Monosomic analysis of response to vernalisation in winter oat

Summary Autumn sown cultivars of oats respond to vernalisation and a monosomic analysis using Sun II monosomics showed that four chromosomes probably carried genes controlling the response. The greatest effect could be attributed to chromosome XVIII.     

Measurement of response to vernalization in Australian wheats with winter habit

Summary Development in wheat is strongly controlled by sensitivity to vernalization and photoperiod, and to a lesser degree by non-vernalizing temperature and intrinsic earliness. A method to measure effect of vernalization in wheats with winter habit is described. Twenty seven wheats with winter habit and eight with spring/facultative habit were studied, comprising breeding lines and cultivars with maturities suited to south-central New South Wales. Effect of vernalization on the development of these wheats was quantified by integrating responses to vernalizing treatments of differing duration. Intrinsic earliness was measured as time for vernalized seedlings to grow to ear emergece in an 18h photoperiod with day/night temperature of 21/16°C, and response to photoperiod as the difference in time to ear emergence between 9 and 18h daylengths. Integrated response to vernalization is sensitive to both cumulative and thresh-hold responses and is applicable to wheats of all habit type. Integrated response to vernalization and intrinsic earliness were positively associated within wheats with winter habit. Wheats were largely of restricted origin, so that there were few allelic differences at Vrn loci to disrupt this association, which suggests intrinsic earliness may modify response to vernalization. Though integrated response to vernalization was measured with artificial treatments, it was strongly associated with ear emergence for wheats with winter habit when grown at a site in New South Wales.     

The influence of photoperiod genes on the adaptability of European winter wheats

Photoperiod response genes play a major role in determining the climatic adaptability of European wheat varieties. Photoperiod insensitivity, in the vast majority of photoperiod insensitive European wheat varieties, is probably determined by a Ppd1 allele originally derived from the old Japanese variety Akakomugi. Analysis of the pleiotropic effects of a Ppd1 allele from the Italian variety Mara shows that, besides accelerating ear emergence time, Ppd1 also reduces plant height, tillering, and spikelet numbers. Increases in spikelet fertilities more than compensate for reduced spikelet numbers, producing increased numbers of grains per ear. In southern Europe, early flowering Ppd1 genotypes produce larger grain and greater yields. In England and Germany, pleiotropic effects of Ppd1 on yield vary annually, depending on prevailing weather conditions, from +9% to -16%, over a 10 year period in the United Kingdom. A possible alternative Ppd1 allele from the CIMMYT variety Ciano 67 was compared to that from Mara. Differences associated with complete substituted chromosomes were found to be due to linked genes rather than different Ppd1 alleles. Examination of an alternative weaker gene for photoperiod insensitivity, Ppd2, shows this to exert similar but less significant pleiotropic effects to Ppd1. In the UK, in each of three years of trialing, Ppd2 increased yield 6% more than Ppd1. Results of 10 years trialing show that in Central European countries, between areas where photoperiod sensitive or photoperiod insensitive varieties have a clear adaptive significance, the annual variations in climate make it extremely difficult for breeders to produce varieties with good adaptability to changing environmental conditions. This revised version was published online in August 2006 with corrections to the Cover Date.     

低温积累与光周期对小麦发育特性调控的分子机理研究进展

温度和光照是影响小麦发育的主要因素,不但决定了小麦生态型的区域分布,也通过调控小麦的发育阶段、器官建成、穗分化起始及进程等因素而影响小麦的产量。本文介绍了低温春化和光周期对小麦发育特性影响的分子基础,对其调控机制及互作模式研究进展进行了综述。     

The distribution,in European winter wheats,of genes that influence ecoclimatic adaptability whilst determining photoperiodic insensitivity and plant height

Summary The adaptability of wheat varieties to precise environmental conditions is known to be influenced to a large extent by photoperiod sensitive genes determining ear emergence time and by the gibberelic acid insensitive dwarfing genes that are regularly used to reduce plant height. A range of European winter wheat varieties were examined to establish whether breeders in different countries have selected genotypes carrying allelic variants of photoperiodic and dwarfing genes that would be expected to provide the best levels of adaptability. In most areas modern cultivars were seen to carry the genotypes predicted to promote good levels of adaptability. Varieties cultivated in Germany however are still predominately of conventional height and late flowering lacking genes that would be expected to enhance adaptability and yield.     

