ALLELE FREQUENCIES OF PPD-D1A , PPD-B1A, AND PPD-B1C OF PHOTOPERIODIC SENSITIVITY GENES IN SPRING BREAD WHEAT VARIETIES ( TRITICUM AESTIVUM L.) OF VARIOUS ORIGIN

Aim. To identify and evaluate allele frequencies of Ppd-D1a , Ppd-B1a , Ppd-B1c and Ppd-1 of the genotypes of spring bread wheat varieties from various climatic zones. Methods. DNA isolation, allele-speci ﬁ c PCR, electrophoresis in agarose and polyacrylamide gel, statistical analysis. Results. 137 varieties of spring bread wheat of various origin were detected to identify Ppd-1 genotypes of Ppd-D1a , Ppd-B1a and Ppd-B1c allele carriers. The results for the total sampling of the varieties under investigation and the sampling of Asian varieties yielded six different Ppd-1 genotypes in each. As for samplings of other regions, there were from two (Mexico) to four (Europe, the USA, Canada, Ukraine) Ppd-1 genotypes. In the total sampling of varieties, there was a high incidence (20.5 %) of genotypes, dominant only in allele Ppd-D1a , varying from 0 (Russia) to 85.0 % (Mexico). The incidence of the genotypes with monogenically dominant Ppd-B1a (7.3 %) or Ppd-B1c (5.1 %) in the total sampling, was considerably lower. These genotypes were most common for the sampling of the varieties from the USA and Canada (25.0 and 16.7 % respectively). Digenically dominant Ppd-D1a Ppd-B1a genotypes were found in the total sampling with relatively low incidence (7.3 %), and were notable for the varieties from Asia (33.4 %), Mexico (15.0 %), Ukraine (13.1 %), and Europe (3.1 %). The digenically dominant genotype Ppd-D1a Ppd-B1 с was found only in the Japanese variety Konosu-25. Gene Ppd-A1 was present in all the spring varieties under investigation in its recessive state. Conclusions . Out of three dominant alleles in the studied sampling, the highest incidence was noted for allele Ppd-D1a (28.5 %). All the varieties from Mexico, present in the set, carry this allele. At the same time, it was not found in any variety from Russia. Allele Ppd-B1a was detected in the varieties from all the regions with the incidence of 7.7 (Russia) – 44.4 % (Asia). Allele Ppd-B1c was sporadically present in the varieties from Russia, Ukraine, the USA, Japan, and Brazil, and its incidence in the total sampling was insigni ﬁ cant (5.8 %). The varieties, identi ﬁ ed by the allelic status of Ppd-1 genes, may be used as donors for selection and determination of the in ﬂ uence of alleles for each gene by the development rate and related economi-cally valuable traits of bread wheat.


INTRODUCTION
The photoperiod-sensitivity of bread wheat plants (Triticum аestivum L.) is mainly controlled by genes of the orthologue series Ppd-1: Ppd-D1, Ppd-B1, and Ppd-A1 (McIntosh RA et al, 2003), localized in short arms of chromosomes ІІ of the homologous group 2А, 2В, and 2D, respectively (Scarth R, Law CN, 1984) and encoding proteins, which induce the manifesta-tion of the blossoming locus TaFT (VRN3) (Yan L et al, 2006;Chen F et al, 2013). At present, each photoperiod gene is viewed as a series of alleles, occurring due to various mutations of their older predecessor forms (Shaw LM et al, 2012;Bentley AR et al, 2013). Wild alleles Ppd-1 contain a site in their promoter, which is involved in suppressing the expression at nighttime. Therefore, "sensitive" or recessive alleles of photoperiod genes are expressed after dawn and prior to the darkness phase. Poor photoperiod-sensitivity is caused by the infl uence of one or more mutant "insensitive" or dominant alleles. The occurrence of the latter is a result of the impaired structure of the promoter due to extensive deletions (genes Ppd-A1a and Ppd-D1a), or insertion (gene Ppd-B1a.1). The presence of these mutations leads to 24-hour-long gene expression under higher activity at nighttime and at dawn. Therefore, the availability of a dominant allele ensures faster accumulation of the inductor protein, which is refl ected in the acceleration of the rate for the period from seedlings to heading/blossoming.
