Wheat breeding is one of the key areas of agricultural research aimed at ensuring sustainable food production in the face of global climate change and the growing world population. Winter wheat holds a significant place in global cereal production due to its high yield and grain quality characteristics. One of the critical aspects affecting the productivity and adaptability of winter wheat is the characteristics of the spike and yield. Research focused on understanding the breeding and genetic basis of spike traits in winter wheat allows the identification of genetic mechanisms governing these traits and facilitates the development of new varieties with improved characteristics.
In recent years, significant progress in this field has been achieved through the application of modern molecular genetic technologies, such as marker-assisted selection (MAS) and high-throughput sequencing. MAS significantly accelerates and improves the accuracy of the breeding process by utilizing molecular markers associated with desirable traits. Its application in winter wheat breeding allows for the effective selection of plants with optimal spike traits, ultimately leading to the creation of high-yielding and stress-resistant varieties. High-throughput sequencing («next-generation sequencing») enables the rapid and accurate sequencing of large amounts of DNA and RNA, the study of plant genomes, and the identification of genes and molecular markers associated with important agronomic traits of the wheat spike. This significantly accelerates the breeding process through precise and large-scale genetic data analysis. This study systematically analyzes the genetic and breeding basis of spike traits in winter wheat, such as the number of grains and the weight of 1000 grains, using marker-assisted selection (MAS) and high-throughput sequencing to analyze genetic variability and identify molecular markers. Special attention is given to the role of microRNAs in regulating grain development and degradome sequencing (as one of the methods of high-throughput sequencing) for identifying genes targeted by microRNAs and annotating their functions.
For the research consisted of the winter wheat varieties Mexican Large Spike (MLS), Bainong 4199 (BN419), and an F2 population (145 plants) created by hybridizing Mexican Large Spike × Bainong 4199.
The research results showed that the parent forms significantly differed in spike traits – the number of grains per spike and the weight of 1000 grains, which corresponds to the principle of parental selection when creating a population for QTL mapping. The traits exhibited a normal distribution and bidirectional segregation, indicating quantitative inheritance. According to the results of the correlation analysis, the number of spikes and the weight of 1000 grains had a highly significant positive correlation with a correlation coefficient of 0.953. A total of 143 pairs of polymorphic markers with distinct differences were tested for polymorphism using 300 pairs of SSR primers. The 143 pairs of polymorphic markers were genotyped, and genetic maps were constructed for the 145 individual plants of the F2 population.
To construct the linkage map, 145 loci of polymorphic SSR markers were used, covering 19 wheat chromosomes, with a total length of 3128.17 cM. The average distance between markers was 25.23 cM, the maximum distance was 113.85 cM, and the minimum distance was 3.57 cM. The genetic density between some markers exceeded 50 cM, which was mainly due to the low density of molecular markers. The distribution of 145 polymorphic marker loci across chromosome groups A, B, and D was uneven. There were 77 marker loci present in chromosome group A, 41 in group B, and only 24 in group D, accounting for 54.22%, 28.87%, and 16.9% of the total number of marker loci, respectively. The SSR markers exhibited the highest polymorphism in chromosome group B and the lowest polymorphism in chromosome group D. Determination and analysis of epistatic QTL loci for number of grains per ear and thousand grain weight showed that nine epistatic QTL loci associated with number of grains per ear and thousand grain weight were identified, which were distributed on chromosomes 1B, 2B, 2D, 3B and 6B, including four associated QTL loci on chromosome 3B, two associated QTL loci on chromosome 6B. and one associated locus each on chromosomes 1B, 2B and 2D. This allows explaining 4.922%~21.1044% of phenotypic variation for the number of grains per ear. QGNS~1B and QGNS~3B2 had large genetic effects and were the main loci explaining 21.1044% and 15.8886% of phenotypic variation. One additive QTL locus controlling thousand grain weight was found at QTGW~3B, which explained 11.4727% of the phenotypic variation.