Multivariate analysis of traits determining adaptation in cultivated barley

Thirty‐nine barley varieties of different origin, representing different growth types, were included in a series of experiments aimed at analysing the variability in vernalization response, photoperiod sensitivity and earliness per se and establishing the types of ecoclimatic adaptability using multivariate analysis. In the case of spring barley varieties there was no correlation between any of the three traits. For winter barleys, a negative correlation was found between photoperiod sensitivity and vernalization response and between photoperiod sensitivity and earliness per se. Vernalization response and earliness per se showed a positive correlation. Among the winter barley varieties large variations were apparent in photoperiod sensitivity, vernalization response and earliness per se, which resulted in a tremendous variation in flowering patterns and frost tolerance. Between the spring barley varieties only wider variations in photoperiod sensitivity were detected. Based on the cluster analysis, the 39 varieties could be separated into seven groups. The spring barley varieties were placed in two groups, and the winter barleys in five groups representing different adaptational types. Among these five groups two represented the two opposing extreme combinations of photoperiod sensitivity and vernalization response. The combination of large photoperiod sensitivity and no vernalization response resulted in better frost tolerance than did the combination of photoperiod insensitivity and large vernalization response.     

Breeding intensive winter bread wheat varieties for Southern Ukraine

Winter wheats with high grain quality for bread making are produced in southern Ukraine. Wheat breeding began more then 80 years ago. Over this time, seven wheat variety changes were made and yield potential increased from 2.73 t ha^-1 to 6.74 t ha^-1. This increase was due to a decrease in photoperiodic sensitivity and the introduction of semidwarf genes. Genes for photoperiodic sensitivity (Ppd) and vernalisation requirement (Vrn) were combined, and the effect of these genes on grain yield, frost and drought resistance, and growth and development rate of plants in autumn and early spring were studied. Breeding was carried out, utilising traditional and non-traditional methods such as anther culture, biochemical and molecular markers, and screening in artificial environments using phytotrons. This approach resulted in the release of several winter wheat varieties with high yield potentials and well expressed adaptation features by the Plant Breeding and Genetics Institute (Odessa). This revised version was published online in August 2006 with corrections to the Cover Date.     

Analysis of adaptation of barley,triticale, durum and bread wheat under Mediterranean conditions

Summary Yield data obtained from a comparative small grain cereals trial, grown for five consecutive growing seasons at a total of 23 environments in Cyprus, were subjected to regression analysis. Within each environment, yield trials consisted of a standard set of three cultivars or elite lines of barley, triticale, durum and bread wheat. The regression coefficient (b) of crop mean on the environmental index (I) and the mean square deviation from regression (sd²) were calculated for each crop. Each crop tended to have its own characteristic value of sd² and its magnitude was an excellent indicator of specific crop-environment interaction. The causes of large sd², for two of the four crops, were the susceptibilith of barley to lodging, when favourable conditions were encountered at high yielding environments, and triticale dependence on late season precipitation. Durum wheat and triticale had an average response to different yielding environments (b>1.19) and both were significantly different from those of bread wheat (1.08) and barley (0.54). Hence, barley, bread and durum wheat are specifically adapted to low, average and high yielding Mediterranean environments, respectively. The cultivation of triticale at the expence of durum wheat is not feasible. Furthermore, interactions between crops and environments demonstrated by the regression parameters, should constitute the basis for decision making, regarding crop adaptation in a region. The average yield in all environments should not be considered as a proper criterion for adaptation. In this study, triticale had a similar mean grain yield (3,842 kg/ha) to that of bread wheat, but was significantly higher yielding than barley or durum wheat (5 and 7%, respectively).     

