Seed production onTriticum aestivumbyAegilops cylindricahybrids in the field

Abstract

Field experiments were conducted to determine if seeds would be produced on Triticum aestivum by Aegilops cylindrica hybrids in the field and, if it were, to determine the viability of the seeds produced. One, five, or 10 hybrids were planted into varying proportions of A. cylindrica and T. aestivum in a replacement series design. Percent seed set ranged from 0 to 5.5% in 1996 and from 0 to 9.2% in 1997. Seeds were set in all treatments. The average seed set was 2.3% in 1996 and 3.8% in 1997. No differences in seed set were found among treatments. The seeds produced were separated according to seed condition, either full or shriveled, and tested for germination. The germination of the seeds produced on the hybrids was not significantly different between years. The average germination for full seeds was 94% in both years and 79 and 84% for shriveled seeds in 1995 and 1996, respectively. Greenhouse studies were conducted to evaluate the rate of self-fertility of the BC1 generation and to identify morphological characteristics that could be used to identify the probable pollen donor parent and to predict the occurrence of seed set. In 1997 4.1% and in 1998 2.1% of BC1 plants set seeds. The average seed set was 0.3% in 1997 and 0.06% in 1998. It was not possible, using any morphological characteristic measured, to determine the identity of the parent serving as the pollen donor in the previous generation or to predict the occurrence of seed set in the BC1 generation. This is the first reported study to show that hybrids between T. aestivum and A. cylindrica have the ability, although limited, to backcross under field conditions and set seeds. Furthermore, the seeds produced are viable and will germinate and produce plants. With the millions of hectares of T. aestivum infested with A. cylindrica, even the limited ability to backcross is of concern for the movement of a herbicide-resistance gene.

Molecular Analysis, Cytogenetics and Fertility of Introgression Lines From Transgenic Wheat to Aegilops cylindrica Host

“…However, germination of BC1 seeds was much lower. In fact, most of the seeds sown were shriveled and did not germinate, as already observed by Rajhathy (1960) and Snyder et al (2000) on reciprocal crosses. At the next generation (BC1S1), germination was again similar to that of pure Ae.…”

“…It is therefore not required to have two additional crosses after hybridization to recover partially self-fertile plants as stated by Zemetra et al (1998). In fact, Snyder et al (2000) obtained partially self-fertile BC1s to either parental species and seed set averaged 0.06 and 0.3% in 2 years; BC1 individuals having Ae. cylindrica as the recurrent parent could have as much as 46% of the florets bearing seeds by selfing.…”

“…Average percentage of seed set in T. aestivum 3 Ae. cylindrica F 1 hybrids, when surrounded by different proportions of the parental species, was 2.3 and 3.8% in 2 different years while self fertility of BC1s averaged 0.3 and 0.06% in 2 years (Snyder et al 2000). In Oregon, female fertility of hybrids collected in the field was 1% but the recurrent parent was not established (Morrison et al 2002a).…”

“…Morphologically, F 1 hybrids are completely uniform and appear to be intermediate between the parental species, although some parental characters, like glume stiffness and hairiness, are dominantly expressed in the hybrids (Belea 1968). This uniformity contrasts with the morphological variation of the offspring of the hybrids [backcross (BC)1] for spike shape, leaf shape, and growth habit, characters that cannot be used to identify the pollen parent (Snyder et al 2000).…”

The biology and ecology of hexaploid wheat (Triticum aestivum L.) and its implications for trait confinement

“…Moreover, naturally occurring hybrids (2n035) have been shown to produce viable, fertile seed. Seed set on jointed goatgrass )wheat hybrids under field conditions averaged 2.3 and 3.8% in year 1 and year 2, respectively, with the germination rate being 94% for both years (Snyder et al 2000). In the same study, an average of 3.1% of BC 1 (first backcross generation) plants (produced in the field) set seed under greenhouse conditions.…”