DIFFERENT PRUNING INTENSITIES INFLUENCES YIELD AND QUALITY OF GUAVA CV. GOLA

The current experiment was carried out at Horticultural Research Institute, Ayub Agricultural Research Institute, Faisalabad, Pakistan during the year 2017-18 to evaluate impact of various pruning intensities on quality and yield of guava fruit ( Psidium guajava L.). Various pruning intensities viz. control (no pruning), 25% pruning, 50% pruning and 75% pruning were carried out after harvesting of winter crop (in the month of April). Results showed that maximum flower count/shoot (18 number), fruit number/plant (2237), yield/plant (172.6 kg/tree), average fruit weight (102 g) and SSC (8.11%) were found with 25% pruning intensity; whereas, minimum fruit number/plant (720) and yield (70.11 kg/plant) was found in trees treated with 75% pruning intensity. Maximum fruit length (57.49 mm) and fruit width (64.75 mm) was observed in 25% pruned trees. It can be concluded that among various pruning intensities 25% pruning level is best to increase quality and yield guava fruit.


INTRODUCTION
Guava (Psidium guajava L.) belongs to family Myrtaceae also known as "the apple of tropics" and important fruit of the tropical region. Guava stands at fourth position in production among various fruit crops being cultivated in Pakistan. Its production was 528,853 tonnes on an area of 54102 ha. Guava is being commercially grown on 54,611 ha area with production 41,4649 tonnes and it stands as the 3 rd most important fruit crop of Punjab (GoP, 2019). It is also considered as super fruit, because it is rich in dietary fiber, pectin, vitamin A and C minerals (potassium, copper, calcium, phosphorus, iron and manganese), ascorbic acid folic acid contains carotenoids, flavonoids (quercetin) and polyphenols (Joseph and Priya, 2011). Guava fruit is used fresh as well as it had vide uses in processing industry for making juice, jam, jellies, pudding, squashes, canned slices in syrup, fruit bar or dehydrated products (Leite et al., 2006). Besides being rich in nutritional composition and 3 rd most important fruit crop of Punjab, it lacks in potential production. There are various reasons for its low production like improper use of fertilizer, improper orchard management like use of FYM, inter culturing, timely irrigation and pruning along with non-mechanized harvesting practices (Khushk et al., 2009). To bring a balance between vegetative and reproductive growth of plants especially in fruit crops of temperate and sub-tropical regions pruning is being practiced (as it is one of the oldest cultural practice) (Suleman et al., 2005). Pruning helps in maintain the tree growth (size and height) as well as enhance fruit quality. Guava tree bears flowers and fruits on current season growth (Thakre et al., 2016;Sawant et al., 2018). After fruit harvesting it is recommended to prune the trees in order to encourage new shoots (Singh et al., 2001). It is the need of time to understand the impact of pruning on productivity and quality of fruits tree. Guava pruning has not received much attention commercially, but looking to its economic importance it could be justified. In prelude to the importance of pruning the present research work was planned to evaluate the impact of various level of pruning on production and quality of fruit of guava cv. Gola.

MATERIALS AND METHODS
The experiment was conducted at experimental fruit orchard, Horticultural Research Institute, Ayub Agricultural Research Institute, Faisalabad, Pakistan (31°404'N; 73°048'E) during 2017-18. Different pruning intensities were done to find out their effect on yield and fruit quality cv. Gola. Treatment plan was comprised as:-T 1 = No pruning T 2 = Pruning @ 25% level T 3 = Pruning @ 50% level) T 4 = Pruning @ 75% level) All the treatments were replicated thrice with two plants in each replication, thus total twenty four plants were observed in the trial. Pruning was carried out in month of April (after harvesting winter crop). Plants selected were of uniform size, health and age (approximately 10 year old). All cultural practices like application of fertilizer, irrigation, insecticide and pesticide were same for all experimental trees. Data regarding flower count/ shoot, fruit numbers/plant were taken continuously. Fruit yield, physical and bio-chemical parameters were recorded after fruit harvesting. Flower count/shoot was taken by counting number of flowers of tagged branches at an interval of fifteen days and then their average was calculated. Number of fruits/ plant was counted at the time of harvest from the whole tree. Fruit yield was taken after harvesting of fruits and weighing total number of fruits. Weight of fruit was measured by weighing individual fruit on weighing balance (SF-400A, China) and their average was calculated. Fruit length and width was measured using digital Vernier calipers and fruit size was measured by multiplying width with length of the respective fruit (Khan et al., 2015). Similarly, core length and width were measured with Vernier calipers in mm. Seeds were counted and seed core to pulp ratio was then calculated. Soluble solid contents (SSC) was calculated by digital refractometer (model: ATAGO, RS-5000, Japan) and expressed as Brix°. Titratable acidity (TA) was measured by doing titration of the juice aliquot with 0.1N NaOH and was expressed in percent citric acid (%) (Khan et al., 2015). SSC: TA ratio was determined by dividing the SSC of each sample by their respective TA (Nasir et al., 2016). Experimental design used for the layout was Randomized Complete Block Design (RCBD). Results were analyzed statistically using Statistix-10 software and difference among the means was calculated by employing least significant difference test (LSD) at level of 5% of probability (Steel et al., 1997).

