Identifying Primary Ecological Drivers and Regional Suitability for High-Quality Diospyros kaki ‘Taishuu’

Abstract

Diospyros kaki Thunb. ‘Taishuu’ is novel fruit cultivar known for its excellent mouthfeel properties and high economic value. This study aimed to identify the ecological adaptability and potential suitable cultivating regions of this persimmon in China. In addition, key ecological factors influencing fruit mouthfeel were also investigated. Differences between key metabolites and mouthfeel properties of 35 persimmon samples from 13 provinces were compared. Subsequently, ecological factors were evaluated to explore interactions among dominant ecological factors, habitat suitability, and fruit quality. An adaptive segmentation map was ultimately created to highlight variations in mouthfeel properties of the persimmon. The findings were summarized as follows: The core ecological suitability zones encompass most warm, temperate and typically subtropical regions of China, spanning 116,200 square kilometers. Habitat suitability influences fruit size but does not affect mouthfeel properties. Key factors affecting mouthfeel properties of D. kaki ‘Taishuu’ include precipitation during the growing period, high temperature during the fruit ripening stage, and low temperatures during dormancy. Persimmons from coastal areas and Yunnan province were characterized by a lusciously sweeter and richer taste, a satisfying crisp texture, and an overall distinctly superior mouthfeel. In contrast, samples from central cultivation areas exhibited higher density, greater firmness, reduced crispness, and inferior flavor quality Based on zoning results, extensive regions show significant potential for high-quality production, making them highly promising for D. kaki ‘Taishuu’ cultivation. For marginally suitable habitats, appropriate cultivation measures should be implemented to mitigate limiting factors such as temperature and soil moisture.

1. Introduction

With the growth of the fruit industry and rising consumption standards, the demand for quality has increased, leading to the introduction of various new fruit varieties [1]. One such variety is Diospyros kaki Thunb. ‘Taishuu’, a non-astringent type with a fragrant aroma and delightful flavor [2]. This fruit originated in Japan and was introduced to China in the 1990s. It exhibits significant commercial appeal, with an average market price ranging from 40 to 50 yuan per kilogram, and potential hectare output value reaching 450,000 to 750,000 yuan. The cultivation of this persimmon is expanding rapidly in southern China, currently covering nearly 2000 hectares, with a substantial annual growth rate [3].

Limited understanding of the complexities of this persimmon has led to hasty and poorly planned promotion, resulting in several issues. For instance, D. kaki ‘Taishuu’ grown in northern regions face challenges such as cold damage, lingering astringency, and smaller fruit sizes [4]. China’s vast geographic diversity and wide range of climatic conditions bring significant differences in fruit quality among the persimmons from different orchards, which will lead to different market acceptance and consumer preference. Chen et al. conducted an initial classification of the ecological adaptation of Japanese sweet persimmons in China using fuzzy analogy preferred ratios, categorizing climate zones into three levels of suitability [5]. Similarly, Fan et al. identified eight cultivation areas for sweet persimmons across China [6]. However, these classifications remain largely theoretical and lack practical application. Therefore, it is essential to compare fruit quality from different cultivation areas and to identify suitable agro-ecological regions for cultivation, which can strategically allocate ecological planting areas.

The concept of fruit quality is comprehensive. Previous research has predominantly focused on aspects such as fruit appearance, sugar content, and nutritional value. Although these traits reflect fruit quality to some extent, mouthfeel is also one of the key factors in determining fruit quality [7]. Sensory evaluation and analysis techniques based on scientific experimental designs are commonly employed to analyze sensory attributes and assess consumer acceptance [8]. Instrumental methods, such as the electronic tongue and texture analyzer, offer more efficient, objective, and sensitive approaches for digitizing fruit quality assessments [9]. Metabolomics provides comprehensive and systematic identification of metabolites, offering valuable insights into the relationship between mouthfeel properties and metabolite composition [10,11]. The combined analysis has the ability to significantly overcome the subjectivity of sensory evaluation and the boundedness of intelligent sensory analysis and metabolomics. It has been successfully applied in numerous studies on quality evaluation [12,13].

