Growth Parameters and Yield Evaluation of Tropical and Temperate Sweetpotato Genotypes Under Acid Soil Conditions

Sweetpotato ( Ipomoea batatas L. Lam) is an important tuber crop with a wide range of eco-physiological adaptability. The analysis of diversified crops could be an approach to explore sweetpotato productivity under acid soil conditions. To observe the yield performance of nine sweetpotato genotypes with temperate origin (Japanese) and tropical origin (Bangladeshi), the experiment was conducted in the acidic soil and tropical environment of Sylhet, Bangladesh. The experiment was laid out in Randomised Complete Block Design with three replications. For the growth studies data were recorded at 30 days after planting (DAP) and morphological and yield parameters were recorded at final harvest. Results showed that the morphological ______________________________________ branches per plant (6.03), dry weight of storage root per plant (323.8 g), total fresh weight per plant (1132 g), total dry weight per plant (362.4 g) and yield of storage roots per hectare (27.05 t) were found in Local 1 whereas the lowest length of storage root per plant (8.70 cm), diameter of storage root per plant (9.37 cm), storage root number per plant (3.17), the storage root dry weight per plant (104.5 g), total fresh weight per plant (550.3 g) and dry weight per plant (152.9 g) were recorded in JSP 1. Among the sweetpotato genotypes, local genotypes were performed better than those of exotic genotypes in acidic soils. The genotypes Local 1 was found suitable with better growth and yield performance in acidic soils.


INTRODUCTION
Sweetpotato (Ipomoea batatas L.), one of the most important tuber crops, is cultivated in almost every area of Bangladesh. As the farmer's perception, this crop has high economic value to fulfil the requirement of food demand of the country which is recognized as the fourth important crop after rice, wheat and potato (Delowar and Hakim, 2014). Its popularity has increased because it can easily be grown in fallow lands, riverbanks, valley areas and homestead areas. Even the plant can survive in adverse environmental and edaphic conditions and it shows flexibility both in planting and harvesting times (Namanda, 2012;Motsa et al., 2015). Moreover, sweetpotato has high nutritional value having a vital source of carbohydrates, vitamins, and minerals (Vargas et al., 2017), in addition, the orange-fleshed cultivars are rich in beta-carotene which has provitamin A and antioxidant activity (Laurie and Heerden, 2012). Therefore, considering its significant importance, expanding the cultivation area to increase production is a crucial need to ensure food security in Bangladesh.
Although sweetpotato is originated from Central America presently it is widely grown in the tropical and subtropical region, and even in some parts of temperate countries (Chandrasekara and Joshephkumar, 2016 (Verma et al., 1994)  in Bangladesh) or in fellow land with no or less care and input (Nazrul, 2018).
That's why its cultivation could not reach its maximum yield potential, resulting in lower yield production. The morphological and yield contributing characteristics like leaf area, leaf production, leaf photosynthesis, tuber formation and development, total dry matter production, and tuber yield depend on genetic and environmental factors (Hayati et al., 2020). For improving sweet potato varieties, the analysis of genotypes at the genetic level with agro-morphological traits (Mahmud et al., 2021;Rosero et al., 2020) can provide more information that will be helpful for the plant breeders.
The soil of our experimental area, Sylhet is slightly acidic (pH 4.80) in nature although Laurie and Niederwieser (2004) suggested the soil pH between 5.6 and 6.6 for higher sweetpotato production. But the rapid growth of the vine and root traits can easily cover the soil which enhances the reduction of soil acidity (Essilfie et al., 2015) and

Experimental Materials and Cultivation
The experiment was conducted at the

Statistical Analysis
The collected data were compiled and

Characteristics of Leaves
The genotypes under the study showed

Characteristics of Vine
Non-significant variation was noticed in vine characters of the genotypes. The vine colour of JSP 2, JSP 3, BARI SP 7, Local 1, Local 2 and Local 3 was green and deep green was observed in BARI SP 9 while JSP 1 vine was in purple (Table 2). Twig colour showed purple only in JSP 3, but all other genotypes showed green colour in twigs. In JSP 1 hair was present in their vine while soft and succulent vine was found in Local 1 and Local 3. Leaf and vine characters are controlled by the genetic makeup of   (2015).

Characteristics of Storage Roots
Storage roots of sweetpotato genotypes showed wide variation in respect of shape ( Figure 2 Hayati et al. (2020).

