Introduction

The potato (Solanum tuberosum) ranks as the world’s fourth-largest cereal crop, with 80% of its yield suitable for human consumption1,2,3. Furthermore, potato flesh is rich in vitamins, sugars, proteins, and other essential nutrients, providing a substantial supply of nourishment for humans4,5. Additionally, potatoes serve as biomass energy crops and industrial raw materials6,7. However, during prolonged storage for sales, processing, and planting, potatoes are susceptible to contamination by dry rot, severely impacting their quality8,9. In China, dry rot causes approximately 10% of potato spoilage during storage, and in severe cases, this figure can reach up to 60%. Dry rot has become a significant disease during potato storage. The primary cause of potato dry rot is contamination by Fusarium spp.10, resulting in decreased quality, reduced marketability, lower planting rates, and severe threats to potato safety during storage11,12. It is a crucial factor limiting the development of the potato industry.

Therefore, researching and developing preservation technologies for agricultural products is of paramount importance13. In this context, radiation preservation technology has been widely applied as an advanced new technique14. Different agricultural products require varying radiation doses for preservation15, and precise control of radiation dosage is critical for radiation preservation16. Researching suitable thermoluminescent dosimeters (TLDs) contributes to the popularization of radiation preservation technology17. An ideal TLD material should possess good sensitivity18, a wide linear range19, stable luminescent performance under high-energy radiation excitation, a high upper dose response limit, and the ability to measure various types of radiation and ions20,21. Currently, several commercially available TLD materials serve different purposes: LiF22 and Li2B4O7: Sm23 are suitable for personal dose monitoring, with good sensitivity but a lower linear response limit (< 50 Gy). Al2O3: C24 and MgB4O7: Dy25 are used for medical dose monitoring, while BeO26, CaSO4: Dy27, and CaF2: Ce28 are employed for environmental dose monitoring. Although their linear response limits have improved somewhat (< 500 Gy), they have not yet reached the accurate measurement of kGy-level irradiation required for radiation preservation29. Other TLD materials like CaWO4: Pr3+30, SrDy2O4: Eu3+31, and BaSi2O5: Dy3+32 are suitable for high-dose area monitoring, with linear response limits reaching kGy levels, albeit with suboptimal linearity.

Therefore, researching TLD materials with stable performance, high sensitivity, and a wide linear response range is crucial for radiation preservation. In this vein, the successful development of Y1.79Bi0.01Eu0.2MgTiO6 thermoluminescent dosimeter material using the high-temperature solid-phase method holds promise for radiation dose monitoring. This material can be used to study the preservation effects of potatoes under different irradiation doses and the inhibitory effects of radiation on microorganisms.

Materials and methods

Materials and preparation

Y1.79Bi0.01Eu0.2MgTiO6 samples were prepared using the high-temperature solid-phase method. A specific amount of Y2O3, MgO, TiO2, Bi2O3, and Eu2O3 (all analytical grade, purchased from Shanghai Aladdin Reagent Co., Ltd.) was weighed according to the stoichiometric ratio. The materials were ground in an agate mortar for 1 h until thoroughly mixed. Using a high-temperature alumina crucible as a carrier, the uniformly mixed material was placed in a muffle furnace for calcination. The calcination was carried out in an air atmosphere, first heating to 800 °C and holding for 3 h for pre-sintering, followed by rapid heating to 1300 °C for 9 h. After cooling to room temperature, block samples were obtained, and powdered samples were prepared by grinding in an agate mortar for subsequent use.

The potatoes were obtained from a crop planting site in Nanning, Guangxi Zhuang Autonomous Region, China, on September 26, 2023. They were individually packaged in transparent polyethylene self-sealing bags, with a total of 5 samples, each containing four potatoes, weighing approximately 900 g per sample.

Equipment and parameters

The measurement of the regeneration dose irradiation and thermoluminescence curve of the dosimeter material was performed using two instruments: Risø TL/OSL-15-B/C Thermoluminescence/Optically Stimulated Luminescence Measurement System: The irradiation source was a 90Sr β radiation source with a dose rate of approximately 0.1 Gy∙s−1. LTTL3DS Thermoluminescence Spectrometer (produced by Guangzhou Reddy Technology Co., Ltd.): The irradiation source was an X-ray tube with an operating voltage of 50 kV and a current of 150 µA, resulting in a dose rate of approximately 0.1 Gy∙s−1.

Irradiation treatment

The irradiation of potatoes (including the dosimeter material) was conducted at the Guangzhou Huangpu District base of Huada Biotechnology Co., Ltd. The radiation source was a 60Co-γ source with an activity of approximately 1,500,000 Ci. Prior to irradiation, 20 mg of the thermoluminescent material Y1.79Bi0.01Eu0.2MgTiO6 (already encapsulated) was placed in each potato sample. The potatoes were then irradiated for 5000, 2500, 1000, 500, and 0 s. After irradiation, the potatoes were stored at room temperature.

