ABSTRACT: Polyethylene glycol (PEG) is an alternative for simulating water stress in vitro. This study developed and validated a methodology for testing water stress tolerance of potato genotypes in vitro. Three experiments were conducted: (1) determination of the optimal PEG concentration in the tissue culture medium for predicting water stress tolerance, (2) evaluation of 12 potato genotypes to adding PEG to the culture medium at two concentrations, 0 and 4.8%, and (3) assessment of the same 12 genotypes in a greenhouse under two irrigation regimes (100% and 50% of soil water retention capacity). The 4.8% PEG treatment promoted a greater water stress effect, enabling genotype differentiation at 15 days after transplanting. The Ana cultivar showed tolerance to in vitro water stress caused by PEG. The potato genotypes showed significant reductions in fresh and dry tuber weights when subjected to water stress, except for the genotype C2397-03, which did not show a decrease under stress. Tolerant genotypes were identified in the in vitro experiment; however, the same tolerance level was not observed for these genotypes in the in vivo experiment. Nevertheless, significant correlations were observed between drought indices in both conditions. The drought index of plant height and the number of nodes per plant in vitro moderately correlated with the drought index of the number of nodes in vivo. Thus, the in vitro screening method using PEG, through moderate correlations between drought indices, was able to predict in vivo water stress in potato genotypes.
Matos et al. (Wed,) studied this question.