Vrn-B1 Alleles Research Articles

Analysis of the Effects of the Vrn-1 and Ppd-1 Alleles on Adaptive and Agronomic Traits in Common Wheat (Triticum aestivum L.).

Wheat heading time is primarily governed by two loci: VRN-1 (response to vernalization) and PPD-1 (response to photoperiod). Five sets of near-isogenic lines (NILs) were studied with the aim of investigating the effect of the aforementioned genes on wheat vegetative period duration and 14 yield-related traits. Every NIL was sown in the hydroponic greenhouse of the Institute of Cytology and Genetics, SB RAS. To assess their allelic composition at the VRN-1 and PPD-1 loci, molecular markers were used. It was shown that HT in plants with the Vrn-A1vrn-B1vrn-D1 genotype was reduced by 29 and 21 days (p < 0.001) in comparison to HT in plants with the vrn-A1Vrn-B1vrn-D1 and the vrn-A1vrn-B1Vrn-D1 genotypes, respectively. In our study, we noticed a decrease in spike length as well as spikelet number per spike parameter for some NIL carriers of the Vrn-A1a allele in comparison to carriers of the Vrn-B1 allele. PCA revealed three first principal components (PC), together explaining more than 70% of the data variance. Among the studied genetic traits, the Vrn-A1a and Ppd-D1a alleles showed significant correlations with PCs. Regarding genetic components, significant correlations were calculated between PC3 and Ppd-B1a (-0.26, p < 0.05) and Vrn-B1 (0.57, p < 0.05) alleles. Thus, the presence of the Vrn-A1a allele affects heading time, while Ppd-D1a is associated with plant height reduction.

Effects of Rht17 in combination with Vrn-B1 and Ppd-D1 alleles on agronomic traits in wheat in black earth and non-black earth regions

BackgroundPlant height is an important wheat trait that is regulated by multiple genes, among which Rht is of the utmost value. In wheat, Rht-B1p (=Rht17) is a mutant allele of the Rht gene that encodes for a DELLA-protein and results in the development of gibberellin-insensitive plants with a dwarfing phenotype. The pleiotropic effects of dwarfing genes on yield are highly dependent on both the genetic background and the environmental conditions. In Russia, the Central Non-Black Earth Region and Krasnodar Krai are two economically important regions that require differing management for sustainable wheat production for food, feed and industry. The purpose of our study was to compare the pleiotropic effects of Rht-B1p on the main valuable agronomic traits in the F3:4 families of the spring bread wheat Chris Mutant/Novosibirskaya 67 in the genetic background of Vrn-B1a/vrn-B1 (spring/winter phenotype) and Ppd-D1a/Ppd-D1b (insensitivity/sensitivity to photoperiod) alleles in a field experiment in Moscow and Krasnodar Krai.ResultsPlant height was reduced on average by 21 cm (28%) and 25 cm (30%), respectively; Ppd-D1a slightly strengthened the dwarfing effect in Moscow and mitigated it in Krasnodar Krai. Grain weight of the main spike was reduced by Rht-B1p in Moscow and to lesser extent in Krasnodar; Ppd-D1a and Vrn-B1a tended to partially compensate for this loss in Krasnodar Krai. Thousand grain weight was reduced on average by 5.3 g (16%) and 2.9 g (10%) in Moscow and Krasnodar Krai, respectively, but was partially compensated for by Ppd-D1a in Krasnodar Krai. Harvest index was increased due to Rht-B1p by 6 and 10% in Moscow and Krasnodar Krai, respectively. Rht-B1p resulted in a delay of heading by 1–2 days in Moscow. Ppd-D1a accelerated heading by 1 day and 6 days in Moscow and in Krasnodar Krai, respectively.ConclusionsRht-B1p could be introduced into wheat breeding along with dwarfing genes such as Rht-B1b and Rht-D1b. Special attention should be paid to its combination with Ppd-D1a and Vrn-B1a as regulators of developmental rates, compensators of adverse effects of Rht-B1p on productivity and enhancers of positive effect of Rht-B1p on harvest index.

