Abstract
<jats:p>Buckwheat (Fagopyrum esculentum Moench) is a pseudocereal crop and a valuable food resource widely used in many regions of the world. It is currently gaining popularity due to its excellent nutritional qualities and the absence of gluten in its seeds. Studying photosynthetic activity has important practical implications for breeding programs, as it allows for more targeted selection to improve the productivity of varieties. Buckwheat photosynthetic activity is crucial for yield formation. The study material consisted of 140 varieties of common buckwheat (Fagopyrum esculentum Moench subsp.) of various ecological and geographical origins: Canada, China, Japan, Kazakhstan, Russia, India, Brazil, Belarus and South Africa. This article presents the main results of an assessment of the photosynthetic activity of 140 buckwheat accessions based on photosynthetic activity indices obtained using a portable gas exchange (MINI-PAM-II/B) and chlorophyll fluorescence measurement system. The MINI-PAM-II/B is a portable pulsed fluorimeter that operates using the pulse-amplitude modulation (PAM) method used to study photosynthesis processes. Measurements were taken on the 3rd to 4th leaf from the top of the main stem of five intact plants in real time. The plant development stage (emergence, budding, flowering), leaf position in the layer (upper, middle, lower), and time of day were taken into account, in accordance with the guidelines. With the onset of the phenophases, 92.5% of the studied collection showed a trend toward increasing photosynthetic activity, ranging from 4.78 to 9.51 μmol CO₂/(m² s). Based on the results of a photosynthesis intensity study during the budding phase, the highest index was observed in the Northern Chinese accession, with an index of ≤10 μmol CO₂/m² s. Photosynthetic system indices can change during the growing season and depend on environmental factors. Therefore, to increase yields, breeding efforts must be conducted taking these indices into account.</jats:p>