Genes for wheat stem rust resistance postulated in German cultivars and their efficacy in seedling and adult‐plant field tests

Stem rust of wheat (caused by Puccinia graminis f.sp. tritici) gained high international attention in the last two decades, but does not occur regularly in Germany. Motivated by a regional epidemic in 2013, we analysed 15 spring and 82 winter wheat cultivars registered in Germany for their resistance to stem rust at the seedling stage and tested 79 of these winter wheat cultivars at the adult‐plant stage. A total of five seedling stem rust resistance genes were postulated: Sr38 occurred most frequently (n = 29), followed by Sr31 (n = 11) and Sr24 (n = 8). Sr7a and Sr8a occurred only in two spring wheat genotypes each. Four cultivars had effective seedling resistance to all races evaluated that could only be explained by postulating additional resistance genes (‘Hyland’, ‘Pilgrim PZO’, ‘Tybalt’) or unidentified gene(s) (‘Memory’). The three winter wheat cultivars (‘Hyland’ ‘Memory’ and ‘Pilgrim PZO’) were also highly resistant at the adult‐plant stage; ‘Tybalt’ was not tested. Resistance genes Sr24 and Sr31 highly protected winter wheat cultivars from stem rust at the adult‐plant stage in the field. Disease responses of cultivars carrying Sr38 varied. Mean field stem rust severity of cultivars without postulated seedling resistance genes ranged from 2.71% to 41.51%, nine of which were significantly less diseased than the most susceptible cultivar. This suggests adult‐plant resistance to stem rust may be present in German wheat cultivars.     

Assessment of genetic variation of bread wheat varieties using microsatellite markers

The DNA fingerprinting profiles of 11 bread wheat cultivars, grown in Turkey, was obtained by using 19 highly polymorphic wheat microsatellites. Up to six randomly selected individuals from each of these cultivars were subjected to analysis. Estimated polymorphism information content (PIC) values among 65 individual genotypes for 19 loci were between 0.36 and 0.87 with an average value of 0.68. The numbers of observed alleles were between 2 and 9, with an average value of 5.42. These relationships were assessed among cultivars and among their individual genotypes using the mean pairwise average square distance (D ₁) (or the delta mu measure of distance (Ddm)) matrix and neighbor-joining method based on `Nei-72' distance matrix, respectively. Two spring cultivars, `Kaklic-88' and `Orso', were closely related to each other; the other 9 winter and facultative cultivars were dispersed. Pedigrees of cultivars represented very little shared information among each other, therefore, they could not been utilized in comparisons. This revised version was published online in July 2006 with corrections to the Cover Date.     

Genetic analysis of flowering and maturity time in high latitude spring wheat

Due to the short growing season in the high northern latitudes, the development of early maturing spring wheat (Triticum aestivum L.) cultivars is important to avoid frost damage which can lower production and quality. We investigated earliness of flowering and maturity, and some associated agronomic traits, using a set of randomly selected high northern latitude adapted spring wheat cultivars (differing in maturity) and their F₁ and F₂ crosses made in a one-way diallel mating design. The parents, and their F₁ and F₂ crosses were evaluated under field conditions over 2 years. Anthesis and maturity times were controlled by both vernalization response and earliness per se genes, mainly acting additively. Non-additive genetic effects were more important in controlling grain fill duration, grain yield and plant height. Additive × additive epistatic effects were detected for all traits studied except time to anthesis. Segregation analyses of the F₂ populations for time to anthesis indicated the presence of different vernalization response genes. Molecular genetic analyses revealed the presence of Vrn-A1 and Vrn-B1 genes in the parental cultivars. Narrow-sense heritability was medium to high (60–86%) for anthesis and maturity times but low to medium (13–55%) for grain fill duration, plant height and grain yield. Selection for early flowering/maturity in early segregating generations would be expected to result in genetic improvement towards earliness in high latitude spring wheats. Incorporation of the vernalization responsive gene Vrn-B1 in combination with vernalization non-responsive gene Vrn-A1 into spring wheats would aid in the development of early maturing cultivars with high grain yield potential for the high latitude wheat growing regions of the northern hemisphere.     

