Research Article

Role of Micronutrients in Improving Fruit Quality and Yield of Strawberry cv. Chandler under Microclimatic Conditions

Sanjeela Sabahat1*, Juliya Abbasi2, Mushtaq Ahmad1, Saima Mumtaz1, Taj Naseeb Khan1, Sudheer Tariq1 and Muhammad Imran1

1Horticultural Research Institute (HRI), NARC, Islamabad, Pakistan; 2Plant Physiology Program, NARC, Islamabad, Pakistan.

Received | December 15, 2020; Accepted | December 23, 2021; Published | January 12, 2022

*Correspondence | Sanjeela Sabahat, Horticultural Research Institute (HRI), NARC, Islamabad, Pakistan; Email: [email protected]

Citation | Sabahat, S., J. Abbasi, S. Mumtaz, S. Tariq, M. Imran, M. Ahmad and T.N. Khan. 2021. Role of micronutrients in improving fruit quality and yield of strawberry cv. chandler under microclimatic conditions. Pakistan Journal of Agricultural Research, 34(4): 897-904.

DOI | https://dx.doi.org/10.17582/journal.pjar/2021/34.4.897.904

Keywords | Strawberry, Micronutrients, Tunnel, Foliar application

Introduction

Strawberry (Fragaria x ananassa Duch.) is an octaploid hybrid of the genus Fragaria (Rubiaceae family). It is a low growing perennial plant cultivated worldwide for its fruit. Botanically, its fruit is described as an aggregate accessory fruit. In 2016, strawberry production reached 9.1 million tonnes, with China accounting for 42 percent of the global output, followed by the US (16 percent) and Mexico and Egypt (5 percent each). (Trejo-Téllez and Gómez-Merino, 2014; Global market update: strawberry, 2019).

In Pakistan, strawberry is grown as an annual crop in parts of Punjab and KPK province (Afridi et al., 2009). The crop is cultivated in November and fruit is ready to harvest in April-May. Its total area under cultivation is 387 hectares with an annual production of 795 tonnes (MNFSR, 2020). The maximum average yield lies between 5-10 tonnes per hectares. Since it is a relatively newly introduced crop, it’s per acre production in Pakistan is not comparable to global production. Its commonly grown varieties include Chandler, Corona, Douglas, Gorella, Toro and Tuft (Rajwana et al., 2017). Chandler is high yielding, has larger fruit size, high photosynthetic activity and can easily be grown under tunnel conditions. (Kadir et al., 2006).

Apart from macronutrients, the importance of micronutrients cannot be denied in plant growth and development. These include iron, copper, zinc, boron, manganese and molybdenum. Iron plays a main role in the biosynthesis of chlorophylls and cytochromes and its deficiency can result in the bleaching of leaves. Zinc plays a vital role in pollination, fruit setting and improving fruit quality parameters such as increased sugar and decreasing acidity levels. Its deficiency can result in immature leaves (Neuweiler et al., 1996; Abedy, 2001; Abdollahi et al., 2012; Hafeez et al., 2013; Singh et al., 2015). Boron is reported to play an important role in plant cell growth and is also involved in many physiological processes such as phenol metabolism and tissue differentiation (Barker and Pilbeam, 2006). Its deficiency results in leaf tip necrosis in younger leaves and a decrease in the flower size. Unlike other micronutrients, copper is of minor importance in strawberries. In case of its deficiency, the leaves and interveinal area become light green (Trejo-Téllez and Gómez-Merino, 2014).

The uptake of these micronutrients from soil depends on the cultivar, cultural practices, and soil’s physical and chemical properties. Over the past few decades, the cropping pattern in Pakistan has increased soil salinity levels and soil pH, which has caused the depletion of these micronutrients. (Ahmad et al., 2010). Their deficiency can be overcome either by foliar or basal application. The choice of method depends upon the crop type (Arevalo-Gardini et al., 2015).

In the modern agriculture system, foliar application of micronutrients is preferred as it allows quick and uniform distribution of micronutrients through leaves and meets the plants’ needs regardless of soil condition (Kerin and Berova, 2003). On the contrary, the basal application might result in leaching down of the applied micronutrients. Moreover, calcareous soils with high pH also hinder the availability of basally applied micronutrients, resulting in stunted growth of new shoots, chlorosis and mottled leaves (Sharma et al., 1990).

The plastic covers or tunnels are getting popular for the production of fruits and vegetables. They can facilitate crop yield by providing a controlled environment, reducing the risk of fruit damage caused by heavy rainfall, hailstorms, or fungal diseases. They also allow extended harvesting periods (Wittwer and Castilla, 1995; Jiang et al., 2003; Jett, 2007). Growing strawberries under the tunnel are reported to have increased photosynthesis rate as light penetration to lower leaves is improved and earlier flowering and fruiting is promoted. (Baeza and López, 2012).