Ekmeklik Buğdayda Geliştirilen Resiprokal Rekombinant Kendilenmiş Hat Populasyonunda Çavdar Translokasyonu Taşıyan Hatların Yarı Bodurluk, Fotoperiyod, Vernalizasyon ve Waxy Genlerinin Taraması

Bu araştırmanın amacı, çavdar translokasyonu taşıyan rekombinant kendilenmiş hatların yarı bodurluk (Rht), fotoperiyod (Ppd) ve vernalizasyon (Vrn) genleri bakımından genotipik olarak taranmasıdır. Rekombinant kendilenmiş hatlar Tosunbey ile Tahirova-2000 ekmeklik buğday çeşitlerinin melezlenmesi sonucu elde edilmiştir ve bu hatlar içerisinden sadece 1BL.1RS çavdar translokasyonu taşıyan hatlar araştırmada kullanılmıştır. Anaçların ve hatların hepsinin yarı bodurluk alleli olan Rht-B1a ve fotoperiyoda hassasiyet taşımayan allel olan Ppd-D1a alleline sahip olduğu belirlenmiştir. Hatların sahip oldukları vernalizasyon allelleri de (Vrn-A1, Vrn-B1 ve Vrn-D1) belirlenmiştir. Her iki anacın ve hatların vrn-A1 allelini taşıdığı ve Vrn-A1c allelini ise taşımadığı belirlenmiştir. 151 adet hat vrn-B1 allelini ve 154 adet hat Vrn-B1 allelini taşırken, 131 adet hattın vrn-D1 allelini, 174 adet hattın Vrn-D1 allelini taşıdığı saptanmıştır. Çalışmada ayrıca unun kabarması, su tutma kapasitesi ve raf ömrü üzerinde etkili waxy allelleri (Wx-A1, Wx-B1 ve Wx-D1) bakımından da moleküler taramalar yapılmıştır. Taramalar sonucunda 141 adet hattın her üç alleli de taşıdığı ve “normal amilozlu buğday” olduğu, 164 adet hattın ise sadece Wx-A1 ve Wx-D1 allellerine sahip olduğu ve “düşük amilozlu buğday” olduğu belirlenmiştir. Elde edilen sonuçlar, araştırmada kullanılan popülasyonun kuraklık başta olmak üzere bazı araştırmalara konu olabileceğini ve buğday ıslah programları için çavdar translokasyonu taşıyan genetik materyal geliştirmek için kullanılabileceğini göstermektedir.

ALLELIC DIVERSITY OF GENES CONTROLLING RESPONSES TO VERNALIZATION AND PHOTOPERIOD AMONG SPRING BREAD WHEAT VARIETIES OF DIVERSE GEOGRAPHIC ORIGIN

Spring bread wheat is the most important cereal crop, cultivated under various climatic conditions and on different latitudes. Modern molecular genetic studies of wheat are aimed at investigating the crop’s genetic potential. By now, molecular markers have been developed to identify alleles of the Vrn (vernalization response) and Ppd (photoperiod response) genes. Vrn genes are responsible for crop development rate regulation and crop yield structure. Ppd genes determine the response of plants to the length of the day, that is, the timing of flowering and the beginning of heading in plants under different cultivation conditions. The use of diagnostic DNA markers made it possible to analyze the presence of allelic combinations of the Vrn and Ppd genes in local and commercial wheat varieties from Europe, Asia, North and South Americas, Africa and Australia. This review summarizes the results of studies on the distribution of alleles of Vrn and Ppd genes in wheat breeding material over different geographical areas of its cultivation. For example, the dominant Vrn-A1a allele was found in 62% of European varieties; 52% of the studied Turkish wheat varieties carried dominant Vrn-B1 alleles. A dominant Vrn-D1 was found in 61% of Pakistani wheat accessions. Vrn-D1 is present in 41.9% of the studied varieties of Chinese wheat. Higher incidence of Ppd-D1A is typical for West European varieties. A Ppd-D1a allele was found in 58.6% of varieties preserved in the Turkish wheat collection, with a 60% frequency of this allele in commercial cultivars. Among local Afghan varieties, 97% are sensitive to photoperiod (carriers of Ppd-D1b); they are distributed throughout the country without much dependence on agroecological zones. All Pakistani varieties are insensitive to photoperiod (carriers of Ppd-D1a). In China, the highest incidence of the Ppd-D1a allele was observed in zone VII (87.5% of varieties).

