POLLEN COLD TOLERANCE OF MAIZE GENOTYPES WITH DIFFERENT ABILITY TO GERMINATE AT LOW-TEMPERATURE

Breeding programs aimed at improving cold tolerance can take advantage from the evaluation of this trait at pollen level, providing there is a good accordance with the plant performance. Two maize (Zea mays L,) populations,whose seeds show different ability to germinate at low te mperature, were obtained after four cycles of a divergent recurrent se lection using as source population the F-2 of the single cross B73 x I abo78 (the former parental line is less tolerant to low temperature at seed germination than the latter). The present work was undertaken to study pollen cold reaction of the two parental lines and of the two s elected populations. Two temperature treatments were applied at tassel s (25 and 12 degrees C) during pollen maturation-storage in the anther s and at pollen (27 and 12 degrees C) during pollen functioning in vit ro (germination and tube elongation). The ion; temperature applied dur ing pollen function affected mainly tube elongation rate, while genoty pes did not differ for the level of tolerance. With treatment at tasse ls, genotypes exhibited different pollen reactions to cold, which were consistent with those of the sporophyte. Iabo78 showed a higher cold tolerance for pollen grain germination and tube elongation rate than B 73, and the population selected for tolerance to low temperature at se ed germination was more tolerant, in terms of tube elongation rate, th an the population selected in the opposite direction. These results in dicate that accordance bem-een plant and pollen cold tolerance can be detected in maize, and that pollen assay can be used for investigating the trait.