EFFECT OF PRE-HARVEST APPLICATION OF GA 3 AND POTASSIUM NITRATE ON YIELD AND QUALITY OF PEACH FRUIT

: The research study entitled “effect of pre harvest application of GA 3 and potassium nitrate on yield and quality of peach fruit” was carried out at Horticulture Research Farm, The University of Agriculture Peshawar during 2019. The plots were arranged using Randomized Complete Block Design (RCBD) with two factors. Three replications were used in the experiment. The experiment was conducted on already established peach orchard of almost 14 years old trees of Early Grande cultivar. The uniform size trees were selected and tagged for the experiment. The plants were managed under uniform cultural practices. The selected plants of peach cv. Early Grande were sprayed with various concentrations of Gibberellic acid (GA 3 ) (0, 20, 40, 60 and 80 ppm) and potassium nitrate (KNO 3 ) (0, 1000, 2000 and 3000 ppm) at berry stage. Peach plants were sprayed with GA 3 and KNO 3 and compared with control. The analysis of data showed that the foliar application of GA 3 and KNO 3 significantly influenced the yield and quality attributes of peach. Maximum fruit weight (111.98 g), chlorophyll content (51.00 SPAD), TSS (14.60 o Brix), fruit juice content (85.80 %), Fruit firmness (2.16 kg.cm -2 ), yield plant -1 (54.56 kg) and yield ha -1 (15.548 tons) were recorded in plants treated with 80 ppm of GA 3 . In case of KNO 3 Maximum fruit weight (101.20 g), chlorophyll content (49.46 SPAD), TSS (13.38 o Brix), fruit juice content (84.86 %), Fruit firmness (2.12 kg.cm -2 ), yield plant -1 (51.56 kg) and yield ha -1 (14.829 tons) were recorded in plants treated with 3000 ppm of KNO 3 . Minimum days to maturity (72.52) and minimum number of fruits kg -1 (9.65) were found in plants sprayed with 80 ppm of GA 3 while in case of KNO 3 minimum days to maturity (76.92) and minimum number of fruits kg -1 (10.62) were found in plants sprayed with 3000 ppm of KNO 3 . Interactive effect of levels of GA 3 and KNO 3 was also found significant for some of the parameters. It is therefore concluded that when peach Early Grande cultivar sprayed with 80 ppm of GA 3 and 3000 ppm of KNO 3 the quality as well as yield of the crop were improved.