Molecular characterization of a novel vernalization allele Vrn-B1d and its effect on heading time in Chinese wheat (Triticum aestivum L.) landrace Hongchunmai

Flowering time of wheat cultivars contributes greatly to the adaptability to environmental conditions and it is largely controlled by vernalization genes. In this study, 262 Chinese mini-core wheat cultivars were used to identify the allelic variation at VRN-B1 locus. A novel dominant allele Vrn-B1d was found in Chinese spring wheat landrace cultivar Hongchunmai. This allele contained several genetic divergence within the first intron comparing to the recessive allele vrn-B1, including one large 6850-bp deletion (670–7519 bp), one small 187-bp deletion (7851–8037 bp), one unique SNP (T to C, 7845 bp), and one 4-bp mutation (TTTT to ACAA, 7847–7850 bp). Meanwhile, it was also different from the three known dominant alleles at VRN-B1 locus. Two pairs of primers were designed to identify the novel allele Vrn-B1d and other four known alleles of VRN-B1. A multiplex PCR was established to discriminate all five alleles simultaneously. The greenhouse experiment with high temperature (non-vernalizing condition) and long light showed that F2 plants containing Vrn-B1d allele headed significantly earlier than those with recessive vrn-B1 allele, suggesting that Vrn-B1d is a dominant allele conferring the spring growth habit. This study provides a useful germplasm and molecular markers for wheat breeding.

Genetic basis of the very short life cycle of \u2018Apogee\u2019 wheat

Background‘Apogee’ has a very short life cycle among wheat cultivars (flowering 25 days after planting under a long day and without vernalization), and it is a unique genetic material that can be used to accelerate cycling breeding lines. However, little is known about the genetic basis of the super-short life of Apogee wheat.ResultsIn this study, Apogee was crossed with a strong winter wheat cultivar ‘Overland’, and 858 F2 plants were generated and tested in a greenhouse under constant warm temperature and long days. Apogee wheat was found to have the early alleles for four flowering time genes, which were ranked in the order of vrn-A1 > VRN-B1 > vrn-D3 > PPD-D1 according to their effect intensity. All these Apogee alleles for early flowering showed complete or partial dominance effects in the F2 population. Surprisingly, Apogee was found to have the same alleles at vrn-A1a and vrn-D3a for early flowering as observed in winter wheat cultivar ‘Jagger.’ It was also found that the vrn-A1a gene was epistatic to VRN-B1 and vrn-D3. The dominant vrn-D3a alone was not sufficient to cause the transition from vegetative to reproductive development in winter plants without vernalization but was able to accelerate flowering in those plants that carry the vrn-A1a or Vrn-B1 alleles. The genetic effects of the vernalization and photoperiod genes were validated in Apogee x Overland F3 populations.ConclusionVRN-A1, VRN-B1, VRN-D3, and PPD-D1 are the major genes that enabled Apogee to produce the very short life cycle. This study greatly advanced the molecular understanding of the multiple flowering genes under different genetic backgrounds and provided useful molecular tools that can be used to accelerate winter wheat breeding schemes.

