INTRODUCTION

Strawberry (Fragaria ananassa Dutch) is a highly appreciated world wide not only for its unique taste and distinct flavor, but also for its health benefits. Strawberries contain usual nutrients, such as minerals and vitamins, and a diverse range of anthocyanins, flavonoids and phenolic acids with biological properties, such as antioxidant, anticancer, anti-neurodegenerative and anti-inflammatory activities (Seeram et al., 2006). The phytochemical composition is influenced through environmental conditions and pre- and post-harvest factors).

The total area harvested in Egypt is about 41.937 fed., which production quantity about 464.958 tons with average of 11.087 tons/feddan (FAO, 2016). The production in Egypt has considerable growth potential because of the definite market windows which is evidenced by its consumption and exports in Europe and Gulf countries increasing each year Egyptian exports of strawberries to Saudi Arabia were estimated at 39,000 tons, valued at some $90 million (FAO, 2017). The high perishability of strawberry, the reason for its relatively short period of harvest, compels the producer to sell his production immediately, evidently prejudicing him with respect to the reduced price due to its sale in large volumes). Due to high moisture (around 90%), sugars (glucose 4%, fructose 5% and saccharose 0.9%) and organic acids (citric 10-18 meq and malic 1-3 meq). Moreover, strawberry fruit have a very short postharvest life, due to microbial load, mechanical injury and desiccation resulted in decay and weight loss. Modified atmospheres with elevated CO₂ levels and low temperatures are effective in reducing the incidence of decay. However, prolonged exposure of berries to high CO₂ concentrations can cause off-flavor development  and low temperature alone is not an effective means of control. Although prophylactic field sprays with systemic benzimidazoles are effective in controlling post-harvest fungal infections, there is an increased concern among consumers about the potentially harmful health effects of chemical residues  and development of chemical tolerance in post-harvest pathogens. Thus alternative approaches are necessary to maintain the marketable quality of strawberries.

Alternatively, safer, cheaper and more ecologically friendly methods in the control of the insects were the modern trends that must be taken into consideration (Okunlola and Ofuya, 2013). Researchers are working in the field of natural products extensively as they are less hazardous, low cost and easily available. The dependency on the use of inorganic fertilizers as a source of plant nutrients by farmers and their high cost is further associated with land and soil degradation and environmental pollution (Phiri, 2010). Thus, there is continuous need to search for alternative safe natural sources of plant nutrients, natural growth regulators even for protecting against disease and insects. Plant hormones can be used to increase yield per unit area because they influence every phase of plant growth and development (Prosecus, 2006).Foliar sprays of some plant extracts on strawberry plants have recently received apparent interest. The various positive effects of applying active plant extracts were attributed to its contents of different nutrients, vitamins, hormones, natural plant growth regulators.

Green tea (Camellia Sinensis),is a good source of polyphenolic compounds haring strong and antioxidant, property which, proved to exhibit antimicrobial activity against some bacteria (Chan et al., 2007). The important polyphenolic compound in tea leaves include catechin,theaflavins and thearubiging. Green tea is proved to exhibit antimicrobial activity against some bacteria and has good antioxidant activity.   The beneficial effects of the phenolic compounds are thought to result from their ability to scavenge reactive oxygen and nitrogen species (Gramza et al., 2006).

Thyme plant and its essential oil (Thymus vulgaris L., Family: Lamiaceae) is known to contain more than 40% of phenolic compositions (thymol and carvacrol), that have strong antiseptics effect. In addition to thymol, caffeic acid and then in existing in essential oil can effectively prevent growth of bacteria, fungus and viruses. The highest value of thymol exists in Thymus vulgaris. According to GC analysis, Thymus captatus contains carvacrol that researchers pointed to its anti-microbial properties and inhibition activity of the existence of these two compounds (Karimi and Rahemi, 2009).

 Chitosan, a deacetylated derivate of chitin, is a high molecular weight cationic linear polysaccharide composed of D -glucosamine and, to a lesser extent, N-acetyl- D -glucosamine with a β-1,4-linkage. Chitosan-based coatings are considered the best edible and biologically safe preservative coatings for different types of fruits, with functional advantages, such as slower respiration rates, extended storage periods, firmness retention and controlled microbial growth (Romanazzi et al., 2015).

