Differential germination pattern of rice cultivars resistant to imidazolinone herbicides carrying different acetolactate synthase gene mutations

Goulart ICGR, Matzenbacher FO & Merotto A JR (2012). Differential germination pattern of rice cultivars resistant to imidazolinone herbicides carrying different acetolactate synthase gene mutations. Weed Research52, 224-232. Summary Different mutations in the acetolactate synthase (ALS) gene can affect the germination pattern and facilitate the occurrence of ALS-inhibiting herbicide resistance in weedy red rice. The aim of this study was to evaluate the germination rates in imidazolinone-resistant rice cultivars carrying three different ALS gene mutations. Plant material consisted of the imidazolinone-resistant rice cultivars IRGA 422 CL, PUITA INTA CL and SATOR CL that carry the ALS mutations Gly654Glu, Ala122Thr and Ser653Asn, respectively, and the susceptible cultivar IRGA 417. Initially, the germination pattern of these cultivars was evaluated at temperatures of 15, 20, 25 and 30 degrees C. Afterwards, five lots of each cultivar were evaluated at temperatures of 20 and 25 degrees C to separate the environmental and genotypic effects. The environmental effect related to the different seed origin did not affect the germination rates of the rice cultivars. However, the germination pattern of the evaluated cultivars was different, mainly at 20 degrees C. The time to reach 50% germination at 20 degrees C for the imidazolinone-resistant rice cultivars IRGA 422 CL, SATOR CL and PUITA INTA CL was 6, 16 and 24 h earlier, respectively, than the susceptible cultivar IRGA 417. The PUITA INTA CL cultivar, which carries the mutation Ala122Thr, showed faster germination than the other herbicideresistant and the susceptible cultivars at 20 degrees C. The faster germination that resulted from the resistance to ALS-inhibiting herbicides could have different consequences for the establishment and competition of weedy red rice.