Variability in the Duration of Stem Elongation in Wheat Genotypes and Sensitivity to Photoperiod and Vernalization

The stem elongation phase in wheat [Triticum aestivum (L.)] is considered critical for yield determination. A longer duration of this phase could hypothetically increase grain set and therefore yield. Genetic variation in the relative duration of the stem elongation phase having been reported, the aim was to pinpoint whether this variability was associated with sensitivity to photoperiod, vernalizing temperatures or to differences in intrinsic earliness. Pairs of cultivars identified as having different duration of the stem elongation phase (from the appearance of the first visible node to anthesis) were grown under natural (short) or extended photoperiod, with or without vernalization. Variability in the duration of this phase, in the cultivars analysed, was related to different sensitivity to photoperiod, while differences in the previous phases were related to sensitivity to both photoperiod (though different to the sensitivity of the following phase) and vernalization.     

Yield Formation in Mediterranean durum wheats under two contrasting water regimes based on path-coefficient analysis

The components of grain yield are altered by adverse growing conditions as the effects of certain environmental factors on crop growth and yield differ depending upon the developmental stages when these conditions occur. Path-coefficient analysis was used to investigate the main processes influencing grain yield and its formation under Mediterranean conditions. Twenty-five durum wheat genotypes, consisting of four Spanish commercial varieties and 21 inbred lines from the ICARDA durum wheat breeding program, were grown during 1997 and 1998 under both rainfed and irrigated conditions in southern Spain. {P}ath-coefficient analysis revealed that under favourable conditions grain yield depended in equal proportion on the three primary yield components (i.e. spikes m⁻², grains spike⁻¹, and mean grain weight), whereas in the rainfed experiments, variations in grain yield were due mainly to spikes m⁻² and to a lesser extent to grains spike⁻¹. Compensatory effects were almost absent under irrigated treatments; however, under water shortage, spikes m⁻² exerted a negative influence on grain spike⁻¹ due mainly to a negative interrelationship between tiller production and apical development. These compensatory effects could partially explain the restricted success in durum wheat breeding observed in water-limited environments of the Mediterranean region. Under rainfed conditions the number of spikes m⁻² depended mainly on the ability for tiller production, whereas in the irrigated experiments the final number of spikes was determined mostly by tiller survival.     

Breeding of white-grained wheats for Japan

The possibility of breeding white-grained wheats tolerant to pre-harvest sprouting under Japanese humid weather conditions is discussed. New genetic dormancy sources, such as, AUS1408, 8019R1 and RyuuMai7, were evaluated for seed dormancy in different weather conditions. Some white-grained dormant wheats showed a strong dormancy similar to that of red-grained dormant wheats in a greenhouse trial, in the field their dormancy expression was much less than the red wheats. Three populations involving crosses with these new sources for winter wheat breeding were examined under repeated selection for seed dormancy. Some dormant white-grained lines, as judged under glasshouse conditions, were developed. Again the level of dormancy in these lines was not sufficient compared to red dormant varieties in field trial. In order to develop truly superior dormant white-grained materials, one population involving crosses with two dormant varieties, AUS1408 and 8019R1, was examined under repeated selection. From these materials we succeeded in breeding lines that had not only a good dormancy but also showed adaptation to Japanese weather conditions, including earliness, scab resistance and good seed appearance. However again the dormancy of these lines in field trial was not sufficient compared to that of red wheats and there was not a clear difference for seed dormancy between breeding lines and their parents. We conclude therefore that more work involving the use of new genetic sources or new breeding techniques, will be necessary for breeding advanced lines that maintain a sufficient tolerance to PHS in humid Japanese weather condition. This revised version was published online in August 2006 with corrections to the Cover Date.     

