Physiological traits can help explain cassava’s (Manihot esculenta Crantz) health and identify superior genotypes for breeding programs. The study objective was to evaluate the performances of various cassava genotypes based on chlorophyll fluorescence, total crop dry weight, and storage root dry weight. The 100 cassava genotypes grown under field conditions ensued from May 2020 to May 2021 (2020–2021) and from May 2021 to May 2022 (2021–2022) at the Field Crop Research Station of Khon Kaen University, Thailand. The chlorophyll fluorescence measurements commenced 3, 6, 9, and 12 months after planting (MAP). Recording of storage root and total crop dry weights occurred at 12 MAP. The results revealed that the appropriate time to observe chlorophyll fluorescence was at 6 and 9 MAP, relating to cassava’s dry weight at the final harvest. Huay Bong 90 proved a superior genotype for storage root and total crop dry weights at 12 MAP and chlorophyll fluorescence at 6 and 9 MAP for both growing season years. A genotype CMR 38-125-77 also performed well in chlorophyll fluorescence for both growing seasons, and it was a distinct top genotype for the 2020–2021 growing season and ranked third for the 2021–2022 growing season based on total crop dry weight at 12 MAP. These genotypes could benefit as an alternative germplasm for cultivation and future breeding programs.

Keywords: Breeding, cassava (Manihot esculenta Crantz), dry weight, physiology, selection, storage root

Key findings: The appropriate growth stages to evaluate chlorophyll fluorescence that relate to dry weight at the final harvest of cassava (M. esculenta Crantz) germplasm were 6 MAP for F_v‘/F_m‘ and 6 and 9 MAP for F_v/F_m. Cassava germplasm classification for this study depended on F_v‘/F_m‘, F_v/F_m, total crop dry weight, and storage root dry weight. The desirable cassava genotypes for both growing seasons were Huay Bong 90 and CMR 38-125-77.