Squash (Cucurbita maxima) is an essential crop cultivated throughout Japan, and viral diseases such as mosaic disease cause a tremendous loss of squash yield in this region. Although surveying and detection of infectious viruses are essential for controlling viral diseases, currently, no in-depth field surveys have yet been conducted. Here, we conducted a field survey in virus-infected squash fields in Okinawa Prefecture, Japan. A total of 138 samples, including 131 from squash and 7 from weeds, were collected from Ishigaki Island, Miyako Island, and Okinawa Main Island. Nine identified viruses were then investigated by reverse transcription-polymerase chain reaction (RT-PCR). Most samples were found to be infected with zucchini yellow mosaic virus (ZYMV), and a few were infected with papaya ringspot virus (PRSV) or both ZYMV and PRSV. No other cucurbit-infecting viruses were detected among the samples. In addition, ZYMV and PRSV were detected in cucurbitaceous weeds grown near squash fields, suggesting that these weeds may act as an infection source for these viruses. Discipline: Agricultural Environment

Aflatoxins and aflatoxigenic fungi are hazardous to food security and safety since mycotoxins and related fungi in cereals significantly affect animal and human health. The relatively high frequency of aflatoxigenic Aspergilli isolates in corn samples remains a concern. Accordingly, we randomly collected corn samples from 10 farms in northern and central Thailand (TM1-TM10) and aimed to detect aflatoxigenic fungi using our recently developed methods: dichlorvos-ammonia (DV-AM) and whole-agar extraction methods. When we placed 100 grains from each sample on 20 agar dish cultures (five grains per dish) to monitor the emergence of fungal colonies, the presence of Aspergillus niger and A. flavus, with an emergence frequency of 1-8 and 1-7 per 100 grains, respectively, was detected. Some isolates of A. flavus produced aflatoxin B₁ and B₂ in the culture media, indicating typical features of aflatoxigenic A. flavus, whereas the non-aflatoxin-producing isolates produced kojic acid, thereby suggesting that they belong to Aspergillus section Flavi. Chemical analysis revealed aflatoxin B₁ and B₂ contamination in some grains and sporadic contamination with fumonisin B₁. Therefore, continuous monitoring and surveillance are required owing to the prevalence of mycotoxigenic fungi in corn.

This study examined how an increase in fertilizer prices will affect the global wheat market and how fertilizer subsidy program will mitigate that impact by developing a partial equilibrium model. All scenarios demonstrated that increasing fertilizer prices drove global wheat prices higher and increased price volatility from a three-year average for 2019-2021 to 2040. Among the countries covered by this model, India and Ukraine are the most vulnerable wheat-producing countries affected by fertilizer price increases. The simulation scenario showed that a fertilizer subsidy program in India will contribute to stabilizing wheat price in the long term, considering the current fertilizer price increase trend. This study concludes that Ukraine will be the most vulnerable country affected by input price change, as well as India. Therefore, to prevent international wheat price increase and volatility, international cooperation is urgently required for Ukraine in mitigating the fertilizer price increase, as well as other input price increases.

Simple and easy methods for producing autotetraploids in polyembryonic citrus were developed. These methods require only colchicine treatment at the time of sowing and do not require special skills or equipment, such as in vitro culture. The ploidy of all growing plants was analyzed by flow cytometry. The percentage of tetraploid induction per seed in five accessions at optimal treatment was 11.0% - 42.5%. The optimum condition for tetraploid production was 0.005% colchicine for 24 h, excluding Kabuchii. The highest percentage of tetraploids was induced with 0.01% colchicine for 24 h in Kabuchii. In Kabuchii and ‘Yoshida Ponkan,’ the proportions of tetraploids were almost the same with 0.005% and 0.01% colchicine. In all accessions studied, 0.002% and 0.02% colchicine were not effective. The ploidy of some plants was confirmed by chromosome observation. The chromosome numbers of tetraploids determined by flow cytometry were 36 (2n = 4x = 36). In sequence-related amplified polymorphism (SRAP) analysis, no difference between tetraploids and original plants was detected in any of the five accessions. Hence, all analyzed tetraploids are considered autotetraploids (true-to-type tetraploids of a given accession).

In durian trees, flower induction is required to guarantee a consistent supply of durian fruit. Paclobutrazol (PBZ) is used extensively to stimulate flowering, and artificial drought stress may stabilize its effectiveness. We investigated the effects of PBZ application combined with drought stress on flower induction. We applied PBZ at three concentrations (0 [control], 1,000, and 1,500 ppm) on 9-year-old durian trees in an orchard in central Thailand 12 days after two groundcover treatments had been established (mulching versus bare ground). Then, we observed flower induction, soil water conditions, and the physiological conditions of the durian trees. Drought stress was confirmed in mulched trees: they had lower soil water potential, lower stomatal conductance, and very low leaf water potential (−0.9 MPa) compared to trees with bare ground. In both mulched and bare-ground trees, PBZ application did not induce flowering. Conversely, compared to the bare-ground treatment, mulching delayed flower bud emergence and the flowering date and reduced flower-cluster density. Therefore, we propose that strong drought stress, regardless of PBZ administration, inhibits flower induction in durian trees.

We clarified the long- and short-term factors affecting the arrival quantity and price of sawlogs in sawmills in Akita Prefecture, the second largest producer of sugi logs (Japanese cedar, Cryptomeria japonica D. Don) in Japan. In this study, we applied the autoregressive distributed lag (ARDL) model to derive long-term multipliers and reparameterize error correction models (ECMs). We used monthly data from a 157-month study period from April 2009 to April 2022. Our findings showed that sawlog (sugi, 24 cm - 28 cm in diameter) price was associated with lumber price (sugi nuki, special grade) in the long term. However, price was not much affected by the arrival quantity of sawlogs in sawmills. We found the arrival quantity of sawlogs to be associated with the quantity of lumber shipment strongly but not considerably affected by sawlog price. The results showed the importance of the supply and value chains in sawmills. Finally, ECM for arrival quantity revealed a faster error correction speed than that of price shown in the price model.