不同光周期对黄瓜幼苗抗冷性的影响

为了探讨光周期对低温胁迫下黄瓜幼苗膜脂过氧化水平和抗氧化酶活性等生理指标的影响。以25℃和10℃ 2种温度处理黑夜补光0,3,6,9,12 h的黄瓜幼苗,研究不同光周期对黄瓜幼苗生理指标的影响。结果表明,2种温度处理条件下,黄瓜幼苗叶片中叶绿体色素含量、可溶性糖和可溶性蛋白含量、CAT和POD活性都是随补光时间的延长而升高,而电解质相对渗漏率和MDA含量随补光时间的延长而下降。与25℃相比较,低温（10℃）处理降低黄瓜幼苗叶绿体色素含量,提高电解质相对渗漏率,MDA、可溶性糖和可溶性蛋白含量,CAT和POD活性;其中,光周期越长,黄瓜幼苗叶片叶绿体色素含量,电解质相对渗漏率和MDA含量的变化幅度越小,可溶性糖和可溶性蛋白含量,CAT和POD活性的变化幅度越大。延长光照时间可通过促进低温胁迫下黄瓜幼苗叶片可溶性蛋白、可溶性糖的大量积累和抗氧化酶活性的提高,来降低膜脂过氧化水平,从而增强黄瓜幼苗的抗冷性。     

温度和光周期对姜荷花生长的影响

为给姜荷花的标准化栽培生产提供一定的参考,以盆栽姜荷花为试验材料,采用不同温度、光周期对姜荷花进行研究。结果表明,25℃是姜荷花生长较适温度,高温对其萌发有一定的促进作用,过高或过低的温度都会导致其不开花;不同温度影响下,姜荷花萌发率、分蘖数及开花数具有一定的相关性,对姜荷花pH、EC的影响较小。光照时长延长至14~16 h时,可打破姜荷花休眠,实现周年生产;姜荷花分蘖数随光照时长的增加而显著提升,对开花时间、开花数未见显著影响;姜荷花各指标之间未呈现显著相关性,对姜荷花pH、EC有一定影响。     

短日照诱导对小豆生长发育、光合和荧光参数的影响

为明确短日照对小豆生长发育、光合和荧光参数的影响,采用不同生育时期短日照诱导处理来调查小豆的形态指标、开花时间及开花节位,在开花期和结荚期测定光合作用和叶绿素荧光。结果表明,与对照相比,短日照诱导使小豆的株高降低、平均茎粗和主茎节数变小、白红2号在开花期和结荚期的节间长度升高,唐山红小豆降低;短日照诱导使小豆的花期提前并降低开花节位;短日照诱导使2个品种的净光合速率在开花期明显升高,在结荚期降低,气孔导度、细胞间CO2浓度和蒸腾速率在开花期无明显变化,在结荚期,白红2号明显降低,唐山红小豆升高;短日照诱导对开花期的叶绿素含量无明显影响,在结荚期明显降低,与对照相比,白红2号在开花期和结荚期的Fv/Fm升高,唐山红小豆在开花期变化规律不明显,在结荚期升高;短日照诱导使小豆的产量构成因素及产量呈下降趋势。以上结果说明短日照诱导对花荚期小豆的生长发育、光合参数及产量具有调控作用。     

Comparative genetic mapping of loci affecting plant height and development in cereals

Restriction fragment length polymorphism (RFLP) mapping data for genes determining dwarfness (GA insensitive and GA sensitive), vernalisation response and photoperiodic response in wheat, rye and barley were compared and their homoeologous relationships discussed. The GA insensitive Rht genes of wheat are not related to the GA insensitive dwarfing genes of rye or barley; however, homoeology is present for two members of the GA sensitive dwarfing genes of wheat (Rht12) and rye (Ddw1), located on the translocated segments of the long arms of chromosomes 5A and 5R, respectively. The comparative mapping of the Triticeae group 5 vernalisation response genes of wheat, rye and barley, and the group 2 photoperiodic response genes of wheat and barley, show that both gene families are located in homoeologous regions of the particular chromosomes. This revised version was published online in August 2006 with corrections to the Cover Date.     

