The damping-off of Pinus radiata D.Don by Fusarium circinatum Nirenberg and O’Donnell represents a limiting factor in nursery production, while seed contamination with the pathogen is one of the main pathways of the pathogen movement between areas. Chemical and physical treatments have been applied with encouraging results and some limitations. In the present study, biocontrol of damping-off by F. circinatum is proposed with Trichoderma spp. complex showing complementary antagonism and biofumigation with commercial Brassica carinata A.Braun pellets with biocidal effect. Experiments were conducted in vitro and in vivo using batches of P. radiata seeds and two F. circinatum isolates. Results were highly positive, showing an excellent efficacy of a combination of Trichoderma spp. in a single preparation to reduce significantly the mortality of P. radiata seedlings in seeds bed experiment. Biofumigation with B. carinata pellets also showed efficacy in controlling the F. circinatum inoculum and reducing seed mortality in inoculated seed batches although showing some phytotoxic effect.

A novel real‐time PCR assay based on the TaqMan probe was developed for the detection of Gnomoniopsis castaneae, causal agent of brown rot of chestnut kernels, and responsible for leaf necrosis, shoot blight and bark canker. A part of the pathogen life cycle is endophytic, colonizing all tissues of chestnut and additional hosts, which is suspected to play a key role in its epidemiology. Thus, a molecular tool for sensitive detection and quantification of G. castaneae in symptomatic and asymptomatic host tissues is urgently required to better understand G. castaneae ecology, biology and epidemiology. Primers and a species‐specific probe for G. castaneae were designed based on the sequence of the single‐copy elongation factor 1 alpha (EF1α) gene. The amplification efficiency of target DNA was 105.3% and the limit of detection of the assay was calculated at approximately 40 fg of pure fungal DNA. The pathogen was consistently detected in artificial mixtures of plant and pathogen DNAs with the same Limit of Detection (LOD) as pure fungal DNA. In naturally infected samples, the assay rapidly revealed the presence of the pathogen in all symptomatic specimens, as well as in asymptomatic tissues. Notably, a significant relationship between the results of a metagenomic HTS analysis and the qPCR assay on DNAs extracted from bulk fruit was found. This molecular tool will be of substantial aid in detecting and quantifying G. castaneae, even in the endophytic state, and in different host tissues.

BACKGROUND The brown rot fungus, Gnomoniopsis castanea, is the main organism responsible for the outbreak of chestnut postharvest decay that is threatening the sustainability of the chestnut market in Europe. Currently, no specific strategy is available to mitigate the impact and remediate the high losses of fruits in postharvest storage. In the present study, the different phases of chestnut handling in a standard facility plant were analyzed by evaluating the amount of fruit rot and infection by G. castanea at each phase. RESULTS The warm bath (48 °C) was identified as the critical phase, requiring strict parametrization to effectively inactivate G. castanea in fruits. Laboratory tests indicated that maintaining fruits at 50 °C for a maximum of 45 min provided optimal conditions to completely inactivate G. castanea inoculum during postharvest handling. However, the warm bath at 50 °C and over was not effective in inactivating the complex of fungal taxa responsible for contamination and development of molds. Higher temperatures and extended treatment times caused significant losses in fruit quality, as indicated by taste panel evaluation. Upscaling of postharvest facilities is discussed and critically evaluated. CONCLUSION The warm bath (50 °C for 45 min) is effective in completely inactivating G. castanea in fruits but did not reduce the impacts of the complex of molds responsible for external contamination and mycotoxin production. © 2021 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

The fungus Gnomoniopsis castaneae is the causal agent of the “brown rot” of sweet chestnut fruits. These days, this pathogen represents one of the main limiting factors for the sustainability of fruit production worldwide. Although heat treatment post-harvest is efficient in completely inactivating the pathogen, the application of appropriate protocols to control “brown rot” in chestnut orchards is required to help in reducing the latent population of the fungus in fruit tissues, and the consequent development of “brown rot” symptoms in the field before the post-harvest handling process. The present study aims to evaluate and compare the efficiency of products at a minimum environmental impact in experimental trials conducted in chestnut orchards in Central Italy for two consecutive years in 2019 and 2020. Phosphonate-based salts and, specifically, Zn-phosphonate were efficient in reducing the impact of the disease and the pathogen inoculum in fruits with an efficacy comparable to the fungicide Tebuconazole. A unique treatment at the blooming time produced the best results for both Zn-phosphonate and Tebuconazole, also giving indirect evidence of female flowers as a main site of infection. Phosphonate salts, and at first Zn-phosphonate, are highly effective to protect chestnut fruits from the ‘brown rot’ fungus G. castaneae. Its use in orchard management may complement the post-harvest heat treatment during the processing of fruits. Although a still ongoing debate on phosphonate salts use and efficacy in agriculture, they can be considered an optimal fungicide in chestnut orchards because of the low environmental impact when used at the recommended doses, the high translocability and stability, and the multiple mechanisms of action.

Authors explored the potential use of Vis/NIR hyperspectral imaging (HSI) and Fourier-transform Near-Infrared (FT-NIR) spectroscopy to be used as in-line tools for the detection of unsound chestnut fruits (i.e. infected and/or infested) in comparison with the traditional sorting technique. For the intended purpose, a total of 720 raw fruits were collected from a local company. Chestnut fruits were preliminarily classified into sound (360 fruits) and unsound (360 fruits) batches using a proprietary floating system at the facility along with manual selection performed by expert workers. The two batches were stored at 4 ± 1 °C until use. Samples were left at ambient temperature for at least 12 h before measurements. Subsequently, fruits were subjected to non-destructive measurements (i.e. spectral analysis) immediately followed by destructive analyses (i.e. microbiological and entomological assays). Classification models were trained using the Partial Least Squares Discriminant Analysis (PLS-DA) by pairing the spectrum of each fruit with the categorical information obtained from its destructive assay (i.e., sound, Y = 0; unsound, Y = 1). Categorical data were also used to evaluate the classification performance of the traditional sorting method. The performance of each PLS-DA model was evaluated in terms of false positive error (FP), false negative error (FN) and total error (TE) rates. The best result (8% FP, 14% FN, 11% TE) was obtained using Savitzky-Golay first derivative with a 5-points window of smoothing on the dataset of raw reflectance spectra scanned from the hilum side of fruit using the Vis/NIR HSI setup. This model showed similarity in terms of False Negative error rate with the best one computed using data from the FT-NIR setup (i.e. 15% FN), which, however, had the lowest global performance (17% TE) due to the highest False Positive error rate (19%). Finally, considering that the total error rate committed by the traditional sorting system was about 14.5% with a tendency of misclassifying unsound fruits, the results indicate the feasibility of a rapid, in-line detection system based on spectroscopic measurements.