## 1 Introduction  
Sweetpotato (_Ipomea buttas_ [PERSON]) is the sixth largest crop in the world and is rich in carbohydrates, dietary fibre, vitamins, minerals, and bioactive compounds (such as phenolic acids, flavonoids, and carotenoids) [1, 2]. Sweetpotatoes are grown in more than 100 countries worldwide, mainly in Asia and Africa. China has the largest sweetpotato plantation areas in the world [3, 4]. According to FAO statistics, in 2020, sweetpotato planting areas in China covered 2.25 million square kilometres, and the total output was about 49 million tons, representing 30.40% and 54.97% of the world sweetpotato planting area and output, respectively. Compared with other crops, sweetpotatoes can support more people per unit of land, and they are the staple food for large populations over the world [5]. However, sweetpotatoes are prone to diseases during postharvest storage and transportation, such as black rot [6], soft rot [7], and root rot [8]. Among them, black rot is the most typical. It is estimated that about 10% to 20% of sweetpotatoes are lost due to black rot disease during postharvest storage and transportation each year [9]. Black rot is caused by _Certainocystis fimbata_ Ellis & Halsted (_C. fimbata_) infection [10], which usually occurs on the wounds and lenticels of sweetpotatoes [11]. The initial symptom is the presence of black, round, slightly depressed spots. With the advancement of infection, the black spotsgradually expand, the depressions increase, and black bristles appear [12]. The disease eventually leads to wilting, ulcers, and rot [13]. After sweetpotatoes are infected with _C. fimbriata_, large numbers of toxins are produced during the disease process [14], mainly ipomeamarone [15], which is seriously harmful to human health. The LD\({}_{50}\) in mice is 230 mg/kg body weight [16]. Ipomeamarone can cause liver and lung poisoning in humans and animals [17; 18], resulting in respiratory distress, pulmonary oedema, congestion, and even livestock death [19]. At present, the discrimination of postharvest disease of sweetpotatoes relies mainly on manual work. However, there are no obvious symptoms on the surface of _C. fimbriata_-infected sweetpotatoes in the early period, resulting in inaccurate identification of infected products as acceptable. Only by removing the infected sweetpotatoes during the incubation period of the disease can large-scale rot be reduced to the greatest extent possible during storage and the economic loss mitigated. It is of great significance to explore the development of a fast, accurate, and non-destructive method of sweetpotato disease detection for use before symptoms are observed on the surface. When agricultural products are infected by pathogens, normal physiological metabolism is disturbed, causing volatile compound contents to change significantly [20; 21; 22]. Therefore, the disease condition can be determined by detecting changes in volatile compounds in _C. fimbriata_-infected sweetpotatoes. At present, the main detection technologies for volatile compounds in agriculture include gas chromatography-mass spectrometry (GC-MS) [23], gas chromatography-ion mobility spectrometry (GC-IMS) [24], and gas chromatography-olfactometry (GC-O) [25]. These technologies have high accuracy; however, there are some disadvantages to these methods, including cumbersome operation, high costs, and long detection times [26]. Therefore, these technologies are usually combined with other rapid detection methods, such as electronic nose (E-nose) and hyperspectral imaging, to achieve rapid detection and accurate identification [27]. Simultaneously, quantitative prediction of physiological indicators can also be achieved [28]. As a non-destructive, rapid, sensitive, and real-time volatile compounds detection technology, E-nose has been widely used in postharvest quality control, freshness measurement, disease detection, and pest infestation of agricultural products [29; 30; 31].