The influence of flowering time genes on environmental adaptability in European wheats

Summary In order to obtain high levels of environmental adaptability in wheat varieties it is essential they flower at times appropriate to particular environmental conditions. The influence of three distinct genetic systems that together determine time of flowering is reviewed here.Vernalization genes are seen to be particularly important to winter wheats for their direct or indirect effects on winter hardiness. Vernalization genes play a minor role in determining flowering time in autumn sown winter wheats but insensitivity is essential if spring sown wheats are to flower.Day length sensitive photoperiod genes play a major role in determining flowering time and adaptability of autumn sown wheats. Insensitivity can promote yield advantages of over 35% in Southern European environments. 15% in Central Europe and offers benefits even in the UK. At present only a single allele of Ppd1 appears to have been introduced into commercial European wheat varieties. The merits of alternative Ppd1 alleles or different loci are discussed.The influence of earliness per se genes that determine flowering time independently of environmental stimuli is less well documented than the effect of photoperiod and vernalization genes. It is likely that genes on chromosomes belonging to groups 2, 3, 4, 6 and 7 may act to modify flowering time independently of environmental stimuli probably by determining numbers of vegetative and floral primordia being initiated or the rate of initiation of the primordia. Earliness per se genes appear to be widespread in European wheats and play a significant role in determining the exact time plants flower.     

CIMMYT's approach to breeding for wide adaptation

Summary The wheat area in developing countries, including China, is around 100 million ha. To address the needs of these very diverse wheat growing areas, CIMMYT has defined 12 wheat mega-environments (ME). A ME is defined as broad, not necessarily continuous often transcontinental area with similar biotic and abiotic stresses, cropping systems and consumer preferences. The factors describing each ME are presented.CIMMYT's breeding methodology is centered around the development of widely adapted germplasm with high and stable yield across a wide range of environments. Segregating populations are alternating screened in two diverse environments in Mexico. One key requirement is that all germplasm is tested under near optimum conditions for its yield potential. The second one is multi-locational testing of advanced lines at sites that represent a given ME (key locations) and careful screening of germplasm for tolerance to abiotic and biotic stresses specific to that environment. This methodology has permitted the pyramiding of a large number of multiple resistance genes for use against a wide spectrum of diseases and tolerance to abiotic stresses within each ME. In addition, the widespread testing of lines allows the identification of traits which are beneficial in several environments. Data from international nurseries are used to further delineate environments within an ME. This approach has proven to be successful since around 70% of the spring wheat area in developing countries (excluding China) is planted to varieties derived directly or indirectly from CIMMYT germplasm. The performance of the bread wheat cultivar Pastor in international trials is given as an example for a wide adaptation.     

Genetic diversity within spelta and macha wheats based on RAPD analysis

Genetic diversity in a crop species is basic to improvement of the species and can be estimated at the molecular level. The objective of this study was to estimate genetic diversity within and between spelta and macha wheats. Random amplified polymorphic DNA (RAPD) analysis was conducted on 69 spelta and 32 macha wheat accessions. The classification of spelta and macha accessions, based on Jaccard genetic similarity coefficients for RAPD markers, was consistent with their geographic origin. The results indicated that the germplasm of macha wheat was more diverse than that of spelta wheat. In the dendrogram of macha wheat, four spelta-like accessions grouped together, separate from the remaining macha accessions, suggesting that these accessions were misclassified. In addition, accessions with identical RAPD patterns were found, indicating that these accessions were probably duplicated. Thus RAPD analysis can be used to estimate genetic diversity and identify duplicate accessions in wheat germplasm collections. This revised version was published online in August 2006 with corrections to the Cover Date.