Allelic Variation of Rht-1, Vrn-1 and Ppd-1 in Korean Wheats and Its Effect on Agronomic Traits

The allelic variations at the Rht-1, Vrn-1 and Ppd-1 of 410 Korean wheat cultivars, including 111 Korean experimental lines, 238 Korean landraces and 61 North Korean collections, were investigated to provide the information of plant height and heading date and to elucidate the relationship between those traits and allelic variation of these genes because earliness is major consideration in Korean wheat production. All Korean wheats displayed vrn-A1 and Ppd-A1b alleles, while Rht-B1a, Rht-D1a, vrn-B1, Vrn-D1, Ppd-B1b and Ppd-D1a alleles were also predominantly found. Most Korean wheats carried both Rht-B1a and Rht-D1a alleles, both vrn-B1 and Vrn-D1 alleles, or both Ppd-B1b and Ppd-D1a alleles. The Rht-B1a, vrn-D1, Ppd-B1b and Ppd-D1b alleles were found to exhibit longer culm and spike length than their counterpart alleles. The Rht-B1a allele also showed longer spike length than Rht-B1b. Vrn-B1b and vrn-D1 alleles exhibited longer days to heading date than their counterpart alleles at the Vrn-B1 and Vrn-D1 loci. Lines carrying both Rht-B1b and Rht-D1b alleles displayed shorter culm and longer spike length and days to heading date than any other combination of alleles at the Rht-B1 and Rht-D1 loci. In contrast, lines carrying both Ppd-B1b and Ppd-D1b alleles exhibited longer culm and spike length than any other combination of alleles at the Ppd-B1 and Ppd-D1 loci.

Study of allelic composition of Vrn-1 and Ppd-1 genes in early–ripening and middle–early varieties of spring soft wheat in siberia

Using allele-specific primers, a combination of the Vrn-A1, Vrn-B1, Vrn-D1, Ppd-D1, and Ppd-B1 alleles was analyzed in 48 early-ripening and middle–early varieties of the spring soft wheat from different breeding centers of Siberia. Six haplotypes were detected, including two most widespread with two dominant genes (Vrn-A1 and Vrn-B1) on the background of recessivePpd-D1b gene (causing sensitivity to the photoperiod). The dominant Ppd-D1a allele was found in combination with dominant Vrn-A1 and Vrn-B1 genes only in one variety (Tulun 15), which is the earliest among all the analyzed varieties. A significant variability in the duration of vegetation was detected within each haplotype assuming a strong influence of the genetic background on the given trait. The results obtained can be used in marker-assisted selection of the most optimal genotypes for specific cultivation conditions.

The relationship between allelic variations ofVrn-1andPpd-1and agronomic traits in Korean wheat cultivars

The allelic variations at the Vrn-1 and Ppd-1 loci of Korean wheat cultivars were determined to evaluate their effects on agronomic traits and response to vernalization treatment. Korean wheat cultivars displayed high frequency of Vrn-D1a and Ppd-B1b alleles, but all of the tested cultivars carried vrn-A1, vrn-B1, Ppd-A1b and Ppd-D1a alleles at the corresponding loci. Regardless of vernalization treatments, Korean wheat cultivars carrying the vrn-D1 allele showed longer days to flag leaf unfolding than those with the Vrn-D1a allele. Unvernalized cultivars carrying the vrn-D1 allele also exhibited larger final leaf number than those with the Vrn-D1a allele. However, there were no significant differences in the response of the Korean wheat cultivars to vernalization treatment based on allelic variation at the Ppd-1 loci. With respect to agronomic traits, the Vrn-D1a allele was related to increased grain yield and decreased thousand kernel weight compared to the vrn-D1 allele. Cultivars carrying both Vrn-D1a and Ppd-B1b alleles produced higher grain yield (5.5 tons/ha) than those with the vrn-D1 and Ppd-B1b alleles (5.0 tons/ha).

Characterization of wild emmer wheat Triticum dicoccoides germplasm for vernalization alleles

The flowering in winter and wild wheats is induced by extended exposure to cold temperatures, a process called vernalization while spring wheats do not have any such requirement. In the present study, we analyzed 45 accessions of wild emmer wheat T. dicoccoides for the allelic composition of the vernalization genes at VRN-A1 and VRN-B1 loci. Three gene based markers for VRN-A1 and two for VRN-B1 locus were used. Thirty five T. dicoccoides accessions had only winter type allele vrn-A1 at VRN-A1 locus. One accession each had VRN-A1a and Vrn-A1d allele, and two accessions each showed the presence of VRN-A1b and Vrn-A1c, potent spring type alleles. Three accessions, however, had multiple alleles at VRN-A1 locus. At the VRN-B1 locus 35 accessions had winter type allele vrn-B1 and 10 accession had dominant Vrn-B1 allele. These T. dicoccoides accessions constitute a very useful resource for incorporation of alternative vernalization alleles in the cultivated wheat gene pool for developing better adaptive wheat varieties.