The differences in the rate of development for bread wheat are mainly related to the impact of dominant gene Ppd-D1а, which spread widely among the varieties in temperate zones (Langer SM et al, 2014), predominantly affecting winter type of development. Allelic differences for gene Ppd-D1 are among the most relevant factors, defi ning the variability of winter wheat varieties in terms of adaptivity and performance in specifi c cultivation regions (Worland AJ et al, 1998;Síp V et al, 2010;Grogan SM et al, 2016), including Ukraine (Bakuma АО et al, 2018). On the contrary, allele Ppd-A1a.1 and Ppd-B1a.1 Seki M et al, 2011) are rare. Allele Ppd-B1a.1 with MITE type insertion in the promoter was detected only in a dozen of related Japanese varieties and not found in the varieties from other regions. However, in Ppd-B1, contrary to two other genes Ppd-1, the dominant form is also presented by multi-copy alleles, which occurred due to CNV-mutations. It is known that there are two, three, and four-copy alleles, indicated as Ppd-B1d, Ppd-B1a, Ppd-B1c, respectively (Cane K et al, 2013). The multi-copy nature is a common phenomenon, including several known copies of the recessive Vrn-A1 (Diaz A et al, 2012;Würschum T et al, 2015) in the genes of CBF family (Würschum T et al, 2017), etc. СNV-mutants of Ppd-B1 do not have any impairments in the promoter structure. At the same time, the increase in transcription activity at nighttime was determined in multi-copy alleles, contrary to the recessive one without any copies (Diaz A et al, 2012;Shaw LM et al, 2012). In addition, it has been recently shown that a difference in the methylation levels for the promoter zone of Ppd-B1a refl ects on its transcription activity and the carriers of the same allele differ in their heading rate (Sun H et al, 2014). Contrary to Ppd-D1a, the frequencies and distribution of dominant Ppd-B1 are practically not studied. The analysis of intramolecular structure of Ppd-1 genes ensured the elaboration of PCR-tests, the application of which allows for the identifi cation of varieties by allelic status of photope-riod genes. The fi rst test of this kind was multiplex PCR, suggested by Bealis (Bealis J et al, 2007) for the detection of dominant and recessive alleles of Ppd-D1 gene by the presence or absence of deletion in the promoter, respectively. The authors also demonstrated that in addition to the functional gene, Chinese Spring variety, a carrier of dominant Ppd-B1, has a pseudogene with partially deleted exon 8, to detect which a respective PCR-test was developed. It was later found that in the Chinese variety Ppd-B1 has four copies, including the shortened one -allele Ppd-B1c (Cane K et al, 2013). The complexity of labelling CNV-mutants is conditioned by the fact that copies are practically identical, just like inter-copy zones, including the insertions of transposons. However, a three-copy gene of varieties Sonora 64 and Timstein was found to have a polymorphous area, which served as a foundation for the elaboration of a PCR-test, identifying allele Ppd-B1a. The varieties of hexaploid wheat T. aestivum were found to have allele Ppd-A1a.1, containing a deletion in the promoter region . However, this allele is rarely detected, and a recessive allele of the gene prevails in bread wheat varieties. Several PCRtests were developed to detect allelic status of Ppd-A1 and to identify the absence/presence of deletions in the promoter (Wilhelm EP et al, 2009).