Results and discussion

Thermoluminescent dose response characteristics of Y1.97Bi0.01Eu0.2MgTiO6

Thermoluminescence glow curve

The thermoluminescence glow curve measurement was conducted using the Risø TL/OSL-15-B/C Thermoluminescence/Optically Stimulated Luminescence Measurement System. A sample of 20 mg Y1.79Bi0.01Eu0.2MgTiO6 powder was placed in the instrument, and the following steps were performed:

  1. (1)

    Preheat the sample to 700 K and hold for 10 s.

  2. (2)

    After cooling to room temperature, irradiate the sample with a 90Sr β radiation source (10 Gy).

  3. (3)

    Heat the sample to 700 K at a rate of 5 K/s and record the thermoluminescence glow curve.

Repeat the above steps, varying the irradiation dose to 20 Gy, 50 Gy, 60 Gy, 70 Gy, 80 Gy, 90 Gy, 100 Gy, 110 Gy, 120 Gy, 150 Gy, 300 Gy, 400 Gy, 500 Gy, 700 Gy, 800 Gy, 900 Gy, and 1,000 Gy, and measure and record the thermoluminescence glow curves. By changing the radiation source to an X-ray tube while keeping other test conditions constant, a series of X-ray irradiation thermoluminescence curves can be obtained.

To ensure reliable experimental data, the thermoluminescence was repetitively tested for different radiation sources and doses. The results showed consistent thermoluminescence curves, as depicted in Fig. 1. The curve exhibits a broad distribution extending from 350 to 700 K and features two distinct thermoluminescence peaks at temperatures of 495 K and 580 K. As the irradiation dose decreases, the shape and peak temperatures of the thermoluminescence curve remain relatively unchanged, while the thermoluminescence intensity systematically decreases33.

Fig. 1
figure 1

Thermoluminescence curves of Y1.79Bi0.01Eu0.2MgTiO6 phosphor irradiated by a 90Srβ radiation source at higher doses (a) and lower doses (b).

Full size image

Dose–response curve

To verify the relationship between thermoluminescence integral intensity and radiation dose, the integral intensity of thermoluminescence curves between 300 and 700 K at different radiation doses was determined. The resulting dose–response curve is shown in Fig. 2. Figure 2a and b represent the dose–response curves under β-ray and X-ray irradiation, respectively. Linear fits were applied to the experimental data points. Notably, neither β-ray nor X-ray irradiation exhibited saturation within the tested range. The dose response remained linear within the range of 10 to 1000 Gy, and even at 1000 Gy, a good linear relationship was maintained. This suggests that the thermoluminescent material may also exhibit a favorable linear response at higher doses. The wide linear range demonstrates the advantages of Y1.79Bi0.01Eu0.2MgTiO6 as a novel thermoluminescent dosimeter material, suitable for applications in dose monitoring34,35,36. Within the 10 Gy to 1000 Gy range, the relationship between thermoluminescence integral intensity (y) and radiation dose (x) is as follows: for β-ray excitation, y = (2.98 ± 0.21)*106 + (142.06 ± 0.51)*103 × and for X-ray excitation, y = (2.96 ± 0.36)*106 + (143.3 ± 1.3)*103x. Both intercepts and slopes are consistent, and the obtained errors fall within the experimentally controllable range, requiring no further adjustments.

Fig. 2
figure 2

Dose–response curves of Y1.79Bi0.01Eu0.2MgTiO6 phosphors under β-ray (a) and X-ray (b) irradiations.

Full size image

Dose measurement of irradiated potatoes

The dose of radiating potato was determined by analyzing the thermoluminescence (TL) curve of the pre-inserted Y1.79Bi0.01Eu0.2MgTiO6 thermoluminescent material which was pre-inserted. The TL curves were measured using a Risø TL/OSL-15-B/C thermoluminescence/optically stimulated luminescence instrument, as shown in Fig. 3a.

Fig. 3
figure 3

The thermoluminescence curve (a) and dosimetry measurement (b) of different time were irradiated by 60Co-γ radioactive source.

Full size image

Remarkably, the TL curves of the material irradiated by the 60Co-γ source closely resemble those obtained from β-ray irradiation. Both curves extend from 350 to 700 K and exhibit two distinct thermoluminescent emission peaks. As the irradiation time decreases, the luminescence intensity also significantly diminishes.

