Early phytotoxic effects of sulfonylurea herbicides in maize lines

Abstract

Maize lines are susceptible to various stressful conditions. One of the main problems in maize seed production is weed control, since there are no herbicides registered for use in maize seed crop, while the herbicides commonly used in hybrid crop could express phytotoxicity to maize lines. The susceptibility of six maize lines to sulfonylurea herbicides (Motivell 6 OD – H1 and Equip – H2), applied in recommended dose – RD and double dose –DD was tested during 2015 and 2016. Herbicides were applied in 5-6 leaves phase (15-16 BBCH). Aboveground parts of maize plants were sampled for phytic phosphorus (Pphy) determination 48 hours after herbicide application. Grain yield was determined after harvest. Irrespective to the variations in grain yield between years, H1 treatment in average increased grain yield of L1, L3, L5 and L6 (mainly in RD) and decreased yield of L2 and L4, while H2 increased average grain yield of L3, L4 and L6 and decreased it of L1, L2 and L5, with slightly higher values obtained by DD, when compared to control. H1 treatment induced mainly decrease in Pphy concentration, while H2 induced increase in Pphy concentration in comparison with control, as a consequence of induced stress. This was underlined mainly by DD of applied herbicides. Variations in Pphy concentration in maize leaves showed significant and positive correlation with grain yield in L2, L3, L4 and L6, while the correlation was negative in L1 and L5. In those lines, H2 mainly induced yield reduction. The highest yield reduction by both herbicide treatments were obtained in L2, line with the highest Pphy increase induced also by herbicides, which defines it as a sensitive genotype. For its production, sulfonylurea herbicides are not recommendable for use.