The aim of this study was to identify and assess the incidence frequencies for alleles Ppd-D1a, Ppd-B1a, Ppd-B1c, and Ppd-1 of genotypes of spring bread wheat varieties from different climatic zones. The identifi cation of carriers of genes Ppd-D1a, and especially multi-copy genes Ppd-B1 is actual, as the information about Ppd-1 genotypes, including Ukrainian spring varieties, is rather scarce. Such information about Ppd-1 genotypes of the varieties is relevant when the latter are used as donors in breeding programs, aimed at the develop of early-maturing varieties, and as the initial material to determine the effects of the alleles of each gene in terms of development rate and related agronomic traits of bread wheat.

MATERIALS AND METHODS
137 varieties of spring bread wheat Triticum aestivum L. of various origin were used as the initial material; the complete list is presented in Table 1. Among the investigated varieties, 32 varieties were from European countries (Germany -14, Sweden -4, France, Switzerland -3, Great Britain, the Netherlands, Finland -2, Austria, Czech Republic -1), 23 -from Ukraine, 26 -Russia, 4 -Kazakhstan. The sampling also contained 12 varieties from the USA and Canada, 20 vari-eties from Mexico, 9 varieties from Asia (Japan, India), 6 -from Africa, 3 -South America and 2 -Australia.
To detect the alleles of Ppd-1 family, we used PCRtests, the primers for which are specifi ed in Table 1. The marking of gene Ppd-D1 was done according to the recommendations of Bealеs (Beales J et al, 2007). This test envisages the identifi cation of recessive alleles of the gene by the absence of deletions in the promoter -fragment 414 bp and dominant allele Ppd-D1a -marking product of 288 bp. The detection of allele Ppd-B1c (four copies of the gene) was also performed by the test, developed by Bealеs (Beales J et al, 2007), where the marker was a fragment of 425 bp. A variant of allele-specifi c PCR, suggested by Chen (Chen F et al, 2013), was used to detect a three-copy gene Ppd-B1a. A marker of this gene was an amplifi cation fragment of 223 bp. As a reference control, Chinese Spring variety was used in the former case and Timstein -in the latter. To detect the intact status of the promoter of gene Ppd-A1, a PCR-test was used where a fragment of 452 bp indicated recessive status of this gene (Williams EP et al, 2009). The absence of the product allows for an alleged presence of a deletion in the promoter and a presence of a dominant allele.
Terzik amplifi er (DNA-technology, Russia) was used for the amplifi cation. The amplifi cation products were fractioned in 10 % polyacrylamide gel and their visualization in PAAG was done by staining with 0.012 М AgNO 3 . The molecular mass of amplifi cation products was determined regarding markers pUC19/MspI and Ledder 1000.
The statistical processing of the obtained results was done by common methods (Rokitskiy PF, 1973).

RESULTS
We identifi ed the genotypes of 137 varieties of spring bread wheat of various geographical origin for genes Ppd-A1, Ppd-B1, Ppd-D1 ( Table 2). The locus Ppd-A1 polymorphism was not found in the sampling of varieties under investigation. A marker fragment of 452 bp was found in all the investigated varieties during DNA amplifi cation, which indicated the absence of deletions in the promoter and the presence of a recessive allele Ppd-A1b in the genotypes.
At the same time, the carriers of dominant and recessive alleles of genes Ppd-D1 and Ppd-B1 were detected in the varieties of the investigated sampling ( Fig. 1, 2). As a result, six different Ppd-1 genotypes were identifi ed in the varieties: recessive in three genes of Ppd-1, monogenically dominant in Ppd-D1a, or Ppd-B1a, or Ppd-B1с, and digenically dominant in Ppd-D1a, Ppd-B1с or Ppd-D1a, Ppd-B1a. The samplings of the varieties from most regions demonstrated from two (Mexico) to three (Russia), or four (Europe, the USA, Canada, Ukraine) Ppd-1 genotypes. And only the sampling of Asian varieties had 6 genotypes (Table 3).
The varieties from different countries or regions did not differ (d < S d´t0.05 ) among themselves in frequencies of genotypes, monogenically dominant in Ppd-B1a or Ppd-B1c and digenically dominant in Ppd-D1a Ppd-B1a or Ppd-D1a Ppd-B1с. In general, the frequencies of the four mentioned genotypes were rather low, varying in different samplings from 0 to 33.4 %.