In Pakistan, farmers lack the basic knowledge of an optimized, cost-effective procedure for the applying micronutrients on strawberries. The following study is carried out to optimize the concentration of different micronutrients through foliar application and study their effect on the growth, quality, and yield of strawberries under tunnel conditions.

Material and Methods

The experiment was performed at the experimental field of Fruit Crop Research Program, Horticulture Research Institute (HRI), National Agriculture Research Centre (NARC), Islamabad, during 2019-2020. The experimental site is located at 33.6844° North, 73.0479° East on the global scale. The runners of the strawberry cultivar “Chandler” were obtained from Swat. The seedlings of uniform size runners were transplanted in a randomized complete block design with three blocks and three replications per block by the end of November. The plant-to-plant distance was 50 x 30 cm. During the study, the minimum temperature ranged from 4 - 5 °C (during December-January), and the maximum temperature ranged from 30-35°C (during May-June). Beds were irrigated at the time of transplanting and later, the frequency of watering was decided based upon the soil moisture status confirmed through visual observation. The soil’s physical and chemical properties are given in Table 1.

Eleven different treatments include Control (T1), individual application of FeSO4 (Iron), CuSO4 (copper) and ZnSO4 (Zinc) in low concentration of 0.2% (T2-T4) and in higher concentration 0.4% (T5-T7). H3BO3 (Boron) was applied at 0.1% (T8), 0.2% (T9) and in combination with 0.4% FeSO4 (0.2% H3BO3+0.4% FeSO4) (T10). Finally, all four micronutrients were applied @0.25% each (T11).

 

Table 1: Physical and chemical properties of the experimental land. Data was taken from the Soil Science Department, Land Resource Research Institute (LRRI), NARC, Islamabad.

Soil Depth (cm)	pH	EC (dc/m)	CaCO3 %	Organic matter %	NaHCO3	Exchangeable Potassium (K)	Zn (mg)	Cu (mg)	Fe (mg)
0-15	8.1	0.16	4.0	2.0	4.9	48	0.34	0.46	6.6
30-45	7.9	0.16	4.0	1.8	2.5	38	0.28	0.50	4.2

 

 

The foliar application was started one month after the transplantation of runners. All plants were sprayed at vegetative (one month after transplantation), flowering (two months after transplantation) and fruiting (three months after transplantation) stage. Data on twelve different parameters were recorded at the time of plant maturity. These include quality parameters such as total soluble salts (TSS), titratable acidity (TA); yield parameters such as number of fruits, Yield per plant, fruit weight, fruit set percentage and other parameters such as days to flowering, plant height, plant spread, number of flowers, fruit length and fruit width. TSS was measured through a hand-refractometer (ATAGO, ATC-1, Tokyo, Japan) and Titratable acidity was determined through acid-based titration method as described by Ozkurt and Altunta (2018). Data were analyzed using R studio (R Core Team, 2020). The mean performance of different treatments was analyzed through analysis of variance (ANOVA) followed by Tukey’s HSD post hoc test. Correlation between different parameters was also calculated.

Results and Discussion

Table 2 showed the results of ANOVA of the effect of different micronutrient treatments on various vegetative, yield and quality parameters of strawberry Chandler. Except for the number of flowers and fruit length, there was a significant difference between all parameters against different treatment applications. 

Table 3 showed the pairwise mean comparison (Tukey’s HSD) effect of all treatments on the mean performance of ten traits in strawberry cv. Chandler. The foliar application of H3BO3 resulted in improved fruit quality. At 0.2 % H3BO3 (T9), the TSS was a maximum of 8.3 °Bx, unlike 6.7 °Bx in the control (T1) and a minimum of 4.5 °Bx against T7. At 0.1 % H3BO3 (T8), the TA was the lowest at 0.22 % compared to the maximum value of 0.51 % for T11. The H3BO3 was also found to have an intermediate effect on improving other parameters such as fruit weight and yield per plant. FeSO4 treatment contributed both towards vegetative and yield parameters. A low concentration of 0.2 % (T2) helped improve vegetative traits such as plant height of 29.89 cm and a plant spread of 35.99 cm against a minimum value of 14 cm and 21 cm, respectively, in T6. Its high concentration of 0.4 % (T5) improved yield parameters such as maximizing fruit set percentage to 87.85 % (minimum 57.26 % in T1) and yield per plant to175.84 g (minimum 69.47 g T6). For ZnSO4, compared to the fruit weight of 13.22 g in control (T1) and fruit width of 13.4mm in T7, maximum fruit weight of 18.22 g and fruit width of 32.66 mm was obtained with T4 (0.2 %) treatment. Also, only T4 resulted in improved yield as the remaining treatments were not significantly different from each other.

