Chromosome Numbers and DNA Content in Some Taxa of Leucaena (Fabaceae Mimosoideae).

Abstract

Leucaena Benth. (Fabaceae, Mimosoideae) is an American genus of tropical and subtrop ical woody shrubs and trees with its center of diversity spanning Mexico. Some taxa of Leucaena are important plant resources contributing to the traditional diet in certain parts of Mexico, where selected taxa have been under cultivation since prehispanic time (Zarate 1982, 1984, in press, Casas et al. 1987). Opinions vary as to the number of species and subspecies in Leucaena. Sorensson and Brewbaker (1994) consider 16 species and 2 subspecies; Huges (1993) proposes 16 species; Zarate (in press) regognizes 14 species and 18 subspecies for Leucaena in Mexico. Table 1 shows species and subspecies of Leucaena studied in this paper, following Zarate's (in press) classification system and their equivalences in Sorensson and Brewbaker's (1994) system. Leucaena species have been reported as having n=26 and n=28 chromosomes. No species in the genus has been found with n=13 or n=14, and consequently species with n=26 (which show 26 bivalents) or n=28 chromosomes (showing 28 bivalents) were treated as diploids (Pan and Brewbaker 1988, Cardoso de Freitas et al. 1988). Because species with n=26 or 28 could have derived from an ancestor with n=13 or 14 chromosomes, the basic chromosome numbers of both x=13 and x=14 have been considered

Genetics of Wild and Managed Populations of Leucaena esculenta Subsp. esculenta (Fabaceae; Mimosoideae) in La Montaña of Guerrero, Mexico

“…The finding of consistent duplication in all enzyme systems and in all Leucaena species studied (data to be published elsewhere) strongly suggests polyploidy to be the cause of duplications (Weeden and Wendel 1989), which is consistent with observed chromosome numbers (see Za´rate 1994;Palomino et al 1995). The apparent disomic inheritance observed suggests allopolyploidy (Weeden and Wendel 1989).…”

The cytogenetics and evolution of forage legumes from Rio Grande do Sul: a review

“…There is still a gap in the cytogenetic data of this genus since most of the available information is restricted to chromosome counts of a few plants per species and meiotic studies in some species and hybrid populations (Gonzales et a1., 1967;Pan and Brewbaker, 1988;Palomino et al, 1995) and also because many of the chromosome counts are imprecise or not confirmed (Hughes, 1998), with even the chromosome number unknown for some species. The main reasons for this scarcity of information include small chromosome size (about l µm), the high number of chromosomes (2n = 52, 56, 104 and 112, according to the literature), which makes chromosome counting difficult, and the lack, until recently, of a defined taxonomy.…”

Genome analysis of Mexican flora

“…paniculata) as well as in cultivated forms (L. confertiflora subsp. adenotheloidea; Palomino et al, 1995).…”