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Strawberry (Fragaria ananassa) belonging to family Rosaceae is a dicotyledonous angiosperm. The cultivated strawberry (Fragaria ananassa Duch), was developed from hybrids of F. Virginiana and F.chiloensis (Hancock et al., 1999). The important genes for large fruit size, large crowns ,firm fruit and distinctive fragrance were inherited mostly from Chilean F. chiloensis (Otterbacher and Skirvin, 1978; Galletta and Bringhurst , 1990).Strawberry is known as the most delicious, refreshing fruit with high nutritive value (Cordenunsi, 2003) and high hexose/sucrose ratio (Nishizawa et al., 2005) to millions of people of the world. Strawberry plants have been generally classified by their response to day length (photoperiod) and its influence on flower induction. There are three recognized groups of plants depending on their sensitivity to seasons: June bearers, Ever bearers, and Day-neutrals (Durner et al., 1984).
Strawberry fruit is a rich source of vitamins and minerals with nice flavor. It contain reasonable amount of ascorbic acid (60mg/100g) and phenolics compound with high antioxidant activity, such as ellagic acid and anthocyanin (Agar et al., 1997; Grace, 2005). Strawberries generally require cooler summers, and are poorly adapted to the hot, arid climates and can tolerate -20°F. They have chilling requirements ranging from 800-1600h. However, it can be grown in varied climatic conditions, ranging from temperate to tropic climate. Since its cultivation is greatly influenced by specific regional adaptation due to critical photoperiod and temperature requirement, its cultural practices are highly variable (Sharma, 2002).
Strawberry is an early maturing fruit crop and can be planted round the year hence; it brings a high and quick economic return to growers. Winter planting is common in Pakistan. However, due to diverse agro-ecological zones in Pakistan, summer, autumn and spring plantings have also been successfully demonstrated by different agricultural research institutes. In Pakistan strawberry has a great potential due to the diverse climatic conditions which are conducive to its growth and can be successfully grown in the central and northern Punjab, and hilly areas of NWFP province, where the plants can be sustained for two to three years. Strawberry growers of the warmer plans are entirely dependent on hilly areas for their planting material requirements, which makes it cultivated in plains less remunerative. The runners, which are received from hilly areas have very limited growth due to short growing season (July - September) as compared to plains (May - November) and thus give ultimate weak runners with poor yield.
Strawberry crop has been recently introduced at the farm level in Pakistan and was demonstrated at various research stations. A few years ago it was adopted by a few innovative growers around Islamabad, Lahore, and Malakand division in NWFP. The main markets of strawberry are only Islamabad and Lahore. However, very little is known about its area, supply schedule, volume, price, etc. In Islamabad, the local and producers from other areas mainly supply strawberry directly to retail supermarkets, big hotels and to local assemblers' cum-processors. The local wholesale market in Islamabad generally does not deal with such perishable commodities. However, in Lahore, strawberry is being traded in the wholesale fruit and vegetable market through commission agents. Producers also supply directly to retailers and processors. The supply of strawberry starts at the end of January and continues until the end of May each year.
The magnitude of strawberry production in Pakistan is very low as compared to USA, Russia, Spain, Turkey, South Korea, Japan, Poland, Mexico, Germany, Egypt, Morocco, United Kingdom, Ukraine, Italy and France. Among these USA is the biggest producer of strawberry (FAOSTAT, FAO statistics Division 2009).These are either eaten fresh or used as value added products like ice-cream, jam, jelly, pickle, cake or milk shake. The magnitude of low strawberry production in Pakistan is due to several factors like the climatic conditions, pre and post harvest handling. By ameliorating the constraints related to quantity, quality and perish ability of the strawberry, it can be air freighted to the U.S.A, Europe and Gulf countries. Many varieties of strawberries are grown in Pakistan. Toro and Douglas obtained from USA are suitable for southern areas of the country and Tufts, Chandler, Cruz and Pocahontas are recommended for Islamabad. Chandler, Corona, Tufts, Honeyo and Gorella are suitable for Swat. The introduction of new varieties that have a longer shelf life would increase the potential of this crop.