At the same time, the frequency of monogenically dominant Ppd-D1a genotypes in Mexican varieties is 85.0 ± 7.98, which is reliably higher by 62.8 ± 15.98 % than that for the sampling of Asian varieties (t = 3.93 at t 0.05 = 2.05) and four other regions, which, in their turn, did not differ much from the Asian varieties.
In general, the share of monogenically or digenically dominant varieties, the carriers of alleles Ppd-D1a, Ppd-B1a or Ppd-B1c in spring varieties from Europe and Russia, is rather low, amounting to 15.5 ± 6.40 and 15.4 % ± 7.07, respectively. This value is insignifi cantly (d < S d´t0.05 ) increasing up to 30.4 ± 9.59 % for Ukrainian varieties and up to 48.4 ± 14.23 % for the varieties from the USA and Canada. But for the Indian variety Kalyansona, all the investigated varieties of Asia and Mexico carry dominant alleles of genes Ppd-D1 and/or Ppd-B1. The presence of dominant alleles of one or two genes of orthologue series Ppd-1 in the genotype of the variety may demonstrate low photoperiodic sensitivity.
The remaining varieties (81 samples or 59.1 ± ± 4.20 %) within this investigation are characterized as carriers of recessive alleles Ppd-1.
Higher frequency in the total sampling of the varieties was noted for allele Ppd-D1a -28.5±3.86 % or 39 varieties (Table 4). The share of the carriers of allele At the same time, signifi cant differences in the frequencies of gene Ppd-D1a were noted between some regions. No variety, carrier of this dominant allele, was found in the sampling of Russian varieties. On the con-trary, among the specifi ed Mexican spring varieties, 100 % of them had allele Ppd-D1a in their genotype, which was reliably 73.9-100 % higher as compared with the value for other regions (t = 8.06-29.94 at t 0.05 = 1.96), except for the sampling of Asian varieties, the differences with which were found to be insignificant (d = 33.3 ± 15.71 %). In its turn, the frequency of this allele in Asian varieties was considerably exceeding the similar index (t = 2.62-4.15 at t 0.05 = 1.96-2.09) in the samplings of the varieties from the USA, Canada, Europe and Russia. The latter three regions did not differ in this index. Signifi cant differences in the frequencies of gene Ppd-D1a were also noted during the comparison of varieties from Ukraine and Russia (t = 2.69 at t 0.05 = 1.96).
DISCUSSION Many genetic studies found that winter and spring wheat varieties, grown in countries of higher latitude, usually have a higher incidence of photoperiod-sensitive alleles. On the contrary, the genotypes, grown in lower latitudes, usually carry photoperiod-insensitive alleles.
The results, presented in this article, demonstrate not a high incidence of dominant alleles of genes Ppd-  2,5,6,7,9,10,12,16,18,19,Koga,Capta,Transec,Chul,Norin 29,Saratovskaya 29,Strela,Struna myronivska,Katiusha,3,4,8,11,13,15,17,20,22, Albis, Aranka, Atys, Loros, Losprout, Timstein (control sample), Udarnitsa, Kometa, Etiud, Azhurna -carriers of allele Ppd-B1a; 14, 23 -marker pUC19/MspI  Note. n -number of varieties in the sampling, р -genotype frequency, S p -standard error The marking of varieties from the USA and Canada demonstrated that dominant genes Ppd-1 are present in the genotype of seven out of 12 investigated samples, and allele Ppd-D1a was detected only in varieties Barton and Red River 68. The donor of gene Ppd-D1a for the variety Barton was a Brazilian spring variety, Frontana (Ppd-D1a), created using an Italian winter variety, Mentana, whose parents, in its turn, are a Japanese variety, Akakomugi, and a Dutch variety, Wilhelmina. The variety Red River 68, in whose development a spring variety, Sonora 64, had been used (Ppd-D1a Ppd-В1a), was often used in breeding as a donor of Ppd-D1a, but it did not inherit the second dominant allele Ppd-В1a from the Mexican parent. Allele Ppd-B1a was marked in varieties Big club, Loros (USA), Losprout (Canada). For instance, a Canadian variety, Lorsprout, also has a Mexican variety, Sonore 64, listed among its parental varieties. Varieties Сhul and Transec were detected to have allele Ppd-B1c, inherited by the former of these from the ancient Uzbek variety (1913), and by the latter -from the Chinese variety, Chinese Spring. It is evident that the presence of dominant genes Ppd-1 in the varieties from North America is not a rare event, which is noted in scientifi c literature (Whittal A. et al 2018), but it concerns only allele Ppd-D1a. It should also be noted that no varieties with digenically dominant control of the trait were found among the investigated spring samples from the USA and Canada.