Fruit qualities are shaped by both genetic traits and planting conditions [14]. Environmental factors—such as light, moisture, temperature, and nutrients—regulate metabolic and transport enzymes in plants, thereby affecting fruit qualities [15,16]. Identifying the key meteorological factors that influence fruit quality traits is essential for fruit cultivation. This study aims to characterize the mouthfeel properties of D. kaki ‘Taishuu’ across different provinces and investigate the relationship between mouthfeel properties and ecological factors. The objectives of this study are threefold: (1) to clarify the geographical trends in fruit quality of D. kaki ‘Taishuu’ with a specific focus on comparing differences in mouthfeel across various cultivation regions; (2) to explore the mechanisms underlying the mouthfeel properties by examining its correlation with environmental factors; and (3) to define the suitable growing areas for high-quality D. kaki ‘Taishuu’. Therefore, the findings will provide a theoretical basis for understanding the mechanisms behind mouthfeel properties formation and offer practical guidance for local agricultural production, optimal orchard distribution, and the cultivation and management of this variety.

2. Materials and Methods

2.1. Experiment Materials

The samples were collected from late September to early October 2022. The rootstock–scion combinations were D. kaki var. silvestris ‘YLSZ6’ and D. kaki ‘Taishuu’. All plants were cultivated following the Technical Regulation of Cultivation for Non-astringent Persimmon (Diospyros kaki Thunb.) (DB33/T 2500-2022) [17]. All samples were fully mature and free from any damage or blemishes. Each orchardist gathered 30 fruits from their orchard and delivered them to the laboratory within a two-day period. This study included samples from 35 counties across 13 provinces, with details of the collections’ geographic and meteorological factors provided in Figure 1 and Table S1. Fruit weight was measured using an electronic balance (Mettler Toledo XPE205, Greifensee, Switzerland), while fruit transverse and longitudinal diameter was measured using a vernier caliper. All evaluations were completed within a three-day period.

2.2. Metabolomic Analysis Method

A total of 25 mg of finely powdered frozen persimmon sample was added into 800 μL of 70% methanol extract (containing 20 μL of 2 mg/L internal standard). After vortexing for 30 s and subsequent refrigerated centrifugation for 15 min, 5 μL of the supernatant was collected. This procedure was repeated, and the resulting supernatants were combined and stored in a sample vial. A 10 μL aliquot from each sample was pooled to create a quality control sample for testing. The LC/MS system used for analysis consisted of a Waters Acquity I-Class PLUS (Waters Corporation, Milford, MA, USA) ultra-high performance liquid chromatograph coupled with a Waters Xevo G2-XS QTOF high-resolution mass spectrometer (Waters Corporation, Milford, MA, USA). The non-targeted metabolomic analysis was performed following the protocol described by Yue et al. [18]. Each sample was measured three times, and the average was taken.

The metabolites were analyzed both qualitatively and quantitatively using Progenesis QI v3.0 software, the online METLIN database and Biomark’s self-built library for identification. The differences among different samples were compared based on the grouping information; differential metabolites were identified using the orthogonal partial least squares discriminant analysis (OPLS-DA) model, with criteria of VIP (variable importance in project) ≥ 1 and p value < 0.05.

2.3. Electronic Tongue-Mediated Analysis

The electronic tongue is an advanced analytical device designed to mimic human taste perception for assessing the flavor quality of samples. It has high reliability, sensitivity, and repeatability. In this study, the taste qualities of D. kaki ‘Taishuu’ were evaluated using an electronic tongue (Insent Corp., Tokyo, Japan). Forty grams of blended fruit pulp from one orchard were mixed with 200 mL of distilled water, centrifuged (Eppendorf centrifuge 5804R, Hamburg, Germany) at 1000× g for 5 min to obtain the supernatant. This supernatant was then analyzed using the electronic tongue, with sensor probes immersed in the infusion to determine taste intensity. Nine taste attributes, including sourness, sweetness, bitterness, saltiness, umami, astringency, aftertaste-B (bitter aftertaste), aftertaste-A (astringent aftertaste), and richness (umami aftertaste), were evaluated. Among these, sweetness, bitterness, umami, saltiness, aftertaste-A, and richness were found to be particularly significant for sweet persimmons and were included in this study [19]. Each sample was prepared in triplicate, and each infusion was measured four times to calculate an average score.

