LLAVALLOL, ARGENTINA

UNLP-CONICET-CIC

Variation of the frequency of multivalents in Zea diploperennis x Z. perennis (2n=30 and 2n=40) hybrids treated with dilute concentrations of colchicine

--C. A. Naranjo, L. Poggio*, M. C. Molina and E. A. Bernatené

*Also affiliated with Depto. de Cs. Biológicas, FCE (UBA).

Having managed immature panicles with colchicine (0.5x10-4M) for 12 hours, we have shown the existence of cryptic homoeology in maize (Z. mays ssp. mays) and Z. perennis, forming quadrivalents in the first one and increasing the frequency of quadrivalents in the second one (Poggio, L. et al., Theor. Appl. Genet. 79:461-464, 1990). These results confirm the allotetraploid nature of maize proposed by Molina and Naranjo (Theor. Appl. Genet. 73:542, 1987) and Naranjo and Molina (MNL 61:62) and suggest that the species have homoeologous genomes (Z. mays ssp. mays, A2A2B2B2; Z. perennis, A'1A'1A"1A"1 C1C1C2C2 which fail to pair, probably due to the present of Ph-like genes (Poggio et al., ibid).

To complete the analysis of genome relationships we have analyzed two artificial F1 hybrids, Z. diploperennis x Z. perennis; 2n=30 (A'1A"1A1 B1C1C2) and 2n=40 (A'1A"1A1A1 B1B1C1C2). The results indicate that the frequency of six or more trivalents was increased from 25.6% in the untreated material to 90% in the treated material of Z. diploperennis x Z. perennis (2n=30). Meanwhile the frequency of five or more quadrivalents was increased from 46.3% in the untreated material to 69.4% in the treated material of Z. diploperennis x Z. perennis (2n=40). Differences between treated and untreated materials were subjected to a test of homogeneity and were found highly significant.

Moreover, Z. diploperennis (2n=20, A1A1B1B1) was treated but we have not found multivalent formation.

The results pointed out greater homoeology among B and C genomes with respect to the untreated material and not between these genomes and the A as shown by the absence of hexavalents and octavalents in the 2n=30 and 2n=40 taxa (MNL 62:74-75).

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