Pakistani strawberry can easily be air freighted to European markets with high efficiency cooling facilities from farm to air transport. The consumer base is restricted to those who have been abroad or have a wide exposure to the outside world especially Europe. The other main users of this commodity in Pakistan are processors of ice cream, jam and cake, marmalade and drinks. It is also used in different medicines and cosmetics. It can be used in both fresh and frozen form around the year. Moreover, a growing awareness regarding the nutritional value of strawberry and overall changing tastes and preferences of urban society suggest that it has bright growth prospects. Also, the available evidence shows that due to the low cost of production and conducive agro-climatic conditions in Pakistan, the export potential of strawberry substantial. Also, it has potential benefits for small farmers in terms of generating rural income and employment. The superior size of the European market indicates that it may be the prime potential market for Pakistani strawberry and it has a sufficient seasonal edge to be a viable competitor. In the European market, Germany is the largest single potential market which can absorb approximately 6,000 metric tons of fresh strawberries per week and still maintain prices which would be profitable to a reasonably efficient Pakistani exporter of strawberry. In addition to Germany, UK, France and Japan are other potential markets and all four markets can absorb roughly 10,000 metric tons per week at prices profitable to a Pakistani producer.
The market "window of opportunity" for Pakistani exporters in these markets is from July to March. However, quality is the key in penetrating these potential markets. The major constraint to strawberry export is the lack of post harvest technology in packing, grading standards and cool chain distribution. Refrigerated transport for such fruit is a vital part of any successful marketing operation under the prevailing climatic conditions in Pakistan. Since this is a new commodity for Pakistani farmers, it requires reasonable production and post-harvest technology. Of course, this can be done through very effective research and development in potential areas of Pakistan.
1.1 Quality attributes and shelf life of strawberry fruit
.Agronomic practices, variety characteristics, grading, processing and finally packaging is a basis of quality of any crop. The lack of any of the component gives rise to low quality product and makes it less acceptable in international markets. Strawberries are among the most favorable consumed fruit. The balance between sugars and acids, which define sweetness and tartness respectively of fruits, give the characteristic flavor of strawberries, while aroma is derived by the combination of volatile molecules (Ayala-Zavala et al., 2004). Superficial color of berries determines the time of harvest, while fruit firmness is associated with shelf life. Recently, the determination of ascorbic acid and anthocyanin has been of major interest (Aaby et al., 2005: Scalzo et al., 2005).
The strawberry fruit is a good source of ascorbic acid (Robards et al., 1999).Ascorbic acid levels varies substantially among cultivars (Darrow et al., 1947). There was no reduction in total ascorbic acid contents of strawberry fruits that have been stored at 0, 10, 20 and 30oC for up to 8 days (Kalt et al., 1999). Vinokur et al., 2002 concluded that the ascorbic acid contents in strawberries kept in controlled atmosphere differed significantly of that in control.
The soluble solid contents of fruit are a good indicator of the sugar content (Haffner and Vestrheim, 1997). It seems that a high fruit load on plants reduces the soluble solid contents in fruit (Anagnostou and Vasilakakis, 1995).Fructose; glucose and sucrose were found to be the major sugars, comprising more than 65% of the total soluble solid contents in strawberry fruit of different cultivars.
Even in early studies there were efforts to breed strawberry verities for firmness (Barritt, 1979). Fruit with firm flesh have a longer shelf life (Mokilla et al., 1999).Firmness is affected by the variety, the nutritional status of plants and type of fertilizers used (Mukkun et al., 2001). Low temperature during the storage of strawberry fruit increases flesh firmness (Lara et al., 2004).
Strawberry is one of the most perishable fruits with short shelf life due to the susceptibility of berries to mechanical injury, water loss, decay and physiological deterioration (Nunes et al., 1995).Much research has been conducted and there were efforts of manipulating preharvest (Mukkun et al., 2001) and post harvest factors (Cordenunsi et al., 2005) that affect fruit quality in order to enhance strawberry shelf life. Moreover, special packaging (Saz et al., 1997) or even photochemical (Baka et al., 1999) and chemical (Morris et al., 1985) treatments, have been tested to improve post harvest quality and shelf life of strawberries.
1.2 Pre-harvest factors for quality and shelf life
1.2.1. Varietals response
In previous years researchers conducted many experiments on the cultivars of strawberries in different areas, region and countries. Results vary from place to place due to many external and internal factors. The same experiment was conducted by Nuzzi et al., (2005) and explained that fruits of strawberry cultivars Miss and Queen Elisa from experimental fields in Cesena and Verona in Italy were picked at full ripeness over 2 weeks during May in 2002 and 2003. Quality was assessed objectively according to the main quality parameters, such as weight, flesh consistency, dry refractometric residue, titratable acidity and ascorbic acid content. Storability parameters were assessed following refrigeration for 3 days at 40C and 1 day at 200C. Sensorial quality of the fruit was evaluated by a taste panel. Queen Elisa differed significantly from Miss, having higher values for fruit weight, acidity and ascorbic acid content. Quality of Miss was more affected by the different areas of cultivation than was Queen Elisa quality. Miss was the more distinctive for most volatile constituents.