INTRODUCTION
Peach (Prunus persica) ranked third among the top growing temperate fruits through the world.It belongs to the family Rosaceae which is mostly grown in temperate zone between the 30-40 o N and S latitude.This area is referred as commercial production area for quality peach.It is most likely assumed that it was developed in Persia; however, China is considered as native country [1].
Peach is famous for its delicious taste, flavor and aroma comprised of 10-14 percent sugar, 2% protein and rich in ascorbic acid.Moreover, vitamins like A and B, iron, phosphorus and calcium could also be obtained.Around the world the most important types are free stone type while Early Grande, Florda King 6-A and 8-A are most popular cultivars dominantly grown in Peshawar and Swat region.Whereas in Baluchistan Golden Early, Shah Pasand and Shireen are grown.On the basis of market availability, Swat valley enjoys not only access to national market but international market as well.At present, peach showed adaption to other environments like subtropical and even some of the recent varieties has low chilling requirements for reproductive growth.Besides its good productivity, the peaches grown in subtropical climate reported to be highly perishable, reducing its quality and ultimately export.In order to overcome this situation farmers usually prefer harvesting before the fruit reached to full maturity keeping in mind handling and transport facility.The operation may give some relief financially but these fruits never reach their full flavor, aroma and consumer acceptance A considerable part of the crop was lost at post-harvest.The mayhem could be possibly resolved through extensive trainings of farmers about mixed farming, preparation of pickles from a part of fruits and other handling operations.Excessive bearing of fruits may prefer by grower but this phenomenon severely influences the size and quality causing poor returns or profit [2].
Physiological maturity function plays a key role in the post-harvest quality and shelf life because peach fruits are more susceptible to losses due to a rapid softening after harvest.Some plant growth regulators like gibberellins have the ability to avoid senescence naturally.Which sometimes may also use for prolong harvesting and marketing seasons.Some researchers reported that pre-harvest application of GA 3 promote growth, improve fruit size and extends the shelf life of peaches.Extended post-harvest storage life for prolong marketing season through delaying the picking of fruits and late season cultivars [3].To achieve this, the possible ways are conventional breeding of potentially prolonged fruit storage cultivars having the characteristic of late ripening or the appropriate use of plant growth regulators to enhance vegetative growth and maturity and fruit development mainly in the indigenous cultivars [4].
Gibberellic acid (GA 3 ) is an important and extensively used growth regulator of plants to manipulate the development and ripening of fruits in number of crops including stone fruit [4].It triggers several processes and pathways, depends on plant development and organs [5].Recent studied showed that GA 3 is valuable in lowering the flowers density, which subsequently increase size of fruit and decreases the crop load in nectarine and peaches [6].Gibberellic acid interrupts the development and ripening of internal breakdown in nectarines when applies at pit hardening [7].However, at the pit hardening stage, it enhances the cell wall and directed maximum percentage of cellulose in the cell wall than the control fruits [8].
Several factors in the pre-harvest stage enhance the fruit quality.Therefore, pre-harvest cultural methods play a vital role in maximizing the fruits quality.One such practice is the use of plant nutrients like potassium, boron and calcium during fruit growth at pre-harvest foliar spray.Potassium increases the fruit firmness [9].Foliar sprays of K have been successfully tried to improve fruit quality in peach.The use of potassium sulphate during foliar spray improves the fruit appearance and maximize the soluble solid contents of the fruit [10].
The most important and common source of potassium is potash muriate, other sources also work will in comparison with muriate.Excess intake of potassium inhibits magnesium and calcium uptake and is thus undesirable.Mineral nutrition also effects the fruit storing quality in several ways [11].
Potassium nitrate improve the effectiveness of photosynthesis in plants [12].The increase in fruit size due to KNO 3 treatments may be due to the reason that K helped in increasing the entry of water into the cells by osmotic processes, and increased cell expansion which affected fruit size [13].The increase in fruit weight with KNO 3 application might be due to the fact that N is extremely mobile and developing fruit acts as a metabolic sink for the nutrient elements.Further, nitrogen has been reported to prolong the phase of fruit cell division resulting in greater number of cells per fruit [14].The potassium application increased fruit weight and fruit size in 'Kinnow' mandarin.Larger fruit size and fruit weight in 'Valencia' orange with dormant, post bloom and summer foliar application of potassium were reported by Boman [15].
Keeping in view the above-mentioned peach problems and benefits of gibberellic acid and potassium nitrate research is designed to study the effect of pre harvest application of GA 3 and potassium nitrate on yield and quality of peach fruit (cultivar Early Grande).

MATERIAL AND METHODS
Experimental site: An experiment was conducted to study the performance of foliar application of gibberellic acid and potassium nitrate on yield and fruit quality of peach, at the Horticultural Research Farm, Malakandher, The University of Agriculture Peshawar, during the year 2019.

Experimental design:
The experiment was conducted on already established peach orchard of 14 years old trees of Early Grande cultivar.The trees were selected and tagged for the experiment.The plants were managed under uniform cultural practices.Selected plants were sprayed with Gibberellic acid and potassium nitrate separately and in combination.The treatments were applied at fruit setting stage in three replicates.Two factorial Randomized complete block design (RCBD) was used for statistical analysis.

Days to maturity:
The number of days from fruit setting to physiological maturity were noted to find out days to maturity and their average was calculated.
Single Fruit weight (g): Five randomly selected fruit from the treated tree were collected and their weight was measured in grams with the help of electrical balance and the mean was calculated.
Chlorophyll Content (SPAD): Chlorophyll content was determined in leaves of randomly selected plants of all treatments through SPAD meter then their average was calculated.