 

Table 3: Means comparison (Tukey HSD) of the different micronutrient application on various traits of strawberry cv. Chandler. Letter indicates significant difference between treatment means.

Labels	Treat-ments	Days to flowering	Plant height	Plant Spread	No. of fruits	Fruit set percent-age	Fruit width	Fruit weight	Yield per plant	Total soluble sugars	Titrable acidity
T1	Control	77.66b	22.10bcde	23.04bc	6.22b	57.26b	25.33abcd	13.22ab	79.25ab	6.7ab	0.29cd
T2	Fe (0.2%)	76.66b	29.89a	35.99a	8.53ab	72.22ab	32.33ab	17.66ab	145.39ab	5.26bcd	0.3cd
T3	Cu (0.2%)	74.66b	28.55ab	34.22a	9.26ab	78.55ab	28.33abc	14.55ab	133.61ab	6.56bc	0.39b
T4	Zn (0.2%)	85.66ab	27.44abc	27.89abc	8.66ab	75.98ab	32.66a	18.22a	175.84a	5.2bcd	0.28cd
T5	Fe (0.4%)	77.23b	20.78cdef	35.22a	10.26ab	87.85a	32ab	17.056ab	156.64ab	6.23bc	0.3cd
T6	Cu (0.4%)	104.66a	14f	21c	7.4b	81.91ab	18.66cd	9.27ab	69.476b	6.06bcd	0.26de
T7	Zn (0.4%)	105.33a	15.22ef	21.44c	9.8ab	81.87ab	17.66d	8.75b	85.59ab	4.5d	0.33bc
T8	B (0.1%)	66.66b	26.11abcd	27.22abc	5.84b	66.20ab	30.66ab	15.33ab	88.18ab	5.63bcd	0.22e
T9	B (0.2%)	83.66ab	23.66abcd	31ab	9.13ab	79.21ab	25.66abcd	13.66ab	122.78ab	8.3a	0.27de
T10	B + Fe (0.2%+ 0.4%)	89ab	19.78def	23.89bc	8.2ab	90.34a	20.33cd	10.97ab	87.57ab	5cd	0.39b
T11	0.25 % each of B+ Fe+ Cu+ Zn	92ab	20.55cdef	24.44bc	12.53a	86.26a	22.66bcd	12ab	150.66ab	5.66bcd	0.51a

 

However, a high concentration (0.4 %) of ZnSO4 (T7) resulted in the decline of both vegetative and fruit quality traits such as a minimum plant spread of 21.44 cm, fruit weight of 8.75 g, TSS of 4.5°Bx, fruit width of 17.66 mm and longest days to flowering of 105 days. Application of CuSO4 at low concentration (T3) helped improve plant spread to 34.22 cm. However, its higher concentrations (T6) resulted in a decline of vegetative traits such as plant height (14 cm), plant spread (21 cm) and also increased days to flowering (104 days). The treatments that involved a combination of micronutrients only improved a few of the traits under study. For example, H3BO3 and FeSO4 treatment (T10) only improved the fruit set percentage (90.34 %). The application of all micronutrients (T11) maximized both the number of fruits (~12) and fruit set percentage (86.26 %). However, both T10 and T11 also resulted in an increased TA of 0.39 % and 0.51 %, respectively. 

The results of the correlation between different growth, quality and yield parameters are indicated in Table 4. The maximum correlation observed for these parameters was 0.99 between fruit width and fruit weight. In contrast, a minimum positive significant correlation of 0.64 was observed for the number of fruits and yield per plant. Fruit width, fruit weight and yield per plant were strongly correlated traits. 

Days to flowering showed negative correlation with plant height, plant spread, fruit width and fruit weight. Plant height showed significant positive correlation with plant spread, fruit width and fruit weight. Plant spread showed positive significant correlation with fruit width, fruit weight and yield per plant. The number of fruits were positively correlated with fruit set percentage yield per plant and titrable acidity. Fruit width showed a significant positive correlation with fruit weight and yield per plant, while fruit weight was positively correlated with yield per plant. 

The mean performance of each treatment application over control is shown in Figure 1. Maximum yield per plant was observed for 0.2 percent of Zinc followed by Iron (0.4 percent). With increased yield per plant in the following treatments, fruit weight and fruit width were also increased. In contrast, fruit weight and fruit width were decreased in combined treatments in T10 and T11. Although 0.2% H3BO3 application maximizes TSS, there is only a 30 percent improvement over the control. The study showed that the micronutrients primarily improved the yield parameters while no effect was found on quality parameters of strawberry fruit except for treatment T8 (0.1 percent boron), where maximum decreased value of titrable acidity was observed. 