Based on this, calculated the integral intensity of the TL curves for irradiation times of 5000, 2500, 1000, and 500 s, resulting in values of 1.45 × 108, 7.45 × 107, 3.1 × 107, and 1.75 × 107, respectively. Using the dose–response curve, the corresponding radiation doses were determined as 999.7 ± 2.1 Gy, 499.4 ± 2.0 Gy, 198.2 ± 0.8 Gy, and 101.5 ± 1.6 Gy. These results are summarized in Fig. 3b. In subsequent observation experiments, the doses were adjusted to 1000 Gy, 500 Gy, 200 Gy and 100 Gy, respectively.

The practical utility of this thermoluminescent material was demonstrated in potato radiation preservation dose monitoring. Additionally, the radiation dose rate of the 60Co-γ source was approximately 0.2 Gy/s.

Preservation effect of potatoes at different radiation doses

After 60Co-γ irradiation, there were no significant changes in the morphology and quality of potatoes. Placed five groups of potatoes in a cool environment to discuss the preservation effect of potatoes under different radiation doses. The morphology of the potatoes was recorded every 5 days. The results are shown in Fig. 4.

Fig. 4
figure 4

Morphological changes of potato within 50 days (The time sequence is from top left to bottom right, interval of 5 days).

Full size image

Each column in the images represents a group of potatoes. From top to bottom, the potatoes are labeled as 1, 2, 3, and 4, and from left to right, they correspond to potatoes exposed to radiation doses of 1000 Gy, 500 Gy, 200 Gy, 100 Gy, and 0 Gy, respectively.

Observations within the first 15 days revealed that the morphology of potatoes remained unchanged under different radiation doses, with no apparent signs of mold or dehydration. This study suggests that proper ultraviolet radiation does not harm pigmented potatoes and may even enhance their oxidative stress tolerance. Additionally, it increases the expression of structural genes related to anthocyanin synthesis, leading to improved yield and quality of potato tubers.

By the 20th day, noticeable changes in the morphology of potatoes occurred as storage time extended under different radiation doses. Examine the potato conditions on the 20th day, as depicted in Fig. 5:

  1. 1.

    Unirradiated (The fifth column):

    1. a.

      All potatoes exhibited significant mold growth.

    2. b.

      Potatoes1, 2 and 4 were visibly shriveled.

  2. 2.

    100 Gy Irradiation (The fourth column):

    1. a.

      Potatoes 1 and 4 remained intact.

    2. b.

      Potato 2 experienced significant water loss.

    3. c.

      Potato 3 showed noticeable mold growth, but water loss was not severe.

  3. 3.

    200 Gy, 500 Gy, and 1000 Gy Irradiation (The third column, the second column and the first column):

    1. a.

      Potatoes irradiated at these doses showed no significant changes in morphology.

Fig. 5
figure 5

Potato morphology at 20 days.

Full size image

As time progressed:

On the 25th day, the 200 Gy-irradiated Potato 1 exhibited clear mold growth.

By the 35th day, 500 Gy-irradiated Potatoes 2 and 4 displayed evident mold growth.

On the 40th day, the morphology of the potatoes is as shown in Fig. 6:

  1. 1.

    Unirradiated (The fifth column):

    1. a.

      All potatoes exhibit significant mold decay and severe water loss.

  2. 2.

    100 Gy Irradiation (The fourth column):

    1. a.

      Potatoes 1 and 4 experience moderate water loss.

    2. b.

      Potatoes 2 and 3 show severe mold growth.

  3. 3.

    200 Gy Irradiation (The third column):

    1. a.

      Potato 1 shows significant mold growth.

    2. b.

      Potatoes 2 and 3 remain intact.

    3. c.

      Potato 4 experiences moderate water loss.

  4. 4.

    500 Gy Irradiation (The second column):

    1. a.

      Potatoes 1 and 3 remain intact.

    2. b.

      Potatoes 2 and 4 exhibit noticeable mold growth and severe water loss.

  5. 5.

    1000 Gy Irradiation (The first column):

    1. a.

      After 40 days of storage, the potatoes show minimal change.

    2. b.

      Potato 1 has a small mold spot, and there is no evidence of water loss.

Fig. 6
figure 6

Potato morphology at 40 days.

Full size image

These observations provide insights into the preservation effects of different radiation doses on potatoes.

Continuing the storage until the 50th day, the moldy potatoes continued to deteriorate. To discuss the internal changes of potatoes under different radiation doses, sliced the potatoes, and the results are shown in Fig. 7:

  1. 1.

    Unirradiated (The fifth column):

    1. a.

      All Potatoes are severely decayed.

  2. 2.

    100 Gy Irradiation (The fourth column):

    1. a.

      All Potatoes show different levels of decay.

  3. 3.

    200 Gy Irradiation (The third column):

    1. a.

      Potatoes 1, 3, and 4 exhibit varying degrees of decay.

    2. b.

      Potato 2 maintains intact internal structure.

  4. 4.

    500 Gy Irradiation (The second column):

    1. a.

