Aims: To find the relationship between the non-destructive and destructive methods for the evaluation of photosynthetic pigments under field condition concerning heat stress conditions. Study Design: The crop was sown in factorial randomized block design in three replication. Place and Duration of Study: The experiment was conducted during the (2016-2018) rabi crop season for two years. The crop was sown under timely and late sown condition in the research farm of Department of Plant Breeding and Genetics, Punjab Agricultural University, Ludhiana Methodology: In the present investigation forty-nine advanced breeding lines of Indian mustard were sown under two planting conditions. The data recorded for photosynthetic pigments by calorimetric method by non-destructive methods at three crop stages i.e vegetative, flowering and siliquing. The relationship between these parameters was carried out by correlation and regression analysis. Results: Regression analysis indicated a non-linear relationship at vegetative stage under both sowing conditions, but at flowering stage, slope of the relationship increased with increasing SPAD and a linear relationship was observed (R2= 0.0362) as compared to vegetative stage. A significant and strong correlation was observed between total chlorophyll (siliquing stage) and SPAD value (flowering stage) in timely sown crop. Positive correlation existed between SPAD value and total chlorophyll at flowering stage and carotenoid content at siliquing stage. Conclusion: The variation in the SPAD value and chlorophyll value is strongly related with the species, distribution of chlorophyll in leaf and hence chloroplast also. The lower value of regression coefficient and insignificant values of correlation might due to non-destructive SPAD values under field condition and sampling for calorimetric estimations.