2.4. Texture Analysis

The texture of this persimmon was assessed using the texture multifaceted analysis test (TPA) method with a TMS-PRO texture analyzer (Food Technology Corporation, Atlanta, GA, USA). The fruits were peeled, sliced across the equator, and cut into small pieces (1.0 × 1.0 × 1.0 cm). Four replicates were taken from each fruit for analysis. Texture measurements were performed with the P/75 probe for TPA. The texture analyzer parameters were set as follows: testing speed, 60 mm/min; sensor range, 1000 N; rising height, 20 cm; compression degree, 15%; and trigger force, 0.3 N [19]. Five parameters, including hardness, springiness, chewiness, cohesiveness, and adhesiveness, were evaluated. Ten fruits were randomly selected from each sample for repeated tests, and the average texture results were recorded.

2.5. Sensory Evaluation

Thirty evaluators (14 males, 16 females; aged 23–46 years) underwent three rounds of screening and five training sessions before conducting sensory evaluations based on the “Sensory Analysis Methodology-General Introduction (GB/T10221-2012)” [20]. The samples from different orchards were cut into pieces, and the evaluators assessed attributes such as pulp fineness (Fin, tightness and graininess of the pulp cells), crispness (Cri, evaluated by slow compression between molars), flavor (Fla, the combined sensory experience of taste (sweetness, acidity, bitterness) and aroma (volatile compounds), and overall taste (Tas, composite experience that integrates multisensory inputs such as taste, smell, and texture). Each trained evaluator quantified the above indicators using a 0–10 scale in three repetitions, with the mean score serving as the final sensory evaluation result for the samples.

2.6. Data Analysis

A total of 19 eco-climatic factors were acquired from https://www.worldclim.org/ (accessed on 15 January 2024). The Maxent 3.4.4 Maximum Entropy model software was employed to assess the contribution rates of environmental variables. Key climate factors and the distribution sites of D. kaki ‘Taishuu’ were incorporated into the MaxEnt model to analyze and predict suitable habitats. Using the habitat suitability index (HSI), the reclassification tool in ArcGIS 10.8 was utilized to manually categorize the prediction results. The classification criteria were as follows: HSI values of 0.475 or below indicate the moderately suitable habitats; values ranging from 0.475 to 0.859 denote the marginally suitable habitats; and values ranging from 0.859 to 0.999 represent the highly suitable habitats. Additionally, compute the area corresponding to each suitability category. The area under the ROC curve (AUC) will be used to assess the accuracy of the model predictions, with a range from 0 to 1. A value closer to 1 signifies a stronger correlation between the climate factors and the model’s distribution, enhancing the reliability of the results. Finally, the results were imported into ArcGIS 10.8 to create a suitable area distribution map for D. kaki ‘Taishuu’ [21].

Differential metabolites, electronic tongue assessments, texture analyses, and sensory evaluations of D. kaki ‘Taishuu’ from various levels of suitable habitats and provinces were analyzed using IBM SPSS Statistics version 25 (IBM Corp., Armonk, NY, USA), while graphs were constructed with Origin 2021 software. The clustering analysis of persimmons from various origins was carried out using SPSS 25.0 software. Initially, the 15 mouthfeel indicators were normalized using Z-score standardization. These standardized indicators were then utilized to perform hierarchical clustering on the 35 different origins, employing squared Euclidean distance as the similarity metric to generate a dendrogram, which grouped the 35 persimmon origins accordingly. The relationship between fruit quality and geo-climatic factors was analyzed using canonical correspondence analysis with Canoco4.5. Two-factor correlation network analysis of climatic factors, fruit secondary metabolite, fruit E-tongue indexes, fruit texture indexes and fruit sensory evaluation were performed using a structural equation model in SmartPLS 4.0.9.5 software [22].

The synergism between sensory evaluation and instrumental detection is widespread. Sensory evaluation can assess the multidimensional characteristics of fruit, including appearance, aroma, taste, texture, and overall preference, and exhibits a high correlation with the results obtained from instrumental detection [23]. This article uses sensory evaluation indexes to reflect the characteristics of E-tongue, texture and metabolite indexes. The co-kriging technique was employed to perform spatial interpolation on the pulp fineness, flavor, crispness, and overall taste indicators of persimmons. The weights for the grid are set to 1:1:1:1 for summation. The resulting interpolated data were then superimposed onto the vector distribution of predicted suitable areas for persimmon cultivation and compared with the actual taste measurements from the samples to create a correction model for persimmon taste quality. Thus, the suitability zoning map of the mouthfeel properties of D. kaki ‘Taishuu’ was obtained [24].

