Cytological mechanism of 2n pollen formation and unilateral sexual polyploidization in Lolium

Abstract

Plants of Lolium perenne, L . multiflorum and L. hybridum (331, 51 and 18, respectively) were screened for 2n pollen production . The screening was based on the size differences that are expected to be found between n and 2n pollen of a plant . It was found that 28 plants of perennial ryegrass -belonging to 13 cultivarsproduced pollen grains of heterogenous size (big and small) . The estimated frequency of big pollen grain production was higher than 10% in ten out of 28 plants and in three of them it reached a value of 100% . Eight plants obtained from two 4x x 2x crosses, in which the male parent had been previously identified as producing pollen grains of heterogenous size, was tetraploid . The cytological mechanism of big pollen grain formation observed in three plants consists in the lack of spindle formation and, consequently, of chromosome migration in anaphase II . From these breeding and cytological results, it was concluded that the big pollen grains observed were viable 2n pollen grains . The nuclei of the 2n pollen grains produced by this mechanism are genetically equivalent to those formed by the restitution of the second meiotic division . The value of these gametophytes in a breeding program of Lolium is discussed .

Relevance of unilateral and bilateral sexual polyploidization in relation to intergenomic recombination and introgression in Lilium species hybrids

“…Application of functional 2n gametes has become an important tool for the production of polyploid cultivars in different plant species like potato (Mendiburu and Peloquin 1977;Den Nijs and Peloquin 1977), wheat (Jauhar 2003), Lolium (Sala et al 1989), Aspagarus (Camadro 1994), Medicago sativa (Barcaccia et al 1998) and Lilium (Lim et al 2001;Barba-Gonzalez et al 2005;Zhou et al 2008). The traditional method to breed the triploid lilies is to obtain the tetraploid as a first step by mitotic polyploidization.…”

Gametes with the somatic chromosome number: mechanisms of their formation and role in the evolution of autopolyploid plants

“…In Solanum plants, 2n pollen production ranged from 2 to 10% whilst 2n egg production ranged from 4-9 to 23% Werner & Peloquin, 1991a). In Dactv/is glotnerata, the frequency of 2n pollen has been found to vary between 0-1 and 14% in different individual plants and 2n egg frequency from 0-1 to 26% , Furthermore, the frequency of 2n gamete production 0-1-4-9 0-14-14 --28 < 1-35-6 (5-5) 1-3-34 0-3-1-9 < 1-28-6 0-11-26 (5-5) 4-9-23 0-014-0-5 0-4-2 Ray & Tokach, 1992Maceira et al, 1992Sala et al, 1989Negri, 1992Hahn et al, 1990Veronesi et al, 1986Bullita & Smith, 1992Shoemaker-Megalos & Ballington, 1988Ortiz et al, 1992De Haan et al, 1992Veronesi et al, 1986Werner & Peloquin, 1991aShoemaker-Megalos & Balhngton, 1988 Masuelli et al, 1992Parrott et al, 1984 has also been found to be highly variable within the flowers of an individual plant (Veilleux & Lauer, 1981;McCoy, 1982;Veilleux, McHale & Lauer, 1982;Veilleux, 1985). For instance, McCoy (1982) reported that 2n pollen production varied from 4 to 37% among flowers of a single plant of Medicago sativa and Veilleux et al (1982) discovered that 2n pollen production ranged from 5-6 to 61-7% among anthers from a single bud in Solanum.…”

“…Wagenvoort et al, 1990Lelley et al, 1987Ramanna, 1983Iwanaga, 1984;Werner & Peloquin, 1987;Jongedijk & Ramanna, 1988;Watanabe & Peloquin, 1993Parrott & Smith, 1984Rabe & Haufler, 1992Vorsa, 1986in Ortiz et al, 1992Nassar, 1992Simpson & Davis, 1983 Werner & Peloquin, 1991a Mok & Peloquin, 1975 Stelly & Peloquin, 1986;Watanabe & Peloquin, 1989;Werner & Peloquin, 1987;Zhang et al, 1988Vorsa, 1986in Ortiz et al, 1992Werner & Peloquin, 1987Sala et al, 1989Zhang et al, 1988Nassar, 1992Ray & Tokach, 1992Mok & Peloquin, 1975Ramanna, 1978;Camadro & Peloquin, 1980;Iwanaga & Peloquin, 1982;Watanabe & Peloquin, 1989;Masuelli et al, 1992 Jones, 1990Orjeda et al, 1990Zhang et al, 1988Vorsa & Bingham, 1979Bingham & McCoy, 1979;Tavoletti et al, 1991aMyers et al, 1984Parrott & Smith, 1984Werner & Peloquin, 1991aRay & Tokach, 1992Werner & Peloquin, 1987Wagenvoort et al, 1990…”

“…Polyploids are extremely common among crop species because of their superior vigour, generally higher vegetative and seed yields and their greater tolerance of environmental stress (Groose et al, 1988;Sala et al, 1989;Singh et al, 1990). Plant vigour is associated with high heterozygosity in many polyploid plants (e.g.…”

Abnormal spindles in second meiosis in canola (Brassica napus and Brassica campestris)

“…The frequency of 2n pollen in Actinidia , for example, ranged from 0.7 to 10.3 (Yan et al, 1997) and was lower in Avena vaviloviana, reaching 1.0% (Katsiotis & Forsberg, 1995). Although the production of 2n gametes is under genetic control (Sala et al, 1989, Katsiotis & Forsberg, 1995Calderini & Mariani, 1997) it can also be affected by environmental conditions. Stein (1970) listed several species in which the frequency of 2n gametes varied with the cultivation conditions.…”