      Potato 1 has relatively intact internal structure.

    2. b.

      Potato 2 shows severe decay.

    3. c.

      Potato 3 experiences minor decay.

    4. d.

      Potato 4 retains good moisture but displays internal mold signs.

  5. 5.

    1000 Gy Irradiation (The first column):

    1. a.

      The flesh of the potato appears healthy, with adequate moisture.

    2. b.

      Potato 1 exhibits slight decay in its flesh.

Fig. 7
figure 7

Potato section at 50 days.

Full size image

These results demonstrate that irradiation effectively prolongs potato storage. Unirradiated potatoes showed noticeable mold after 15 days, whereas irradiated potatoes delayed the onset of mold. The delay time is related to the radiation dose: higher doses lead to later mold development. At a dose of 1000 Gy, potatoes only showed mold after 40 days of storage, and by the 50th day, the mold had not significantly spread.

To investigate the cause of potato deterioration, assessed the symptoms observed during potato storage. After 15 days of storage, signs of decay became evident: localized darkening and browning of the potato skin, accompanied by increased water loss. The surface of the tubers exhibited wrinkling, indentation, and hard brown lesions. During the mid-storage period, white mycelium growth was prominent on the potatoes. In the later stages of storage, irregular concentric rings appeared within the potato flesh, leading to necrosis. Internally, the potatoes began to rot, displaying colors such as black, dark brown, light brown, or yellow–brown. These cavities were filled with white mycelium, resulting in a noticeable reduction in potato weight37,38.

All these symptoms align with the characteristics of dry rot disease, which is the primary ailment affecting potatoes during storage39. Figure 8 illustrates the changes in weight and mold area of potatoes under different radiation doses during various storage periods. Notably, unirradiated potatoes suffered significant weight loss and extensive mold growth, with an approximately 80% reduction in weight after 50 days of storage. However, 1000 Gy-irradiated potatoes effectively prevented dry rot disease, maintaining weight and quality without significant changes. For potatoes irradiated at 500 Gy, 200 Gy, and 100 Gy, weight losses after 50 days of storage were 23%, 44%, and 51%, respectively.

Fig. 8
figure 8

Weight (a) and mouldy area (b) of potato at different storage times.

Full size image

These results demonstrate that appropriate radiation doses can partially prevent potato dry rot disease and inhibit mold proliferation, ensuring potato quality during storage.

Pathogenic fungi in potato

The primary cause of potato dry rot disease is the invasion of Fusarium spp40. To identify the specific Fusarium species, initially observed the colony morphology on potato surfaces41. Initially, these colonies appeared white and velvety. However, as storage time increased and mold growth occurred, the colony color gradually changed to yellow. Under a microscope at 400 × magnification, examined the morphological features of their conidia (asexual spores) and conidiophores (structures that produce conidia)42. Based on these observations, Provisionally classified the potato strains into two categories:

Fusarium solani (Fig. 9, upper section): This type of Fusarium produces oval-shaped conidia, with numerous small conidia showing septation (division). Some large conidia exhibit a “matte” shape with rounded ends, often divided into three segments43.

Fig. 9
figure 9

Fungal morphological characteristics of non-irradiated potato stored for 20 days.

Full size image

Fusarium oxysporum (Fig. 9, lower section): This Fusarium species produces elongated conidia, with most small conidia lacking septation. Large conidia have a sickle-like shape, pointed at one end44.

To explore how fungal morphology and species change over time, further observed the potato fungi after 50 days of storage (Fig. 10). Although the number of fungi increased significantly, the species remained consistent. The primary pathogens responsible for potato disease were still identified as Fusarium oxysporum and Fusarium solani. Notably, the fungal morphology closely resembled that observed at 20 days.

Fig. 10
figure 10

Morphological characteristics of Fusarium solani.

Full size image

Different radiation doses mitigated the invasion and spread of these two fungi to varying degrees. Among them, 1000 Gy irradiation had the most pronounced effect. This demonstrates that radiation effectively suppresses the infection and dissemination of Fusarium solani and Fusarium oxysporum.

Conclusion

In this study, the possibility of using Y1.79Bi0.01Eu0.2MgTiO6 as a thermoluminescent dosimeter material in the field of dose monitoring was determined by evaluating the thermoluminescence curve and dose response curve of Y1.79Bi0.01Eu0.2MgTiO6 material. The thermoluminescence dosimeter material was applied to the monitoring of potato radiation preservation dose. It was found that the storage time of potato under different irradiation doses was significantly prolonged, and the quality of potato irradiated with 1000 Gy was still good after 50 days of storage. The quality and morphology of potato will not be affected by irradiation treatment, and irradiation can effectively prevent potato dry rot and inhibit the infection and spread of Fusarium.