Meiotic pairing in the hybrid (Zea diploperennis×Zea perennis)×Zea mays and its reciprocal

Abstract

Genomic formulae, fertility, chromosome pairing, and the cryptic intergenomic pairing (induced by using diluted colchicine solution) were analysed in the tri-hybrid (MDP), obtained by crossing DP40 (2n=40, which was inferred in previous studies to have originated from the fusion of an unreduced gamete of Zea diploperennis with a normal gamete of Z. perennis) with the maize inbred line Zm40 (2n=40). MDP (2n=40) showed a higher fertility (90% of the seeds are viable) than Zm40 (60%) and DP40 (80%). A regular migration of 20 chromosomes to each pole occurred in 92% of the cells in anaphase I, while bridges were observed in the other 8% of the cells. When Zm40 was used as female of the crossing (Zm40 x DP40), ears were similar to corn. Conversely, ears resembled those of the wild species when cytoplasm was donoured by Zd. Then, it can be stated the existence of cytoplasmic influence on MDP ear type. MDP had almost no I or III, with an average of 0.04I + 10.90II + 0.01III + 4.50IV. The most frequent meiotic configuration was 10II + 5IV (43.93% of the cells). On average, 33.81 chiasmata/cell were observed (17.34, 0.05 and 16.42 average numbers of chiasmata/cell in bivalents, trivalents and tetravalents, respectively). It can be inferred that the 5IV were the product of homoeologous chromosome pairing of A genomes from the three species. On the other hand, the 10II configuration suggests separate pairing of the 5 homologous B chromosomes from maize and the 5 homoeologous B chromosomes from Zp and Zd.

Cryptic homoeology analysis in species and hybrids of genus Zea

“…Previous results (Molina and Naranjo 1987, Molina et al 2004, Molina 2011, Poggio et al 1990, Naranjo et al 1989, González and Poggio 2011 support the theory that consider Zea as an autotetraploid with two subgenome with different level of conservation (Swigonová et al 2004.…”

“…and their hybrids with diluted colchicine solutions (Poggio et al 1990, Molina and García 1999, 2000, Molina et al 2004, 2005, Molina 2011, González and Poggio 2011. Up to 5 quadrivalents have been observed in maize and hybrids with 2n = 20, while a higher number of quadrivalents has been found in Zea perennis when compared to untreated controls.…”

“…Colchicine treatment has been observed to favor homoeologous chromosome pairing, and more than one mechanism has been proposed to explain such effect, modification of the position of the chromosomes in the nuclear membrane or alteration in the formation of the bouquet (Bass et al 2000), and annulment of the expression of a maize gene, equivalent to the Ph gene of wheat (Poggio et al 1990, Molina et al 2004). …”

Molecular Evidence for a Natural Primary Triple Hybrid in Plants Revealed from Direct Sequencing

“…The first includes papers on experimental triple hybrids (e.g. Dionne, 1963;Hermsen and Ramanna, 1973;Kalasa Balicka, 1976, 1980Bothmer et al, 1988Bothmer et al, , 1989Maekawa et al, 1991;Gadella, 1992;Molina et al, 2004;Mra ´z and Paule, 2006). An outstanding, notable experiment was carried out by Nilsson (1954), who as a result of successive artificial hybridization obtained a hybrid involving 13 different species of Salix (Salicaceae).…”