Major elements such as nitrogen, potassium, and phosphorous play an essential role in the growth development and production of strawberries. However, the importance of the secondary elements such as iron, boron, zinc, copper, etc., cannot be denied as they served as a catalyst to maintain the growth and yield.

 

Table 4: Correlation coefficients between different traits of strawberry cv. Chandler.

	DTF	PH	PS	No. Fr	FrS	FrWi	FrW	YPP	TSS	TA
DTF		-0.81**	-0.67**	0.33ns	0.50ns	-0.82**	-0.76**	-0.33ns	-0.31ns	0.24ns
PH			0.73**	-0.13ns	-0.41ns	0.84**	0.84**	0.51ns	0.16ns	-0.10ns
PS				0.19ns	0.02ns	0.79**	0.79**	0.74**	0.30ns	-0.09ns
No. Fr					0.69**	-0.11ns	-0.06ns	0.64**	-0.07ns	0.75**
FrS						-0.35ns	-0.29ns	0.30ns	-0.19ns	0.51ns
FrWi							0.99**	0.67**	0.15ns	-0.32ns
FrW								0.72**	0.12ns	-0.27ns
YPP									0.08ns	0.28ns
TSS										-0.20ns
TA

 

 

Their deficiency may result stunted growth in plants (Casteel, 2004; Ahmad et al., 2010). Foliar application of these micronutrients assures equal distribution to the plants. And the use of plastic tunnels aid in maximizing their uptake and in the early maturity of the crop (Smoleń 2012; Singh et al., 2012). 

The role of micronutrients in improving the vegetative growth, fruit quality and yield of strawberry has been reported by Abdollahi et al. (2012), Domoto (2011) and Farid et al. (2020). Our findings that application of FeSO4 in two different concentrations, 0.2% and 0.4%, improves vegetative parameters and yield respectively are inconsistent with Bakshi et al. (2013) and Ekka et al. (2018). They showed that 0.4 % and 0.6 % FeSO4 improve the growth, quality, and yield of strawberries. However, unlike Bakshi et al. (2013) who showed 0.6 % ZnSO4 improved fruit quality, our findings showed that only 0.2% ZnSO4 improves fruit parameters and a high concentration of 0.4% decreases growth fruit quality. These results are consistent with Shafeek et al. (2014) findings that the application of micronutrients in higher concentrations resulted in reduced plant vigor and fruit quality. Our results that both zinc and iron play a significant role is also supported by Singh et al. (2015), who showed that both FeSO4 and ZnSO4 improve vegetative and fruiting parameters. Since iron is a vital component of plant’s chlorophyll preparation machinery, its foliar application can result in an increased photosynthesis activity, which can ultimately contribute towards plant yield (Gajc-Wolska et al., 2014). Meanwhile, the role of zinc in plant sustenance can be explained by the fact that it acts as a cofactor for different enzymes and proteins (Sarwar et al., 2012).

Similarly, our findings of the role of boron in improving the fruit quality by reducing titrable acidity and maximizing TSS are consistent with Wojcika (1999), (2005) and Nagy et al. (2008). The role of boron in sugar translocation could help improve fruit quality parameters (Gauch and Dugger 1953; Sathya et al., 2010). Moreover, the deficiency of boron aggravate the quality of fruit by increasing titrable acidity and its application improves the quality of fruit (Haider et al., 2019). The combined effect of these three micronutrients (Iron, Zinc & Boron) resulted in improvement of yield and quality of fruit as discussed by Bhoyar and Ramdevputra (2016). Although copper acts as a cofactor for different enzymes and its role in photosynthesis and respiration are well established, our study showed no significant role of copper in improving the growth and yield parameters of strawberries. 

Conclusion and Recommendations

Based upon our findings, we suggest that the foliar application of ZnSO4 at 0.2 % along with FeSO4 0.4% can be recommended for improved yield of strawberry under tunnel condition. Similarly, the application of 0.2% boron can affect the quality of fruit. For future studies, the combined effect of these concentrations on strawberry cv. Chandler production is suggested.

Novelty Statement

This is an original study performed at Horticultural research institute, NARC, Islamabad.

This manuscript was not send to any other journal for publication

Author’s Contribution

Sanjeela Sabahat: Conceived and designed the experiment, performed the experimental work, wrote the first draft of the paper.

Juliya Abbasi: Performed statistical analysis, wrote the first draft of the paper.

Mushtaq Ahmad: Gave technical guidance.

Saima Mumtaz: Helped in data collection.

Taj Naseeb Khan: Procurement of strawberry germplasm, provided field space for conduction of experiment.

Sudheer Tariq: Conceived and designed the experiment.

Muhammad Imran: Procurement and identification of germplasm.

Conflict of interest

The authors have declared no conflict of interest.

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