Dispersal of wild sunflower by seed and persistant basal stalks in some areas of Central Italy

Abstract

In some sites of Central Italy wild sunflowers are spreading from marginal areas into cropped fields. Crops like maize, tomato, tobacco, alfalfa are often infested with wild sunflowers. Hybrid sunflower crops are also infested with wild material. Plants and populations of wild sunflower also spontaneously grow at the edge of the fields, and along the ditches and roads. We have observed that wild sunflower is partially dispersed by its seed, but possibly it can propagate vegetatively by its perennial basal stalk when it survives the mild winter seasons. We have evidence that sunflower seeds maintain germination capacity for years after being plowed into the soil. This wild sunflower phenotypically resembles H. annuus, but the strong root system is not usual for an annual sunflower species. Concerning its origin, we observed variations indicating naturalization by either an introgression process involving wild species or a segregation of a hybrid variety and the enrichment of genes conferring seed dispersion and root persistence. It is possible that a similar process occurred a few centuries ago, after its introduction to Europe when sunflower escaped botanical gardens and began to colonize Eastern European areas.

Occurrence, distribution and distinctive morphological traits of weedy Helianthus annuus L. populations in Spain and France

“…This hypothesis has already been mentioned for Spain and Italy (Vischi et al 2006). This origin has been demonstrated for other species, for instance weed beets (Boudry et al 1993).…”

“…Fig. 1), have been described for decades in Italy (Vischi et al 2006), Spain (Faure et al 2002) and Central Europe (Holec et al 2005). They were officially confirmed in France in 2004 (Muller et al 2006) although some farmers have been confronted with them since as early as 1990.…”

“…The situations of the naturalized sunflower outside its area of origin are quite diverse and show that this species has adapted to a variety of environments . In Italy, it infests sunflower and other crops such as maize, tobacco, alfalfa, but also spontaneously grows along roads and in ditches (Vischi et al 2006). In the Czech Republic, it is mainly observed in non arable land, but it has recently been pointed out to be a weed in sunflower fields (Holec et al 2005).…”

Migration pattern suggested by terrestrial proximity as possible origin of wild annual Helianthus populations in central Argentina

“…Wild, weedy and feral sunflower populations are of concern in several regions of the world because of their invasive capacity and crop interference (Bervillé et al 2005;Vischi et al 2006;Müller et al 2006;Stanković-Kalezić et al 2007). The invasive capacity of H. petiolaris is unknown, since Argentina is the only reported case of this species' invasion in the world.…”

Phylogenetic relationships of Pterocarya (Juglandaceae) with an emphasis on the taxonomic status of Iranian populations using ITS and trnH-psbA sequence data

“…Additionally, the present study is the first attempt to elucidate the status and intraspecific relationships in Pterocarya genus from the Hyrcanian and Zagrossian forests of Iran. Although the trnH-psbA spacer has been discussed as a potential barcoding region (Kress et al 2005;Vischi et al 2006;Kress & Erickson 2007), it did not show any polymorphisms in the genus Pterocarya. However, we have found that the two main populations of P. fraxinifolia species (Iranians and from GeneBank) differed in their secondary structure and repeat sequences of ITS2 region, which was recently suggested to be a DNA barcode.…”