In an other experiment Yommi et al., (2003) evaluated fruit quality of different strawberry (Fragaria ananassa) cultivars, cold-stored plants of cvv. Aromas, Gaviota, Camarosa and Selva and fresh plants of Camarosa, Earlibrite, Rosa Linda, Gaviota, Tud New and Sweet Charlie were planted in a winter production system. Periodically the fruits were harvested and samples of 15 fruits (>75% red colour) per cultivar were subjected to analysis during June, July and August. The quality parameters of fruit assessed were fruit weight, pulp color, firmness, ascorbic acid, soluble solids acidity and TSS/acidity ratio. Acidity contents varied among varieties when compared with Camarosa as the most acidic. However, Tud New possessed high fruit weight, firmness and vitamin C, which is desirable in terms of quality, TSS ratio was low. The cv. Camarosa was found with high levels of firmness, total soluble solids and acidity contents. The cv. Earlibrite showed high level fruit weight, firmness, total soluble solids, ascorbic acid and acidity. Whereas, cv. Sweet Charlie exhibited higher total soluble solids, moderate firmness and lower acidity.
Cordenunsi et al., (2002) narrated that six strawberry cultivars grown on the same commercial plantation in Brazil were evaluated for their chemical composition and quality attributes at the ripe stage. The profiles of the main soluble sugars, ascorbic acid, and anthocyanin were also obtained during the developmental stages. Results showed significant differences among cultivars in all of the investigated parameters
The strawberry cultivar Chandler planted in mid-September under micro irrigation system using black polythene as mulch produced higher yield and good quality fruit in Northern plains of India (Singh et al., 2007). Lareau and Lamarre (1993) demonstrated the use of black plastic mulch in hill strawberry planting system. They also compared straw mulch with black plastic mulch and concluded that black plastic mulch increased yield, number and weight of crowns but decreased fruit size of Tribute and Tristar strawberries. Sharma et al., (2008) concluded that mulching with black plastic and erection of row covers in winter is very beneficial for better growth and production of strawberry in sub-tropical conditions.
1.2.3. Environmental conditions
Strawberry can be grown in wide climatic conditions, ranging from temperate to tropic climate. Since its cultivation is greatly influenced by specific regional adaptation due to critical photoperiod and temperature requirement, its cultural practices are highly variable (Sharma, 2002). Its cultivars grown in specific areas are adapted to the day length and temperature of that region. Nevertheless, heat stress is one of the challenges that face strawberry production. Reduction in plant growth by high temperature is well established in horticultural crops such as tomato (Adams et al., 2001) grape (Chaumont et al., 1997) and strawberry (Renquist et al., 1983). Damage to crops by high temperature has been reported in many regions around the world. Temperature above 350C is common during the growing season.
High temperature adversely affects the vegetative growth and fruit quality. Heat stress affects photosynthesis, which is highly sensitive to thermal inhibition (Henning and Brown, 1986) whether stress occur early or late in the growing season. Strawberry cells subjected to 300C grew slowly and did not proliferate normally in suspension cultures (Zang et al., 1997), strawberry vegetative growth (Hellman and Travis, 1988), root growth (Fukuda and Matsumoto, 1988), fruit set (Nishiyama et al., 2003), pollen viability (Ledesma and sugiyama, 2005), fruit weight (Mori, 1998), fruit quality (Polito et al., 2002) and leaf protein expression (Gulen and Eris, 2004; Ledesma et al., 2004) were negatively affected by high temperatures, however strawberry plants resistant to high temperature have the ability to maintain high rates of photosynthesis, stabilize proteins and synthesize new proteins (Gulen and Eris, 2004) and by proper selection of cultivars to the region.
Some strawberry cultivars behave as short-day plants requiring day lengths shorter than about 14 hour or temperatures less than about 15oC for flower induction. Whereas low temperatures between 10 and 15oC induce flower formation even in long photoperiods, temperatures less than about 10oC resulted in a chilling response (Guttridge, 1985).According to studies of Kronenberg et al., (1976) plants need to be dormant to give chilling response. Judged by the subsequent vegetative growth of plants transferred into warm glasshouses at different times in autumn and winter, deepest dormancy is attained in November in northern latitudes (Jonkers, 1965; Lee et al., 1970).
