A new drought resistant gymnosperm taxon Duartenia araripensis gen. nov et sp nov (Cheirolepidiaceae?) from the Early Cretaceous of Northern Gondwana

A new gymnosperm taxon from the Lower Cretaceous (upper Aptian to possibly lower Albian) Crato Formation of Brazil, Duartenia araripensis gen. nov. et sp. nov. is described. The most prominent specimen, a branch with attached lateral branches of higher orders exhibits a distinct anisotomous branching pattern. The very dense wood is composed of tracheids with spaced and partly contiguous uniseriate pits and low rays with one pit per cross-field (mixed protopinaceous type). When foliage is not abraded, Duartenia exhibits coriacious Brachyphyllum-type leaves. Duartenia may be linked to cheirolepid conifers, however, the systematic affinity remains uncertain. The dense wood, characteristic growth pattern and thick, scale like, trichome bearing leaves may be related to ecological conditions that reflect a seasonally dry climate.

Developing high yielding wheat for water limited environments in northern Australia

A novel strategy linking physiology with plant breeding, molecular biology and computer simulation modelling is outlined here which aims to enhance selection of high yielding wheats with superior performance under conditions of water scarcity for the northern, subtropical, winter cereals region of Australia. In previous research, a source of high yield and performance under dry conditions for the target region was identified in a drought resistant parent. A large population of fixed lines for molecular genetic studies has been developed using the drought resistant line and widely grown current Australian variety. A preliminary study comparing the parent varieties was conducted in the winter of 2003. The two varieties were similar in many aspects of phenology, morphology and physiology. However, several important traits were identified that likely contribute to higher grain mass and yield of the drought resistant parent, including differences in the number and dry mass of tillers and spikes during development and the ability of drought resistant line to retain green leaves longer during grain filling.

干旱对不同冬小麦旗叶光合产物供应能力的影响

研究干旱对小麦旗叶光合产物供应能力的影响,揭示小麦抗旱高产的生理机制,为提高小麦的抗旱能力及高产稳产提供理论依据。【方法】在防雨池栽培条件下,以旱地冬小麦品种长武134(抗旱性强)和水地冬小麦品种陕253(抗旱性弱)为试材,以适宜水分处理为对照(CK,土壤含水量为田间持水量的70%～75%),研究干旱处理(土壤含水量为田间持水量的50%～55%)对不同冬小麦旗叶光合产物供应速率(净光合速率和蔗糖合成能力)和供应持续期的影响。【结果】与对照相比,干旱处理降低了冬小麦灌浆中后期旗叶净光合速率,缩短了净光合速率高值持续期(PAD),其中长武134降幅较小,净光合速率较高;干旱处理提高了冬小麦灌浆初期旗叶的蔗糖磷酸合成酶(SPS)活性,其中长武134增幅较大,且在灌浆中后期依然能保持相对较高的蔗糖供应能力;干旱处理缩短了冬小麦叶绿素含量缓降期(RSP),提高了丙二醛(MDA)含量,加速了旗叶的衰老,缩短了光合产物的供应持续期,其中长武134受干旱影响较小;干旱处理降低了冬小麦灌浆中后期主茎穗粒质量积累量及其速率,其中长武134降幅较小。【结论】干旱条件下,抗旱品种长武134旗叶在灌浆中后期可维持较高的光合产物...

小麦抗旱生态分类中适合性聚类方法的研究

探索了适合于小麦品种抗旱生态分类的聚类方法 .选用 2 1个农艺性状和 15个冬小麦品种 (系 ) ,在聚类分析的各环节上 ,通过采用不同的策略 ,大规模进行了各种分类结果的比较 .结果表明 ,在与专家经验分类接近程度上 ,数据转换方法中 ,原始数据法依次大于普通相关阵基础上的方差极大正交旋转法、Promax斜交旋转法、主成份法 ;相似性度量上 ,欧氏距离大于马氏距离 ;聚类方式上 ,对应分析法和模糊聚类法大于最短距离法、最长距离法、类平均法 ;所有可组合的方法中 ,以对应分析法和直接用原始数据的模糊聚类法的分类结果最接近专家经验分类 .结合各方法理论上优缺点的分析与检验 ,认为这两种方法也是较理想的方法 .