Allele frequencies in the VRN-A1, VRN-B1 and VRN-D1 vernalization response and PPD-B1 and PPD-D1 photoperiod sensitivity genes, and their effects on heading in a diverse set of wheat cultivars (Triticum aestivum L.).

Heading of cereals is determined by complex genetic and environmental factors in which genes responsible for vernalization and photoperiod sensitivity play a decisive role. Our aim was to use diagnostic molecular markers to determine the main allele types in VRN-A1, VRN-B1, VRN-D1, PPD-B1 and PPD-D1 in a worldwide wheat collection of 683 genotypes and to investigate the effect of these alleles on heading in the field. The dominant VRN-A1, VRN-B1 and VRN-D1 alleles were present at a low frequency. The PPD-D1a photoperiod-insensitive allele was carried by 57 % of the cultivars and was most frequent in Asian and European cultivars. The PPD-B1 photoperiod-insensitive allele was carried by 22 % of the genotypes from Asia, America and Europe. Nine versions of the PPD-B1-insensitive allele were identified based on gene copy number and intercopy structure. The allele compositions in PPD-D1, PPD-B1 and VRN-D1 significantly influenced heading and together explained 37.5 % of the phenotypic variance. The role of gene model increased to 39.1 % when PPD-B1 intercopy structure was taken into account instead of overall PPD-B1 type (sensitive vs. insensitive). As a single component, PPD-D1 had the most important role (28.0 % of the phenotypic variance), followed by PPD-B1 (12.3 % for PPD-B1_overall, and 15.1 % for PPD-B1_intercopy) and VRN-D1 (2.2 %). Significant gene interactions were identified between the marker alleles within PPD-B1 and between VRN-D1 and the two PPD1 genes. The earliest heading genotypes were those with the photoperiod-insensitive allele in PPD-D1 and PPD-B1, and with the spring allele for VRN-D1 and the winter alleles for VRN-A1 and VRN-B1. This combination could only be detected in genotypes from Southern Europe and Asia. Late-heading genotypes had the sensitivity alleles for both PPD1 genes, regardless of the allelic composition of the VRN1 genes. There was a 10-day difference in heading between the earliest and latest groups under field conditions.Electronic supplementary materialThe online version of this article (doi:10.1007/s11032-014-0034-2) contains supplementary material, which is available to authorized users.

Molecular characterization of vernalization and photoperiod genes in wheat varieties from different agro-climatic zones of India

Ninety-nine wheat cultivars from six different agro-climatic zones of India were analyzed for the Vrn-1, Vrn-2, Vrn-B3, Vrn-4 and Ppd-D1 composition with DNA sequenced based allele specific or linked markers for the above-mentioned genes. A majority of the germplasm carried the dominant Vrn-A1a allele alone or in combination with Vrn-B1 and Vrn-D1. The three dominant genes were cumulatively present in 30 cultivars among all the zones, whereas double dominant combination, Vrn- A1/Vrn-B1 was identified in 18 cultivars, Vrn-A1/Vrn-D1 in 6 cvs and Vrn-B1/Vrn-D1 in 16 cvs. The combination of the dominant alleles of all three genes was most frequent in cvs of Northern Western Plains Zone. Northern Hill Zone had vrn-B1 and vrn-D1 alleles in higher proportions compared to the dominant alleles Vrn-B1 and Vrn-D1 indicating successful spring/winter wheat cross breeding. All of the cvs had the recessive Vrn-B3 allele. Most of the cvs had photoperiod insensitive allele in all the zones and only 9% cvs possessed the photoperiod sensitive allele (b) of the Ppd-D1 gene. This information will be useful in selecting parental lines for crossing to maximize diversity at these loci and for future molecular marker assisted breeding for cultivar improvement.