It is well known that cultivars have different chilling needs (Bailey and Rossi 1965; Lee et al., 1986 & 1970). Those cultivars with small chilling requirement, such as Tioga, need only 2-4 weeks cold; others, like Sequoia, Glass and Gorella, need 5-8 weeks and Redgauntlet, a cultivar with a large chilling requirement, needs more than eight weeks cold (Kronenberg and Wassenaar, 1972). Changes in vegetative growth induced by chilling are striking and resemble the effects of increasing day length. The responses to chilling and to long day lengths are at least additional, and neither substitutes for the other, at least not for petiole responses. Chilling increases the plant's response to daylength (Guttridge, 1985)
Existing fruit trusses are increased in size by chilling. The length of peduncles, secondary branches and pedicels are increased by chilling. The magnitude of the chilling response depends on the stage of development reached by the truss at dormancy (Guttridge, 1985). Piringer and Scott (1964) studied responses to chilling in Sparkle, Tennessee Beauty and Missionary by recording runner production during forcing. In all three cultivars, chilling stimulated runner production. Wahdan and Waister (1984) confirmed the need for a chilling stimulus to induce runner formation. In a study by Bailey and Rossi (1965) on Catskill, it was indicated that plants required greater than 504 hours below 7.2oC to stimulate runner production. They also suggested that more chilling was necessary to affect runner growth than petiole length, leaf number, or size.
In the literature the temperature at which it is assumed that strawberry perceive chilling, ranges from -2oC to 10oC. The evidence to the effect of chilling on the production of flowers and fruit is not consistent. The data for Catskill indicate strongly that the numbers of flowers produced increased with increased field chilling (Bailey and Rossi, 1965). Conversely, the result of Guttridge (1960), and Voth and Bringhurst (1958) showed a decrease in flower production with increased chilling. Bailey and Rossi (1965) pointed out that this discrepancy is probably due to the different environment and different methods used in the experiments. In fact they wondered if the increase in the number of flowers was due to increased flower bud initiation in the field with later digging or to increased chilling or both.
In a study conducted by Guttridge (1958a) on Royal Sovereign, chilling for 36 and 72 days in a cold room (1.1-3.8oC) delayed flower initiation. Durner and Poling (1988) pointed out that cultivars vary in their response to photoperiod and chilling with respect to induction, initiation, and differentiation. Yanagi and Oda (1993) claimed that the number of inflorescences produced by Hokowase (Junebearer) and Kletter (Intermediate) decrease with the duration of chilling. In this work plants had different lifting dates in autumn (6 Nov, 15 Nov, 15 Dec, and 15 Jan) and were put in the glasshouse at different times. Therefore, the lifting date and duration in glasshouse may have affected the number of flowers initiated and subsequent flower production.
Independent greenhouse forcing tests by Durner et al., (1987) indicated that short days tended to enhanced floral induction and initiation but delayed differentiation. Slight chilling (50 hrs at 4.4oC) enhanced macroscopic flower production while greater amounts (150 hrs) delayed emergency by up to three weeks in Earl Glow. Voth and Bringhurst (1985) indicated that increased nursery chilling increased vegetative vigor and concentrated fruit production into a brief harvest. Durner et al. (1987) in a work on four cultivars of strawberry (Douglas, Tufts, Pajaro and Chandler) concluded that chilling enhanced early season yield if it was accumulated prior to the optimum photoperiod date. Nestby (1989) concluded that the forcing period could be shortened by increasing the chilling period. However, the effect of chilling on fruit production has not been explored properly.
1.2.5 Gibberellic acid (GA3)
Gibberellic acid is hormone that seems to have been explored most widely in relation to its effect on dormancy. Application of GA3 to some plants has produced growth responses which are similar to those caused by certain natural environmental factors such as long days and chilling. It has induced flowering on non-chilled biennial plants (Lang, 1957) and broken the dormancy of seeds (Fogle, 1958) and buds (Walker, 1959), thereby substituting for chilling.