Markers for seedling and adult plant crown rot resistance in four partially resistant bread wheat sources

Key message: QTLidentified for seedling and adult plant crown rot resistance in four partially resistant hexaploid wheat sources. PCR-based markers identified for use in marker-assisted selection. Abstract: Crown rot, caused by Fusarium pseudograminearum, is an important disease of wheat in many wheat-growing regions globally. Complete resistance to infection by F. pseudograminearum has not been observed in a wheat host, but germplasm with partial resistance to this pathogen has been identified. The partially resistant wheat hexaploid germplasm sources 2-49, Sunco, IRN497 and CPI133817 were investigated in both seedling and adult plant field trials to identify markers associated with the resistance which could be used in marker-assisted selection programs. Thirteen different quantitative trait loci (QTL) conditioning crown rot resistance were identified in the four different sources. Some QTL were only observed in seedling trials whereas others appeared to be adult plant specific. For example while the QTL on chromosomes 1AS, 1BS, and 4BS contributed by 2-49 and on 2BS contributed by Sunco were detected in both seedling and field trials, the QTL on 1DL present in 2-49 and the QTL on 3BL in IRN497 were only detected in seedling trials. Genetic correlations between field trials of the same population were strong, as were correlations between seedling trials of the same population. Low to moderate correlations were observed between seedling and field trials. Flanking markers, most of which are less than 10 cM apart, have now been identified for each of the regions associated with crown rot resistance.

Assessment of wheat cultivars for drought tolerance via osmotic stress imposed at early seedling growth stages

A study was conducted in the Department of Plant Breeding and Genetics,Sindh Agriculture University, Tandojam, Pakistan during the year 2009. Sixteen spring wheat cultivars (Triticum aestivum L.) were screened under osmotic stress with three treatments i.e. control-no PEG (polyethylene glycol), 15 percent and 25 percent PEG-6000 solution. The analysis of variance indicated significant differences among treatments for all seedling traits except seed germination percentage. Varieties also differed significantly in germination percentage, coleoptile length, shoot root length, shoot weight, root/shoot ratio and seed vigour index. However, shoot and root weights were non-significant. Significant interactions revealed that cultivars responded variably to osmotic stress treatments; hence provided better opportunity to select drought tolerant cultivars at seedling growth stages. The relative decrease over averages due to osmotic stress was 0.8 percent in seed germination, 53 percent in coleoptile length 62.9 percent in shoot length, 74.4 percent in root length, 50.6 percent in shoot weight, 45.1 percent in root weight, 30.2 percent in root/shoot ratio and 68.5 percent in seed vigour index. However, relative decrease of individual variety for various seedling traits could be more meaningful which indicated that cultivar TD-1 showed no reduction in coleoptile length, while minimum decline was noted in Anmol. For shoot length, cultivar Sarsabz expressed minimum reduction followed by Anmol. However, cultivars Anmol, Moomal, Inqalab-91, and Pavan gave almost equally lower reductions for root length suggesting their higher stress tolerance. In other words, cultivars Anmol, Moomal, Inqalab-91, Sarsabz, TD-1, ZA-77 and Pavan had relatively longer coleoptiles, shoots and roots, and were regarded as drought tolerant. Correlation coefficients among seedlings traits were significant and positive for all traits except germination percentage which had no significant correlation with any of other trait. The results indicated that increase in one trait may cause simultaneous increase in other traits; hence selection for any of these seedling attributes will lead to develop drought tolerant wheat cultivars.

