Mechanism of extreme genetic recombination in weedy Amaranthus hybrids

Abstract

Interspecific hybridization of Palmer amaranth and common waterhemp produce hybrids with unique DNA fragments not found in either parent. The objective of this research was to investigate the mechanisms involved in the formation of the polymorphic fragments. Six novel fragments were cloned and sequenced. Five of the six were significantly similar to plant transposons, the sixth was similar to squamosa promoter–binding proteins from other plant species. Southern blot analysis using one of the novel fragments as probe revealed a consistent pattern of repetitive DNA that was species and biotype specific. These results indicate that transposon-like elements may play an important role in the formation of new fragments in Amaranthus hybrids derived from interspecific hybridization, suggesting that considerable instability of the hybrid genome may occur.

The Biology of Invasive Alien Plants in Canada. 3. Amaranthus tuberculatus (Moq.) Sauer var. rudis (Sauer) Costea & Tardif

“…rudis and A. palmeri was intermediate between the parents. Other morphological characters may not be intermediate between the two parents (Steinau et al 2003), as has also been reported for hybrids between monoecious species of the section Amaranthus (Costea and Tardif 2003b;Costea et al 2004). The presence of morphological characteristics absent in parent species may be explained by the formation of polymorphic DNA fragments resembling transposon-like elements (Wetzel et al 1999b;Steinau et al 2003).…”

“…Other morphological characters may not be intermediate between the two parents (Steinau et al 2003), as has also been reported for hybrids between monoecious species of the section Amaranthus (Costea and Tardif 2003b;Costea et al 2004). The presence of morphological characteristics absent in parent species may be explained by the formation of polymorphic DNA fragments resembling transposon-like elements (Wetzel et al 1999b;Steinau et al 2003). First generation hybrids between dioecious and monoecious, or between monoecious Amaranthus species, have reduced fertility, low vigor and slow growth, distorted leaves, abnormally shaped inflorescences, and numerous, densely packed bracteoles.…”

“…Flowers are unisexual (diclinous), and in the dioecious species, male and female flowers occur on separate plants. Steinau et al (2003) observed that a hybrid between A. tuberculatus var. rudis and A. hybridus had predominantly female flowers, but also a small male inflorescence making such plants monoecious.…”

“…rudis and other dioecious species from the subgenus Acnida, as well between var. rudis and monoecious species from the subgenus Amaranthus (Thellung 1914;Wetzel et al 1999b;Franssen et al 2001a;Costea and Tardif 2003b;Steinau et al 2003;Costea et al 2004). First generation hybrids between A. tuberculatus (variety unspecified) and A. hybridus were dioecious .…”

Nonhybrid Progeny from Crosses of Dioecious Amaranths: Implications for Gene-Flow Research

“…Hybridization among different species has been widely reported within the genus Amaranthus (Sauer 1950;Trucco et al 2005). Wetzel et al (1999) reported transfer of ALS resistance via hybridization and backcrossing between Palmer amaranth and common waterhemp, although Franssen et al (2001), Steinau et al (2003), and Trucco et al (2007) found very low levels of hybridization with most hybrid progeny from this cross either nonviable or sterile. Gaines et al (2012) also reported low levels (, 0.2%) of interspecific hybridization between Palmer amaranth and common waterhemp, with even lower levels (, 0.01%) of hybrid formation between Palmer amaranth and smooth pigweed (A. hybridus L.).…”