María del Carmen Molina

NaCl effects in Zea mays L. x Tripsacum dactyloides (L.) L. hybrid calli and plants

High salt concentrations in soils negatively affect maize growth. Techniques such as remote hybridization and in vitro selection have been extensively used to accelerate breeding processes. In order to determine the usefulness of Tripsacum to improve salt tolerance in maize, the effects of NaCl, in vitro and in vivo , were evaluated in an intergeneric hybrid (MT) obtained from crossing Zea mays with Tripsacum dactyloides . Organogenic calli, induced from immature MT hybrid embryos, were exposed to different NaCl concentrations and the survival and regeneration percentages were calculated. Plants of the MT hybrid, obtained from the organogenic calli, were exposed to NaCl concentrations considered harmful for maize. The shoot dry weights of plants exposed to 250 mM NaCl did not show significant differences respect to the control ones. Although sodium content in shoots was incremented 2,5 fold, it was not toxic for this material. The MT hybrid showed better behavior, in vitro and in vivo , that maize genotypes exposed to similar conditions.

First report of Alternaria alternata causing discoloration on Amaranthus seeds in Argentina

Alternaria alternata is recorded as the causal agent of seed discoloration of Amaranthus caudatus ssp. mantegazzianus for the first time in Argentina.

Meiotic study of Zea mays ssp. mays (2n = 40) x Tripsacum dactyloides (2 n = 72) hybrid and its progeny

Maize (2n = 40) x Tripsacum dactyloides (2n = 72) F1 hybrid plants (2n = 56) were obtained by embryo rescue and induction of somatic embryogenesis/organogenesis. Hybrid plants showed Tripsacum -like phenotypes, tolerance to stresses such as NaCl salinity and low temperatures. The more frequent meiotic configurations were 28II (24%), 24II + 2IV (19%) and 26II + 1IV (12%), with an average per cell of 0.55I + 25.18II + 1.19IV. Significant differences between plants were not observed. Pollen fertility ranged from 0% to 50%. After pollination with maize or Tripsacum , 20% of F1 plants have developed viable seeds, which originated the progeny. Thirty five percent of the progeny showed 2n = 56 chromosomes and F1 like-phenotypes, which suggests they have apomictic origin. The remaining plants were fertile and they showed maize-like phenotypes and different chromosome numbers (2n = 22, 24, 26, 28 and 30), because they kept the complete maize chromosome complement and some of the Tripsacum chromosomes. Meiotic cells showed pairing between chromosomes from both parental species, which suggests the possibility of genetic recombination between them.