In strawberry the effect of GA3 has been considered more as a substitute of long days and has been shown to have some effects similar to chilling such as; increasing heights of the trusses, inhabitation of flower formation and increasing the number of flowers (Porlingis and Boynton, 1961; Tafazoli and Vince-Pure, 1978). Application of gibberelic acid can replace the chilling requirements for some fruit tree buds (Hatch and Wlaker, 1969). This suggests that gibberellic acid may play a part in dormancy release. Avigdori-Avidov et al., (1977) have reported the involvement of endogenous gibberellins in the chilling requirement of strawberry. The chilling of plants initially for 2 months decreased the gibberellins levels which later on increased when shifted to the growth chambers, indicating a high gibberellins biosynthesis potential which comes into action mainly after the termination of chilling. However, it is more likely that the onset, control and termination of dormancy are regulated by a balance of growth inhibitors and promoters than by one single chemical (Amen, 1968).
Nigam and Kumar, (2001) described that fruits harvested from Rose Scented (L. chinensis) trees planted in Pantnagar, U.P, India, on different dates were subjected to various post harvest treatments (fruits dipped in GA3 @ 200 ppm or in wax emulsion applied as 16.6, 20.0 and 25.0% for 2 minutes) and kept under ambient (21.8-29.00C and 41.0-98.0% RH) or in cold storage (50C and 85% RH) for 8 days. They found increase in physiological weight loss and spoilage, and decrease in acidity with the increase in storage period. They noticed increase in total soluble solid contents at 5th day of storage, and started decreasing afterwards. Fruits harvested on different dates have shown lower physiological weight loss (3.94 and 4.76%, respectively) when 25% wax emulsion was applied and it was 4.32 and 4.43%, respectively under cold conditions. The fruits picked on 3rd June have shown lower spoilage incidence when stored at ambient temperature (25.64%) as compared to cold conditions (26.33%). Where as, fruits harvested on 6th June and kept in cold storage resulted in less spoilage incidence (39.86%) when compared with ambient temperature storage (51.12%). Lowest spoilage incidence (15.75 and 32.47%, respectively) was found in gibberellic acid treatment whereas, higher TSS content (20.74 and 20.550 Brix, respectively) was found in fruits harvested on 3rd and 6th June.
1.3 Post harvest treatments for quality and shelf life
1.3.1 Storage temperature
Storage temperature is an important factor that affects shelf life of strawberry fruits. Storage of strawberry fruits at room temperature ranging from 18 - 200C have shown good results (Perez et al., 1999). Researcher have pointed out that temperature manipulation is the most important tool for shelf life extension and quality maintenance in fresh fruits and vegetables. Adisa, 1986 found gradual decrease in ascorbic acid contents of fruits and vegetables when there was increase in storage temperature or duration.
Strawberry fruits are highly perishable and metabolitically active liable to be deteriorated in very short time even without invasion of pathogens (DeEII, 2006).Strawberries produce very little ethylene (<0.1 ppm per kg per hour at 20 0C) and do not respond to ethylene treatments. Temperature manipulation is an important and frequently used way to enhance shelf life of strawberry fruit. A number of scientists have made alternate efforts to prolong the shelf life of strawberry fruit rather than chemicals to evade residual effects from the fruit itself (Peng and Sutton, 1991; Wszelaki and Mitcham, 2003; Zhang et al., 2007).The strawberry quality is affected by the storage time which resulted in decreased total soluble solids, acidity, glucose and sucrose levels while increased fructose (Ozkaya et al., 2009). An investigation conducted by Cordenunsi et al., 2003 revealed that low temperature used to increase shelf life of strawberry could also cause changes in some of the quality parameters such as ascorbic acid.
1.3.2 Packing materials
For strawberries, different types and sizes of packaging material are used. In Islamabad, 250 and 500 gm cardboard boxes and 500 gm cane baskets are usually used. On the other hand, in the Lahore market, the produce is traded in cane baskets containing 8 to 9 kg and also in 250 gm capacity hard paper packets. Krivorot and Dris, 2002 stated that packing strawberries in polyethylene bags decreased respiration, maintained quality and prolonged the shelf life from 7 to 22 days depending upon the cultivar use. Ozkaya et al., 2009 concluded that modified atmosphere packaging can be advantageous for minimizing weight loss and rottening in strawberry after10 days of storage.
