Identification Of Vernalization Photoperiod Genes And The Process Of Young Spike Differentiation In Kazakhstan Wheat

Wheat(Triticum aestivum L.)is an essential grain crop with a wide distribution,diverse ecological types and distinctive characteristics of regionalised cultivation.Vernalization and photoperiod genes are important genetic factors influencing wheat tassel and flowering and are closely related to wheat adaptation;the length of the differentiation period of young spike development,an important period in the morphological establishment of the wheat spike,is a major difference in the composition of the yield structure of wheat.The vernalisation and photoperiod genes of Kazakh wheat germplasm were identified and the effect of sowing date on the differentiation process of young spikes and the main agronomic traits was studied,which is important for its introduction and selection of breeding material.In this study,the vernalization genes Vrn-A1,Vrn-B1,Vrn-D1 and photoperiod genes PpdA1,Ppd-B1 and Ppd-D1 were identified in 65 Kazakhstan wheat germplasm to clarify their distribution frequencies and allele combinations;18 of these germplasm were used as materials,winter wheat varieties(XN 511,PB 151 and XN 866)and spring wheat germplasm(DX 48,NC35 and XC 8).The effects of three sowing treatments on the differentiation process,yield and quality of young spikes were studied on 3 October 2022(S1),16 October 2022(S2)and 29 October 2022(S3)to provide a theoretical basis for seed introduction and rational selection of parental materials.The results of the study are as follows:1.Polymorphism analysis of four vernalization loci(vrn-A1,vrn-B1,vrn-D1 and vrn-B3)identified a total of eight alleles,including vrn-A1,vrn-A1 a,vrn-B1,vrn-B1,vrn-D1,vrn-D1,vrn-B3 and vrn-B3 b.Among the vernalization loci,the recessive allele distribution was dominant.The four vernalisation loci constituted a total of six allelic combinations in all Kazakhstan wheat,with the vrn-A1/vrn-B1/vrn-D1/vrn-B3 vernalisation gene combination dominating at 46.2 %.2.A total of four polymorphisms were identified at the photoperiodic gene Ppd-D1 locus,resulting in ten haplotypes(Ppd-D1＿Hapl＿I-Ppd-D1＿Hapl＿X).Of these,haplotype PpdD1＿Hapl-I(photoperiod insensitive type)had the highest proportion of 56.9 % of the 65 Kazakh wheat germplasm.At the Ppd-B1 b locus,55 materials were photoperiod-sensitive Ppd-B1 b and 10 materials had no PCR amplified bands.The Ppd-A1 b locus was the photoperiod-sensitive Ppd-A1 b for all materials.3.The rate and duration of differentiation at different stages of spike differentiation differed significantly between the materials.The differences among the materials were small at the monocot stage,increased after the dichotomous stage and became smaller when they entered the pharmacophore stage.Most of the Kazakh wheat germplasm showed an overall "slow and then fast" differentiation process;germplasm 19XW004,19XW006,19XW005,19XW007,19XWB07 and 19XS024 were slow in all stages of development,while 19XS010 and Astana were faster in all stages.19XS010 and Astana were faster at all times.The winter wheat control varieties showed an overall "fast then slow" development,while the spring wheat control varieties all developed faster.4.The sowing period significantly affected the process of young spike differentiation in Kazakhstan wheat germplasm,with late sowing shortening the time of young spike differentiation.Under S1 and S2 sowing,the spike differentiation process showed a general trend of "slow then fast";under S3 sowing,the spike development process was accelerated in all cases;after the florets were differentiated,the development process did not differ significantly among the three sowing stages.However,the timing of the spikelet development process was not sensitive between varieties and between different sowing dates for the same variety.As sowing was delayed,the duration of each differentiation period of the young spike of the main stem before the androgynous differentiation period was significantly reduced,and after the androgynous differentiation period,the differences in the differentiation of the young spike between different sowing periods gradually decreased,shortening the whole time of the differentiation of the young spike.5.The number of spikelets per acre of different wheat germplasm tended to decrease as sowing was delayed due to the different sensitivity of different materials to different temperature and light responses due to their own specificity.Early sowing increased the number of spikes per mu of winter and semi-winter wheat,while late sowing increased the number of spikes per mu of weak spring wheat,indicating that late sowing of weak spring wheat germplasm can make full use of temperature and light resources to improve the decline in the number of spikes due to late sowing,so as to achieve a coordinated development of the three elements of yield composition.The thousand grain weight of Xinnong 511 was more stable in different sowing periods,while the thousand grain weight of Pubing 151 and Xinnong886 decreased under late sowing conditions.Early sowing is beneficial to the accumulation of protein and wet gluten content in wheat grain,while starch content changes relatively little with delayed sowing,so appropriate sowing adjustments can improve wheat yield and quality.