​Response of Strawberry Cultivars to Different Planting Dates and Growing Conditions in Jorhat, Assam

Strawberry (Fragaria ananasa Duch.) is one of the most attractive fruit widely grown all over the world due to the acceptance for its sweet flavour, aroma and nutritional values. It belongs to the family Rosaceae and is native of America. The fruit is popular for its tantalizing aroma (Sharma and Yamdagni, 2000), eye-catching colour, nutrient compositions and worthy pharmaceutical properties (Rahman et al., 2015).

Strawberry basically, is a fruit plant of temperate climate. However, in recent years, there has been phenomenal increase in its area and production in tropical and subtropical plains of India (Sharma and Sharma, 2004). Moreover, after the entry of the day neutral cultivars this crop had made a successful trade in the tropical and sub tropical regions also (Sharma et al., 2003). It is consumed as raw and also processed for preparing jams, jellies, squashes, ice creams, canned strawberry, wine and other soft drinks (Mitra, 1991; Joshi et al., 2005). Assam has also recently found to have some good results with future prospect for the crop. But, the available information for the suitable cultivars in Assam conditions is very scanty. Choice of cultivars is of paramount importance for successful strawberry cultivation (Asrey and Singh, 2004; Ahsan et al., 2014).

Due to inadequate information on specific growing conditions and suitable cultivars, its commercial cultivation could not become popular in a state like Assam. Under these circumstances, an experiment has been conducted to evaluate the best cultivar, date of planting and growing environment for Assam conditions.

The present experiment was carried out in the Experimental Farm, Department of Horticulture, Assam Agricultural University, Jorhat (26°442  N and 94°102  S with 90 m above mean sea level) during the year 2015-16 to 2016-17. The soil of the experimental plot was a sandy loam having pH of 5.06. The study was conducted with 07 (seven) treatments viz. T₁- Sabrina, T₂- Winter Dawn, T₃- Chandler, T₄- Sweet Charlie, T₅- Cristal, T₆- Selva, T₇- Camarosa and 04 (four) planting dates viz. S₁-1^st November, S₂-15^th November, S₃-^1st December, S₄-15^th December under open field conditions and protected conditions (50% shade net condition). The experiment was laid out in split plot design with three replications. Healthy tissue cultured planting materials with uniform crown and well developed root systems were planted in Hill row system in 15-20 cm raised beds with spacing of 30 cm x 60 cm. The outer leaves were pinched off and coco peats of the roots of the seedlings were washed properly.

The experimental area (open condition and 50 per cent shade net house) was thoroughly ploughed followed by harrowing and levelling. For one date of planting seven equal sized plots each measuring 90 cm x 180 cm were laid out accommodating nine plants in each plot. Each treatment contained three number of replication accommodating nine plants in each plot. A gap of 50 cm was left between two adjacent plots. 05 (Five) uniformly grown plants in each plot were selected to record the observations on some biochemical parameters like total soluble solids (TSS), titrable acidity (%), ascorbic acid (mg/ 100 g), total sugars (%), reducing sugars (%), non- reducing sugars (%), calcium and phosphorus. Observations were recorded at proper time during the crop cycle.

The results of the experiment are detailed as below along with the supported tables.
 
Anthocyanin
 
Anthocyanin is one of the most important compounds which determine antioxidant activity in strawberries. It depends on many factors, like choice of cultivar, agricultural conditions, light availability, nitrogen content in soil, degree of fruit ripeness and storage temperature (Bacchella et al., 2009; Roussos et al., 2009). In this study, significant variation was found among the varieties (Table 1). Maximum mean values for anthocyanin content was found in variety Sweet Charlie, both in open conditions as well as in 50% shade net conditions. To be precise, highest value was evident in case of the second date of planting i.e 15^th November (S₂) in open conditions (21.88 mg/100 g) and 50% shade net conditions (19.55 mg/100 g) with the lowest values in the variety Chandler in S4 (13.39 mg/100 g in open conditions and 13.04 mg/100 g in 50% shade net). This variation in anthocyanin might be due to the genetic factors and edaphic-climatic factors and degree of maturity. Wang and Hsin-Shan (2000) also reported that total anthocyanin content in strawberry increased with maturity.


 
Total Soluble Solids (TSS)
 
Pertaining to the Table 2, it was understood that the changes in TSS followed the trend of increasing with the advancement of maturity and ripening. Fruits under the experiment showed considerable variation with respect to TSS ranging between 7.86°Brix to 4.17°Brix. In open condition the highest (7.6°Brix) and the lowest (5.26°Brix) contents were recorded in Sweet Charlie (V4) and Camarosa (V7), respectively. Again in 50 per cent shade net condition the highest TSS (6.88°Brix) is recorded in Sweet Charlie and lowest (5.64°Brix) was recorded in Camarosa variety. Whereas, the highest mean values in case of date of planting was found highest in S2 (6.64°Brix in open conditions and 6.39 °Brix in 50% shade net conditions) and lowest in S4 (6.26 °Brix in open conditions and 6.04°Brix in 50% shade net conditions) for both the conditions.