Calcium is an important nutrient that plays a key role in the structure of cell walls and cell membranes, fruit growth, and development, as well as general fruit quality (Kadir, 2004).

Therefore, the aim of the present study is to investigate the effects of some natural extracts and different sources of calcium to obtained best growth and high yield  as well as  good fruit quality  of strawberry.

MATERIALS A AND METHODS

Two pots  experiments were  conducted at the Baramoon Res. Station, Mansoura, Dakahlia Governorate, Egypt  during of 2014/2015 and 2015/2016, to study the effect of some plant extracts and some calcium sources on growth, productivity and quality  of strawberry.

Plant materials

Fresh transplants of Festival cultivar were obtained from local nursery and dipped in 0.2% Rhizolex solution as fungicide for 20 minutes before planting and transplanted on 8^th and 12^th October in pots 26 cm in diameter and 25 cm deep  it contained mixed substrate (peat moss, clay, sand and vermiculite) (2: 1: 1: 1 v./v.) and was sterilized by sun for 15 days before planting during the 1^st and 2^nd seasons, respectively.

Plant extracts 

Plant materials (green tea leaves, mushroom head, full herb thyme) were obtained from the local market, washed with distillated water and dried in the shad. They were finely grinded to powder. Fifty grams of each plant material in powder form was homogenized by laboratory blender in 200 ml of methanol (96%) and distilled water (20:80 v/v) for 10 min, and then left dark glass bottles for 72 h for complete extraction. The extracts were filtered through thin cheesecloth sheets. The final extracts were collected separately in other dark glass bottles and exposed to 60 °C in water bath for 30 min for methanol evaporation. The collected extracts were then stored in a refrigerator at 5 °C until needed. Plant extracts was subjected to GC-MS analysis using a Gas Chromatograph (Singh et al., 2005).

Chitosan: It is commercial product by India. It includes chitosan 90-95%. (2-Amino-2-deoxy-beta-D-glucosamine) at 1%, i.e., 10 g from chitosan dissolved in 0.1 NaOH and completed to 1 liter of distilled water was used. 

Table 1: The main compounds identified in the methanol extract of tested plant extracts by using GC-MS.

Treatments

This experiment contains eight treatments as foliar spray  as  follows:

Green tea, thyme and mushroom extracts  at 2 ml/l, chitosan   solution  at 1%,  calcium chloride  at 1%, calcium citrate  at 2.5 ml/l, calcium nitrate  at 0.5 ml/l and control  treatment ( tap water).

The strawberry plants were sprayed with plant extracts, chitosan  and  different  calcium sources  three  times i.e.,  at  the beginning  of runners formation, beginning  of  fruits  coloring and  half fruits coloring, untreated plants were left as a control treatment and sprayed with tap water.

The agricultural practices concerning cultivation, irrigation, fertilization with macro and micro nutrients and insect as well as disease control were conducted according to the recommendation by the Ministry of Agriculture for strawberry commercial production.

Experimental design

These treatments were arranged in a randomized complete block design with three   replicates, each treatment contain four pots. This experiment included 96 pots, i.e., 8 treatments x3 reps. x4 pots =96 pots

Data Recorded.

A random sample of two pots from each replicate was taken after 120 days from transplanting in the two growing seasons for measuring the vegetative growth, and leaf pigments as follows:

Vegetative growth parameters: 

Plant height (cm), fresh weight (g) ,number of leaves / plant and leaf area (cm)² were evaluated.

Flowering parameters

Number of runners per plant, number of flower / plant, number of crown plant and crown diameter / plant (cm).

Photosynthetic pigments

Disc samples from the fourth upper leaf were randomly taken from every plot and determine chlorophyll a, b, (a+b) and carotenoids in both seasons, according to the method described by Wettestein (1957).

Yield and its Components

Two other pots were used to measure the yield parameters and fruit quality.

