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.High salt concentrations in soils negatively affect maize growth and, consequently, produce a large drop in yield (Pasternak et al. 1995). In many countries of the world soil salinity is a serious problem for agriculture and,

Since corn has been classified as one of the most sensitive crops to soil salinity, the evaluation of NaCl toleranceof a hybrid of Zea mays ssp. mays (2n=40) and Tripsacum dactyloides (2n=72), was considered of interest to determinethe possibility of using this germplasm in corn tolerance improvement. Long-term organogenic calli, obtainedfrom immature hybrid embryos, have shown high rates of multiplication and plant regeneration. After in vitro treatmentof these calli with different levels of salinity, the survival and regeneration percentages and the daily relativeweight increments were calculated. Regenerated plants were transplanted to pots and watered with NaCl solution (6.1dS m-1) in order to assess tolerance at a whole plant level. Measurements of height, number of leaves per plant, andfresh and dry weights were taken. Exposure to 170 mM NaCl in vitro during 35 days and in vivo during 20 days produceda fresh weight decrease of 51% in calli and 31% in plants, respectively. These results indicate an improved toleranceof the maize/Tripsacum hybrid to salinity stress, in vitro and in vivo, compared with results from previous reportsusing other corn genotypes under similar conditions.

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