Number of fruits kg:
One-kilogram fruits from each treatment were selected and their number of fruits were counted and their average was taken for further analysis.
Fruit firmness (kg.cm -2 ): Fruit firmness was measured on two pared sides of each fruit using a penetrometer fitted with an 8-mm diameter plunger.
Fruit juice content (%): Fruits from each treatment were weighted through electric balance, their juice were extracted with juicer, the juice were weighted and juice content was found out by using the given formula.Juice content = Juice weighted (g) ----------------------x 100 Fruit weighted (g) Total soluble solids ( o Brix): A wedge-shaped slice (approx.5 g) was removed from each fruit.Slices were passed through an electric juicer for the measurement of total soluble solids by using hand refractometer.
Yield tree -1 : All the yield of fresh fruits were weighed through electronic balance.The yield was calculated in kg plant -1 after taking weight of individual plant tree yield.
Yield ha -1 : The yield per hectare was found by using the following formula: Yield ha -1 = Number of plants ha -1 x yield plant -1   Statistical analysis: A computer package statistic version 8.1 was used for analyzing field and laboratory data by ANOVA technique and the means were compared by LSD-test of significance, when the F-values was found significant [16].

RESULTS AND DISCUSSION
Results of the studied parameters were analyzed, compared and discussed with the results of other researchers in this chapter.Tables from 4.1 to 4.09 represent the mean data while Tables from 4.1a to 4.09a shows analysis of variance (ANOVA).Original replicated data of the studied parameters in research are given in Appendices from I. IX.

Days to maturity:
Data regarding days to maturity of peach are presented in mean table 4.1 whereas ANOVA is shown in table 4.1a.Original replicated data are given in Appendix-I.The analyzed data showed that days to maturity of peach was significantly affected by foliar application of gibberellic acid and potassium nitrate.The interaction of GA 3 and KNO 3 was found non-significant for days to maturity of peach.
The foliar application of GA 3 significantly affected number of days to maturity of peach at various concentrations.Data pertaining GA 3 reveal that less number of days to maturity of peach (72.52) was noted in plants sprayed with 80 ppm of GA 3 which was statistically different from days to maturity (77.17) of peach when plants were sprayed with 60 ppm of GA 3 .
The highest days to maturity (85.92) was recorded in plants of control treatment.
Data regarding KNO3 shows that minimum days to maturity (76.92) were noted when plants were sprayed with 3000 ppm of KNO3 which was significantly different from days to maturity (79.32) when KNO3 was sprayed on plants with 2000 ppm.The maximum days to maturity (83.94) was recorded in control treatments.
The above results are supported by the findings of Sankar et al. [17] who noted early maturity of fruits during their work effect of plant growth regulators on growth and yield of "Le Conte" Pear.This might be due to the fact that GA 3 and KMNO3 stimulates the conversion of starch into sugar and ripen the fruits earlier.

