engleski

Expression of seed dormancy in Croatian grown winter wheats at different germination temperatures

The level of seed dormancy at harvest time is the main component of pre-harvest sprouting resistance in wheat and is determined by genetic as well as environmental factors. Temperature is an important environmental factor, which influence the induction of seed dormancy during seed development and maturation as well as the expression of seed dormancy during germination. The aim of this study was to determine the effect of germination temperature on expression of seed dormancy in different wheat genotypes. Twenty one winter wheat cultivars widely grown for commercial production in Croatia, two promising breeder lines and two checks, the line RL4137 possessing a high level of seed dormancy at harvest as well as cultivar Sivka with a low level of grain dormancy at harvest, were included in the study. Genotypes were grown in the field at two locations in Croatia during 2008/2009 growing season in a randomized complete block design with two replicates. From each plot 30 spikes were harvested at harvest ripeness (approximately 14% moisture content on a wet weight basis). Three germination tests (experiments) were conducted with hand threshed seeds under controlled environment at temperatures of 15, 20 and 25°C in darkness. The first germination test was started immediately after harvest (Time 1) whereas the second and third germination tests were conducted after 10 (Time 2) and 20 (Time 3) days of seed afterripening at 20°C, respectively. Germinated seeds were counted after three and six days and germination rate, expressed as weighted (by day) germination index (WGI), was calculated for each genotype by temperature combination. Combined analysis of variance across locations revealed significant (P<0.05) differences among locations (L) and genotypes (G) as well as significant G x L interaction for WGI for all three germination tests (Time 1, Time 2 and Time 3) and germination temperatures (15, 20 and 25°C). Mean WGIs for all genotypes across locations decreased as germination temperature changed from 15°C to 25°C in all three germination tests. Most genotypes responded with decreasing WGI mean values (increasing dormancy), as temperatures changed from 15 to 20°C in all three germination tests. Some genotypes like Srpanjka and Divana at Time 1, Adriana at Time 2 and Adriana and Golubica at Time 3 had similar WGI values at both 15 and 20°C while Patria showed an increase of WGI mean values as temperature increased from 15 to 20°C. All genotypes in all three germination tests showed a decrease of WGI mean values with further increase of germination temperature from 20°C to 25°C. Rates of WGI mean value decrease with increasing germination temperatures varied among genotypes in all three germination tests. Examples of different genotype response to germination temperatures at Time 1 were Barbara and Renan, which at 15°C had similar WGI mean values (0.42 and 0.43) while at 25°C their WGIs were 0.06 and 0.23, respectively. Similarly, at Time 2 Superzitarka, Srpanjka and Petra, at 15°C had WGI mean values of 0.66, 0.65 and 0.63 and at 25°C 0.25, 015 and 0.08, respectively. The number of genotypes with the same level of seed dormancy as dormant standard RL 4137 at all three germination temperatures decreased from six (Time 1) to four (Time 3). In all three germination tests the number of genotypes ranked similar to standard RL4137 was lower at 25°C compared to other two germination temperatures. At 15°C the ranges (maximum-minimum) of genotypic WGI mean values decreased from Time 1 (0.75) to Time 3 (0.45), at 20°C ranges of WGIs were similar for 15 and 20°C (0.80 and 0.82, respectively) and decreased to 0.75 at Time 3, whereas at 25°C ranges of WGIs increased from Time 1 (0.67) to Time 3 (0.81). This indicates that maximum differences in dormancy among genotypes included in the current study occurred at different stages of afterripening depending on germination temperatures. We concluded that combination of lower and intermediate germination temperatures are suitable for testing dormancy level at harvest time while at later terms (after a period of afterripening) including the tests at higher germination temperatures are recommended.

seed dormancy; germination temperatures; germination index (WGI);

nije evidentirano