Inheritance of apomeiosis (diplospory) in fleabanes (Erigeron, Asteraceae)

Abstract

Unreduced egg formation (apomeiosis) in flowering plants is rare except when it is coupled with parthenogenesis to yield gametophytic apomixis via apospory or diplospory. Results from genetic mapping studies in diverse apomictic taxa suggest that apomeiosis and parthenogenesis are genetically linked, a finding that is compatible with the conventional rationale that apomeiosis is unlikely to evolve independently because of deleterious fitness consequences. An Erigeron annuus (apomictic) Â E. strigosus (sexual) genetic mapping population, however, included a high proportion of plants that were highly apomeiotic (diplosporous) but nonapomictic; that is, they lacked autonomous seed production. To evaluate the function and inheritance of diplospory in Erigeron, a diplosporous triploid (2n ¼ 3x ¼ 27) seed parent was crossed with a sexual diploid (2n ¼ 2x ¼ 18) E. strigosus pollen parent to produce an F1 of 31 plants. Chromosome numbers and molecular markers (AFLPs) document the inheritance of the maternal genome through unreduced eggs resulting in recombinant but predominantly (77%) tetraploid F1s (2n ¼ 4x ¼ 36; 2n þ n, B III ). Quantitative evaluation shows continuous variation in the proportion of diplosporous (vs meiotic) ovules (41-89%) in tetraploid F1s despite the presumed equal genetic contribution from the diplosporous mother. These findings demonstrate the functional independence of diplospory and suggest that variation in the trait in F1s is likely due to segregating paternal modifiers. In addition, of six aneuploid (4xÀ1, 4xÀ2) F1s, three lack a subset of maternal AFLP markers. These plants likely arose from aberrant megagametogenesis resulting in the loss of maternal chromatin prior to fertilization.

Seed development and inheritance studies in apomictic maize-Tripsacum hybrids reveal barriers for the transfer of apomixis into sexual crops

“…Although genomic accumulation was predominant, genetic variation within progeny arose through a number of mechanisms. While incomplete nucleus restitution at meiosis I is a known side effect of diplosporous pathways (Nogler, 1984, Noyes, 2005, Richards, 1996 likely promoted by meiotic asynchrony between the maize and Tripsacum chromosomes in our materials (Grimanelli et al, 2003, Harlan et al, 1970, parthenogenesis in reduced gametes and spontaneous chromosome doubling did not occur at greater incidences than that observed in many sexual plant species (de Wet, 1979, Kimber andRiley, 1963) or in interspecific hybrids (Nasrallah et al, 2000, Soltis andSoltis, 1999).…”

“…Td: Tripsacum dactyloides. mutation have been reported as well (Hair, 1956, Noyes, 2005, Richards, 1996.…”

“…Variation in the reproductive behavior within a single individual is common in both natural and artificial apomicts (Koltunow et al, 2000, Leblanc, 1995, Nogler, 1984, Noyes, 2005, Richards, 1996, Van Dijk et al, 1999. In order to assess the nature and the extent of variation in reproductive behavior in 38C, an apomictic clone, we collected flow cytometrical, cytogenetical and molecular data within progenies obtained after pollination using 2x maize progenitors.…”

Sexual and asexual (apomictic) seed development in flowering plants: molecular, morphological and evolutionary relationships

“…(Pessino et al 1998) and P. squamulatum (Ozias-Akins et al 1998) where apomeiosis and autonomous embryogenesis are controlled by a single dominant locus. However, it is difficult to rationalise when multiple independent loci control the different components, which is the case for species such as T. officinale (van Dijk et al 1999), E. annus (Noyes 2005) and H. caespitosum (Catanach et al 2006). The chance that two mutations could occur almost simultaneously in a plant or population and subsequently give rise to viable apomictic progeny is highly unlikely (Asker and Jerling 1992).…”

Identification of Candidate Genes Related to Polyploidy and/or Apomixis in <i>Eragrostis curvula</i>

“…In grasses, diplosporous apomixis is genetically controlled by several independent loci, which separately govern apomeiosis (formation of a non-reduced megaspore), parthenogenesis, and endosperm development [7,[15][16][17][18][19]. In Erigeron annuus, apomeiosis and parthenogenesis are controlled by genes that map to independent linkage groups [15][16][17].…”