Relationship Between Spad Value and Grain Yield Can Be Affected by Cultivar, Environment and Soil Nitrogen Content in Wheat

SPAD-502 (Minolta Ltd, Osaka Japan), a hand-held chlorophyll meter is widely used in the synchronization of N supply with actual crop demand, however it is also known, that genotype and environment may effect SPAD value. Consequently, the aim of this study was to evaluate the genetic and environmental variation in SPAD value and to determine the relationship between SPAD value at heading (GS 59) and grain yield. Field experiments were conducted in three consecutive cropping seasons between 2012 and 2015 in Hungary and forty winter wheat varieties were tested at two nitrogen levels. Strong significant positive correlation was found between grain yield and SPAD values, but it was highly influenced by cultivars. The proportion of the phenotypical variance explained by the cultivars was different in each growing season and was ranged from 12.50 to 59.04 %. Additionally, it was revealed that the cultivars can be categorised by different SPAD-yield relationship and modern cultivar can be separated into five groups. While same SPAD value can predict different yield level in different cultivars it can be concluded, that SPAD value should be calibrated for cultivar. Based on regression analysis, such an option is also presented here for forty important wheat cultivars. Hence, cultivar specific SPAD value at heading can provide a more accurate estimate of the final yield in wheat.