Testing of black nightshade (Solanum nigrum L.) on resistance to triazine herbicides

Abstract

Herbicide resistant weed biotypes usually occur after repeated application of herbicides. Atrazine was used in Serbia for many years and after its ban in 2006, herbicides with the same mode of action containing terbuthylazine started to be used for control of broadleaved annual weeds in maize. The aim of the study was to testa sensitivity of Solanum nigrum L. to PS II inhibiting herbicides. Seeds of the tested populations were sampled from sites on which atrazine had been continuously used (R) and from sites on which herbicides had never been used before (S). The PSII herbicide terbuthylazine (500 g l-1 a.i.) was applied as a commercial formulation by cabinet sprayer at rates of 187.5, 375, 750 and 1500 g of a.i per ha at the 4 leaves stage, and the chlorophyll fluorescence was measured one hour, one day and two days after treatment. Maximum quantum efficiency of PS II photochemistry (Fv/Fm) was calculated. The PCR analysis was also conducted with designing of specific primers for psbA gene. The R population plants were more tolerant than S population after application of all terbuthylazine rates, except for the highest. One day after herbicide application, the Fv/Fm values were higher for R (0.588) than for S population (0.405) at recommended rate. The sequence analysis did not show the nucleotide exchange in the specific region of the psbA gene responsible for resistance and we did not prove that the resistance is target site based.

Rezistentni biotipovi korova se najčešće javljaju nakon višegodišnje primene herbicida. Nakon zabrane primene atrazina, 2006. godine, u upotrebu je uveden terbutilazin, herbicid iz grupe triazina sa istim mehnizmom delovanja - zaustavljanjem procesa fotosinteze putem blokade transporta elektrona u PS II. Cilj rada je utvrđivanje rezistentnosti vrste Solanum nigrum L. na PS II inhibitore. Semena S. nigrum su uzorkovana sa mesta na kojima nikada nisu primenjivani herbicidi (potencijalna S populacija) i sa mesta na kojima je atrazin primenjivan kontinuirano dugi niz godina (potencijalna R populacija). Herbicid na bazi terbutilazina (500 g l-1 a.m.), je primenjen kao komercijalna formulacija u količinama 187,5, 375, 750 i 1500 g a.m. po ha, u fazi 4 lista korova. Fluorescencija hlorofila je zatim merena 1 sat, 1 dan i 2 dana nakon tretiranja i izračunata je maksimalna kvantna efikasnost PS II (Fv/Fm). Nakon toga, PCR analiza je sprovedena korišćenjem specijalno dizajniranih prajmera za psbA gen. Biljke R populacije su bile tolerantnije na delovanje herbicida i razvile veću biomasu u odnosu na biljke S populacije.Vrednosti maksimalne kvantne efikasnosti (Fv/Fm) su, dan nakon primene terbutilazina u preporučenoj količini, bile veće kod biljaka R populacije (0,588) nego kod biljaka S populacije (0,405). Analiza sekvenci genoma nije pokazala da je došlo do promene u nukleotidu u specifičnom regionu psbA gena odgovornog za rezistentnost prema triazinskim herbicidima tako da nije potvrđeno da je osnova povećane tolerantnosti ili rezistentnosti vrste S. nigrum prema triazinskim herbicidima genetska modifikacija u mestu delovanja.