Chlorophyll content (SPAD):
Data pertaining chlorophyll content of peach are shown in mean table 4.2 whereas ANOVA is shown in table 4.2a.Original replicated data are given in Appendix-II.The analyzed data showed that chlorophyll content of peach was significantly affected by foliar application of Gibberellic acid and potassium nitrate.The interaction of GA 3 and KNO 3 also significantly influenced the chlorophyll content of peach.
Data regarding GA 3 reveal that chlorophyll content of peach was found higher (51.00 SPAD) when plants were sprayed with 80 ppm of GA 3 which was statistically different from chlorophyll content (48.40 SPAD) when plants were sprayed with 60 ppm of GA 3 .The low chlorophyll content (43.65 SPAD) was recorded in plants received no GA 3.
Data regarding KNO 3 shows that maximum chlorophyll content (49.46 SPAD) was noted when plants were sprayed with 3000 ppm of KNO 3 which was significantly different from chlorophyll content (47.90) when KNO 3 was sprayed on peach plants with 2000 ppm.The minimum chlorophyll content (44.50 SPAD) was recorded in control treatments.
The interaction of GA 3 and KNO 3 for chlorophyll content was significantly affected.The highest chlorophyll content (55.80) was found when plants received 80 ppm GA 3 and 3000 ppm KNO 3 .The minimum chlorophyll content (42.10) was noted in control treatments.
The enhancement of chlorophyll content with increasing GA 3 and KNO 3 may be due to the fact that these plant growth regulators play role in improving vegetative growth of the plant which improve the green pigment in plant leaves and increase in chlorophyll content take place.Findings of the present results are supported by the findings of Ahmad and Sharma [18] who performed their experiment on influence of GA 3 , KNO 3 and I.A.A on performance of strawberry.Increase in chlorophyll content was also noted by Ingram et al. [19] when they carried experiment on peach.The analyzed data showed that the fruit weight of peach significantly affected by foliar application of Gibberellic acid and potassium nitrate.The interaction of GA 3 and KNO 3 was also found significant.
Data regarding GA 3 shows that fruit weight of peach was found higher (111.98 g) when plants were sprayed with 80 ppm of GA 3 which was statistically different from fruit weight (103.88 g) when plants were sprayed with 60 ppm of GA 3 .Minimum fruit weight (85.10 g) was recorded in plants received no GA 3 and is statistically similar to fruit weight (87.95 g) of plants that received 20 ppm GA 3 .
Data regarding KNO 3 shows that maximum fruit weight (101.20 g) was noted when plants were sprayed with 3000 ppm of KNO 3 which was significantly different from fruit weight (98.10 g) when KNO 3 was sprayed on plants with 2000 ppm while minimum fruit weight (93.06 g) was recorded in control treatments.
The interaction of GA 3 and KNO 3 shows that the fruit weight was significantly affected.The highest fruit weight (119.00 g) was found when plants received 80 ppm GA 3 and 3000 ppm KNO 3 .The lowest fruit weight (80.10 g) was noted in control treatments.
The increase in fruit weight with the application of high doses of GA 3 and KNO 3 was recorded in the present experiment which are in agreement with the results of Nomis et al. [20] who found improvement of fruits weight during their research on improvement of growth, yield and chemical composition of Apple (Pyrus malus) through plant hormones.GA 3 and KNO 3 helps the plants to increase their photosynthesis which improve the availability of food and hence increase fruit weight.The analyzed data showed that fruit firmness of peach was significantly affected by foliar application of gibberellic acid and potassium nitrate.The interaction of GA 3 and KNO 3 was found non-significant for fruit firmness.Data regarding GA 3 shows that fruit firmness of peach was found higher (2.51 kg.cm -2 ) when plants were sprayed with 80 ppm of GA 3 which was statistically different from Fruit firmness (2.00 kg.cm -2 ) when plants were sprayed with 60 ppm of GA 3 while lower fruit firmness (1.27 kg.cm -2 ) was recorded in plants of control treatment .
Data regarding KNO 3 shows that maximum fruit firmness (2.12 kg.cm -2 ) was noted when plants were sprayed with 3000 ppm of KNO 3 which was significantly different from fruit firmness (1.95 kg.cm -2 ) when KNO 3 was sprayed on peach plants with 2000 ppm.Minimum fruit firmness (1.33 kg.cm -2 ) was recorded in control treatments.
In the present study, increase in fruit firmness was noted with the increase in concentrations of gibberellic acid and potassium nitrate.The enhancement of fruit firmness will help to prolong the post-harvest life of peach.These findings are in line with the findings of Shukla et al. (2007) who recorded increase in fruit firmness with the increase of concentrations of PGRs after performing an experiment on influence of PGRs on growth, quality and yield of peach (Pronus persica) var.Florida king.This might be due to the fact that these PGRs slows down the metabolic process of fruit which enhance their firmness.The analyzed data showed that the number of fruits per kg of peach significantly affected by foliar application of gibberellic acid and potassium nitrate.The interaction of GA 3 and KNO 3 was found non-significant for this parameter.Data regarding GA 3 shows that less number of fruits per kg of peach (9.65) were recorded when plants were sprayed with 80 ppm of GA 3 which was statistically different from number of fruits per kg (10.25) of peach when plants were sprayed with 60 ppm of GA 3 .Maximum number of fruits per kg (12.53) of peach was recorded in plants received no GA 3 .
Data regarding KNO 3 shows that minimum number of fruits per kg (10.62) of peach was noted when plants were sprayed with 3000 ppm of KNO3 which was significantly different from number of fruits kg -1 (10.40) when KNO3 was sprayed on plants with 2000 ppm, whereas maximum number of fruits per kg (11.94) of peach was recorded in control treatments.