Number of fruits / plant, fruit set percentage, average fruit yield / plant, total yield (g) was  recorded from each  pots  all over the  harvested season up to the mid of May.

Fruit quality:

They were measured after six weeks from the first harvest as follows:

Total soluble solids contents (TSS),total titratable acidity (TA %):

Samples of 100g fruits from each experimental pots at full ripe stage were randomly chosen to determine the total titratable acidity of juice by titration with 0.1 NaOH soluation, using phenol phthalein indicator, according to the method described in A.O.A.C. (2000).

Anthocyanin content

It was determined according the method described by (Geza, et al., 1984).

Total, reducing and non-reducing sugars (%) were determined as described by Forsee (1938).

Pectin was quantified in juice, through McCready and McComb (1952) method and Bitter and Muir (1962) technique was used for dosage, and the results were expressed in mg of polygalacturonic acid per 100 g of fresh fruit.

Statistical analysis

Statistical analysis was conducted for all collected data. The analysis  of variance  was calculated according  to Snedecor and Cochran (1980), means separation were done according to LSD  at 0.05  level.

RESULTS AND DISCUSSION

Vegetative growth parameters  

Data in Table (2) show that spraying  strawberry plants with different  plant extracts, i.e.,  green  tea,  thyme, and  mushroom extracts  at 2 ml/l of each  and chitosan 1% and different sources of calcium such as calcium chloride at 1 % , citrate calcium at 2 ml/l and nitrate calcium at 0.5 %  had significant effects on plant height, fresh weight, number of leaves per plant and leaf area than unsprayed plants in both  growing seasons under pots experiment. Moreover, spraying plants with green tea and mushroom extracts exhibited significant effect in all traits compared to other treatments and control without any significant differences between them in both seasons.

Chemical compounds found in green tea and mushroom that are useful for the growth of agricultural (Table 1) epigallocatechingallate 112.26 mg/g gallated 158.18 mg/g epigallocatechin 40.34 mg/g in green tea extract from mevalonic acid which has similar effect to GA₃ in reducing complex compounds to simple ones utilized by plants to build new proteins necessary for growth (Babilie et al., 2015). In addition, magnesium (main element in mushroom) plays a role in increasing foliage growth, cell division, and biological plant activities (Moses et al., 2002). Mercy et al. (2014) found that the application of fruit peel powder and extract increased the growth of plants (rice, rye, mustard and fenugreek) and gave the higher yields.

Photosynthesis pigments 

           Data in Table (3 ) show that,  all   treatments  had significant  effect  on  all  photosynthesis pigments  such as  chlorophyll a, b , total (a+b) and carotenoides in leaf tissues  than  control treatment in  both seasons.  However, spraying strawberry plants with green tea and mushroom  extracts at 2 ml/l  gave the highest values  of  chlorophyll a , total chlorophyll and carotenoides in leaf tissues without significant differences with  Ca citrate or  Ca nitrate concerning total chlorophyll.  On the other side , spraying  strawberry plants with  Ca nitrate  recorded the highest value of chlorophyll b in leaf tissues.

The plant extracts rich Mg. In plant Mg is a central component of chlorophyll and vital for photosynthesis and S is important for amino synthesis.

Flowering parameters

Data in Table (4) show that, spraying green tea and  mushroom extracts  increased significantly number of runners and flowers/ plant, number of crown/plant, crown diameter/plant compared with the other treatments or control treatment. 

The observed increment on number of runners and number of flower due to green tea and mushroom extracts that are rich in combined manure with            

Table (2): Effect of foliar spray with some plant extracts and some sources of calcium on vegetative growth of strawberry plants during 2014/2015 and 2015/2016 seasons

Table (3): Effect of foliar spray with some plant extracts and some sources of calcium on photosynthetic pigments ( mg/g DW) of strawberry plants during 2014/2015 and 2015/2016 seasons

potassium and boron (Table 1). These extracts when used as foliar spraying might be related to the improvement of physical conditions of the soil and supplying plant with nutrients for a longer period thorough the season            of growth, as reported by Arancon et al. (2004). In addition, the role of potassium is necessary for the activation of some enzyme systems, the translocation of carbohydrates and osmosis regulation. Furthermore, boron

Table (4): Effect of foliar spray with some plant extracts and some sources of calcium on flowering parameters of strawberry plants during 2014/2015 and 2015/2016 seasons

plays a role in cell differentiation and carbohydrate metabolism (Wang and Lins, 2002).

