Resistance to pre-harvest seed sprouting in different cultivars of rice (Oryza sativa L.)

In order to evaluate and identify theresistant cultivars of rice (Oryza sativa L.) to pre-harvest sprouting, this study was conducted in a randomized complete block design with three replications in a personal farm located at the lalevajesar village, Bandar Kiashahr, Guilan province, Iran in2014. Twenty cultivarswere investigated including 16 local cultivars and 4 improved cultivars. Heading date, flowering date and seedling growth stage of Zadoks92 were recorded on the field. The spikes were harvested at Zadoksstage 92 and the seeds moisture content was measured immediately after harvesting.Two methods were used to evaluate pre-harvest sprouting including sprouting score and sprouting index under laboratory condition. The studied traits were as follows: seed dormancy, after ripening period, α-amylase activity and embryo protein levels under laboratory conditions. In both methods, high resistance to sprouting on the spike was observed in cultivars with high levels of seed dormancy.Significant differencesamong studied cultivars were observed forphenological, physiologicalandbiochemical characteristics of rice grain.Meanwhile, there were significant positive correlations between sprouting score, and sprouting index with α-amylase activity, there were significant negative correlationbetween these two traits with seed dormancy index (dormancy severity) and after-ripening regression coefficient (dormancyduration). Significant differencesfor protein content ofseed embryo between dormant and non-dormant seeds inthe earliest stages ofwater absorption under heattreatments were determined. Cultivars classified into three groups based on cluster analysis. Our findings provide further evidence of appropriate genetic diversity among cultivars in the case ofstudied traits that underscore the importance to use in breeding programs for resistance to pre-harvestsprouting.