Regeneration capacity after exposure to freezing in wild oat (Avena ludoviciana Durieu.) and turnipweed (Rapistrum rugosum (L.) All.) in comparison with winter wheat

Abstract

Wild oat (Avena ludoviciana Durieu.) and turnipweed (Rapistrum rugosum (L.) All.) are the most important annual weed species of winter wheat (Triticum aestivum L.) in the Khorasan Razavi province of Iran. This study investigated freezing tolerance in wheat (cv. Mihan) and these two weeds based on electrolyte leakage (EL), survival (SU), regrowth characteristics and maximum photochemical efficiency of photosystem (PS) II (F'v/F'm). Significant differences in EL% at freezing temperatures were noted between these plant species. By decreasing the freezing temperatures, EL% of the leaf in all three plants was increased. The lowest and the highest temperature causing 50 % EL (TEL50) of leaves belonged to wild oat (−16.6℃) and wheat (−15℃), respectively. At a temperature of -12℃, SU% of wheat and turnipweed decreased by 15 % and 20 % compared to the SU% at 4℃, respectively. However, the decrease in SU% in wild oat from 4℃ to −12℃ was not significant. Lethal temperature for 50 % SU (LT50su) of wheat, wild oat, and turnipweed was −13.7, −14.3, and −13.5℃, respectively, and there was no significant difference between wheat and turnipweed. A general trend observed in our study was that species with higher freezing tolerance scores had a higher regrowth capacity. During the first 24 h after the freezing treatment, the F'v/F'm levels in wheat, wild oat, and turnipweed decreased by 33 %, 33 %, and 28 %, respectively, compared to before the freezing stress. Therefore, the presence of these weeds in wheat fields after freezing stress will be possible. Under optimal conditions and lack of integrated weed management programs, these weeds, especially wild oat, will emerge, set seeds and enrich the soil seed bank and thereby continue to be a problem in the cold climates of Iran, especially in the Khorasan Razavi province. Winter weed management using tillage, non-successive planting of annual winter crops, and crop rotation will reduce the dispersal of these weeds.