Reproductive growth
Various pruning intensities showed positive effect on reproductive growth of guava cv. Gola (Table 1). Highest flower count/shoot were observed in 25% pruned trees (18 numbers), while minimum number of flowers were counted on plants 75% pruning with (3 numbers) (Table 1). Similarly, maximum increase in number of fruit/plants (2237 numbers), fruit weight (102 g) and yield (172.6 kg/plant) were noted with 25% level of pruning and the increases was 2.02-times, 1.45-fold and 2.22-fold more than the control plants, respectively ( Table 1). The increase in number of flowers/shoot and number of fruits/plant could be justifiable by the fact that at 25% level of pruning plant undergo stress that result in profuse flowering as compared to control plants, whereas in case of severe pruning (i.e., 75%) plants undergo severe stress and number of shoots also reduced which result in less number of flowers and fruits per shoot. Moreover, light pruning increased the reproductive growth and severely pruned trees gave rise to more vegetative growth (Lian et al., 2019). Maximum number of fruits, fruit weight and yield were found with 25% level of pruning (Table 1). The increase in fruit number, weight and yield could be attributed to the fact that light pruning put plant under little stress that improves the reproductive growth of plant resulting higher yield. Parallel findings were stated by Basu et al. (2007) and Lian et al. (2019) who observed that increased pruning intensity reduced number of fruits and yield in guava fruits. Boora et al. (2016) and Meena et al. (2016) reported increase in yield of guava due to light pruning as compared to intensive pruning. The means having the same letter within a column are non-significant (P≤0.05).

Fruit length, width and size
Various pruning intensities significantly affect the fruit length, width and size of guava cv. Gola (Table 2). Maximum increase in fruit length (57.5 mm), width (64.8 mm) and size (3722 mm) were recorded with 25% pruning level and the increase was almost 0.83fold, 1.23-fold and 0.67-fold higher than unpruned trees, respectively. Core length, width and size didn't show any significant change after pruning (Table 2). However, core: pulp ratio was significantly affected by different pruning intensities and minimum core: pulp ratio (0.19) was observed with 25% pruning level ( Table  2). The increase may be attributed to the fact that after 25% pruning the number of fruits was reduced and the plant was under less stress as compared to 50% and 75% pruning, respectively. The results showed that the different pruning levels effect the fruit size and core: pulp ratio. The results are further supported by findings of Dalal et al. (2000); Brar et al. (2007) and Sawant et al. (2018) who found increase in fruit size of guava after pruning at different intensities. Since there was no change observed in core size it is due to the fact that different pruning levels do not cause any change on core size. The findings are in disagreement as significant increase in core size of guava was observed after pruning (Sawant et al., 2018).

Fruit bio-chemical analysis
Fruit quality of guava was significantly affected by various pruning intensities (Table 3). Maximum SSC was found in fruits that were pruned at 25% level i.e., 8.11%, whereas, minimum SSC was observed in 75% pruned trees. The increase in SSC due to 25% pruning could be attributed to the fact that more carbohydrates reserved stored in shoots that may be available to guava fruits during growth (Sawant et al., 2018). Similarly, increase in SSC of guava fruits after pruning was observed by Singh and Dhaliwal (2004) and Mohommad et al. (2005). Kumar et al. (2010) reported increase in soluble solid content of peach fruits after heavy pruning. Similarly, Meena et al. (2016) observed improvement in SSC content of guava trees after pruning. Likewise, maximum acidity 0.9% was observed in 25% level pruned trees and minimum acidity was recorded in controlled trees 0.5% (Table  3). The increase in acidity is due to fact that the 25% pruned trees have more carbohydrates that result in higher TA in fruits as compared to control fruits. The observations disagreed from the results of Sawant et al. (2018) who found decrease in TA after pruning. Maximum SSC: TA ratio was calculated in control trees ( Table 3). The increase or decrease in this index was due to deviation in these two indices in response to pruning (Sawant et al., 2018).

CONCLUSION
The present study revealed the significant effect of different pruning intensities on guava crop cv. gola. It was found that among various pruning intensities 25% pruning level showed maximum yield and improved fruit quality.  The means having the same letter within a column are non-significant (P≤0.05). Not significant was represented by NS. The means having the same letter within a column are non-significant (P ≤ 0.05), SSC: Soluble solid contents, TA : Titrateable acidity