Evaluation of sweet potato (Ipomoea batatas (L.) Lam.) genotypes for sensory quality and tolerance to Sweet Potato Leaf Curl Virus (SPLCV) under eastern Indian conditions

Introduction

Sweet Potato (Ipomoea batatas (L.) Lam) is a dicotyledonous crop that belongs to the family of Convolvulaceae (Barkessa, 2018) [5] . It originated from the Central or southern America region and it is recognized as the primary center of genetic diversity (Austin, 1978) [4] . It was domesticated in tropical America around 6000 BC and later spread to Polynesia, Hawaii and New Zealand before the Columbus times and later it was introduced to Philippines by the Spanish in the 16th century from where it was spread to Asia, Portuguese travellers have introduced it to Europe, Africa, India and Southeast Asia (Yen, 1976) [17] . It is rich in βcarotene and anthocyanins, which have been used for the extraction of food colourants (Bovell-Benjamin, 2006) [6] . Sweet potato is considered a highly valuable crop due to its exceptional nutritional content and its ability to yield more food per hectare compared to other crops (George et al., 2024) [10] . Its starch can be used for the preparation of food, industrial products and biofuel preparation (Lyu et al., 2020) [15] . It is cultivated across 119 countries worldwide, covering a total area of 92,020 hectares and yielding approximately 86.41 million metric tonnes (FAO, 2022) [9] . China leads globally in sweet potato cultivation, accounting for 36.54% of the total area and contributing 63.64% to the global production. In India it is generally called as "Shakarkand" and is grown on about 106,000 hectares, with an annual output of 1,121,000 tonnes (FAO, 2022) [9] . Consumer preference is one of the most important factors determining the adoption and commercial success of sweet potato varieties. Sensory characteristics such as colour, taste, flavour, texture and overall acceptability largely influence consumer choice and market demand. Therefore, sensory evaluation has become an integral component of varietal evaluation and breeding programmes. Ellong et al. (2014) [8] reported significant variation among sweet potato genotypes for sensory attributes, suggesting ample scope for selecting consumer-preferred cultivars.

Similarly, Hernández et al. (2024) [13] observed considerable diversity in physicochemical and organoleptic characteristics among sweet potato landraces, highlighting the importance of sensory evaluation in identifying superior genotypes. Sweet potato production is severely constrained by viral diseases, among which Sweet Potato Leaf Curl Virus (SPLCV) is one of the most economically important. SPLCV belongs to the genus Begomovirus and is transmitted by the whitefly (Bemisia tabaci). Since sweet potato is propagated vegetatively, infected planting materials facilitate rapid virus spread and accumulation over successive generations (Clark et al., 2012; Andreason et al., 2021) [7,2] . Infection results in leaf curling, chlorosis, vein thickening, stunted growth and considerable reductions in storage root yield and quality (Hou et al., 2020) [14] . Previous studies have demonstrated significant variability among sweet potato genotypes for SPLCV incidence and disease severity, indicating the presence of valuable sources of resistance. Arkorful et al. (2015) [3] , Abebe et al. (2023) [1] , Griyaningsih et al. (2023) [11] and Yusuf et al. (2024) [18] reported differential responses of sweet potato genotypes to SPLCV and emphasized the importance of identifying resistant genotypes for sustainable disease management and resistance breeding. Although several studies have evaluated sweet potato genotypes for either sensory attributes or resistance to viral diseases, information on genotypes combining superior eating quality with tolerance to Sweet Potato Leaf Curl Virus (SPLCV) under eastern Indian conditions remains limited. Identification of such genotypes is essential for developing cultivars that satisfy both consumer preference and field performance, thereby enhancing productivity and market acceptance. Therefore, the present investigation was undertaken to evaluate thirtyfive sweet potato genotypes for sensory quality and tolerance to Sweet Potato Leaf Curl Virus (SPLCV) and to identify promising genotypes suitable for utilization in future crop improvement programmes.

Materials and Methods

The experiment was conducted at the Regional Station, ICAR-Central Tuber Crops Research Institute, Bhubaneswar, Odisha, India. This experimental area is located in the eastern coastal region of India. The experimental site located at an elevation of 45 m above mean sea level (20.40°N latitude, 85.78°E longitude), featured sandy loam soil. Thirty-five sweet potato genotypes collected from different sources were evaluated under field conditions. The experiment was laid out in a Randomized Block Design (RBD) with two replications following the recommended package of practices for sweet potato cultivation. Healthy vine cuttings of each genotype were planted at a spacing of 60×20 cm, and all intercultural operations were carried out uniformly throughout the crop growth period. Freshly harvested storage roots from each genotype were washed thoroughly and boiled until adequately cooked. The boiled roots were peeled and cut into uniform pieces before evaluation. Sensory evaluation was carried out by a panel of eight semi-trained judges, comprising scientists and technical staff of ICAR-CTCRI, Regional Station, Bhubaneswar. The samples were evaluated for colour, taste, flavour, texture and overall acceptability using a 9-point hedonic scale following Ranganna (2008) [16] (Table 1). The hedonic scale ranged from 9 (like extremely) to 1 (dislike extremely). The mean score for each sensory attribute was used for statistical analysis. The experimental genotypes were screened under natural field conditions for their reaction to Sweet Potato Leaf Curl Virus (SPLCV). Disease assessment was based on visual observation of characteristic symptoms such as leaf curling, chlorosis, vein thickening and leaf deformation. Five representative plants from each plot were randomly selected and tagged for recording disease observations. Disease severity was assessed using the 0-5 disease rating scale proposed by Hahn et al. (1981) [12] , where 0 = no visible symptoms; 1 = very mild symptoms; 2 = mild symptoms; 3 = moderate symptoms; 4 = severe symptoms; and 5 = very severe symptoms. The Percentage Disease Index (PDI) was calculated using the following formula

