Heat shock treatment (HST) and UV-B irradiation can reduce pathogen infection in crops. However, information on the mechanism of UV-B action is limited. Here, we investigated the mechanism of UV-B-induced resistance against powdery mildew in cucumber and compared it to that of heat-shock-induced resistance. We measured the percentage of leaf area showing disease symptoms and examined the expression levels of defense- and heat-shock-related genes across treatment groups. UV-B irradiation (intensity, 5 µW/cm²) for 4 h/d followed by pathogen inoculation reduced the appearance of powdery mildew by 21.17% compared with the control group. Unlike HST—which induces systemic resistance—UV-B irradiation induced local resistance in cucumber, as indicated by local changes in gene expression (Chi2 and ETR2). UV-B-treated plants inoculated with powdery mildew showed higher expression levels of Chi2, ETR2, and LOX6 than plants that were either treated with UV-B or inoculated. UV-B had no major effects on systemic acquired resistance or heat shock transcription factors, which are known to be affected by HST. Combined HST and UV-B had a strong synergistic effect in reducing powdery mildew in cucumber. Our results indicate that UV-B treatment likely operates through a different mechanism than HST in triggering cucumber resistance against powdery mildew infection.

Blossom end enlargement (BEE) is a postharvest deformation that may be related to the influx of photosynthetic assimilates before harvest. To elucidate the mechanism by which BEE occurs, expression marker genes that indicate the physiological condition of BEE-symptomatic fruit are necessary. First, we discovered that preharvest treatment with a synthetic cytokinin, N-(2-Chloro-4-pyridyl)-N’-phenylurea (CPPU), promoted fruit growth and suppressed BEE occurrence. This suggests that excessive assimilate influx is not a main cause of BEE occurrence. Subsequently, the expression levels of seven sugar-starvation marker genes, CsSEF1, AS, CsFDI1, CsPID, CsFUL1, CsETR1, and CsERF1B, were compared among symptomatic and asymptomatic fruits, combined with and without CPPU treatment. Only CsSEF1 showed a higher expression level in asymptomatic fruits than in symptomatic fruits, regardless of CPPU treatment. This was then tested using fruits stored via the modified-atmosphere packaging technique, which resulted in a lower occurrence of BEE, and the asymptomatic fruits showed a higher CsSEF1 expression level than symptomatic fruits, regardless of the packaging method. CsSEF1 codes a CCCH-type zinc finger protein, and an increase in the expression of CsSEF1 was correlated with a decrease in the fruit respiration rate. Thus, CsSEF1 may be usable as a BEE expression marker gene.

Blossom-end enlargement (BEE) is a physiological disorder in cucumbers (Cucumis sativus L.) that affects postharvest quality and results in commercial loss due to reduced product value. Pre-cooling using modified atmosphere packaging (MAP) has been encouraged as a preventive method of BEE; however, BEE can still be observed under actual distribution conditions. This study reexamined the process from harvesting in midsummer to arriving at the market (550 km) and storage, while considering the impact of packaging materials, packaging methods, and human factors on BEE occurrence. More than 18 h were required from harvest to delivery at the pre-cooling warehouse at the common shipping site; however, despite using a refrigerated truck, the temperature inside the packaging increased again during transportation. The temperature then dropped during 24 h of pre-cooling; however, it did not reach 10 °C, the appropriate storage temperature for cucumbers. MAP suppressed the occurrence of BEE compared to conventional film packaging; however, the BEE index varied greatly between individuals who performed the packaging. We determined that tying both ends of the packaging film increases the degree of airtightness as individual differences decrease and is more effective at suppressing BEE. Porous mineral-containing film (PM) packaging, which generates a modified atmosphere (MA), significantly suppressed BEE compared to conventional perforated film (C). In 2019 transport trials, the BEE index at 6 DAH for C film was 77.3, while for PM film it was only 12.0. Furthermore, we found that the effectiveness of PM film was significantly affected by human-related operational factors. The novel packaging method of tying both ends of the film (PM-T) provided the most consistent BEE suppression and lowest BEE index regardless of the packaging worker, demonstrating its superior potential in standardizing airtightness and minimizing human-related operational variability.

BIOCONTROL POTENTIAL OF NEMATODE-TARGETING FUNGI FROM COFFEE PLANT RHIZOSPHERE AGAINST PRATYLENCHUS COFFEAE ROOT LESION NEMATODE