Organic acids are abundant constituents of ripe fruits and are responsible for their sourness. In addition, they contribute to their flavour. In many fruits, the most abundant organic acids are malic and citric. The aims of this review are two-fold. The first is to provide a clear overview of malic and citric acids in the flesh of fruits. The abundance of different organic acids in commercially grown fruits is described. How this abundance changes during fruit development is outlined. The metabolic pathways used in the synthesis and dissimilation of malic and citric acids in fruits are described. The functions of malic and citric acids in the flesh of fruits are discussed. Secondly, how environmental and cultural practices can alter the organic acid content of fruits is considered.

Potato tuber sugar content is an indicator of management conditions during crop growth, since it affects the degree of maturity, quality and sprouting. In this study, potato growth and yield under field conditions were assessed. Soluble sugar content in tubers at different physiological ages was determined, as was the effect these sugars have on seed-tuber sprouting during storage. To this end, four tuber samplings were carried out in four potato cultivars: one during tuber dormancy and three at different physiological ages. Determinations were made using high-performance liquid chromatography (HPLC). The variety Alpha had the longest biological cycle among all genotypes, and its yield was similar to that of the varieties Gigant and Vivaldi (659 g), which had yields 58 % greater than that of the variety Atlantic. Potato tubers with the physiological age of apical dominance (109 days after harvest, DAH), multiple sprouting (153 DAH) and senescence (237 DAH) had the highest sucrose, glucose and fructose contents (7.10 to 7.89 mg·g-1), and the variety Vivaldi had the highest amount of sucrose and reducing and total sugars. The length and dry weight of the potato sprout showed a high positive and significant association with the content of reducing and total sugars. 

In the development of the theory of synthetic varieties (SVs) of crop species such as maize (Zea mays L.) and onion (Allium cepa L.), formed with single-cross hybrids, it has been shown that genetic erosion may occur during their formation. This erosion increases inbreeding and reduces yield. This gene loss is caused by the mating of heterozygous genotypes, the finite number of their progeny, and the randomness of the genetic mechanism. The main objective of this study was to determine the number of non-identical by descent (NIBD) genes lost during the development of the individuals that represent the double-cross (DC) or three-way (TW) line hybrids that in turn will be parents of a SV. The initial lines were assumed to be inbred and unrelated and each hybrid derived from them was represented by m individuals, and formulae for the mean, variance and number of lost NIBD genes per hybrid were derived. The number of lost NIBD genes of a DC (TW) was expressed as the number of NIBD genes in the 4 (3) initial lines minus the mean of NIBD genes forming the genotypes of the m individuals representing each DC (TW). It was found that each DC and TW loses on average 4/2m and 2/2m NIBD genes, respectively. The magnitudes of these losses reflect the effect of the sample size (m) and the number of loss sources (the single crosses) of the parents of the DCs (2) and TWs (1). The largest NIBD gene losses per parent were 2 (DC) and 1 (TW), which occur when m = 1. However, when m is large (m ≥ 12), as should occur in reality, the losses and the variance of the number of NIBD genes are nearly zero.

The pipiana pumpkin is an important element in the diet of south-central Mexico residents. Its seeds are consumed directly toasted and seasoned with salt, and they are also the main ingredient used for making typical dishes such as green mole or pipian, as well as various traditional sweets. Some soil microorganisms cause severe damage in fruit, which reduces yield. The aim of the study was to identify morphologically and molecularly the oomycete causing rot in pipiana pumpkin fruits, and evaluate options for chemical and biological control in greenhouses. During August and September 2011, in the northern region of the state of Guerrero, pipiana pumpkin fruits with rot symptoms were collected. Morphological identification was performed with the keys proposed by Gallegly and Hong (2008), and molecular identification was by polymerase chain reaction (ITS-PCR). Both tests identified Phytophthora capsici as the causal agent of rot in pipiana pumpkin fruits. The sequences obtained showed 99 % similarity with the GenBank-held sequences for P. capsici in watermelon from the United States and pumpkin from Italy. The active ingredients propamocarb + fosetyl and metalaxyl + chlorothalonil delayed the presence of the pathogen in the fruits by six days, whereas the biocontrol agents delayed it by four days.

Currently, the state of Queretaro is a major wine producer in Mexico; however, marketing these wines is difficult due to their lack of quality and typicity, factors in which wine yeasts play an essential role. Saccharomyes are responsible for ethanol production and non-Saccharomyes (nS) can provide metabolites that enhance wine quality, so their use in mixed cultures is of great interest. In this study, yeasts isolated from the spontaneous fermentation of grape musts from three local vineyards were differentiated as nS in lysine medium. Their β-glucosidase activity and SO2 (30 mg·L-1) and ethanol (6 %) tolerances were evaluated. Outstanding yeasts were tested in mixed microvinifications along with S. cerevisiae (K1-V1116) and identified through analysis of the 26S gene. Of 197 isolated strains, 146 were differentiated as nS; 90 showed βglucosidase activity and eight (NB1, NA4, NB27, NB31, NB39, NR77, NR90, NB108) were selected based on tolerance tests, being identified as belonging to the genus Hanseniaspora. The nS did not interfere with the fermentative activity of K1-V1116, finding no differences in the parameters evaluated between the wines obtained by mixed cultures and the control (K1-V1116). The values obtained for pH, total acidity, volatile acidity and alcohol were considered to be of acceptable quality for dry wines. The strain NB39 stood out for its glycerol production, obtaining the highest value (7.45 g·L-1). We conclude that there are nS yeast strains in the region with enological potential to be used at a commercial level.