Screening of Saccharum spp. genotypes for sugarcane yellow leaf virus resistance by combining symptom phenotyping and highly precise virus titration

Abstract Yellow leaf disease (YLD), caused by sugarcane yellow leaf virus (SCYLV), has been reported to infect sugarcane worldwide causing significant yield losses and is considered a major disease of this crop. A panel composed of 98 genotypes encompassing basic germplasm, commercial cultivars, and elite clones was assayed in the nursery and a replicated field for resistance to SCYLV, combining symptom expression and virus quantification. Virus symptom intensity was evaluated using a diagrammatic scale while virus titer was estimated by DAS-ELISA (Double Antibody Sandwich-ELISA) and RT-qPCR (Reverse Transcription Quantitative PCR) in the nursery and field trials, respectively. Resistance was evaluated alongside symptom development kinetics. Based on the symptom intensity, 52 (53.06%) genotypes were classified as resistant in the nursery and 42 (42.86%) in the field. Twenty-nine (29.59%) genotypes showed no symptoms in the nursery and field trial. Moderately resistant genotypes showed a low correlation between virus titer and symptom intensity. The kinetics of symptom development increased over time in moderately susceptible and susceptible genotypes. The SCYLV incidence assessed by RT-qPCR was 92.55%, which was detected in 83% of the asymptomatic genotypes. The broad-sense heritability based on symptom expression and relative quantification was 52.62% and 68%, respectively. The virus quantification assays allowed for the identification of potential genotypes immune to SCYLV.