3. Results

3.1. Regionalization Results of Ecological Adaptation and the Main Ecological Driving Factors

The AUC (Area Under Curve) index of the Maxent model, based on 19 ecological factors derived from 35 D. kaki ‘Taishuu’ samples, was 0.985, indicating the model’s reliability in assessing ecological suitability.

The results from the maximum entropy model revealed that ecological factors with contributions exceeding 1% include the precipitation of the driest month (39.1%), the minimum temperature of the coldest month (21.8%), mean temperature of the coldest quarter (December, January, February, 14.3%), the maximum temperature of the warmest month (9.4%), precipitation of the driest quarter (December, January, February, 3.1%), isothermality (2.4%), annual precipitation (2.4%), precipitation of the wettest quarter (June, July, August, 2.4%), and mean temperature of the wettest quarter (June, July, August, 1.0%).

Based on the habitat suitability index (HSI), the ecological suitability for D. kaki ‘Taishuu’ can be categorized into three areas: the highly suitable habitats (0.859–0.999), the moderately suitable habitats (0.475–0.859), and the marginally suitable habitats (0.086–0.475) (Figure 2). The highly suitable habitats include the southeast coastal regions of China, the Middle-Lower Yangtze plains, the east of the Fenhe River–Weihe River Valley, and the basin valleys in Yunnan Province, covering an area of 116,200 square kilometers. This optimal area requires an average annual temperature between 13.79 °C and 23.20 °C, with the lowest extreme temperature exceeding −13.8 °C and annual precipitation ranging from 11 to 1830 mm. The moderately suitable habitats span 742,300 square kilometers, with the required average annual temperature between 12.53 °C and 25.68 °C, the minimum extreme temperature exceeding −14.6 °C, and annual precipitation from 12 to 1901 mm. The marginally suitable habitats are located between latitudes 21° N and 35° N in China, covering 1,456,000 square kilometers, where the average annual temperature ranges from 7.52 °C to 28.28 °C, the extreme low temperature is above −19.1 °C, and annual precipitation varies from 14 to 2725 mm.

3.2. Fruit Qualities of Different Levels of Cultivation Suitability

Significant differences were observed in fruit weight, transverse diameter, and longitudinal diameter across different levels of cultivation suitability, suggesting that persimmons grown in optimal areas tend to produce larger fruits (Figure 3A–C). However, when it comes to the variations of fruit mouthfeel properties among different levels of cultivation, they were minimal (Figure 3D–O). Based on the above parameters, the 35 cultivation areas were categorized into three groups. The western region, including Yunnan, Shanxi, and Shaanxi provinces, was classified into the first group; Zhejiang and Jiangxi provinces were placed in the second group, while Anhui, Fujian, Guangdong, Hunan, Jiangsu, Henan, Hubei, and Guangxi provinces were grouped into the third (Figure 4). These results indicate that the level of cultivation suitability does not significantly influence the mouthfeel properties of D. kaki ‘Taishuu’. Instead, the primary factors affecting the properties are closely linked to geographical and climatic characteristics.

3.3. Fruit Quality of Different Provinces

Metabolome data, electronic tongue and texture indexes, as well as sensory evaluation, were employed in this study. Since 23 metabolites are closely related to the fruit mouthfeel properties, we compared the contents of these 23 metabolites in the samples from different provinces (Figure 5). The contents of most metabolites, such as L-ornithine, L-pipecolic acid, rifamycin Z, aminoacetone, 6-aminohexanoate, 3β,6β-dihydroxynortropane, ganoderic acid eta, rifamycin W-hemiacetal, (E)-2-methylbutanal oxime, 8-methoxy-6,7-methylenedioxycoumari, Pro-Gly-Trp-Arg, Pro-Asn-Arg-Ile, taurocholate, Pro-Arg-Arg-Ala, isoleucyl-tryptophan, oxaloglutarate, and so on in the samples from Jiangsu, Zhejiang, and Yunnan provinces, were significantly higher than those in the samples from Guangxi, Shanxi, and Shaanxi provinces.

