Correlation between photosynthetic traits and yield in sunflower

The impact of sowing dates (early, normal and late) on the crop physiological parameters (leaf area index (LAI), chlorophyll content (SPAD)) and yield of sunflower cultivars (NK Neoma, NK Ferti, PR64H42) was observed in 2012, 2013, and 2014 on chernozem soil in Eastern Hungary. The obtained LAImax values were 5.1-5.3 m2/m2 (early sowing date), 4.5-5.2 m2/m2 (normal sowing date) and 4.4-5.2 m2/m2 (late sowing date). Pearson's correlation analysis revealed a close negative correlation between LAImax and sowing date in 2013 and 2014 (r = -0.920**,r = -0.813**) and an average, non-significant correlation between LAImax and sunflower yield (r = 0.575ns, r = 0.509ns). The relative chlorophyll content was not significantly affected by either growing year, sowing date or genotype in the period between May and July (~40). In the case of high infection index (Ii) values (2012), sunflower cultivars had the highest yield in the late sowing date (4.3-5.3 t/ha). However, average Ii values (2013) were associated with the highest yields in normal sowing date (5.1-5.3 t/ha) and moderate Ii values (2014) showed the highest yields in early sowing dates (4.6-5.1 t/ha).