Relative performance of Canadian spring wheat cultivars under organic and conventional field conditions

Producing higher yields under organic conditions is generally hampered by weeds and lesser nutrient supply. In wheat certain adaptive traits like early season vigour, taller plants, and shorter life cycle have been reported to help plants compete with weeds and produce satisfactory yields. In this experiment we tested the hypothesis ‘that early flowering and maturity conferred by insensitive vernalization alleles Vrn-A1a and/or Vrn-B1 has a yield advantage under organic conditions’ in Canadian spring wheat germplasm. We genotyped 32 cultivars for their vernalization gene composition (Vrn-A1a, Vrn-B1 and Vrn-D1) and studied these cultivars in organic and conventional management systems. We found 88 % of the cultivars possessed vernalization (Vrn) insensitive allele Vrn-A1a either alone or in combination with Vrn-B1. There were no differential affects between the cultivars having insensitive Vrn allele at either single locus (Vrn-A1a) or two (Vrn-A1a, Vrn-B1) under organic and conventional field conditions; except for days to maturity, where cultivars having only Vrn-A1a allele matured earlier. This earlier maturity did not translate to any yield advantage under organic field conditions. Overall, the cultivars grown under organic conditions were earlier flowering, lower yielding with lower test weight compared to the conventional management system. Significant cultivar × environment interactions were found for grain yield, grain protein content and grain fill rate. For grain protein content, cross-over interactions of the cultivars between the management systems were observed. Three cultivars (Marquis, Unity and Minnedosa) exhibited minimal comparative loss in grain yield and grain protein content under organic field conditions, and hence could potentially serve as parents for organic wheat breeding programs.     

Genes conferring low seedling reaction to Mexican pathotypes of Puccinia recondita f. sp. tritici,and adult-plant responses of recent wheat cultivars from the former USSR

Fifty-five spring bread wheat (Triticum aestivum L.) cultivars, mostly released between 1975 and 1991 in eight leaf rust-prone spring wheat growing regions of the former USSR, were tested in the seedling growth stage for reaction to 15 Mexican pathotypes of Puccinia recondita f. sp. tritici. In total, seven known and at least two unknown genes were identified, either singly or in combinations: Lr3 (7 cultivars), Lr10 (14), Lr13 (5), Lr14a (1), Lr16 (1), Lr23 (3); the unknown genes were identified in 14 cultivars. The first unknown gene could be either Lr9, Lr19, or Lr25; however, the second unknown gene in 9 cultivars was different from any named gene. Twelve of the 15 pathotypes are virulent for this gene, hence its use in breeding for resistance will be limited. The cultivars were also evaluated at two field locations in Mexico with two pathotypes in separate experiments. The area under the disease progress curve and the final disease rating of the cultivars indicated genetic diversity for genes conferring adult plant resistance. based on the symptoms of the leaf tip necrosis in adult plants, resistance gene Lr34 could be present in at least 20 cultivars. More than half of the cultivars carry high to moderate levels of adult plant resistance and were distributed in each region.     

Effect of alien 5R(5A) chromosome substitution on ear-emergence time and winter hardiness in wheat-rye substitution lines

Ear emergence time and response to vernalization were investigated in 12 alien substitution lines in which a pair of chromosomes 5A of recipient spring wheat cultivars was replaced by a pair of chromosomes 5R of Siberian spring rye ‘Onokhoiskaya’. The recipients were 12 spring cultivars of common wheat, each carrying different Vrn genes. Spring rye ‘Onokhoiskaya’ had the Sp1 (now called Vrn-R1) gene for spring growth habit located on chromosome 5R, but its expression was weaker. The Vrn-R1 gene had no effect on growth habit, ear emergence time and response to vernalization in wheat-rye substitution lines. Ears emerged significantly later in the 5R(5A) alien substitution lines than in the recipient wheat cultivars with the Vrn-A1/Vrn-B1/vrn-D1 or Vrn-A1/vrn-B1/Vrn-D1 genotypes. No difference in ear emergence time was found between most of the 5R(5A) alien substitution lines and the cultivars carrying the recessive vrn-A1 gene. The presence of the Vrn2a and Vrn2b alleles at the Vrn2 (now called Vrn-B1) locus located on wheat chromosome 5B was confirmed.The replacement of chromosome 5A by chromosome 5R in wheat cultivars ‘Rang’ and ‘Mironovskaya Krupnozernaya’, which carries the single dominant gene Vrn-A1, converted them to winter growth habit. In field studies near Novosibirsk the winter hardiness of 5R(5A) wheat–rye substitution lines of ‘Rang’ and ‘Mironovskaya Krupnozernaya’ was increased by 20–47% and 27–34%, respectively, over the recurrent parents.     

