Paulo H da Silva Santos1,2, João R Vieira Manechini2, Carlos Kantack2, Mauro Xavier2, Samira Domingues Carlin Cavalari2, Dilermando Perecin1, Thiago G Marconi4, Leandro G Marconi4, Elisson Romanel5 and Luciana R Pinto1,2
1Faculdade de Ciências Agrárias e Veterinárias, UNESP, Campus Jaboticabal, Brazil
2Instituto Agronômico de Campinas, Centro de Cana, Ribeirão Preto, Brazil
3Departamento de Biotecnologia, Escola de Engenharia de Lorena/Universidade de São Paulo, Lorena, Brazil
4Fenotipagem Digital Serviços Agrícolas – Votuporanga, SP, Brazil
5EEL/USP, 12602-810, Lorena-SP, Brazil
High-throughput phenotyping (HTP) using unmanned aerial vehicles is a valuable approach to accelerate the collection of phenotypic data in large field trials. Our primary objective was to investigate the differences between early (EF) and late (LF) sugarcane flowering time groups in an association mapping panel based on vegetation indices (VI), such as canopy cover (CC), excess greenness (EXG), plant volume and plant height obtained from RGB images, and stalk number by manual counting. The experiment used an augmented block design at the IAC Sugarcane Crossing Station (Uruçúca, Bahia, Brazil) and images were captured at the first ratoon cane from August 2023 to June 2024 using a DJI Mavic 3 Enterprise. Agisoft Metashape and QGIS were used for orthomosaic assembly of raw RGB images and VIs estimation, respectively. There was a significant difference in the CC and EXG indices between the EF and LF groups during October to February (p < 0.05), while there was no significant difference during the inflorescence emission phase (April-May). Plant height and volume showed no significant differences between EF and LF groups. There were significant differences among genotypes (p = 0.0006) regardless of their flowering time group for stalk number. The stalk number (68.99) was higher in the EF group than in the LF group (53.10) (p < 0.05), with differences within the genotypes of the EF group (p = 0.0009). The average CC and EXG over the months showed a pattern consistent with the expected phenological development of sugarcane in both flowering time groups. The CC and EXG indices increased during the first months of plant development (August to December), corresponding to the phenological growth phase, reached a maximum in February, and decreased thereafter. Our results suggest that the CC and EXG indices are potential candidates for phenotypic measures to be used in association mapping studies for flowering time in sugarcane.