CMS Lines for Evaluation of Pollen Flow in Sunflower Relevance for Transgene flow Mitigation

Abstract

ABSTRACTSunflower pollen flow over long distance was evaluated. Plants from three CMS lines were cultivated at distances 10 m, 1.0 km and 1.5 km from the male fertile line used as pollen donor. The assessment of the seed set of the CMS plants showed a decrease in the pollination with the distance from the pollen donor plants. The microsatellite analysis of bulk samples from the collected seeds demonstrated pollen dispersal from the pollen donor plants over all three tested distances. Further analysis of individual seeds suggested that a small portion of the collected seeds may have resulted from selfpollination of studied CMS lines and crosspollination between them. The observed restoration of fertility in the CMS lines was most probably caused by the excessive rainfall and lower average temperatures during the period of the flowering of the CMS lines. The stability of a wider range of CMS lines carrying cytoplasms from H. petiolaris, H. argophylis, H. rigidus and H. praoxes species were evaluated within three years (2006–2008) in two different locations in Bulgaria. Sixteen CMS lines, studied in 2006, were sterile in tested environmental conditions. Six of the CMS lines were further assessed in the period 2007–2008 after two periods of sowing and parallel cultivation in greenhouse. The investigated CMS lines differed in regard to the stability of cytoplasmic male sterility. Four of them were fully sterile across all nine different environmental conditions in the period 2006–2008. Two CMS lines showed unstable sterility that varied under the different environmental conditions. The restoration of fertility in these CMS lines was partial and affected only few individual plants. Taken together these data suggest that the climatic condition (temperature, humidity and daily light intensity) may affect the stability of sterility of the sunflower CMS lines depending of their genotype.The results from the present study indicated that long distance pollen dispersal is a major factor limiting the cultivation of transgenic sunflower plants. The prevention of transgenic pollen spread through cultivation of transgenic CMS plants has to be well evaluated in direction to the stability of the used CMS lines for each specific location, multiple periods of cultivation and various climatic conditions.