In the sampling of Mexican varieties, allele Ppd-D1a was detected in all the varieties under investigation. It is clear that the distribution of Ppd-D1a among Mexican spring varieties results from the selection under naturally shorter light day, aimed at development a genotype with a poor response to photoperiod. In the pedigree data of varieties Seri-82, Sitta, Sitella, Bobwhite, the donors of gene Ppd-D1a are winter varieties Bezostaya 1, Kavkaz, Avrora. However, most varieties of the sampling inherited allele Ppd-D1a from Mexican or Brazilian spring varieties, whose pedigree data also contain the varieties, created using a Japanese variety Akakomugi. Three Mexican varieties (Alondra, Mexique-45, Turaco) were also found to have allele Ppd-B1a in addition to gene Ppd-D1a in the genotype which is probably caused by the involvement of variety Timstein, a carrier of a three-copy gene Ppd-B1а, in the breeding. It should be noted that no carriers of allele Ppd-B1c were found among the investigated Mexican varieties.
Out of the occasional identifi ed spring samples from South America (a total of three varieties), the most widespread use in the breeding was noted for the variety Frontana, which inherited allele Ppd-D1a from an Italian winter variety, Mentana. A Brazilian variety, Bage, was detected to have allele Ppd-B1c, probably transferred from an Argentinian variety, Chino, created using the variety Chinese Spring. An ancient Argentinian variety, Lin calel (1927), carries only recessive alleles of Ppd-1. Even though the sampling of South American spring varieties is limited, it is possible to assume that ancient varieties had strong response, the decrease in which was achieved during the breeding. Over 70 % of the investigated Argentinian varieties carry dominant alleles of Ppd-1 (Vanzetti LS et al, 2013).
The sampling under investigation has only two Australian varieties, which carry recessive alleles of genes Ppd-1. Cane et al (Cane K et al, 2013) noted a wide variability of Ppd-genotypes in Australian wheat varieties. For instance, the authors demonstrated the presence of monogenically dominant Ppd-D1а, or Ppd-B1a, or Ppd-B1c and digenically dominant varieties, carriers of multi-copy genes Ppd-B1 in the combination with gene Ppd-D1a, and the varieties with strong photoperiod-sensitivity, where only recessive alleles are present.
High variability of Ppd-genotypes was demonstrated for Asian varieties, the sampling of which was small. Three Indian varieties were identifi ed, out of which the ones, widely used in the breeding, were Kalyansona -recessive Ppd-1 genotype, Sonalika -digenically dominant in genes Ppd-D1a Ppd-B1a. Line С591 has allele Ppd-B1a. Among Japanese varieties, Norin 29 was detected to have gene Ppd-B1c, varieties Norin 61 and Norin 17 -Ppd-D1a; Shiroganekomugi, Zenkojkomugi were shown to have a combination of alleles Ppd-D1a and Ppd-B1a, Konosu-25 -Ppd-D1a and Ppd-B1c. The sampling of Japanese spring varieties was not found to have samples with the presence of only recessive allele Ppd-1 and the varieties with monogenically dominant Ppd-B1a-control, which is likely to result from a limited sampling. At the same time, (Seki M et al, 2013) demonstrated that most (90 %) Japanese spring wheat varieties did not carry photoperiod-sensitive alleles of genes Ppd-1. In Korea, the varieties-carriers of genes Ppd-B1b and Ppd-D1a (Eun et al 2015) are mostly wide-spread. All 59 Pakistani spring varieties, investigated by M. Iqbal (Iqbal M et al, 2011), with a single exception, carry gene Ppd-D1a.