Percentage disease index (PDI)

The Percentage Disease Index (PDI) was calculated to quantify the overall disease severity in percentage form based on the disease rating scale. Disease severity scores recorded from individual plants were used for computation. The PDI was calculated using the following formula PDI = ∑ of all disease scorings Total number of plants assessed × maximum grade × 100

Where the maximum grade is 5 as 0-5 scale is used.

Disease incidence was recorded to determine the proportion of plants infected with the disease under field conditions.

Observations were taken at regular intervals (30 DAP and 60 DAP) by visually inspecting all plants in each experimental plot. The total number of diseased plants and the total number of plants observed were recorded and expressed in percentage. It is calculated by using this formula.

Disease incidence(%) = Number of infected plants Total number of plants observed × 100

Results and Discussion

Sensory evaluation of sweet potato genotypes Considerable variation was observed among the thirty-five sweet potato genotypes for colour, taste, flavour, texture and overall acceptability, indicating substantial genetic diversity for eating quality ( [8] , who observed considerable variability in sensory attributes among sweet potato genotypes and highlighted the importance of organoleptic evaluation in identifying consumer-preferred cultivars. Likewise, Hernández et al.

(2024) [13] reported significant differences in the physicochemical and nutritional characteristics of sweet potato landraces, which contributed to variation in their eating quality. Overall, the results demonstrate that sensory evaluation is an effective approach for identifying sweet potato genotypes with superior eating quality. The substantial variability observed among the evaluated genotypes provides valuable opportunities for selecting cultivars with enhanced consumer acceptability and for their utilization in sweet potato quality improvement programmes. Although several genotypes exhibited superior sensory attributes, their suitability for cultivation also depends on their tolerance to major diseases such as Sweet Potato Leaf Curl Virus (SPLCV). Therefore, the same genotypes were further evaluated for their reaction to SPLCV under field conditions.

Screening of sweet potato genotypes for SPLCV tolerance

Considerable variation was observed among the thirty-five sweet potato genotypes for Percentage Disease Index (PDI), disease severity and disease incidence, indicating the presence of substantial genetic variability for tolerance to Sweet Potato Leaf Curl Virus (SPLCV) (Table 3). The PDI ranged from 6.2 to 41.6%, disease severity from 0.3 to 2.1, and disease incidence from 14.8 to 60.3%, reflecting marked differences in the response of the genotypes to natural SPLCV infection under field conditions.Among the evaluated genotypes, DPS/30 recorded the lowest PDI (6.2%), followed by DPS/31 ( [3] , Abebe et al. (2023) [1] and Griyaningsih et al. (2023) [11] , who identified resistant and susceptible genotypes based on disease incidence and severity under field conditions. Likewise, Hahn et al. (1981) [12] emphasized the importance of exploiting genetic resistance as a practical approach for minimizing yield losses caused by virus complexes in sweet potato. The observed variability for SPLCV tolerance provides valuable genetic resources for resistance breeding and varietal improvement programmes. Genotypes exhibiting lower disease severity and PDI may serve as potential donor parents for developing high-yielding cultivars with enhanced virus tolerance, thereby contributing to sustainable sweet potato production.

When the results of sensory evaluation (Table 2) and SPLCV screening (Table 3) were considered together, SP 95/4 emerged as the most promising genotype, combining superior sensory quality with relatively low PDI (8.1%) and disease incidence (17.9%). Similarly, SB537/16 and Bhu Krishna exhibited desirable eating quality along with comparatively higher tolerance to SPLCV. In contrast, DPS/30, DPS/31 and VII recorded the lowest PDI values, indicating their potential as valuable genetic resources for improving SPLCV tolerance in sweet potato breeding programmes. These findings demonstrate that simultaneous evaluation of consumer-preferred quality traits and disease tolerance is an effective approach for identifying superior sweet potato genotypes for future crop improvement.

Acknowledgement

AcknowledgementThe authors gratefully acknowledge ICAR-Central Tuber Crops Research Institute (CTCRI), Regional Station, Bhubaneswar, for providing the research facilities and Odisha University of Agriculture and Technology (OUAT), Bhubaneswar, for academic support.

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