Preliminary Studies on Detection of Fusarium Basal Rot Infection in Onions and Shallots Using Electronic Nose

Abstract

The evaluation of crop health status and early disease detection are critical for implementing a fast response to a pathogen attack, managing crop infection, and minimizing the risk of disease spreading. Fusarium oxysporum f. sp. cepae, which causes fusarium basal rot disease, is considered one of the most harmful pathogens of onion and accounts for considerable crop losses annually. In this work, the capability of the PEN 3 electronic nose system to detect onion and shallot bulbs infected with F. oxysporum f. sp. cepae, to track the progression of fungal infection, and to discriminate between the varying proportions of infected onion bulbs was evaluated. To the best of our knowledge, this is a first report on successful application of an electronic nose to detect fungal infections in post-harvest onion and shallot bulbs. Sensor array responses combined with PCA provided a clear discrimination between non-infected and infected onion and shallot bulbs as well as differentiation between samples with varying proportions of infected bulbs. Classification models based on LDA, SVM, and k-NN algorithms successfully differentiate among various rates of infected bulbs in the samples with accuracy up to 96.9%. Therefore, the electronic nose was proved to be a potentially useful tool for rapid, non-destructive monitoring of the post-harvest crops.

Application of a Low-Cost Electronic Nose to Detect of Forest Tree Pathogens: Fusarium oxysporum and Phytophthora plurivora

“…Our results can be compared to other reports for the cases when measurements and classification of similar types of samples were reported. Lebanska et al [59] used PEN3 commercial electronic nose for detection of Fusarium basal rot infection in onions and shallots and reached classification accuracy up to 89.6%. In our previous research, we investigated the possibility of recognition of similar pathogenic fungi and oomycetes species.…”

Early Detection of Fusarium Basal Rot Infection in Onions and Shallots Based on VOC Profiles Analysis

“…Bulbs were subjected to a thorough examination to ensure health status; any with symptoms of Fusarium basal rot or other diseases including being soft, damaged, or having a “corky” basal plate indicative of an early FOC infection or insect infestation were discarded. Next, 20 healthy onion and 10 shallot bulbs were inoculated with an agar plug culture of FOC isolate FUS2 following a similar procedure described by Taylor et al as detailed in our previous work . Briefly, a 2–3 mm slice of the basal plate of the bulbs was removed, and the bulbs were sprayed with 70% ethanol.…”

“…Next, 20 healthy onion and 10 shallot bulbs were inoculated with an agar plug culture of FOC isolate FUS2 following a similar procedure described by Taylor et al 25 as detailed in our previous work. 24 Briefly, a 2−3 mm slice of the basal plate of the bulbs was removed, and the bulbs were sprayed with 70% ethanol. Next an 8 mm plug of potato dextrose agar with the actively growing edge of a FOC isolate FUS2 colony was inverted and placed on the cut basal plate of each bulb.…”

“…Negligible differences in the abundance of sulfides between healthy control and infected samples stored at 4 °C were found again suggesting that the lower temperature of storage significantly inhibits the development of fungal FOC infection as found in previous studies. 24 Next, VOCs collected from the internal space of the containers with healthy control and infected brown onion, red onion, and shallot bulbs during the second experiment were analyzed using GC-TOF-MS. A total of 49 significant volatile compounds were found and identified by using TOF-MS software. A list of the VOCs and their relative abundances of compounds detected in both experiments is shown in Table 3.…”

“…In our previous research, we demonstrated the capability of the PEN 3 electronic nose for long-term monitoring of Fusarium basal rot progression in onion and shallot bulbs stored under different temperatures. 24 In this work, we focus on early detection of Fusarium basal rot, i.e., before visual symptoms occurred, predicting infection duration, as well as identification of detected VOCs. The volatile profiles of infected and healthy bulbs were characterized using GC-IMS and gas chromatography-time-of-flight mass spectrometry (GC-TOF-MS).…”