Digital Theses Archive


Tesi etd-03312023-193206

Type of thesis
Approaching the identification of grain yield components controlling genes in durum wheat
Scientific disciplinary sector
Istituto di Scienze della Vita - PHD IN AGROBIODIVERSITY
  • QTL
  • RNA expression
Exam session start date
Wheat grain yield is a complex trait influenced by a variety of genetic and environmental factors. The number of grains per spike, one of the three major components that determine yield, is closely related to the number of fertile spikelets and fertile florets per spikelet. A population of recombinant inbred lines (RILs) resulting from the cross of a Triticum durum cultivar (Latino) and a Triticum dicoccum (MG5323) provides a useful tool for studying this trait because genetic variability in the number of florets per spikelet and spike morphology varies widely across the domestication history of durum wheat. In the present study, spike morphology and florets-related traits were investigated in two environments for three consecutive seasons. The Pearson correlation matrix showed a highly significant and positive correlation between the traits spike weight, total floret number (FRT), net floret (NFRT), total spikelet number (SPK), and net spikelet number (NSPK). There was also a positive and highly significant correlation between the trait spike length and NSPK, SPK, and spike weight. On the other hand, a negative and significant correlation was found between heading date and florets traits. A total of ninety-four QTLs were detected along all chromosomes using high-density genetic map. We identified several genomic regions associated with spike morphology and florets, explaining a portion of the phenotypic variance ranging from 5.9 to 33%. QTL regions were detected for SPK and NSPK on chromosomes 2A, 4A, 4B, 5A, 5B, 6B, 7A, and 7B with stable QTLs on chromosome 2A were detected consistently in all test environments including the multi-environment. In addition, QTL regions for FRT and NFRT were identified on chromosomes 1B, 2A, 3A, 3B, 4A, 4B, 5A, and 6A. Notably, the FRT and NFRT QTL identified on chromosome 2A were consistently and stably detected under all tested environments. The SPK and FRT QTL identified in this study were distinct and non-overlapping. Finally, the release of the reference genome sequence of T. durum allowed us to define the physical interval of our QTL and hypothesize a novel QTL for this study and new candidate genes by examining the gene content of the genomic regions associated with the target traits. A novel QTL on chromosome 4A which is associated with the trait FRT was detected. Known genes involved in inflorescence meristem development and spike morphology, such as FUL2, FUL3, PPD -1, FT2, VRN-B1, and Q-5A, are colocalized in our QTL regions. RNA expression profile of genes involved in inflorescence meristem development across different phases in cultivated durum and emmer wheat. Total RNA was isolated from each developmental phases of the two wheat species and followed by qRT-PCR analysis. The relative gene expression between the two species was investigated. Results showed that there was higher expression of genes such as GNI1B, FUL2A, miR156 in MG5323 than in Latino. In contrast, relatively higher expression of the gene miR172 was observed in Latino. Microdissection of inflorescence meristem on both Latino and MG5323 demonstrated variations in the time required for the onset of double ridge or the transition from vegetative to inflorescence meristem. Post vernalization period, MG5323 revealed that it takes a longer time to switch into the reproductive phase compared to Latino. Moreover, the number of floret meristems formations were higher in Latino (6 to 8) than MG5323 (4). The results suggest that the differences in inflorescence meristem development between the two species may be explained, at least in part, by their differential expression profiles. This study provides a better understanding of the molecular basis of meristem development in wheat and could lead to the development of new breeding strategies.