The objective of this review was to bring together concepts related to studies aimed at elucidating defense mechanisms against disease-causing agents, mainly in postharvest. Like plants, fruits are exposed to attack by pathogens that cause rot during postharvest storage, resulting in considerable losses. To control these pathogens, synthetic chemicals are used; however, since they are toxic, genetic resistance is regarded as a viable alternative. Fruits can withstand pathogens by means of physical barriers (presence of thick cuticular or trichome layers) and chemical ones, or through induced defenses that are activated once the host detects the presence of the pathogen, triggering the oxidative burst during the early hours of interaction. This burst entails the generation of reactive oxygen species (ROS), such as superoxide (O2ˉ), hydroxyl radical (OHˉ) or hydrogen peroxide (H2O2), and the activation of genes involved in several metabolic pathways. The study of such mechanisms may allow detecting disease-resistant genetic materials, thus reducing the use of toxic products.

The aim of this study was to evaluate the effect of low temperatures on antioxidant activity and enzyme activity in sage (Salvia officinalis L.). To do this, terminal buds of this plant, previously packed in polyethylene bags at 0, 6 and 23 °C (control), were stored for 21 days. Every three days, total phenolic content (TP), antioxidant capacity (AC), and the activity of the enzymes catalase (CAT), superoxide dismutase (SOD), peroxidase (POD) and polyphenol oxidase (PPO) were evaluated. In the 0 and 6 °C treatments, TP content increased from 4.52 to 5.07 mg∙kg-1 FW up to 12 days after storage (das). A 6 °C, AC had the highest values at 12 das with 53.75 to 88.57 mg VCEAC∙g-1 FW. SOD activity decreased considerably at 9 das in the cooling treatments, falling from 5.2 to 3.2 U∙mg-1 P. On the other hand, low storage temperatures increased CAT activity, relative to the control, although during storage it was on the decrease. Cooling decreased POD and PFO activity relative to the control, but at 12 das the highest activity of these enzymes in the three treatments was observed. The cooling decreased total phenolic content, antioxidant capacity and the enzyme activity of POD, and increased the activity of PFO, CAT and SOD.

An experiment was conducted under protected conditions using soilless culture to determine the internal nitrogen requirement (INR) for habanero pepper (Capsicum chinense Jacq.) variety Big Brother. Treatments consisted of four concentrations of nitrate (NO3-) in nutrient solution (5, 10, 15 and 20 meq∙L-1). The response variables were dry matter (DM) production and N concentration in the different plant organs. The results indicate that a plant produces an average of 357.1 g DM, of which 64.5 % is fruit, while the rest is distributed in stem, leaves and flowers. However, with regard to DM weight, leaves and flowers concentrated more N than fruit, with 2.3 and 3.3 % respectively, while fruit concentrated 1.5 % N. It was found that the NO3- concentration in the nutrient solution had a significant effect on the N concentration in total DM, ranging from 1.06 to 2.74 %. The highest yield was obtained in plants treated with the 15 meq∙L-1 NO3- concentration, while the concentration with 20 meq∙L-1 significantly reduced fruit yield. The minimum N concentration in total biomass when maximum fruit yield was reached was 2.2 %, a value that was considered as the INR for the crop. Based on this value, the N requirement for habanero pepper variety Big Brother is 5.1 kg per ton of fruit.

Jalapeño pepper is consumed both green (unripe) and red (ripe), so it is important to evaluate the components present in both states. The aim of this study was to evaluate the effect of storage time (30 days) at room temperature (25 °C) on the physicochemical, antioxidant and textural parameters of Capsicum annuum var. annuum. During this period, there was a significant increase (P ≤ 0.05) in the soluble solids content, acidity, and reducing sugars, whereas moisture, ash, and pH decreased. The firmness of the pericarp varied from 5.17 N to 2.88 N. The capsaicin in green state was lower than that found for the red state. Some antioxidant compounds showed a significant increase (P ≤ 0.05) from day 15 of storage. The radical scavenging of DPPH was higher (58.35 %) in the red state of maturity in comparison with the green state of maturity (19.42 %). Some properties analyzed in Jalapeño pepper showed significant changes (P ≤ 0.05) between day 15 and 20 of storage, coinciding with the color change from green to red. Jalapeño pepper at the red stage is a good source of antioxidants including ascorbic acid, carotenoids and polyphenols.

In Chile, avocado cultivation has incorporated the use of uniconazol-p via irrigation in plantations where rootstocks from seed predominate. This study suggested that the effectiveness of applying uniconazole-p to the soil base of ‘Hass’ avocado trees depends on the origin of the rootstock. Nine-month-old ‘Hass’ trees were used in Duke 7 clonal rootstock and Mexícola rootstock from seed, together with 0, 0.0035, 0.007 and 0.014 g·L-1 uniconazol-p. Measurements were made in the canopy of the plants, at the level of vegetative growth, bud development and earliness in flowering. It was found that the differences among variables were at rootstock level; Duke 7 showed greater vigor and earlier flowering than trees with Mexícola. In addition, Duke 7 had no response to the application of uniconazol-p, contrary to what was presented by Mexícola, where the uniconazole-p concentration above 0.007 g·L-1 showed no effect on either shoot length or the proportion of potential flower buds in relation to the total number of buds.