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The initial photochemical quantum efficiency of photosystem II (Fv/Fm) and performance index (PI), describing the ability of the photosynthetic apparatus to collect light energy, have been used to screen tolerance to drought stress by ten maize accessions, monitored by leaf relative water content (RWC) and soil water content (SWC). The Fv/Fm, PI, and RWC values were significantly reduced in drought-stressed plants. The analysis of chlorophyll a fluorescence induction rise from the basic dark-adapted fluorescence yield to the maximum (OJIP transient), distinguished accession Zea 1006 from Libya and Zea 612 from Italy, as the most tolerant and the least tolerant genotypes. The maize genotypes were classified using the Principal Component Analysis (PCA) and clustering methods, based on Fv/Fm and PI values, leaf RWC and SWC. Genotypes from Egypt and Libya were differentiated from genotypes from Europe, Russia and the USA.
Badr et al. (2020) studied this question.