African varieties are presented in a limited number, including three varieties from Kenya. The variety Beacon was identifi ed to have allele Ppd-D1a, inherited from the variety Frintana, and the variety Salmayoallele Ppd-B1a, most probably inherited from its Mexican parent. A recessive status of photoperiod genes was demonstrated for the variety Kenia farmer, widely used in the breeding of Australian and American varieties.
The results of marking spring varieties from the CIS countries and Ukraine are of most interest. The sampling of Russian spring varieties mainly included ancient local varieties and those, developed in the late previous century in the Volga region, Western Siberia, and the Urals. No variety from this sampling had allele Ppd-D1a. Likhenko et al. (Likhenko IE et al, 2014) analyzed 48 modern early-maturity and mid-early spring bread wheat varieties from Siberia and found only one variety Tulun 15, which carried allele Ppd-D1а. All the remaining ones had allele Ppd-D1b in the genotype. At the same time, the marker analysis demonstrated that Russian varieties Udarnitsa and Kometa had allele Ppd-B1a in their genotype, and varieties Zhnitsa and Strela -allele Ppd-B1c. Four varieties from northern Kazakhstan, investigated by us, carry recessive alleles of genes Ppd-D1 and Ppd-B1, and by the phenotype, they are characterized as strongly photoperiod-sensitive genotypes .
Contrary to the varieties from Russia and Kazakhstan, Ukrainian spring varieties have both ancient and modern varieties, created in this century. In the investigated sampling of Ukrainian varieties, allele Ppd-D1a was detected in 6 varieties, three of which -Azhurna, Elehia myronivska, Etiud -were found to have allele Ppd-B1a in addition to allele Ppd-D1a in the genotype. The variety Struna myronivska carries only allele Ppd-B1c, and this allele was inherited by the latter from one of parental varieties -a winter variety, Ekspromt. The variety Etiud was developed by crossing the variety ТАМ-200 (USA) and a Mexican spring variety, Turaco (Ppd-D1a Ppd-B1a-genotype). Parental genotypes of the variety Elehia myronivska are a spring variety, Maris Dove (Great Britain), and a winter variety, Myronivska 40. As British varieties are traditionally the ones with the highest photoperiod-sensitivity, the donor of two dominant genes may be a winter variety, Myronivska 40, created using a Mexican spring variety, Siete-Cerros. In general, spring varieties of different climatic zones of Ukraine were shown to have a wide distribution of allele Ppd-D1b. According to actual data, almost all modern winter wheat varieties of Ukrainian breeding, including the ones, created in the south of Ukraine, carry allele Ppd-D1a . The results of the marker analysis and the pedigree data demonstrate that until the last decade of the previous century the varieties with high photoperiodsensitivity prevailed among spring varieties both in Ukraine in most European countries. The decrease in the response from some modern spring varieties may be a targeted process, but there might be a possibility of a chance in these events, which is conditioned by the application of parental genotypes of the carriers of dominant genes Ppd-1. The urgency of creating genotypes with poor photoperiod-sensitivity requires the study of the impact on development rate of both specific alleles and Ppd-genotype in general, which may be facilitated by the information, obtained while marking the varieties of Ukrainian and foreign breeding.
