Genotype-environment interaction in the variability of yield associated indices under stress conditions in sunflower

Abstract The impact of biotic (infestation with the Orobanche cumana) and abiotic stress (drought) factors on the productivity indicators of sunflower hybrids was evaluated in two years, 2020 and 2021, which were significantly different regarding to the weather conditions. The Principal Component Analysis (PCA) was applied on 10 parameters: plant height (PH); leaf number (LN); leaf area (LA); seed yield (SY); leaf area index (LAI); chlorophyll a content (Chla); chlorophyll b content (Chlb); carotenoids content (Car); chlorophyll pigment ratio (Chla/b); total of chlorophyll pigments (Chla+b), that are directly or indirectly associated with the productivity of sunflower hybrids. The first two PCs explained 75 % (drought stress for 2020) and 83 %, respectively (stress caused by broomrape infestation), of the total variance of parameters or hybrids. A higher number of positive correlations were identified between the studied morpho-physiological indices differentiating the hybrids. The SY index correlated with PH, LN, LAI, LA (r = 0.54–0.78) under biotic and abiotic stress. Also, seed yield related with the content of pigments (r = 0.65–0.79) in the case of infested hybrids with broomrape. The infested hybrid H11, in both years, showed the highest values for most of the analyzed indices, indicating a relatively high degree of tolerance to the combined stressors.