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Pere Arús, Carmen Olarte, Miguel Romero and Francisco Vargas

Ten isozyme genes were studied after analyzing the variability of eight enzyme systems—glucose phosphate isomerase (GPI), phosphoglucomutase (PGM), aspartate aminotransferase (AAT), leucine aminopeptidase (LAP), 6-phosphogluconate dehydrogenase (6PGD), isocitrate dehydrogenase (IDH), shikimate dehydrogenase (SDH), and aconitase (ACO)—in the progeny of five crosses among almond [Prunus amygdalus Batsch, syn. P. dulcis (Miller) D. A. Webb] cultivars. Six of these loci were found to be located in two linkage groups, one containing four loci (Pgm-2, Gpi-2, Aat-2, and Lap-1) and two more in the other (Idh-2 and Aat-1). Genetic configurations of pairs of loci specific to segregating F1 progeny of crosses between heterozygous parents were found in our data, for which we derived the estimate of the recombination fraction and its variance. Linkage data for the gene pairs that could be estimated in various crosses were used to obtain a joint estimation of the recombination fraction.

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Francisco Vargas, Miguel Romero, Joan Clavé, Jaume Vergés, Josef Santos and Ignasi Batlle

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Martha Edith López-López, José Ángel López-Valenzuela, Francisco Delgado-Vargas, Gabriela López-Angulo, Armando Carrillo-López, Lidia Elena Ayón-Reyna and Misael Odín Vega-García

‘Keitt’ mango is one of the most important cultivars, and it is usually stored at a low temperature during its commercialization to extend shelf life and reach distant markets. However, it is susceptible to chilling injury (CI) and some prestorage treatments are required to reduce the incidence of this disorder. This research shows for the first time the protective effect of a combination hot water-calcium lactate (Ca) against CI in mango fruit cv. Keitt. Fruit were subjected to hot water treatment (HWT) (46.1 °C, 75–90 minutes) or treated with 0.5% Ca or with the combination HWT + Ca, stored at 5 °C for 20 days, and ripened at 21 °C for 7 days. CI index (CII), electrolyte leakage (EL), malondialdehyde (MDA) production, bioactive compounds, antioxidant capacity [2,2′-azino-bis-3-ethylbenzthiazoline-6-sulphonic acid (ABTS) and 2,2-diphenyl-1-picrylhydrazil (DPPH)], and activity of antioxidant enzymes [superoxide dismutase (SOD), catalase (CAT), and ascorbate peroxidase (APX)] were analyzed in mango samples after 0, 10, and 20 days of cold storage and after ripening. Hot water treatments (HWT and HWT + Ca) were more effective than Ca in providing protection against CI as evidenced by lower incidence of symptoms and lower EL and MDA. HWT + Ca increased the content of phenolics, flavonoids, and carotenoids during the cold storage, which correlated with the antioxidant capacity by ABTS. SOD and APX showed higher activity in HWT + Ca–treated fruit, whereas CAT activity was higher in fruit with HWT and Ca. These results suggest that HWT + Ca provided CI tolerance of ‘Keitt’ mango by activation of the enzymatic and nonenzymatic antioxidant systems.

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Misael O. Vega-García, Greici López-Espinoza, Jeanett Chávez Ontiveros, José J. Caro-Corrales, Francisco Delgado Vargas and José A. López-Valenzuela

Tomato (Solanum lycopersicum) fruit is susceptible to chilling injury (CI), a physiological disorder caused by low, non-freezing temperatures that affects fruit postharvest quality. Little is known about the biochemical basis of CI, and the aim of this study was to identify proteins related to this disorder in ‘Imperial’ tomato fruit. CI and protein expression changes were analyzed during fruit ripening (0, 4, 8, and 12 days at 21 °C) after storage under chilling (5 °C) and non-chilling conditions (21 °C) for 5, 15, and 25 days. The main CI symptoms observed were uneven fruit ripening and color development, pitting, and decay. Protein analysis of two-dimensional gels showed that 6% of the detected spots (≈300) changed their expression in response to cold. The identified proteins are involved in carbon metabolism, oxidative stress, photosynthesis, and protein processing and degradation; two were related to cold stress, showing higher accumulation in non-damaged tissue of chilled fruit: thioredoxin peroxidase (TPxI) and glycine-rich RNA-binding protein (GR-RBP). This is the first report suggesting an important role for TPxI and GR-RBP in cold response during tomato fruit ripening, and they may be acting through redox sensing and regulation of gene expression at low temperature. These enzymes and the other chilling-related proteins might be working together to maintain the cellular homeostasis under cold stress conditions.