Deciphering inter-relationship between disease incidence and disease severity and prediction of yield loss in lentil-stemphylium pathosystem

Exploring the relationship between disease incidence (DI) and disease severity (DS) of Stemphylium blight (SB) in lentil, the study aimed to assess the feasibility of using DI as a predictive measure for DS, reducing workload of disease quantification while ensuring accuracy. Quantifying disease is a critical task in field surveys, resistance breeding programs, and timely disease management strategies. Data on DI and DS of SB were collected from 35 different genotypes of lentil over three consecutive years, enabling the development of mathematical model which was validated using the widely cultivated lentil variety ‘Moitree’ (WBL 77) grown in West Bengal. The quadratic regression model, derived from independent datasets on DI and DS of genotypes, demonstrated a highly satisfactory fit, expressed as Y = −16.17 + 1.849X − 0.008X2; R2 = 0.95. This model showcased remarkable consistency across multiple growing seasons under varying disease pressures, confirming its reproducibility for other lentil varieties too. Critical point of DS (with cut-off value = 0.395) was also determined to take up timely crop protection measures. Yield loss estimations revealed for every unit increase in DS, an estimated 13.34 kg/ha yield loss could be expected, aligning well with observed field data.