It has been noted that less number of fruits were found due to good when high concentration of GA 3 and KNO 3 were sprayed on peach plants.Similar results were found by Mosa et al. [21] when they performed their research on quince.The present findings are also similar with records of El-Ese and Finder who worked on effect of plant growth regulators on mango.Foliar application of GA 3 and KNO 3 improved fruit productivity and quality as compared to control [22].The analyzed data showed that the TSS of peach significantly affected by foliar application of gibberellic acid and potassium nitrate.The interactive effect was also found significant.Data pertaining GA 3 reveal that TSS of peach was found higher (14.60 o Brix) when plants were sprayed with 80 ppm of GA 3 which was statistically different from TSS of peach (12.58 o Brix) when plants were sprayed with 60 ppm of GA 3 .The minimum TSS (10.37 o Brix) was recorded in plants received no GA 3 and is statistically similar to TSS (11.01 o Brix) of plants that received 20 ppm GA 3 .
Data regarding KNO 3 shows that maximum TSS (13.38 o Brix) was noted when plants were sprayed with 3000 ppm of KNO3 which was significantly not different from TSS (12.45 o Brix) when KNO 3 was sprayed on plants with 2000 ppm.The minimum TSS (10.90 o Brix) was recorded in control treatments.
In the present study increase in TSS was recorded with increase in conc. of plant growth regulators such as GA 3 and KNO 3 .This may be due to the facts that GA 3 and KNO 3 enhance the metabolic conversion of starch and pectin into sugars which improve the TSS.GA 3 and KNO 3 also improve the fast transformation of carbohydrates into sugars as well as rapid metabolites from source to sink such as fruits which ultimately increase the TSS of peach fruits.The same results were found by Shahid and Tariq [23] after performing work on effect of PGRs on Apple where they recorded increase in TSS with increase in conc. of plant growth regulators.Data pertaining GA 3 reveal that fruit juice content of peach was found maximum (85.80 %) when plants were sprayed with 80 ppm of GA 3 which was statistically different from fruit juice content (84.65 %) when plants were sprayed with 60 ppm of GA 3 .The minimum fruit juice content (80.17 %) was recorded in control treatment plants .
Data regarding KNO 3 indicate that maximum fruit juice content (84.86 %) was noted when plants were sprayed with 3000 ppm of KNO 3 which was significantly different from fruit juice content (84.18 %) when KNO 3 was sprayed on plants with 2000 ppm.The minimum fruit juice content (81.84 %) was recorded in control treatments.
In the current study increase in fruit juice content were found with increase in concentration GA 3 and KNO 3 .These results are in line with the findings of Azlan et al. [24] who obtained high fruit juice content with increase in concentration of plants growth regulator.GA 3 and KNO 3 helps the plants in the availability of nutrients as a result of which fruits get good size.The improvement in size enhances the pulp of fruits which give high fruit Juice content.The analyzed data showed that the yield tree -1 of peach was significantly affected by foliar application of gibberellic acid and potassium nitrate.The interaction of GA 3 and KNO 3 for yield tree -1 was found non-significant.Data pertaining GA 3 reveal that yield tree -1 of peach was found higher (54.56 kg) of peach when plants were sprayed with 80 ppm of GA 3 which was statistically different from yield tree -1 (51.73 kg) of peach when plants were sprayed with 60 ppm of GA 3 .The minimum yield tree -1 (45.80 kg) was recorded in plants received no GA 3.
Data regarding KNO3 shows that maximum yield tree -1 (51.56 kg) of peach was noted when plants were sprayed with 3000 ppm of KNO 3 which was significantly different from yield tree -1 (50.52 kg) when KNO 3 was sprayed on plants with 2000 ppm.The minimum yield tree -1 (48.14 kg) was recorded in control treatments.
It has been found that application of GA 3 and KNO 3 improve the cropping of peach trees and consequently increase the yield [25].It might be due to the fact that GA 3 and KNO 3 helps in cell elongation and cell wall formation which cause increase in fruit size and hence improve the yield tree -1 .Similar results were found by Essa et al. [26] after doing work on the effect of plants hormones on apple and pear.The analyzed data showed that yield hac -1 of peach was significantly affected by foliar application of gibberellic acid and potassium nitrate.The interaction of GA 3 and KNO 3 for yield hac -1 was found significant.Data regarding GA 3 indicate that yield hac -1 of peach was found higher (15.548 tons) when plants were sprayed with 80 ppm of GA 3 which was statistically different from yield ha -1 (15.115 tons) when plants were sprayed with 60 ppm of GA 3 .The minimum yield hac -1 (13.137 tons) was recorded in plants received no GA 3.
Data about KNO 3 shows that maximum yield hac -1 (14.829 tons) was noted when plants were sprayed with 3000 ppm of KNO 3 which was significantly different from yield hac -1 (14.637 tons) when KNO 3 was sprayed on plants with 2000 ppm.The minimum yield hac -1 (14.206 tons) was recorded in control treatments.
In present research we recorded the increase in yield with the increase in the concentration of GA 3 and KNO 3 .These findings are supported by the finding of Maryam and Sana [27] who found the increase in yield per hectare when they carried an experiment on the influence of plant growth regulators on performance of plum.This may be due to the fact that plant growth regulators GA 3 and KNO 3 act as ethylene inhibitor due to which softening of fruit do not occur and fruits get good size and weight which ultimately enhance the yield per hectare.