GA-responsive dwarfing gene Rht12 affects the developmental and agronomic traits in common bread wheat.

Opportunities exist for replacing reduced height (Rht) genes Rht-B1b and Rht-D1b with alternative dwarfing genes, such as the gibberellin-responsive gene Rht12, for bread wheat improvement. However, a comprehensive understanding of the effects and mode of action of Rht12 is lacking. In the present study, the effects of Rht12 were characterized by analyzing its effects on seeding vigour, seedling roots, leaf and stem morphology, spike development and carbohydrate assimilation and distribution. This was carried out in the four genotypes of F2:3 lines derived from a cross between Ningchun45 and Karcagi (12) in two experiments of autumn sowing and spring sowing. Rht12 significantly decreased stem length (43%∼48% for peduncle) and leaf length (25%∼30% for flag leaf) while the thickness of the internode walls and width of the leaves were increased. Though the final plant stature was shortened (40%) by Rht12, the seedling vigour, especially coleoptile length and root traits at the seedling stage, were not affected adversely. Rht12 elongated the duration of the spike development phase, improved the proportion of spike dry weight at anthesis and significantly increased floret fertility (14%) in the autumn sowing experiment. However, Rht12 delayed anthesis date by around 5 days and even the dominant Vrn-B1 allele could not compensate this negative effect. Additionally, grain size was reduced with the ability to support spike development after anthesis decreased in Rht12 lines. Finally, grain yield was similar between the dwarf and tall lines in the autumn sowing experiment. Thus, Rht12 could substantially reduce plant height without altering seeding vigour and significantly increase spikelet fertility in the favourable autumn sowing environment. The successful utilization of Rht12 in breeding programs will require careful selection since it might delay ear emergence. Nonetheless, the potential exists for wheat improvement by using Rht12.

The effect of two differentially expressed wheat VRN-B1 alleles on the heading time is associated with structural variation in the first intron

We measured the level of VRN-B1 transcripts within near-isogenic lines of Triticum aestivum cultivar 'Bezostaya 1' carrying two VRN-B1 alleles from cultivars 'Saratovskaya 29' and 'Diamant 2' (VRN-B1c and VRN-B1a, respectively). Both lines have similar kinetics of VRN-B1 transcript accumulation at the third to fifth leaf stages. However, quantitative PCR analysis at the third leaf stage showed that the VRN-B1c allele was transcribed 10 times faster than the VRN-B1a allele. The F1 hybrid between the lines is more similar to the line carrying the VRN-B1a allele with regard to the level of VRN-B1 transcription. The difference in the transcript levels of the VRN-B1 alleles appears to be due to the previously identified structural changes in the first intron of VRN-B1c (deletion of 0.8kb and duplication of 0.4kb) as compared with VRN-B1a, as no other differences were revealed in the present study. We suggested that the first intron structural changes in the VRN-B1c allele as compared with VRN-B1a result in a higher level of VRN-B1 transcripts and an earlier heading time. We confirmed that the expression of the dominant VRN-1 gene induces transcription of the recessive homoeoalleles, coupled with the reduction of the transcript level of a flowering repressor VRN-2.

Distribution of different Vrn-B1 alleles in hexaploid spring wheat germplasm

In wheat, the transition from the vegetative to reproductive stage is primarily controlled by the series of vernalisation (Vrn-1) genes located on the homoeologous group 5 chromosomes. Up to 2009, only two alleles at the Vrn-B1 locus were known: one dominant, spring, allele (now designated Vrn-B1a) and the other recessive, winter, (vrn-B1) allele. Recently, two additional dominant alleles, Vrn-B1b and Vrn-B1c, were described. In this study, we screened a range of hexaploid spring wheat germplasms for the presence of different Vrn-B1 alleles using new diagnostic molecular markers. Our results show that the Vrn-B1a allele was the most prevalent, being present in 55.3 % of the 2,495 accessions examined, followed by the recessive vrn-B1 allele, which occurred in 31.5 % of the accessions. The novel alleles Vrn-B1b and Vrn-B1c were found in 5.3 and 7.9 % of all accessions, respectively.