The variation in TSS contents might be due to genetic makeup of the varieties of strawberry. The results found are in line with the experiments of Bakshi et al., (2014). Moreover, Rahman (2014) also reported that TSS content of fruits was highly influenced by interaction effect of time of planting and cultivars and found that fruits of early planting contained more TSS than late planting which might be due to the exposure of favourable environment and getting enough time for sugar and acid accumulation in early planting. The favourable temperature and relative humidity especially in night during fruit growth and ripening period might have led to higher TSS contents in strawberry fruits (Sharma and Sharma, 2002).
 
Titratable acidity
 
In the present study (Table 3), significant differences were observed among the treatments. Under open conditions, highest mean values were recorded for Chandler (0.61%) and lowest for Sweet Charlie, Cristal and Camarosa which were at par with 0.53%. In case of 50% shade net conditions, variety Winter Dawn and Chandler recorded highest Titrable acidity with 0.62% and lowest was found in case of Sweet Charlie (0.54%). The findings are in line with that of Bakshi et al., (2014). Probably lower acidity might be due to the difference between day and night temperatures which were very narrow. Similar opinion was also put forwarded by Wani et al., (2007).


 
Ascorbic acid
 
It is one of the most important components which determine the quality of a strawberry fruit. The data on ascorbic acid content (Table 4) revealed that the varieties under the study differed significantly. In both the growing conditions, highest mean value was found in Cristal (30.29 mg/100 g in open conditions and 26.19 mg/100 g in 50% shade net conditions) whereas, lowest values are observed in Sweet Charlie (25.24 mg/100 g and 19.96 mg/100 g). The results of present study are more or less in close proximity with the report of Bakshi et al., (2014). Lee and Kader (2000) reported that the ascorbic acid content in fruits and vegetables is affected by many factors, such as genotypic differences, climatic conditions, cultivation and fruit ripening conditions and the time of storage. Date of planting also recorded a notable difference pertaining to the ascorbic acid content. Highest value was found when planted in 15^th November (S₂) by the variety Cristal (31.59 mg/100 g) and lowest when planted in 15^th December (S₂) by the variety Sweet Charlie (22.67 mg/100 g) under open field conditions. Similar trend was followed in case of 50% shade net conditions as well. Highest value was found for S₂ whereas and S4 recorded the lowest in Cristal (27.55 mg/100 g) and Sweet Charlie (21.36 mg/100 g) respectively.


 
Sugars
 
In the present experiment, significant variations were observed in the percentages of total sugar, reducing sugar and non reducing sugar among the varieties. The highest value of total sugar (7.01% and 5.43%), reducing sugar (3.81% and 2.96%) and non reducing sugars (3.88% and 2.63%) were observed in Sweet Charlie (T₄) in both open and 50 per cent shade net conditions. The variation in sugar contents might be due to the varied rates of hydrolysis of starch into soluble sugars such as glucose, sucrose and fructose. The results are in line with the experiments of Jami et al., (2015). In addition, sugar content in strawberries differ not only due to cultivar, but also depends on cultivation conditions, such as irrigation (which is particularly important in blossoming phase and fruit setting phase), fertilization (mainly NPK), as well as the health condition of the plantation From the Table 5, 6 and 7 it is clearly evident that there are significant differences among the different dates of planting. The mean values for total sugar, non-reducing and reducing sugar contents were significantly higher in S₂ (15^th of November) in both open conditions (6.32%; 3.23% and 3.20%) and 50 per cent shade net conditions (4.55%, 2.36% and 2.18%) respectively. Whereas, lowest values for total sugars and reducing sugars are recorded by S₄ and for non reducing sugars S₁ is found to record lowest in case of open conditions. On the part of 50% shade net, it was for S₄ which recorded the lowest values of all the three sugar parameters. The variation in total sugar content might be due to the exposure of the plants to sunlight in as sunlight is necessary for hydrolysis of starch into sugars. The findings are in agreement with the results of Singh et al., (2008).



​

​

Finally it can be concluded that the variety Sweet Charlie was found to have the best results followed by Winter Dawn in terms of biochemical parameters when grown both in open conditions as well as under 50 per cent shade net conditions. Moreover, the best date of planting was found to be the S₂ i.e 15^th of November which sowed encouraging results in comparison to the other dates. Thus, the variety Sweet Charlie can be considered the best variety and preferably 15^th of November should be the time of planting Strawberry runners under Assam conditions.