Meiotic studies of spontaneous hybrids of Amaranthus: genome analysis

Abstract

The meiotic behaviour of 13 spontaneous interspecific F, hybrids of Amaranthus was studied. The hybrids between species with n = 16 chromosomes had 16 bivalents but varied considerably in pollen stainability (0-55%). These results suggest the existence of cryptic structural hybridity. The hybrids involving A. cruentus {n = 17) and species with n = 16 {A. caudatus and A. quitensis) always formed 15II+1III with very low pollen stainability (5-7%). Further observations indicated that Amaranthus species are allotetraploids with basic numbers of .\-= 8 and X = 9 but exhibit x = 16 and x = 11 as secondary basic numbers, as demonstrated by (a) the frequent presence of 811 -I-171 in the meiosis of the hybrid A. spinosus {n = \l)x A. hybridus {n = 16); and the occurrence of secondary associations between bivalents in MI. Genomic formulae are proposed for each species, on the basis of the meiotic behaviour of the hybrids studied.

Cytogenetic study of Amaranthus L. species in Iran

“…Among Amaranthus species and varieties studied A. blitoides, A. cruentus, A. graecizans and A. albus possessed 2nϭ2xϭ32 while the other species possessed 2nϭ2xϭ34 chromosome numbers (Table 1), supporting the previous reports on these species (for example, Pal et al 2000, Greizerstein and Poggio 1994, 1995. The occurrence of two basic chromosome number of xϭ16 and 17 in a single species and also the role of aneuploidy in chromosome evolution of the genus Amaranthus is a well-known fact (Pal et al 2000).…”

“…The relationship of A. cruentus and A. hybridus has also been shown in our protein and morphometric studies. It has been suggested A. hybridus is the progenitor of A. cruentus (Greizerstein and Poggio 1994). Therefore it seems that the Amaranthus species relationships revealed by cytogenetic data generally agrees with the results of morphometric and protein analyses as well as Amaranthus phylogenetic consideration.…”

“…The occurrence of two basic chromosome number of xϭ16 and 17 in a single species and also the role of aneuploidy in chromosome evolution of the genus Amaranthus is a well-known fact (Pal et al 2000). It has been suggested that the gametic number nϭ17 has originated from the nϭ16 through trisomy (Pal et al 2000, Greizerstein and Poggio 1994, 1995.…”

Development, Characterization, and Linkage Mapping of Single Nucleotide Polymorphisms in the Grain Amaranths (Amaranthus sp.)

“…T HE GENUS Amaranthus (Caryophyllales: Amaranthaceae) contains three domesticated grain species, collectively referred to as the grain amaranths (A. hypochondriacus L., A. cruentus L., and A. caudatus L.;Sauer, 1976). Th ese species, along with their putative progenitor species (A. hybridus L., A. quitensis Kunth, and A. powellii S. Watson) are classifi ed in what is termed the A. hybridus complex and are considered paleo-allotetraploids (2n = 4x = 32; Greizerstein and Poggio, 1994;Greizerstein and Poggio, 1995;Pal and Khoshoo, 1982). Amaranth was a major domesticated food crop of the pre-Columbian New World civilizations, likely having been domesticated multiple times over thousands of years ago (Mallory et al, 2008;Sauer, 1950).…”

Use of Multicopy Transposons Bearing Unfitness Genes in Weed Control: Four Example Scenarios

“…This rapid evolution is further exacerbated by the facts that Amaranthus spp. are wind pollinated, many of the species are obligate outcrossers, and many species hybridize intragenerically, thus often resulting in their being allotetraploids (Greizerstein and Poggio, 1995). This polyploidy facilitates rapid evolution, because gene duplication through whole-genome duplication leads to the buffering of mutations due to the redundancy of each gene.…”