There were notable differences in electronic tongue indexes (Figure 6A–F). Sweetness values ranged from 14.12 to 16.09. Samples from Fujian and Guangxi provinces showed higher sweetness levels, while those from Anhui, Guangdong, Jiangsu, Jiangxi, and Zhejiang provinces had lower values. Shanxi and Shaanxi provinces had the highest bitterness values of 5.32 and 4.60, respectively, while Jiangxi province had the lowest bitterness value at 2.85. Umami and richness were effective taste indicators for persimmon, with Guangxi province achieving the highest umami value of 14.15, in contrast to Shaanxi’s lowest value of 9.99. Zhejiang province had the highest richness value at 4.75, while Anhui, Fujian, and Guangxi provinces had the lowest values of 1.03, 1.08, and 0.94, respectively. The highest aftertaste-A value, indicating a strong astringent aftertaste, was found in Anhui and Shanxi provinces. Shanxi (−7.4) and Zhejiang (−8.0) provinces recorded the highest saltiness values, while Fujian province had the lowest at −9.3.

There were significant differences in hardness, spring, chewiness, cohesiveness, and adhesiveness among persimmons from different provinces (Figure 6G–K). Samples from Shanxi, Shaanxi, Hunan, and Yunnan provinces exhibited greater hardness and chewiness, while those from Fujian, Guangdong, and Guangxi provinces were less firm. Hunan province had the highest spring value (1.15), whereas Fujian and Zhejiang provinces recorded the lowest (0.95 and 1.03, respectively). The highest cohesiveness values were observed in Shaanxi and Guangdong provinces (0.57 and 0.55, respectively), with Jiangxi province having the lowest at 0.48. Yunnan and Fujian provinces showed the highest adhesiveness values (0.18 and 0.17, respectively), in contrast to the lower values in Shanxi, Anhui, and Guangdong provinces (0.08, 0.08, and 0.07, respectively).

From the results of sensory evaluation, we found significant differences in pulp fineness, flavor, crispness, and comprehensive indicators among samples from different provinces (Figure 6L). The data showed that Jiangsu province had the highest pulp fineness score of 7.91, which was 1.27 times greater than the lowest score from Shaanxi province. The fruit flesh crispness ranged from 6.94 (Yunnan province) to 8.03 (Jiangxi province). Zhejiang province had the highest flavor score of 8.07, while Jiangxi province had the lowest score at 6.45. The overall taste score varied from 6.23 in Jiangxi province to 8.35 in Guangxi province. Overall, samples from Jiangsu, Zhejiang, Fujian, Guangxi, and Yunnan provinces had higher fruit sensory scores, whereas those from Shaanxi, Jiangxi, and Henan province scored lower.

The conclusions could be drawn from above results that D. kaki ‘Taishuu’ from the Jiangsu, Zhejiang, Fujian, Guangdong, Guangxi, and Yunnan provinces were characterized by a lusciously sweeter and richer taste, a satisfying crisp texture, and an overall distinctly superior mouthfeel. In contrast, samples from the other provinces exhibited higher density, greater firmness, reduced crispness, and inferior flavor quality.

3.4. The Main Factors Influencing Fruit Mouthfeel Properties

The CCA (canonical correspondence analysis) was conducted to identify the key geographic and climate factors influencing the taste, texture quality and metabolite of the persimmons (Figure 7). The results showed that the main factors affecting the electronic tongue indexes were annual precipitation, precipitation from May to August, the maximum temperature in August, and the minimum temperatures in July and August. For texture indexes, the main factors were the maximum temperature from July to October and precipitation in July, September, and October. For metabolite accumulation, the main influencing factors were precipitation in July, the maximum temperature in January, February and November, and the minimum temperature in July and August. The main influencing factors on evaluation results were latitude, precipitation from August to September, and the minimum temperatures in August and September.

The partial least squares path modeling of climatic factors, fruit metabolite, E-tongue indexes, texture indexes and sensory evaluation were conducted in this study. The results showed that there were lesser or moderate influences between the provenance of climate conditions and fruit quality factors, as well as among each factor. This might be due to the limited sample size and the lack of sufficiently precise climatic data. Temperature conditions of production areas had a significant negative correlation with metabolites, fruit texture indexes and sensory evaluations. Metabolites had a significant positive correlation with fruit texture. There were tenuous interplays among fruit metabolite, fruit E-tongue indexes (richness and umami), fruit texture indexes (hardness, spring, chewiness, cohesiveness) and fruit sensory evaluation (fruit flavor, crispness, and comprehensive indicators) (Figure 8).

