Gas exchanges and water use efficiency in the selection of tomato genotypes tolerant to water stress.

Water stress can affect the yield in tomato crops and, despite this, there are few types of research aiming to select tomato genotypes resistant to the water stress using physiological parameters. This experiment aimed to study the variables that are related to the gas exchanges and the efficiency in water use, in the selection of tomato genotypes tolerant to water stress. It was done in a greenhouse, measuring 7 x 21 m, in a randomized complete block design, with four replications (blocks), being five genotypes in the F2BC1 generation, which were previously obtained from an interspecific cross between Solanum pennellii versus S. lycopersicum and three check treatments, two susceptible [UFU-22 (pre-commercial line) and cultivar Santa Clara] and one resistant (S. pennellii). At the beginning of flowering, the plants were submitted to a water stress condition, through irrigation suspension. After that CO2 assimilation, internal CO2, stomatal conductance, transpiration, leaf temperature, instantaneous water use efficiency, intrinsic efficiency of water use, instantaneous carboxylation efficiency, chlorophyll a and b, and the potential leaf water (Ψf) were observed. Almost all variables that were analyzed, except CO2 assimilation and instantaneous carboxylation efficiency, demonstrated the superiority of the wild accession, S. pennellii, concerning the susceptible check treatments. The high photosynthetic rate and the low stomatal conductance and transpiration, presented by the UFU22/F2BC1#2 population, allowed a better water use efficiency. Because of that, these physiological characteristics are promising in the selection of tomato genotypes tolerant to water stress.

Mini tomato genotypes resistant to the silverleaf whitefly and to two-spotted spider mites.

The mini tomato production has expanded, becoming an amazing alternative for enterprise. Despite all commercial potential, the cultivation has the occurrence of pests as main obstacle during the crop development. Nowadays, there are no researches that aimed obtaining genotypes with high acylsugar content, capable of providing a broad-spectrum resistance to pests. This study aimed the selection of mini tomato genotypes, with high acylsugar content, and checking the resistance level to the silverleaf whitefly [Bemisia tabaci (Gennadius)] and to the two-spotted spider mites (Tetranychus urticae Koch). Sixteen genotypes were evaluated, from which 12 were on the generation F2BC1, originated from the interespecific cross between Solanum pennellii versus Solanum lycopersicum L. and 4 were check treatments, being three of cultivated tomatos (cv. Santa Clara, UFU-02, and UFU-73) and the wild accession LA-716 (S. pennellii). The variables analyzed were acylsugar content, repellency to the silverleaf whitefly, repellence to the two-spotted spider mites, and density of glandular trichomes. The genotypes UFU-22-F2BC1#9 and UFU-73-F2BC1#11 have high acylsugar content and both are resistant to the pests that were evaluated. New studies must be conducted seeking for inbred lines, obtained from the selected genotypes, aiming to get commercial hybrids with high acylsugar content.

Studies on bioavailability of some bulk and trace elements in Mexican tortilla using an in vitro model.

An in vitro gut model was used to investigate the bioavailability of calcium, magnesium, cadmium, chromium, iron, manganese, and lead in the Mexican (maize) tortilla. The samples (4 g) were digested in quartz tubes using concentrated nitric acid (12 mL) at 65 degrees C (2 h) and then at 120 degrees C (4 h). Total element concentration was determined by atomic absorption spectrometry. Enzymatic hydrolysis was carried out in two steps: first, with pepsin in a hydrochloric acid medium (pH 1.8) and then after neutralization with sodium bicarbonate (pH 6.0), with the mixture of pancreatine, amylase, and bile salts extract. Elements under study were determined in the supernatant by atomic absorption spectrometry. The bioavailable fraction of each element in tortilla was evaluated as the percentage of total element content found in the solution after enzymolysis. The obtained results showed relatively low bioavailability of the selected elements (from 2% to 32%), which possibly may be ascribed to the presence of dietary fiber in tortilla.