Markers for seedling and adult plant crown rot resistance in four partially resistant bread wheat sources

QTL identified for seedling and adult plant crown rot resistance in four partially resistant hexaploid wheat sources. PCR-based markers identified for use in marker-assisted selection. Crown rot, caused by Fusarium pseudograminearum, is an important disease of wheat in many wheat-growing regions globally. Complete resistance to infection by F. pseudograminearum has not been observed in a wheat host, but germplasm with partial resistance to this pathogen has been identified. The partially resistant wheat hexaploid germplasm sources 2-49, Sunco, IRN497 and CPI133817 were investigated in both seedling and adult plant field trials to identify markers associated with the resistance which could be used in marker-assisted selection programs. Thirteen different quantitative trait loci (QTL) conditioning crown rot resistance were identified in the four different sources. Some QTL were only observed in seedling trials whereas others appeared to be adult plant specific. For example while the QTL on chromosomes 1AS, 1BS, and 4BS contributed by 2-49 and on 2BS contributed by Sunco were detected in both seedling and field trials, the QTL on 1DL present in 2-49 and the QTL on 3BL in IRN497 were only detected in seedling trials. Genetic correlations between field trials of the same population were strong, as were correlations between seedling trials of the same population. Low to moderate correlations were observed between seedling and field trials. Flanking markers, most of which are less than 10 cM apart, have now been identified for each of the regions associated with crown rot resistance.

The role of root architectural traits in adaptation of wheat to water-limited environments

Better understanding of root system structure and function is critical to crop improvement in water-limited environments. The aims of this study were to examine root system characteristics of two wheat genotypes contrasting in tolerance to water limitation and to assess the functional implications on adaptation to water-limited environments of any differences found. The drought tolerant barley variety, Mackay, was also included to allow inter-species comparison. Single plants were grown in large, soil-filled root-observation chambers. Root growth was monitored by digital imaging and water extraction was measured. Root architecture differed markedly among the genotypes. The drought-tolerant wheat (cv. SeriM82) had a compact root system, while roots of barley cv. Mackay occupied the largest soil volume. Relative to the standard wheat variety (Hartog), SeriM82 had a more uniform rooting pattern and greater root length at depth. Despite the more compact root architecture of SeriM82, total water extracted did not differ between wheat genotypes. To quantify the value of these adaptive traits, a simulation analysis was conducted with the cropping system model APSIM, for a wide range of environments in southern Queensland, Australia. The analysis indicated a mean relative yield benefit of 14.5% in water-deficit seasons. Each additional millimetre of water extracted during grain filling generated an extra 55 kg ha-1 of grain yield. The functional implications of root traits on temporal patterns and total amount of water capture, and their importance in crop adaptation to specific water-limited environments, are discussed.

DAQ00141 Recurrent Selection Program in Hexaploid Wheat

Joint project with the University of Queensland that will use the recurrent selection breeding method to produce adapted, high-yielding and disease resistant wheat parents to breeders.

Temporal and spatial patterns of soil water extraction and drought resistance among genotypes of a perennial C-4 grass

The objective of this study was to investigate patterns of soil water extraction and drought resistance among genotypes of bermudagrass (Cynodon spp.) a perennial C-4 grass. Four wild Australian ecotypes (1-1, 25a1, 40-1, and 81-1) and four cultivars (CT2, Grand Prix, Legend, and Wintergreen) were examined in field experiments with rainfall excluded to monitor soil water extraction at 30-190 cm depths. In the study we defined drought resistance as the ability to maintain green canopy cover under drought. The most drought resistant genotypes (40-1 and 25a1) maintained more green cover (55-85% vs 5-10%) during water deficit and extracted more soil water (120-160 mm vs 77-107 mm) than drought sensitive genotypes, especially at depths from 50 to 110 cm, though all genotypes extracted water to 190 cm. The maintenance of green cover and higher soil water extraction were associated with higher stomatal conductance, photosynthetic rate and relative water content. For all genotypes, the pattern of water use as a percentage of total water use was similar across depth and time We propose the observed genetic variation was related to different root characteristics (root length density, hydraulic conductivity, root activity) although shoot sensitivity to drying soil cannot be ruled out.