Distribution of the photoperiod insensitive <Emphasis Type="Italic">Ppd-D1a</Emphasis> allele in Chinese wheat cultivars

Photoperiod response is of great importance for optimal adaptation of bread wheat cultivars to specific environments, and variation is commonly associated with allelic differences at the Ppd-D1 locus on chromosome 2D. A total of 926 Chinese wheat landraces and improved cultivars collected from nine wheat growing zones were tested for their genotypes at the Ppd-D1 locus using allele-specific markers. The average frequency of the photoperiod-insensitive Ppd-D1a allele was 66.0%, with the frequencies of 38.6 and 90.6% in landraces and improved cultivars, respectively. However, the Ppd-D1a allele was present in all improved cultivars released after 1970 except for spring wheats in high latitude northwestern China, and winter wheats in Gansu and Xinjiang. The presence of the Ppd-D1a allele in landraces and improved cultivars increased gradually from north to south, illustrating the relationship between photoperiod response and environment. Ppd-D1a in Chinese wheats is derived from three sources, Japanese landrace Akagomughi and Chinese landraces Mazhamai and Youzimai. The current information is important for understanding the broad adaptation of improved Chinese wheat cultivars. F. P. Yang and X. K. Zhang contributed equally to this work.     

小麦TaFT基因编码区序列多态性及其与开花期的关系

春化基因VRN-B3是小麦开花素基因TaFT,为探索该基因在品种间的保守性及其与小麦开花早晚的关系,根据TaFT基因序列(GenBank accession No.: DQ890162)设计特异PCR引物,扩增了13个品种中该基因的编码区。通过测序和序列比对,发现不同品种间该基因编码区的DNA序列存在多态性,序列翻译发现5个品种的表达产物FT蛋白发生变异。利用中国春的非整倍体材料将TaFT基因定位在7BS染色体上。参考品种的冬春性及开花时间,推测冬性品种正常的FT蛋白(同DQ890162翻译的氨基酸序列一致)可加速开花,FT蛋白变异则延迟开花;春性品种的FT蛋白变异与否对开花期影响不大,推测TaFT基因的效应可能被春性品种的显性春化基因所掩盖。     

Enhanced leaf rust resistance in wheat conditioned by resistance gene pairs with Lr13

Summary Leaf rust resistance gene Lr13 is present in many North American hard red spring wheat cultivars that have shown durable resistance to leaf rust. Fifteen pair-wise combinations of Lr13 and seedling leaf rust resistance genes were developed by intercrossing near isogenic Thatcher lines. In both seedling and adult plant tests, homozygous paired combinations of specific resistance genes with Lr13 had enhanced resistance relative to either parent to rust isolates that had intermediate avirulent infection types to the additional genes. In field tests, homozygous lines were more resistant than either parent if the additional leaf rust gene conditioned an effective level of resistance when present singly.     

The association of culm anatomy with lodging susceptibility in modern spring wheat genotypes

Selection for lodging resistant cultivars in cereal breeding programs is difficult due to the challenge of screening for this trait under natural field conditions. The identification of easily measurable culm traits related to lodging resistance would simplify the selection process. The present study was conducted to determine if differences in culm anatomy exist among modern wheat genotypes differing in lodging susceptibility, and to determine the association between culm characters and lodging. From a 2-year field study conducted in Edmonton, Alberta, 13 spring wheat cultivars were chosen based on predetermined susceptibility to artificially induced lodging. Morphological and anatomical culm measurements were made visually and with an environmental scanning electron microscope. Genotypes differed (P < 0.05) for plant height, number of internodes per culm, basal internode length and diameter, culm wall thickness and the number of vascular bundles, but not for adventitious root frequency, lumen diameter or sclerenchyma ring thickness. Mean genotype field scores for artificially induced lodging were correlated (P < 0.05) with plant height (r= 0.51) and the length of the fourth basal internode (r= 0.51). Short, wide basal internodes and thick culm walls were characteristic of three lodging tolerant genotypes: Kohika, Sapphire and Olso. Nevertheless, despite such apparent genotype specific association between culm anatomy and field lodging, general applicable associations were not observed for most traits. The most practical and easily selectable trait for lodging resistance within a wheat breeding program remains plant height. This revised version was published online in July 2006 with corrections to the Cover Date.     