1.3.3 Chemical treatments
Calcium treatment has been applied on different fruits and vegetables to increase their shelf life. By immersing strawberry fruits calcium chloride solution for five minutes and thereafter storing them in polythene bags showed on increase in firmness and weight loss is reduced in treated fruits (Morris et al., 1991). Dipping the strawberry fruits in 1% calcium chloride solution was the most effective treatment for increasing the calcium content of the fruit, for controlling post harvest decay and for maintaining their firmness and total soluble solids content (Garcia et al., 1996). Same results were observed by Bhattarai and Gautam, 2006 during their experiment on the effect of harvesting method and calcium on post harvest physiology of tomato. On the contrary, Souza et al.,1999 during their research evaluated the effects of calcium chloride on quality and prolongation of post harvest life of strawberry fruits stored in cold room, maintained at 4oC, observed that 0,0.5% and 1% calcium chloride had not significantly effected pH, total soluble solids (TSS), total and soluble pectin contents. Calcium chloride was also used in combination with other chemicals to enhance its functioning. Asrey and Jain, (2005) while studying the impact of several post harvest treatments on storage life of strawberry cv. Chandler, using ascorbic acid and calcium salts found that CaCl2 (0.05%) prolonged shelf life with lower acid, moderate total soluble sugar, higher ascorbic acid contents and lower weight loss. Another combined treatment of 1-Methylcyclopropene, calcium chloride and controlled atmosphere was studied on fresh cutted strawberries which showed less softening, deterioration rate, titrable acidity and microbial growth (Aguayo et al., 2006). Calcium chloride combined with chitosan increased the firmness and nutritional value by increasing the calcium content of fruit, during its post harvest application on strawberry kept under refrigerated storage (Pilar et al., 2008)
Use of plastic film maintains high humidity inside the package during the storage (Lil et al., 1998). The high humidity inside the package reduces the loss of weight. Decreased respiration, maintain quality and prolonged shelf life from 7 to 22 days (Krivorot and Dris, 2002). Same results were observed by Hietaranta et al., 2002 while using non perforated plastic film. Better color retention was also observed in fruits kept under plastic films (Collins and Veazie, 1993). Other forms of plastic material, like polystyrene foam trays covered with perforated polythene or stretched film were also successful for increasing storage life of strawberry cultivars (Koyuncu and Askin, 2000). Polythene covers together with UV-C light exposure reduce the %age of rotting (Malgarim et al., 2006). The PVC packing produces the rides of Botrytis, and gives the product with excellent quality, as the package being responsible for building up high level of carbon dioxide which in turn is effective on the control of fungus (Paulis, 1990). Same results were observed by Malgarim et al., in 2006 during their experiment on strawberries kept at UV-C light exposure and Polythene films.
Keeping quality of strawberries stored for 8 days was improved. Firmness was maintained at 0, 5 and 10oC but softening occurred at 15, 20 and 25oC (Kim et al., 1996). Similar results were obtained by Shin et al., in 2007. Storage conditions together with storage temperature also affect the shelf life of strawberry. By using polyethylene pouches and storing strawberries at room temperature (26oC) and fridge, resulted in higher weight loss at room temperature (26oC) and lower in fridge (Kumar and Manimegalai, 1998). The ascorbic acid contents in strawberries kept in controlled atmosphere differ significantly than that at room temperature.
Dris et al., (2000) described that, fruits of Lobo apple when subjected to pre harvest spray of calcium chloride, heat treatment (pre-storage), and calcium chloride in combination with heat treatment, were kept at 2oC and 90-95% RH for the period of 24 weeks. They found that there was a little decrease in respiration and ethylene production rates of heat-treated apples and increase in calcium chloride treated apples. However, calcium chloride (CaCl2) treatment did not enhance fruit firmness or calcium concentration but combined CaCl2 + heat treatment and heat treatment have shown increasing trend in pH. The firmness of heat and calcium chloride + heat-treated fruits was lesser at the start of storage but it was greater than control fruits when the storage period was ended. After 24 weeks of storage, lowest incidence of disorder and disease symptoms was observed in the CaCl2 + heat treatment
1.4 Aims and objectives of the study
The present investigation was aimed to improve yield, quality and shelf life of strawberry. These objectives were achieved by conducting following experiments:-
Selection of varieties with better yield, fruit quality and shelf life through screening of seven cultivars.
Improvement in growth, yield, quality and shelf life through appropriate pre-harvest treatments like mulching, chilling, use of GA3 and growing under suitable environmental conditions viz, polytunnel, shade house and open field conditions.
Evaluation of an appropriate post harvest treatment to prolong shelf life and improve the quality of strawberry fruit.