Vine Length
All the genotypes of sweetpotato showed significant variation in vine length (Figure 3). Results revealed that vine length increased until 90 DAS followed by a rapid increase till maturity (150 DAS) parallel to the increase in rainfall pattern.

Leaf Area per Leaf at Different Days of Planting
There was a noticeable variation observed in the leaf area on different days after planting (   Malawi having alfisol and lithosol soil types and found that genotype LU06/0428 produced the highest leaf area of 130.9 cm 2 followed by BV/009 with 97.7 cm 2 .

Leaf Area Index at Harvest
The leaf area index also showed a noticeable variation at 150 DAP shown in (Table 3). At 150 DAP, the highest leaf area index was found in JSP 1 (13.40) and the lowest leaf area was recorded in BARI SP 7 (2.73) which was statistically similar to Local 3 (3.26) and JSP 2 (3.60). Hossain et al. (2018) reported that leaf area increased gradually up to 120 DAP.

Chlorophyll and Carotenoid Content in Leaves
Chlorophyll-a content of all genotypes increased up to 60 days of planting and then it decreased except for genotype BSP 9, where it increased up to 90 days of planting (Table 4).

Number of Branches per Plant
The

Dry Weight of Leaves per Plant
There were noticeable wide variations among the genotypes in respect of the dry weight of leaves (Table 5). The highest dry weight was found in Local 2 (30.87 g) and the lowest was found in BARI SP 7 (5.8 g) (Table 5). Delowar and Hakim (2014) mentioned that the dry weight of leaves in genotypes is affected by soil acidity.

Dry Weight of Vine, Absorbing Roots and Storage Roots per Plant
Variations were observed among different sweetpotato genotypes in respect of the dry weight of vines, absorbing roots and storage roots (Table 5). The highest dry weight of vine was found in Local 2 (27.20 g) which was statistically similar to BARI SP 9 (27.03 g) and the lowest was found in BARI SP 7 (11.53 g). The maximum dry matter of absorbing roots was   (Hossain et al., 2018).

Number of Storage Roots per Plant
The number of storage roots per plant was significantly varied and shown in Table 6. The maximum number of storage roots was found in JSP 2 (7.60) and the lowest number was recorded in JSP 4 (3.37). Due to genetic variability with acid tolerance, the number of storage roots varied among different sweetpotato genotypes. Rahman et al (2015) reported that according to their study, the number of storage roots per plant varied from 2 to 7.33 which is in agreement with our findings.

Length and Diameter of Storage Roots
The maximum length (12.73 cm) of storage roots was observed in the genotypes BARI SP 9 which was statically similar to Local 2 (12.07 cm) and Local 1 (12.03 cm) ( Table 6). The lowest length of storage roots was observed in the genotype JSP 2 (8.70 cm). It is clearly indicated that the highest storage root length producing genotypes of sweetpotato in acidic soil influences the higher production of yield. The diameter of storage roots per plant was significantly different ranging from 15.50 to 9.37. The maximum diameter (15.50) was recorded in the genotypes Local 3 followed by Local 1 (14.63) and Local 2 (14.27). The lowest mean diameter of storage roots was observed in the genotype of JSP 2 (9.37). The diameter of storage roots differs from various genotypes due to variations in growth habits as well as their capacity to tolerate acidic soil (Hossain et al., 2018).

Yield of Storage Roots
The data on yield of storage roots of nine sweetpotato genotypes were measured and presented in Table 6.
Storage roots yield (t ha -1 ) of sweetpotato genotypes had statistically significant variation. The highest storage roots yield (27.05 t ha -1 ) was produced by the genotype Local 1. The lowest yield (5.43 t ha -1 ) was found from the genotype JSP 4 which was statistically similar to the genotype JSP 1 (5.67 t ha -1 ). The results of our study are close to the findings of Kareem (2013) where the yield of storage roots of different genotypes of sweetpotato ranged from 5.43 to 10.90 t ha -1 . We also observed the correlation of higher tuber fresh weight with higher tuber yield that was reported by Hayati et al. (2020) and Hossain et al. (2018).

CONCLUSION
Based on the findings of the study, the genotypes Local 1 showed the best performance in yield and growth parameters whereas genotypes JSP 2 and JSP 3 which were orange-fleshed had higher beta carotene content. As future work nutritional quality of the genotypes such as Local 1, JSP 2 and JSP 3 need to be undertaken for improving purpose.