中国小麦育成品种和农家种中慢锈基因Lr34/Yr18的分子检测

Lr34/Yr18是重要的慢叶锈和慢条锈基因, 携带该连锁基因的小麦品种被广泛种植于世界许多国家。利用STS标记csLV34对慢叶锈和慢条锈基因Lr34/Yr18进行分子检测的结果表明, 我国231份育成品种(系)中仅有14份材料携带Lr34/Yr18基因, 占6.1%。不同麦区分布频率不同, 其中北部冬麦区为零, 黄淮冬麦区、长江中下游冬麦区、西南冬麦区和西北春麦区分别为3.0%、21.4%、16.7%和33.3%。在422份农家种中, 359份含有Lr34/Yr18基因, 占85.1%。Lr34/Yr18基因在不同麦区的分布频率也存在差异, 北部冬麦区、黄淮冬麦区、长江中下游冬麦区、西南冬麦区、南部冬麦区和西北春麦区分别为89.6%、77.4%、93.1%、93.8%、96.6%和61.1%。csLV34标记扩增产物为150 bp和229 bp的片段, 能有效鉴别品种是否携带Lr34/Yr18基因, 是一个重复性好、准确率高的分子标记, 可用于小麦Lr34/Yr18基因的鉴定与选择。     

Estimation of the Response to Anther Culturing in 60 Genotypes of Different Wheat Species

Sixty genotypes of different wheat species (30 cultivars of common wheat, 12 durum wheat and 18 wild wheat relatives) were estimated for response to anther culturing and capability of plant regeneration. The 4 level of responding anthers out of the total number of anthers cultured was proposed as the criterion for genotype fitness for breeding with the aid of anther culture. Among common wheat cultivars, 13 exceeded this level. Among durum wheat, none of the genotypes investigated exceeded the 4% level. Among other species, 5 cultivars of T. dicoccum as well as T. petropavlovsky and T. dicoccoides spont. exceeded the 4 value.     

Prevalence of a novel puroindoline b allele in Yunnan endemic wheats (Triticum aestivum ssp. yunnanense King)

Grain hardness is a major factor influencing the classification and end-use quality of bread wheat. In this study, 40 Yunnan endemic wheats, 21 historical cultivars and 66 current cultivars and advanced lines were investigated for kernel hardness and puroindoline alleles using molecular and biochemical markers. The frequencies of soft, mixed and hard genotypes were 10.0%, 5.0% and 85.0%, respectively, in Yunnan endemic wheats, whereas the corresponding frequencies were 47.6%, 23.8% and 28.6% in historical cultivars, and 36.3%, 6.1% and 57.6% in current cultivars and advanced lines. Four known puroindoline alleles, Pina-D1b, Pinb-D1b, Pinb-D1d and Pinb-D1e, were found in the hard wheat cultivars. Compared with endemic wheats and historical cultivars, current cultivars from Yunnan province have relatively high frequencies of Pina-D1b and Pinb-D1b alleles at 43.5% and 16.1%, respectively. All 32 hard Yunnan endemic wheats (Triticum aestivum ssp. yunnanense King) contained a new puroindoline b allele, designated Pinb-D1u, that was characterized as a single nucleotide (G) deletion at position 127 in the coding sequence of the Pinb gene, leading to a shift of the open reading frame (ORF) from position 14 in the deduced amino acid sequence and a stop codon corresponding to position Leu-18. The average SKCS hardness of genotypes with Pina-D1b (68.2) is significantly higher than those of Pinb-D1b (60.3) and Pinb-D1u (60.5). The study of puroindoline alleles in Yunnan germplasm could provide useful information for improving processing quality and further understanding the molecular basis of kernel hardness in bread wheat.     

Growth and yield of spring cereals during transition to zero tillage on clay soils

Due to the high cost of fuel and labour associated with conventional tillage, and because of their advantageous environmental consequences, interest in reduced and zero tillage systems has increased. Direct drilling into zero tilled (ZT) soil of two spring barley (Hordeum vulgare L.) cultivars (six-rowed Rolfi and two-rowed Saana), spring oats (Avena sativa L., cultivar Roope), and spring wheat (Triticum aestivum L., cultivar Kruunu) was compared with conventional tillage (CT) and drilling into ploughed soil. Two field experiments were conducted on clay soils (clay content > 50%) between latitudes 60° and 61° N. Seed and fertilizer were placed in the same row in ZT and in separate rows in CT. Oats was the most productive spring cereal species in ZT. Establishment of spring wheat was often poor. Barley was most vulnerable to water surplus during early growth and drought during late growth. High levels of crop residues caused problems in soil drying in spring and growth of monocultures of oats and wheat. A higher seeding rate was advantageous in zero tilled clay soil. The substantial grain yield decrease suggests need for improving ZT.Long-term trials are required to determine whether ZT suits clay soils as soil structure can change over time and weather conditions play a major role in the productivity of differently tilled soils.     

