MEIOTIC ANALYSIS OF A CROSS BETWEEN CULTIVATED AND WILD SUNFLOWER (Helianthus annuus L.)

¹ Universidad Autónoma Agraria Antonio Narro. Departamento de Fitomejoramiento. Buenavista, Saltillo, Coah., Mexico. C.P. 25315

² INIFAP (CIRNOC). Km 4.5, Carr. Durango-Mezquital, A.P. 186, Durango, Dgo., Mexico.

³ Universidad Autónoma Agraria Antonio Narro. Departamento de Botánica. Buenavista, Saltillo, Coah., Mexico. C.P. 25315

⁴ Centro de Investigación y Estudios Avanzados. Instituto Politécnico Nacional. A.P. 629. Irapuato Gto., Mexico.

Wild Helianthus annuus L. populations grow in the area of Saltillo, in the state of Coahuila, Mexico. They were identified as Helianthus annuus L. ssp. texanus Heiser. Plants from these populations were crossed with an inbred strain of cultivated sunflower (AN-3), using the wild material as the male parent. The F₁ was polycephalic, although with less branches than the wild sunflower, and with an intermediate head size. Meiotic cells from both parents and the hybrid, were analyzed in diakinesis and metaphase I. Meiotic pairing was normal in the three materials, with absence of univalents and multivalents; only chain and ring bivalents were observed. The average number of chain bivalents was 3.36 for the cultivated parent, 6.43 for the wild parent, and 7.05 for the F₁. The differences in chain bivalent frequencies were statistically significant among the three materials. This behavior may reflect differences in chiasma numbers and thus recombination. The reduced frequency of chromosome arms being chiasmate in the hybrid, revealed by the highest frequency of chain bivalents, seems to reflect a reduced homology among the wild and cultivated genomes. We postulate that the well known genome fluidity of H. annuus affects the meiotic pairing of the hybrids between populations that have been reproductively isolated from each other.