APPLICATIONS OF DIGITAL IMAGING IN PLANT PHENOTYPING: MORPHOLOGY, PHYSIOLOGY, AND GENOTYPING

Plant phenotyping using digital imaging plays a crucial role in many aspects of plantsciences, from determining plant morphology and physiology which can then be used in determining phenotype-genotype associations. In the current work, three main studies were conducted using digital imaging. In the first study, three alleles were sequenced of a SUN family gene believed to control fruit size and shape in watermelon (Citrullus lanatus). KASP assays (SUN2-1 and SUN2-2) were developed as molecular tools to distinguish three ClSUN2 alleles (WT, KBS and DEL) and their effect on ovary and fruit shape traits were determined in both a cultivar panel and segregating populations. Digital imaging was used to collect information about fruit size and shape of watermelon in three separate populations to validate the KASP assays. The second study involves two experiments using plants that were phenotyped using digital images: one investigating the effect of supplemental far-red light (700-800 nm) gradient over a narrow photosynthetic photon flux density (PPFD; 400-700 nm) and the other investigating the effect of supplemental far-red light over a broader range of PPFD. The far-red gradient study showed that increasing supplemental far-red light increased leaf length and width which was associated with increased projected canopy size (PCS). The higher PCS was associated with increased cumulative incident light received by the plant, which increased dry matter accumulation. In the perpendicular gradient study, far-red light was 57% and 183% more effective at increasing the amount of light received by the plant, as well as 92.5% and 162% more effective at increasing plant biomass at the early and late harvests, respectively, as compared to PPFD. The third study utilized a chlorophyll fluorescence imaging system to detect herbicide induced stress before otherwise visible. The pixel intensity was calculated from the images and was negatively correlated with the quantum yield of PSII (p < 0.0001) and positively correlated with fluorescence measurements acquired through a reflectance system (p < 0.0001). The last chapter contains a theoretical framework to produce a cheaply producible photodiode array that could help detect the amount of light in an area.