A multi-faceted approach involving laboratory assay, glasshouse, and field experiments in identifying stem rot (incited by Sclerotium rolfsii Sacc.) resistance in advanced breeding lines of groundnut

Stem rot disease, caused by Sclerotium rolfsii Sacc., is a major impediment to groundnut production in Asia, sub-Saharan Africa and the Americas. The present study focused on identifying potential sources of resistance by screening a set of groundnut advanced breeding lines in laboratory, glasshouse, and field conditions. Two experiments in a glasshouse and a field were conducted during the rainy seasons of 2022 and 2023 at ICRISAT, India. Disease incidence was recorded at 15, 30, 45, and 60 days after inoculation. The results identified five lines–ICGV 171025, ICGV 181035, ICGV 181458, ICGV 211107, and ICGV 171002–as moderately resistant, with less than 30% incidence. The remaining lines were susceptible, with more than 30% incidence in both field and glasshouse experiments. In the laboratory experiment, the response to oxalic acid assay was conducted using detached stems (laterals and mains), and the results revealed differential reaction after immersing in 0-, 20- and 50-mM oxalic acid, and the response was recorded at 12-, 18-, and 24-hours intervals. Significant wilt symptoms were observed at 24 h for laterals and mains in 20mM oxalic acid concentration, whereas in 50mM concentration wilting was exhibited at 18-hour intervals for laterals and 18 to 24-hour intervals for main stems when compared to control. Four lines–ICGV 171025, ICGV 181035, ICGV 171002, and ICGV 211107–were reconfirmed as moderately resistant through this assay, consistent with field and glasshouse findings.