Yield and its components

Data in Table (5) indicate that, spraying strawberry plants with different plant extracts and different sources of calcium had significant effect on number of fruits/ plant,  fruit set percentage,  average fruit weight and  total yield / plant than unsprayed plant , moreover, spraying plants with green tea  extract or calcium nitrate proved to be the superior treatments in this respect in both seasons.

The increases in total yield/ plant were about 78.94 and 68.48 % for spraying plants with green tea extract and 55.93 and 62.56 % for spraying plants with  calcium nitrate over unsprayed plants ( control treatment ) in the 1^st and 2^nd seasons, respectively.

Plant extracts are rich in amino acids, vitamins and growth stimulating photo-hormones that increases the activity of apical meristem tissue resulting in cell division and elongation (Elfalleh et al., 2011 and Singh. 2013). The above findings agreed with those reported by Nasser et al., (2014), they found that spraying fenugreek plants with licorice extract led to more absorption of nutrients from the soil, which accelerated growth and increased their production. The tannin-rich ellagitannins and phenolic acids (Table 1) of Punicagranatum peel have antibacterial activity (Supayang et al., 2005), which turned on productivity.

Table (5): Effect of foliar spray with some plant extracts and some sources of calcium on yield of strawberry plants during 2014/2015 and 2015/2016 seasons

Fruit quality

Data in Table (6) reveal that, spraying  plants with different plant extracts and calcium sources had significant improve of anthocyanin, vitamin C, acidity, TSS content of strawberry fruits  than  unsprayed plants  in both seasons.

 In general, the plants  which sprayed with  green tea  gave the highest values of vitamin C and lowest values of total acidity in fruits , while mushroom extract   gave the highest  anthocyanin  contents  in fruits.  TSS content in fruit   was the highest with thyme extract in both seasons .

These results could be attributed to the effect of plant extract on the increase of nutrient absorption and photosynthesis process that lead to more  accumulation of metabolites in reproductive organs which in turn improve  fruits quality of strawberry (Wang and Lins, 2002; Hagreaveset al., 2009).  Adding potassium and boron as foliar spraying plays a key role in improve size of fruits and stimulates fruits color. It is necessary for the translocation.

Chemical composition in fruit

The obtained  results in Table (7) indicate that, all  spraying treatments significantly increased the percentage of pectin, total sugars, reducing and non reducing sugars in fruit as compared with the control treatment in the two seasons, however,  spraying plants with green tea  extract  was the best treatment for increasing  the content of pectin in fruits (2.42 and 2.35 %),  total

Table (6): Effect of foliar spray with some plant extracts and some sources of calcium on quality of strawberry plants during 2014/2015 and 2015/2016 seasons

Table (7): Effect of foliar spray with some plant extracts and some sources of calcium on chemicals of strawberry plants during 2014/2015 and 2015/2016 seasons

sugars (8.95 and 8.87 %),  reducing sugars  ( 2.62 and  2.58  % ) , non reducing sugars  ( 6.33 and 6.29 % ) against (1.02 and 1.09 %),  (4.65 and 6.16 %),  (1.38 and 1.0 %),  ( 4.78 and 3.65 %) for  control treatment in the 1^st and 2^nd seasons, respectively.

Sugar and formation of carbohydrates consequence increase fruits quality. These results are in agreement with reported by Velez Ramos et al. (1991).

Conclusively, from the  foregoing results of this study, it could be concluded that, under the same conditions  , spraying  strawberry plants  with  plants extracts such as green tea or  mushroom  extracts at 2 ml / l or  calcium nitrate at 0.5 ml/l  were the best treatments for  increasing  growth , yield and gave the best fruits quality .