3.5. Adaptability Zoning Results Based on Sensory Evaluation

An intuitive quality distribution map was generated using GIS technology combined with fruit comprehensive mouthfeel indicators (Figure 9). From the map we can see that samples from Yunnan, Guangxi, Guangdong, Fujian, Zhejiang, Jiangsu, Shandong, Shaanxi, and Chongqing exhibited a crumbly and soft texture characteristic, richer flavor profiles and higher taste preference compared to other provinces. Quantitatively, key mouthfeel properties showed a gradient decline from peripheral cultivation zones toward the central core areas.

4. Discussion

4.1. Geographical Trends of Mouthfeel Properties from Different Cultivation Regions

D. kaki ‘Taishuu’ is a typical subtropical fruit capable of thriving in diverse climatic and soil conditions [25]. Persimmons grown near the northern cultivation limit often exhibit lower mouthfeel properties, with reduced sugar content, increased firmness, and a lack of flavor. This is probably because of the low average annual temperature, short growing season, low-temperature stress in winter, and insufficient light conditions [26,27]. Additionally, fruits from coastal areas generally have superior quality compared to those from inland regions, which aligns with previous research. For example, the soluble solids, soluble sugar contents, and sugar–acid ratios in coastal waxberries (Myrica rubra) and Indian jujube (Ziziphus mauritiana) were higher than those of inland samples [28,29]. In terms of aroma components, Vitis vinifera ‘Muscat Hamburg’ from coastal areas had higher total aroma content and greater levels of rose oxide, nerolin, and linalool compared to inland samples, giving them a more typical flavor [30]. This is mainly due to the milder climate, more abundant rainfall, and better sunlight conditions in these areas [28]. However, Yunnan province, an inland area, presented a unique exception. This region benefits from the synergistic effects of a low-latitude plateau monsoon climate, characterized by a small annual temperature range, large diurnal temperature variation, concurrent rainfall and heat, high effective accumulated temperature, and strong ultraviolet radiation [31]. Its special climatic conditions impart a distinct taste and flavor to its fruits, such as V. vinifera and Eriobotrya japonica [32,33].

4.2. The Main Influencing Factors for Mouthfeel Properties

Geographic and climatic conditions play crucial roles in influencing fruit productivity, size, base color, and nutrient content on most hemerophyte [34,35], as well as affecting mouthfeel properties [36,37]. This impact is particularly significant during fruit development stages. The mouthfeel of sweet persimmon is largely determined by the content of sugar, tannin, and other metabolites, including ornithine, tyrosine, glycine and so on [19,38]. Sugar content is closely linked to temperature fluctuations between day and night and the cumulative hours of sunlight throughout the growing season [39]. This is likely because higher temperatures promoted the activities of sucrose synthase (SSC) and sucrose phosphate synthase (SPS) [40]. As a non-astringent variety, D. kaki ‘Taishuu’ showed a decline in soluble tannin content to 1.5% in June and 0.5% in July [41]. A lack of sufficient accumulated active temperature during the deastringenting process, especially in the late stage of fruit growth, can lead to a loss of desirable quality in sweet persimmon [42]. This is probably because alcohol dehydrogenase (ADH) plays a role in the deastringency process during persimmon ripening, with optimal activity observed at 25 °C [43]. Among the identified key metabolites related to fruit quality, L-ornithine is a precursor for arginine and proline synthesis and has a significant effect in suppressing bitterness [44]. Aminocrotonate, 6-aminohexanoate and L-pipecolic acid are intermediates in amino acid metabolism. They may affect the contents of some delicious amino acid (DAA), such as alanine and lysine, thereby influencing taste characteristics [45]. Alanine, arginine, isoleucine, and other branched-chain amino acids in several peptides are converted into volatile flavor compounds, imparting a unique flavor to persimmon fruits [46]. Aromatic compounds, such as 8-methoxy-6,7-methylenedioxycoumarin and 2-hydroxy-6-oxo-6-(2-hydroxyphenyl) -hexa-2,4-dienoate, are important compounds that contribute to the characteristic aroma of mature sweet persimmons [47,48]. Environmental stress, such as drought, high light intensity, and temperature extremes, activate the shikimate pathway, aromatic amino acids (AAA) pathways, and downstream pathways from AAAs, altering the expression of ornithine decarboxylase (TcODC) [49], glutamate synthase (GS), glutamate synthase (GOGAT) [50], tyrosine hydroxylase (TH), and alcohol acyltransferase (AAT) genes [51]. These changes lead to variations in amino acid and aromatic compound levels, resulting in a decline in fruit quality.