In this study, Ppd-1 genotypes were characterized only from the standpoint of the presence of dominant Ppd-D1a, Ppd-B1a and Ppd-B1c, which have a more considerable infl uence on the increase in the photoperiod-sensitivity. Allele Ppd-A1a.1 is absent from the investigated spring varieties, and its distribution in the global assortment is limited. The donor of this allele is considered to be an ancient variety, Purplestraw (1822), and Purcam, used in the breeding in the USA, and later in the breeding of Japanese varieties (Seki M. et al 2013). In addition to alleles Ppd-B1a (three cop-ies) and Ppd-B1c (four copies), gene Ppd-B1 is known to have one more dominant allele -Ppd-B1d (two copies), which was not marked in this study. The scientifi c data demonstrate that a two-copy gene is sometimes present in bread wheat varieties but is more likely to be in combination with Ppd-D1a. For instance, in spring Australian varieties Ppd-B1d is present only in combination with another dominant gene (Chen F et al, 2013). Due to the low level of polymorphism, reliable PCR-tests for detection of a two-copy allele have not been developed. In some studies, it was suggested that it is relevant to mark dominant Ppd-B1 using microsatellite analysis for loci Xgwm257 and Xgwm148, the difference in allelic status between which are associated with recessive and dominant status of the gene (Chen F et al, 2013;Mohler V et al, 2004). The application of associative markers is possible, but the effectiveness of the analysis is not absolute, especially considering the data of scientifi c literature and the results of marking, obtained in this study. Presuming that Ppd-B1d is present in the combination with Ppd-D1a, the possibility of the presence of carriers of a two-copy cnv-mutant, for instance, in the investigated Ukrainian spring varieties, is incredibly low. There could be single cases of the presence of Ppd-B1d in European varieties under investigation.
Certainly, the variability of Ppd-1 genotypes is not limited by the presence of marked dominant alleles. The varieties of the specifi ed sampling may have allelic differences in terms of genes Ppd-A1 and Ppd-D1 with known mutant recessive alleles. The differentiation between genotypes, carriers of different recessive alleles of Ppd-1 will ensure obtaining more detailed information about Ppd-genotypes of the varieties, presented in this study.

CONCLUSIONS
The carriers of alleles Ppd-D1a, Ppd-B1a, and Ppd-B1c were identifi ed in 137 spring bread wheat varieties of various origin using molecular markers. The highest variability of Ppd-1 genotypes was observed in Asian varieties. The varieties from other regions had from two (Mexico) to four (Europe, the USA, Canada, Ukraine) Ppd-1 genotypes. Most varieties of the investigated sampling are carriers of only recessive Ppd-1 (81 variety). A different ratio of genotypes, carriers of dominant Ppd-D1 and Ppd-B1 (39 and 28 varieties, respectively) is mostly conditioned by the priority use of Ppd-D1a carriers in the breeding. According to the pedigree data, the donor of Ppd-D1a for most varieties was a winter Japanese variety, Akakomugi. Most frequently, the predecessor varieties-donors for alleles Ppd-B1a and Ppd-B1c were varieties Sonora 64, Timstein, and Chinese Spring. The incidence of carriers of the alleles of a three-copy Ppd-B1a is higher than for four-copy Ppd-B1с (20 and 8 varieties, respectively). Modern Ukrainian spring monogenically dominant Ppd-D1а or Ppd-B1c varieties and the varieties with digenically dominant Ppd-D1a Ppd-B1a control were identifi ed. The digenically dominant genotype Ppd-D1a Ppd-B1с was found only in a Japanese variety, Konosu-25. The varieties, identifi ed by Ppd-1 genes, may be used to study the infl uence of specifi c alleles and their combinations on the development tempo and other economic traits, and the application of marker analysis ensures the selection of breeding material with optimal combination of alleles of photoperiod genes.
Adherence to ethical principles. All experiments described in this paper were non animal based. Confl ict of interest. Authors declare no confl ict of interest.
Financing. This study was not fi nanced by any specifi c grant from fi nancing institutions in the state, commercial or non-commercial sectors.