Disomic Inheritance, Suppressed Recombination, and Allelic Interactions Govern Apospory in Buffelgrass as Revealed by Genome Mapping

Abstract

lecular markers within mapping populations (Wendel and Parks, 1984;Torres et al., 1985; Molecular tools have not identified the gene(s) governing apomixis Paterson et al., 1988Paterson et al., , 1991Saito et al., 1991; Lyt-nor have they been used to successfully transfer the trait to important, sexually reproducing food crops. Several molecular studies addressing tle, 1991;Schon et al., 1991; Zivy et al., 1992; Causse et apomixis in grasses have used interspecific and intergeneric hybrids. al., 1994; Chittenden et al., 1994). This loss of specific The failure to recover specific F 1 genotypes from these wide crosses genotypes from the progeny may be due to interactions can be caused by unfavorable interactions between the gametes, zybetween genes of the two species within gametes, zygote, embryo, endosperm, and/ or maternal tissue. These interactions gote, embryo, endosperm, or maternal tissue (Hadley can eliminate recombinant genotypes with valuable information toand Openshaw, 1980). Differential viability of offspring wards linkage analyses of the trait. Buffelgrass [Pennisetum ciliare because of allelic interactions has been reported in (L.) Link syn. Cenchrus ciliaris L.], a polymorphic species with intermaize (Zea mays L.)-Tripsacum hybrids (Maguire, fertile apomictic and sexual genotypes, offers an opportunity to genetically map apomixis by means of intraspecific hybrids with euploid 1963), tomato, Lycopersicon esculentum Mill. (Rick, genomes. This study reports a linkage map of the apospory region in 1966), wheat, Triticum aestivum L. (Manabe et al., 1999), buffelgrass. Apospory, classified by progeny testing and cytologically and rice,

The polyploid nature of Cenchrus ciliaris L. (Poaceae) has been overlooked: new insights for the conservation and invasion biology of this species – a review

“…This no doubt results from the apomictic reproductive mode of C. ciliaris that leads to the formation of seeds genetically identical to the mother plant (Ozias-Akins et al 2003;Akiyama et al 2005). As stated above, apomixis is a heritable trait (Grimanelli et al 2001;Jessup et al 2002;Curtis and Grossniklaus 2007;Ozias-Akins and Van Dik 2007;Yadav et al 2012), but is rarely obligatory, and such is the case for C. ciliaris. In mixed breeding systems (sexual and apomictic), the genetic factors controlling apomixis can be potentially transferred from an apomictic individual to the offspring of a sexual plant via pollen.…”

“…In C. ciliaris, apospory inherits as a dominant trait under genetic control of a single locus and transmits with an aposporyspecific genomic region (ASGR) located on a single chromosome (Roche et al 1999;Jessup et al 2002;Ozias-Akins and Van Dik 2007). Cytogenetic investigations of tetraploid C. ciliaris have demonstrated that the ASGR is located near the centromere in a genomic region that is hemizygous and heterochromatic (condensed part of chromatin genetically inactive) (Goel et al 2003(Goel et al , 2006Ozias-Akins et al 2003;Akiyama et al 2005).…”

Comparative Physical Mapping of the Apospory-Specific Genomic Region in Two Apomictic Grasses: Pennisetum squamulatum and Cenchrus ciliaris

“…Since the AFLP map of P. squamulatum provided only one closely recombining marker, we chose a second recombining marker from buffelgrass ( Jessup et al 2002), linked with the ASGR at a distance of 10.7 cM, to investigate by using BAC-FISH. The probe used to generate this marker in buffelgrass was from a sorghum cDNA library (HHU27, GenBank nos.…”

“…Our survey of 16 Pennisetum and two Cenchrus species has identified one that shows the presence of two ASGR-carrier chromosomes (Y. Akiyama, S. Goel, W. W. Hanna, P. Ozias-Akins, unpublished results). Jessup et al (2002) reported recombination of numerous markers and apospory in C. ciliaris even though some markers previously had been shown to be tightly linked with apospory (UGT197 and Q8) in both P. squamulatum (Ozias-Akins et al 1998) and a different population of C. ciliaris (Roche et al 1999). We investigated one of their recombining markers (HHU27) by isolating a BAC clone from C. ciliaris (C1000) that contained sequences from this marker.…”

“…We investigated one of their recombining markers (HHU27) by isolating a BAC clone from C. ciliaris (C1000) that contained sequences from this marker. According to the map published by Jessup et al (2002), two of these markers (UGT197 and HHU27) flanked the apospory locus on opposite sides at a distance of 1.4 and 10.7 cM, respectively. In our analysis we could not detect any recombination between SCAR markers developed from BAC C1000 and the apospory trait.…”