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Ploidy manipulations are achieved by utilizing unreduced gametes, somatic chromosome doubling or haploidization. Apomixis, the asexual mode of reproduction through seeds, involves two of these phenomena viz., apomeiosis (unreduced embryo-sac formation) and parthenogenesis (fertilization-independent embryogenesis). The two components when partitioned may yield high frequencies of triploids and haploids, and thus, serve as a tool to manipulate ploidy levels when appropriately supplemented with hybridization schemes. Utilizing this ybridization-supplemented pomixis-components artitioning pproach (HAPA), the largest ploidy series in a crop plant was generated in guinea grass ( Panicum maximum Jacq.). Eighty-nine diverse guinea grass accessions were characterized for their reproductive capacities to identify tetraploid (2 n = 4 x = 32) accession(s) with high apospory but reduced parthenogenetic capacity, thereby producing a high frequency of hexaploid seeds. Seeds from accession IG 04-164 were utilized to produce a ploidy series by appropriately combining partitioned apomixis components and hybridizations in two seasonal cycles. We successfully obtained plants representing ploidies 3 x, 4 x, 5 x, 6 x, 8 x and 9 x, all derived from a single 4 x progenitor. Production methodology, reproducibility and utilization of HAPA in cytogenetic and molecular studies are discussed. [ABSTRACT FROM AUTHOR]

The wheat progenitors and other wild relatives continue to be important sources of genes for agronomically desirable traits, which can be transferred into durum wheat ( Triticum turgidum; 2 n = 4 x = 28; AABB genomes) cultivars via hybridization. Chromosome pairing in durum × alien species hybrids provides an understanding of genomic relationships, which is useful in planning alien gene introgression strategies. Two durum cultivars, ‘Lloyd’ and ‘Langdon’, were crossed with diploid wheatgrass, Thinopyrum bessarabicum (2 n = 2 x = 14; JJ), to synthesize F1 hybrids (2 n = 3 x = 21; ABJ) with Ph1. ‘Langdon’ disomic substitution 5D(5B) was used as a female parent to produce F1 hybrids without Ph1, which resulted in elevation of pairing between durum and grass chromosomes – an important feature from the breeding standpoint. The F1 hybrids were backcrossed to respective parental cultivars and BC1 progenies were raised. ‘Langdon’ 5D(5B) substitution × Th. bessarabicum F1 hybrids were crossed with normal ‘Langdon’ to obtain BC1 progeny. Chromosome pairing relationships were studied in F1 hybrids and BC1 progenies using both conventional staining and fluorescent genomic in situ hybridization (fl-GISH) techniques. Multicolour fl-GISH was standardized for characterizing the nature and specificity of chromosome pairing: A–B, A–J and B–J pairing. The A–J and B–J pairing will facilitate gene introgression in durum wheat. Multicolour fl-GISH will help in characterizing alien chromosome segments captured in the durum complement and in their location in the A and/or B genome, thereby accelerating chromosome engineering research. [ABSTRACT FROM AUTHOR]

Abstract The multiploid mutant of durum wheat is a genotype that produces unreduced gametes. Our objective was to test the recovery of pentaploid hybrids in crosses of the mutant with rye and Triticum monococcum L. Compared with check crosses, the mutant had a two-third reduction in percent seed set for rye crosses, but had only a slight decrease in crossability with T. monococcum . Pentaploid hybrids were associated with plump seeds of the mutant/rye cross, and with shrivelled seeds of the mutant/T. monococcum cross. We suggest that the endosperm balance number hypothesis explains the association of pentaploid hybrids with endosperm type. This association made for easy recovery of pentaploid hybrids from crosses to both species. Mature, plump seeds from the mutant/rye cross were germinated and pentaploid hybrids were recovered. One pentaploid hybrid was recovered for every 50.5 and 15.1 florets pollinated with rye and T. monococcum , respectively. Unreduced gametes in the multiploid mutant will facilitate interspecific hybridization by reducing the time to produce pentaploid plants. [ABSTRACT FROM AUTHOR]

Successful hybridization between Lilium concolor and Lilium longiforum has not been reported but ovary slice culture technique, after cut-style pollination has now been used to produce diploid and triploid interspecific hybrids between these species. Reciprocal crosses between diploid cultivars (2n = 2x = 24) were conducted. 5, 10, 15, 20, 25, 30, 35, 40, and 45 days after pollination (DAP), ovaries were sliced and cultured on a modified Murashige and Skoog (MS) medium without growth regulators and NH[sub4]NO[sub3], supplemented with 6% sucrose, 50mg/I yeast extract and 0.25% gelrite at pH 6.3. For the L. concolor x L. longiflorum cross, embryo germination was found to be best at 20 DAP, while for the L. longiflorum x L concolor at 25 DAP. After transfer to a MS (half-strength) medium supplemented with 1.5% sucrose, 0.25% gelrite and 0.2% active charcoal at pH 5.8, diploid and triploid hybrid plants were developed. All regenerated plants were identified as hybrids on the basis of karyotype and isozyme analyses. Ovary slice culture technique as a method of producing polyploids is discussed. [ABSTRACT FROM AUTHOR]

Self-sterile interspecific hybrids between diploid Lolium perenne and either Festuca arundinacea or F. gigantea (both hexaploids) set some seeds when subjected to a heavy pollen cloud from the amphiploids derived from the hybrids. All the progeny were octoploid and were formed from the fertilization of unreduced gametes in the F[SUB1] hybrid by amphiploid pollen. The significance of the results in relation to breeding efforts within the Lolium/Festuca complex is discussed. [ABSTRACT FROM AUTHOR]