Inheritance of resistance to wheat midge, Sitodiplosis mosellana, in spring wheat

Inheritance of resistance to a wheat midge, Sitodiplosis mosellana (Géhin), was investigated in spring wheats derived from nine resistant winter wheat cultivars. F₁ hybrids were obtained from crosses between resistant winter wheats and susceptible spring wheats, and used to generate doubled haploid populations. These populations segregated in a ratio of 1:1 resistant to susceptible, indicating that a single gene confers the resistance. The F₂ progeny from an intercross among spring wheats derived from the nine resistance sources did not segregate for resistance. Therefore, the same gene confers resistance in all nine sources of resistance, although other genes probably affect expression because the level of resistance varied among lines. Heterozygous plants from five crosses between diverse susceptible and resistant spring wheat parents all showed intermediate levels of response, indicating that resistance is partly dominant. Susceptible plants were reliably discriminated from heterozygous or homozygous resistant ones in laboratory tests, based on the survival and development of wheat midge larvae on one or two spikes. This powerful resistance gene, designated Sm1, is simply inherited and can be incorporated readily into breeding programmes for spring or winter wheat. However, the use of this gene by itself may lead to the evolution of a virulent population, once a resistant cultivar is widely grown.     

Identification of the leaf rust resistance genes Lr9, Lr26, Lr28, Lr34, and Lr35 in a collection of Iranian wheat genotypes using STS and SCAR markers

Brown rust or leaf rust is one of the most important diseases of wheat occurring almost in all wheat-producing regions and reduces crop yield. In order to produce resistant cultivars, it is necessary to identify resistance genes in different germplasms and combine them in (a) suitable stock(s). To identify the presence of the leaf rust resistance genes using STS and SCAR markers, 83 Iranian wheat genotypes, Lr near-isogenic lines in Thatcher (positive controls), and the cultivar Thatcher (negative control) were used. After growing plants in the greenhouse, DNA was extracted by SDS method. Following that, polymerse chain reaction was performed for the markers of the resistance genes Lr9, Lr26, Lr28, Lr34, and Lr35 which amplified 1,100, 1,100, 378, 150, and 900 bp bands, respectively. Based on the results, the resistance genes Lr9 and Lr35 were only present in the positive controls. The resistance gene Lr26 was only detected in four cultivars; Arta, Pishtaz, Shiroodi, and Falat, and the gene Lr34 was present in six cultivars (Akbari, Bam, Tajan, Khazar 1, Sistan and Niknezhad). The Lr28 primer amplified a band of the same size in all genotypes even the negative control and therefore the presence/absence of this gene could not be validated. These results indicate the necessity for designing a specific primer for Lr28. In general, only the genes Lr26 and Lr34 were present in some genotypes. The genes Lr9 and Lr35 were not present in this collection and as based on rust surveys, no virulence has been detected for Lr9 and Lr28, so they could be transferred to suitable lines from donor sources.     

The influence of a spring habit gene, Vrn-D1, on heading time in wheat

The adaptability of wheat cultivars to environmental conditions is known to be associated with a vernalization requirement, that is, spring/winter habit. To clarify the genetic effect of the spring habit gene, Vrn‐D1, on heading time in the field, recombinant inbred lines (RILs) with or without the Vrn‐D1 gene were produced from F₂ plants of the cross between ‘Nanbukomugi’ and ‘Nishikazekomugi’, non‐carrier and carrier cultivars of this gene, respectively. Using growth chambers with a controlled temperature and photoperiod, three components of heading time, i.e. vernalization requirement, photoperiodic sensitivity and narrow‐sense earliness (earliness per se), were evaluated in each RIL. RILs with the Vrn‐D1 gene (E lines) showed greatly reduced vernalization requirements and slightly shorter narrow‐sense earliness than RILs without Vrn‐D1 (L lines), although no difference in photoperiodic sensitivity was observed between the two groups. RILs were planted at four different sites in Japan and examined for their heading time in the field. E lines headed significantly earlier than L lines at all locations, indicating that the earliness of E lines is stable in various environmental conditions. These results indicated that spring habit caused by Vrn‐D1 gene, as well as narrow‐sense earliness, was responsible for heading time in the field.     