The combination of the Ppd and Vrn gene alleles determines the heading date in common wheat varieties

Combinations of the Ppd-D1, Vrn-A1, Vrn-B1, and Vrn-D1 gene alleles were analyzed using allele-specific primers in 56 varieties and lines of common wheat that were selected in the Lukyanenko Agricultural Research Institute. The significant influence of the combination of these alleles on the time of the beginning of the heading of the studied varieties was determined, which is manifested differently under conditions of long and short photoperiods, as well as depending on whether vernalization occurs. Molecular labeling of wheat Vrn and Ppd gene alleles allows breeders to consciously manipulate the original material (by having information in advance about the adaptive potential of the plants that are involved in the breeding process), as well as to select the allele combinations that are optimal for specific conditions of cultivation.

Genetics of flowering time in bread wheat Triticum aestivum: complementary interaction between vernalization-insensitive and photoperiod-insensitive mutations imparts very early flowering habit to spring wheat

Time to flowering in the winter growth habit bread wheat is dependent on vernalization (exposure to cold conditions) and exposure to long days (photoperiod). Dominant Vrn-1 (Vrn-A1, Vrn-B1 and Vrn-D1) alleles are associated with vernalization independent spring growth habit. The semidominant Ppd-D1a mutation confers photoperiod-insensitivity or rapid flowering in wheat under short day and long day conditions. The objective of this study was to reveal the nature of interaction between Vrn-1 and Ppd-D1a mutations (active alleles of the respective genes vrn-1 and Ppd-D1b). Twelve Indian spring wheat cultivars and the spring wheat landrace Chinese Spring were characterized for their flowering times by seeding them every month for five years under natural field conditions in New Delhi. Near isogenic Vrn-1 Ppd-D1 and Vrn-1 Ppd-D1a lines constructed in two genetic backgrounds were also phenotyped for flowering time by seeding in two different seasons. The wheat lines of Vrn-A1a Vrn-B1 Vrn-D1 Ppd-D1a, Vrn-A1a Vrn-B1 Ppd-D1a and Vrn-A1a Vrn-D1 Ppd-D1a (or Vrn-1 Ppd-D1a) genotypes flowered several weeks earlier than that of Vrn-A1a Vrn-B1 Vrn-D1 Ppd-D1b, Vrn-A1b Ppd-D1b and Vrn-D1 Ppd-D1b (or Vrn-1 Ppd-D1b) genotypes. The flowering time phenotypes of the isogenic vernalization-insensitive lines confirmed that Ppd-D1a hastened flowering by several weeks. It was concluded that complementary interaction between Vrn-1 and Ppd-D1a active alleles imparted super/very-early flowering habit to spring wheats. The early and late flowering wheat varieties showed differences in flowering time between short day and long day conditions. The flowering time in Vrn-1 Ppd-D1a genotypes was hastened by higher temperatures under long day conditions. The ambient air temperature and photoperiod parameters for flowering in spring wheat were estimated at 25°C and 12 h, respectively.

A Novel Retrotransposon Inserted in the DominantVrn-B1Allele Confers Spring Growth Habit in Tetraploid Wheat (Triticum turgidumL.)

