Intrapopulation variation in Ambrosia artemisiifolia L. seed germination

Previous researches suggested existence or lack of intrapopulation variation for different weed species but as we know so far no data was available for Ambrosia artemisiifolia seed germination. So, the idea of this study was to check whether intrapopulation variation in common ragweed germination exists. The aim of the research was to estimate the difference in final germination and germination speed between seeds collected from 10 different plants at 100 m2 of experimental field located in the southwest Croatia (45°40'18˝N 15°39'03˝E). In autumn 2014 seeds were collected separately from each previously marked plant two to three meters away from each other. Seeds were cleaned and storage at dry and dark conditions until the beginning of the experiment. During 2017, germination test were conducted in germination chamber with photoperiods of 12:12 (light:dark) at alternating 25/15°C (day:night) temperatures. Non-germinated seeds were subjected to tetrazolium test to distinguish dormant from dead seed. Results indicate significant (P < 0.001) difference in final germination and germination speed among all individuals (10 plants) within researched location, ranged from 50 to 99%. Furthermore, germination speed required to achieve 10% of germination ranged from 3, 0 to 10, 0 days, with the average of 4, 7 days. According to time needed for 50% of the germination 10 plants were divided into three groups. First group of four plants were determined to have achieved 50% germination within 4, 9 to 7, 6 days. Second and third group of three plants to achieve 50% of germination needed from 8, 4 to 11, 3 days and from 12, 0 to 15, 4 days, respectively. Finally, to reach 90% of germination seeds needed from 6, 5 to 43, 8 days, with an average of 20, 9 days. Due to sexual reproduction and exchange of genetic material as well as variation in microclimate of environment, differences in germination can be observed even within the plants growing in the same location. Though existing of the certain pattern in the time needed for half of the population to germinate, this data should highlight the need for creating suitable sample of mixed seeds (from different plants) to get reliable results in experiments such as estimation of biological parameters. Furthermore, high intrapopulation variation in germination of the Ambrosia artemisiifolia seed should be taken into consideration when extrapolating germination results and developing predictive weed emergence models.