Production of 2n pollen of Asiatic hybrid lilies by nitrous oxide treatment

Abstract

Tetraploid varieties of lilies have superior agronomic traits such as large flowers and resistance to physiological disorders. In the present study, we attempted to induce 2n pollen of Asiatic hybrid lilies by arresting the meiotic process with nitrous oxide (N 2 O) gas. To determine which meiotic stage is optimal for induction of 2n pollen, plants with attached buds at different meiotic stages were treated with N 2 O for 24 h in a pressure-tolerant cylinder. A few 2n pollen grains were induced using plants with anthers in prophase I, whereas mixed pollen grains of differing size were produced using plants undergoing meiotic metaphase predominantly in anthers. Although normal lily pollen grains are elliptical, nitrous oxide exposure induced giant pollen grains that appeared spherical. Flow cytometry analysis showed that the giant pollen grains were diploid. When mixed pollen that included normal and giant pollen was crossed to tetraploid cultivars, the resulting seedlings were tetraploid and aneuploid, indicating that the giant pollen grains were diploids that could generate tetraploid seedlings through fusion to diploid eggs supplied from a tetraploid female parent. Thus, treatment with N 2 O is useful for the production of 2n lily pollen and may provide a new approach for tetraploid lily breeding.

Mechanism of action of nitrous oxide gas applied as a polyploidizing agent during meiosis in lilies

“…When most of the sampled pollen mother cells were undergoing meiotic metaphase I, buds that were of the same size as the sampled bud were treated with N 2 O for 24 h (Okazaki et al 2005;Akutsu et al 2007). …”

“…1). Previous experiments using flow cytometric analysis and crossing demonstrated that these pollen grains are diploid and can fertilize eggs (Akutsu et al 2007).…”

“…Arresting meiosis with N 2 O induces 2n pollen in tulips, and triploids can be formed by crossing diploids and N 2 Otreated pollen (Okazaki et al 2005). N 2 O is also very useful for polyploidy breeding in lilies; the optimal timing for induction of diploid pollen is metaphase I (Akutsu et al 2007). Treatment of interspecific lily hybrids with N 2 O gas induces 2n pollen and partially restores pollen fertility (Barba-Gonzalez et al 2006).…”

Microsporogenesis and Induction of Unreduced Pollen with High Temperatures in Rubber Tree Clone RRIM 600

“…The diameter of 2n pollen was approximately 30% larger than that of n pollen; this has been reported in Ipomoea batatas, Tulipa, Lilium, and Achillea borealis [31][32][33][34][35]. In some species, unreduced pollen is larger than n pollen by much more than 30%, such as the giant pollen grains (n = 8x) of A. borealis [35].…”

Occurrence and cytological mechanism of numerically unreduced pollen in diploid Populus euphratica

“…Numerically unreduced (2n) gametes occur occasionally in stead of the expected haploid (n) gametes and likely played a key role in formation of polyploid series (HARLAN and DE WET, 1975;DEN NIJS and PELOQUIN, 1977;VEILLEUX, 1985;RAMSEY and SCHEMSKE, 1998;RAMSEY, 2007;RIESEBERG and WILLIS, 2007). The induction of sexual polyploidization via controlled crosses between naturally occurring and aritificially induced-2n gametes have also been widely used in the breeding of forest trees (SEITZ, 1954;ZHANG et al, 2004;ZHU, 2006), potato (MENDIBURU et al, 1974;RAMANNA, 1979;CARPUTO and BARONE, 2005), grain crops (VEILLEUX, 1985;JAUHAR, 2003), fruit-bearing trees (SUGIURA et al, 2000), and ornamental plants ( VAN TUYL and LIM, 2003;AKUTSU et al, 2007).…”