Vernalization genes determine winter/spring growth habit in temperate cereals and play important roles in plant development and environmental adaptation. In wheat (Triticum L. sp.), it was previously shown that allelic variation in the vernalization gene VRN1 was due to deletions or insertions either in the promoter or in the first intron. Here, we report a novel Vrn-B1 allele that has a retrotransposon in its promoter conferring spring growth habit. The VRN-B1 gene was mapped in a doubled haploid population that segregated for winter-spring growth habit but was derived from two spring tetraploid wheat genotypes, the durum wheat (T. turgidum subsp. durum) variety ‘Lebsock’ and T. turgidum subsp. carthlicum accession PI 94749. Genetic analysis revealed that Lebsock carried the dominant Vrn-A1 and recessive vrn-B1 alleles, whereas PI 94749 had the recessive vrn-A1 and dominant Vrn-B1 alleles. The Vrn-A1 allele in Lebsock was the same as the Vrn-A1c allele previously reported in hexaploid wheat. No differences existed between the vrn-B1 and Vrn-B1 alleles, except that a 5463-bp insertion was detected in the 5′-UTR region of the Vrn-B1 allele. This insertion was a novel retrotransposon (designated as retrotrans_VRN), which was flanked by a 5-bp target site duplication and contained primer binding site and polypurine tract motifs, a 325-bp long terminal repeat, and an open reading frame encoding 1231 amino acids. The insertion of retrotrans_VRN resulted in expression of Vrn-B1 without vernalization. Retrotrans_VRN is prevalent among T. turgidum subsp. carthlicum accessions, less prevalent among T. turgidum subsp. dicoccum accessions, and rarely found in other tetraploid wheat subspecies.

Distribution of vernalization and photoperiod genes (Vrn-A1, Vrn-B1, Vrn-D1, Vrn-B3, Ppd-D1)in Turkish bread wheat cultivars and landraces

Vernalization and photoperiod response genes play a significant role in the geographical adaptation, agronomic performance and yield potential of crops. Therefore, understanding the distribution pattern and allelic diversity for vernalization and photoperiod genes are important in any wheat breeding program. In this study, we screened 63 bread wheat cultivars and 7 bread wheat landraces from Turkey for photoperiod (Ppd-D1) and vernalization genes (Vrn-A1, Vrn-B1, Vrn-D1 and Vrn-B3) using diagnostic molecular markers. The photoperiod insensitive dominant allele, Ppd-D1a, was present in 60% of wheat cultivars and 42% of landraces, whereas, all other genotypes carried the photoperiod sensitive allele Ppd-D1b as recessive allele. Twenty-four cultivars and two landraces contained recessive alleles for all four VRN loci, whereas 39 wheat cultivars and 6 landraces contained one or more dominant VRN alleles. The highest percentage of Turkish wheat cultivars contained the dominant Vrn-B1 allele followed by Vrn-D1 and Vrn-A1. Information for vernalization and photoperiod alleles in Turkish germplasm will facilitate the planning and implementation of molecular markers in wheat breeding programs. This information will be helpful to develop elite wheat cultivars carrying suitable vernalization and photoperiod alleles with higher grain yield potential and better quality suitable for different production environments through marker assisted selection.

A new multiplex PCR test for the determination of Vrn-B1 alleles in bread wheat (Triticum aestivum L.)

Winter wheat requires vernalization, a long exposure to low but non-freezing temperatures, to promote reproductive development. The vernalization requirement in bread wheat (Triticum aestivum L.) is mainly controlled by the Vrn-1 genes that are located on chromosomes 5A, 5B and 5D. Dominant alleles confer spring habit and are epistatic to the recessive winter alleles which means that spring varieties carry at least one dominant allele. To date, two dominant and one recessive Vrn-B1 alleles have been described. Vrn-B1a (formerly designated as Vrn-B1) differs from the winter vrn-B1 allele by a large deletion in intron 1. Vrn-B1b has an additional small deletion and is probably derived from Vrn-B1a. The novel allele described here and designated as Vrn-B1c also has a large deletion within intron 1 but with different breakpoints from Vrn-B1a or b, and sequence duplication, showing that this is an independently derived spring allele. By combining an exon 1 primer with previously published PCR primers it was possible to develop a multiplex PCR that distinguished all four alleles simultaneously. The multiplex PCR was validated by testing 320 winter wheat and 137 spring wheat varieties. This demonstrated that the novel Vrn-B1c allele was present in 25 spring varieties of diverse origin, showing this allele to be widely distributed.