IDENTIFICATION OF MAINTAINER LINES AND EVALUATION OF EXPERIMENTAL HYBRIDS DERIVED FROM A BRAZILIAN TROPICAL ONION POPULATION

The four to five-fold price of onion hybrid seeds accounts for the wide use of open pollinated onion populations in Northeastern Brazil. Here we report the identifi-cation of maintainer and male-sterile onion lines within the ‘Alfa São Francisco’ yellow onion population, after three years of work, associating random field pairing of male-fertile plants with selected male-sterile plants and a PCR-based marker cytoplasm monitoring system. Male-sterile plants produced flowers with light green anthers which were easily detected in the field. A 2.0% frequency of male-sterile plants was estimated in the ‘Alfa São Francisco’ sampled population. Male-sterile plants produced the 5’cob-marker 180-bp and the orfA501-marker 473-bp fragments, suggesting the T-cytoplasm type, while the maintainer line produced only the 5’cob-marker 180-bp. Pairing ‘A’ line with a red onion resulted in 100% F1 red bulbs produced from harvested seed in the ‘A line’, confirming that a stable CMS system was identified within the Brazilian tropical ‘Alfa São Francisco’ population. Hybrids produced with another ‘Baia periforme’ onion population (Line ‘C’) and the ‘A’ identified lines’ have resulted in a 38% bulb yield increase compared with the best parent, ‘Alfa São Francisco’. The identified ‘A’ and ‘B’ lines, associated with other developed S1 and S2 populations (‘C’ lines) will be used to produced commercial hybrids well adapted to Brazilian low latitudes and with affordable prices for growers.