Genetic effects of Vrn genes on heading date and agronomic traits in bread wheat

Summary The Vrn1, Vrn2 and Vrn3 genes have different values of effects on heading date and related yield components. The genetic background and environment do not affect the ranking of Vrn genotypes according to earliness within near-isogenic line sets; however, they do influence the level of differences between heading dates of particular genotypes and between effect values, respectively. The frequencies of defined Vrn genotypes in the global set of spring bread wheat cultivars are associated with grain weight per plant predicted on the basis of Vrn gene effects averaged over backgrounds and over environments. Peculiarities of backgrounds and environments alter the grain yield ranges of Vrn genotypes. For early photoperiod-insensitive wheats, planted in stress conditions at grain filling, the highest yield was predicted for double dominant Vrn genotypes with Vrn3. This gene is rarely used by the breeders in middle latitudes and its wider adoption is encouraged.     

Molecular examination and genotype diversity of vernalization sensitivity and photoperiod response in old and modern bread wheat cultivars grown in Iran

Understanding the genetic factors governing developmental patterns and flowering time in breeding materials is required for the development of new wheat varieties for a specific environment. Iran is among the largest wheat producers in the arid and semi-arid regions of the Middle East and North Africa. The wheat germplasm grown in Iran is either developed nationally or is introduced from the CIMMYT global wheat program. For decades, the wheat breeding program in Iran focused on generating new varieties better able to grow in the predominant Iranian climatic conditions such as humidity at the reproductive stage, high temperature during reproductive stages (terminal heat stress), moderate temperature during the cropping season, and high probability of frost damage during early stages of growth. There have also been sub-programs aimed at developing drought and salinity-tolerant wheat cultivars in Iran. Knowledge of cultivars’ growth habits in Iran is currently limited to flowering in spring-sown nurseries. We identified allelic diversity in loci involved in vernalization response (Vrn) and photoperiod sensitivity (Ppd) in 60 bread wheat cultivars developed in Iran, CIMMYT, or ICARDA. This study revealed that the spring growth habit observed in most of the cultivars is conferred by a combination of recessive vrn-A1 and dominant Vrn-D1, Vrn-B1, and/or Vrn-B3 loci. This implies that most of the cultivars have minimal vernalization requirements for overwintering. Perhaps cold winters, even in the southern regions of Iran, provide sufficient vernalization conditions for cultivars possessing the recessive vrn-A1 allele. The germplasm investigated in this study revealed no evidence indicating selection for or against any specific Vrn and Ppd allele in our wheat breeding program.     

Distribution of photoperiod-insensitive allele Ppd-A1a and its effect on heading time in Japanese wheat cultivars

The Ppd-A1 genotype of 240 Japanese wheat cultivars and 40 foreign cultivars was determined using a PCR-based method. Among Japanese cultivars, only 12 cultivars, all of which were Hokkaido winter wheat, carried the Ppd-A1a allele, while this allele was not found in Hokkaido spring wheat cultivars or Tohoku-Kyushu cultivars. Cultivars with a photoperiod-insensitive allele headed 6.9–9.8 days earlier in Kanto and 2.5 days earlier in Hokkaido than photoperiod-sensitive cultivars. The lower effect of photoperiod-insensitive alleles observed in Hokkaido could be due to the longer day-length at the spike formation stage compared with that in Kanto. Pedigree analysis showed that ‘Purple Straw’ and ‘Tohoku 118’ were donors of Ppd-A1a and Ppd-D1a in Hokkaido wheat cultivars, respectively. Wheat cultivars recently developed in Hokkaido carry photoperiod-insensitive alleles at a high frequency. For efficient utilization of Ppd-1 alleles in the Hokkaido wheat-breeding program, the effect of Ppd-1 on growth pattern and grain yield should be investigated. Ppd-A1a may be useful as a unique gene source for fine tuning the heading time in the Tohoku-Kyushu region since the effect of Ppd-A1a on photoperiod insensitivity appears to differ from the effect of Ppd-B1a and Ppd-D1a.