Table 4 .2a. Analysis of variance table for chlorophyll content (SPAD) of peach as affected by application of GA 3 and potassium nitrate.
Fruit weight (g):Data regarding weight of peach are presented in mean table 4.3 whereas ANOVA is shown in table 4.3a.Original replicated data are given in Appendix-II.

Table 4 .3. Fruit weight (g) of peach as affected by application of GA 3 and potassium nitrate.
Means followed by different letters are statistically dissimilar at 1% significance level.LSD value for levels of GA 3 at 1% level of probability = 4.10 LSD value for levels of KNO 3 at 1% level of probability = 2.50 LSD value for levels of interaction at 1% level of probability = 2.10

Table 4 .5. Number of fruits kg -1 of peach as affected by application of GA 3 and potassium nitrate.
Means followed by different letters are statistically dissimilar at 1% significance level.LSD value for levels of GA 3 at 1% level of probability = 0.11 LSD value for levels of KNO 3 at 1% level of probability = 0.13

Table 4 .5a. Analysis of variance table for number of fruits kg -1 of peach as affected by application of GA 3 and potassium nitrate.
Data regarding total soluble solids ( o Brix) of peach are presented in mean table 4.6 whereas ANOVA is shown in table 4.6a.Original replicated data are given in Appendix-VI.

Table 4 .6a. Analysis of variance table for total soluble sugar ( o Brix) of peach as affected by application of GA 3 and potassium nitrate.
Data regarding fruit juice content of peach are shown in mean table 4.7 whereas ANOVA is shown in table 4.7a.Original replicated data are given in Appendix-VII.The analyzed data showed that the fruit juice content of peach significantly affected by foliar application of gibberellic acid and potassium nitrate.The interaction of GA 3 and KNO 3 was found nonsignificant.

Table 4 .8a. Analysis of variance table for yield tree -1 (kg) as affected by application of GA 3 and potassium nitrate
Data regarding yield hac -1 of peach are shown in mean table 4.9 whereas ANOVA is shown in table 4.9a.Original replicated data are given in Appendix-IX.

Table 4 .9. Yield ha -1 (tons) of peach as affected by application of GA 3 and potassium nitrate.
Means followed by different letters are statistically dissimilar at 1% significance level.LSD value for levels of GA 3 at 1% level of probability = 510 LSD value for levels of KNO 3 at 1% level of probability = 170

Table 4 .9a. Analysis of variance table for yield ha -1 (tons) of peach as affected by application of GA 3 and potassium nitrate.
Keeping in view the results obtained from the experiment, it is concluded that the yield and quality of peach (cv.Early grande) increased with increasing levels of GA 3 and KNO 3 .Application of GA 3 at the rate of 80 and 3000 ppm increased the quality and yield of peach.