、95.8%和57.8%;共检测到9种基因型,其中基因型D_ⅰD_ⅱB、D_ⅰB和D_ⅰD_ⅱ有较高的分布频率,分别为45.1%、28.2%和8.5%。从单一位点分析,分支酶活性与SBEⅠ位点有显著的相关性,与SBEⅡ位点相关性不显著。由此可见,小麦籽粒胚乳淀粉分支酶同工酶不同基因位点和基因型对酶活性具有不同的遗传效应。     

Relationship between allelic variation of Glu-1 and Gli-1/Glu-3 prolamin loci and gluten strength in hexaploid wheat

Summary Allelic variation of prolamin loci was examined in the F₂ from crosses between the hexaploid wheat varieties: Cajeme 71, Yécora 70, Ablaca, Anza, Pané 247 and Axona. Different allelic blocks for gliadins and LMW glutenin subunits were determined in Gli-1, Gli-2 and Glu-3 loci. A percentage of recombination of 1.5 ± 0.3 was determined between Gli-A1 and Glu-3 in the F₂ progeny of Yécora 70 x Axona. A significant positive association was found between gluten strength, measured by SDS-sedimentation volume, and the prolamins coded by Anza Gli-D1/Glu-D3 loci and Yécora 70 Gli-A1/Glu-A3 loci. Interactions between non homeologous loci Glu-1 and Gli-1/Glu-3 were also found.     

Grain yield, and dry matter and nitrogen accumulation and remobilization in durum wheat as affected by variety and seeding rate

The influence of crop density on the remobilization of dry matter and nitrogen from vegetative plant parts to the developing grain, was investigated in the durum wheat (Triticum durum Desf.) varieties Creso, Simeto and Svevo cultivated in the field at three seeding rates, 200, 250 and 400 seeds m⁻². Variety × seeding rate interaction was unsignificant for all recorded characters. Grain yield declined in the order Svevo > Simeto > Creso. Yield differences mainly depended on the different number of kernels per unit land and, secondly, on mean kernel weight. Spike components differed among varieties: Svevo and Simeto showed more kernels per spikelet and Creso more spikelets per spike. Grain yield was highest with 400 seeds m⁻² primarily due to the higher number of spikes per unit area, and secondly, to the higher mean kernel weight. Post-heading dry matter accumulation was highest in Svevo and lowest in Creso, but varieties showed a reverse order for dry matter remobilization and contribution of dry matter remobilization to grain yield. The increase of seeding rate increased both the post-heading dry matter accumulation and the dry matter remobilization from vegetative plant parts to grain. Nitrogen uptake of the whole crop and N content of grain was higher in Simeto and Svevo than in Creso. The N concentration of grain did not vary among varieties, but Svevo showed a markedly lower N concentration and N content of culms at maturity, which may be consequence of the high N remobilization efficiency performed by this variety. The N uptake by the crop was highest with 400 seeds m⁻², but the N concentration of culms, leaves and even grain was slightly lower than with the lower seed rates. The post-heading N accumulation was by far higher in Simeto and Svevo than in Creso, whereas remobilization was highest in Svevo and lowest in Simeto. The percentage contribution of N remobilization to grain N was by far higher in Creso than in the other two varieties. Post-heading N accumulation and N remobilization were highest with the highest plant density, but the contribution of N remobilization to N grain content did not differ between seeding rates.     

Evaluation of common wheat cultivars for tan spot resistance and chromosomal location of a resistance gene in the cultivar 'Salamouni'

A total of 50 wheat (Triticum aestivum L.) cultivars were evaluated for resistance to tan spot, using Pyrenophora tritici‐repentis race 1 and race 5 isolates. The cultivars ‘Salamouni’, ‘Red Chief’, ‘Dashen’, ‘Empire’ and ‘Armada’ were resistant to isolate ASC1a (race 1), whereas 76% of the cultivars were susceptible. Chi‐squared analysis of the F₂ segregation data of hybrids between 20 monosomic lines of the wheat cultivar ‘Chinese Spring’ and the resistant cultivar ‘Salamouni’ revealed that tan spot resistance in ‘Salamouni’ was controlled by a single recessive gene located on chromosome 3A. This gene is designated tsn4. The resistant cultivars identified in this study are recommended for use in breeding programmes to improve tan spot resistance in common wheat.     

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.     

Assessment of partial resistance to powdery mildew in Chinese wheat varieties

Field trials in two cropping seasons and two locations in central China were conducted on 60 Chinese autumn‐sown wheat varieties to assess their partial resistance to powdery mildew. Mean levels of disease severity ranged from close to 0 to more than 90%. The method of inoculation and the location in which trials were conducted affected the relative performance of the varieties, but these effects were much smaller than the main effect of variety. The area under the disease progress curve was highly correlated with final disease severity, but both were poorly correlated with apparent infection rate. Disease severity was regressed against frequencies of virulence in the Blumeria graminis (syn. Erysiphe graminis) f sp. tritici populations in the trial plots. A vertical distance (D) from the mean mildew severity to the fitted line was calculated for each variety and was used to quantify partial resistance. Five of the 60 varieties, ‘Hx8541’, ‘E28547’, ‘Chuan1066’, ‘Zhe88pin6’ and ‘Lin5064’, consistently expressed relatively low levels of disease despite high frequencies of virulence in the pathogen and had consistently high D‐values. They may therefore have good levels of partial resistance.