Moreover, fruit texture is closely linked to the morphology of pulp parenchyma cells and the composition of the cell wall [52,53]. The presence of cellulose and pectic substances, along with their degrading enzymes, significantly influences the pulp texture of persimmons [54]. Under conditions of high humidity and temperature, the pectinase and cellulase activities increase, leading to the disintegration of cell wall structure and instability of cellular integrity [55]. There were significant correlations between hardness, brittleness, and the contents of polygalacturonase (PG), cellulase (CS), water-soluble pectin (WSP), and covalently bound pectin (CSP) [56]. The activities of PG and CS also show a significant negative correlation with altitude, accumulated temperature, and annual average temperature, but a significant positive correlation with annual precipitation [57]. As temperature rises, pectin content decreases, resulting in reduced hardness and brittleness [58]. As indicated above, producing high-quality D. kaki ‘Taishuu’ depends on optimal climatic conditions. Higher temperatures may delay fruit expansion and ripening at harvest [59], ultimately shortening the growing season and causing fruit deformities and decline [60]. Rainfall amount and distribution during the growth period significantly affect fruit quality [61]. Additionally, temperature fluctuations also play a key role in fruit set, growth, and the quality of sweet persimmons [62,63].

4.3. Zoning for High-Quality D. kaki ‘Taishuu’

Currently, very few scholars have focused on quality differences and climatic zoning of sweet persimmons. Soqanloo found that local climate condition significantly (p < 0.01) influenced persimmon biochemical characteristics. Arid and semi-arid districts enhance fruit quality [64]. Priscila et al. employed BRAMAZOS software to assess climate risk for persimmon cultivation under climate change in Brazil [65]. Additionally, sporadic studies have evaluated the adaptability of different sweet persimmon varieties introduced into China. However, the optimal production areas of D. kaki ‘Taishuu’ are notably narrower compared to other sweet persimmon varieties [6]. This study integrates multiple disciplines—such as meteorology and ecology—and employs intelligent sensory technology and metabolomics to conduct an in-depth investigation of the ecological adaptability of this variety. Our findings differ somewhat from previous studies. The cultivation of D. kaki ‘Taishuu’ reaches its northern limit at 35 degrees north, which is farther south than ‘Yangfeng’, ‘Hanagosho’, and other sweet persimmon varieties [66]. While the North China Plain is highly suitable for other sweet persimmons, its rapid autumn cooling and shorter growing period limit its suitability for D. kaki ‘Taishuu’. Furthermore, excessive rainfall and unbalanced heat and water conditions in this region negatively affect fruit quality [67]. Similarly, the southwestern Sichuan province, another favorable area for other sweet persimmons, faces challenges such as high summer temperatures and drought. These conditions often lead to coarse pulp. However, the rainy ripening phase also hinders fruit coloration and maturation, making the region unsuitable for this fruit [6]. The southeastern coastal regions of China, which share a climate similar to the variety’s native environment in Japan, and Yunnan Province, known for its distinctive climate favorable to various fruit trees, are the highly suitable habitats for cultivating high-quality D. kaki ‘Taishuu’.

5. Conclusions

This research has identified the suitable areas for D. kaki ‘Taishuu’ cultivation based on fruit mouthfeel properties, which helps to enhance adaptive strategies informed by scientific understanding. The sample collection period covers only one harvest season. Although 2022 was a relatively stable year in terms of climate conditions, it still cannot comprehensively assess the impact of interannual climate change on persimmon quality. Sample collection in future research from multiple harvest seasons should be carried out to cover the climate change in different years and to resolve the mechanism of climate action on mouthfeel.

Currently, the cultivated area of D. kaki ‘Taishuu’ in China is nearly 2000 hectares. According to the results, the highly and moderately suitable habitats exceed 85,000 square kilometers, indicating significant potential for development. Since precipitation during the growing season, high summer temperatures, low temperatures during dormancy and fruit development are not only the key climatic factors influencing fruit yield [67,68], but also influencing persimmon mouthfeel, targeted cultivation measures and adaptive horticultural practices should be implemented to enhance fruit mouthfeel. Further research is necessary to comprehend the molecular pathways by which ecological factors, such as temperature and precipitation, influence fruit quality. It is beneficial for breeding efforts aimed at enhancing fruit quality.