Influence of paclobutrazol on vegetative growth, flowering and fruiting of guava (Psidium guajava L.) cv. L-49

Introduction

Guava (Psidium guajava L.) is truly an important economic fruit plant in the tropical and subtropical regions of the world. The plant belongs to the family Myrtaceae and has a diploid chromosome number of (2n) 22. Its native place in tropical America. It has been naturalized and commercially grown in many temperate and tropical countries because of its shrub habit, profuse bearing, high levels of vitamin C, delicious flavor, and aromatic properties. The genus consists of about 150 species; however, this number is considered to be highly debated. There are several species of wild guava; Psidium guajava is the most widely cultivated and used for food, beverages, and pharmaceuticals. It has been found to be the most extensively grown economic fruit plant in the world. The fruit is well-known for its nutritional properties; for instance, it is rich in vitamin C, fibers, and antioxidants. All these qualities make it an attractive fruit for human consumption and industrial processing into jams, juices, jellies, and other products. Psidium guajava L. (Common Guava): It is the most widespread and commercially important guava species. It is a shrub-like plant bearing fruit profusely with high content of vitamin-C, aroma and good flavour. In northern India guava plants flower two or three times in a year. In this regard, Ambe Bahar refers to the spring flowering of guava plant whereas Mrig Bahar refers to the June or monsoon flowering and Hasth Bahar refers to the October flowering. The fruits of Ambe Bahar are harvested in July-September and the fruits of Mrig Bahar are harvested in November-February. On the contrary, the fruits of Hasth Bahar are harvested in spring season i.e. in summer. A guava tree is comparatively smaller in height with spreading branches. The trees are more or less easy to recognize on account of the fact that their bark is copper coloured, smooth and flakes off to reveal the green underneath layer. Paclobutrazol is a triazole type tree growth retardant which inhibits gibberellin biosynthesis and are involved in reducing abscissic acid, ethylene and indole-3-acetic acid while increasing cytokinin levels (Reddy et al. 2008) [14] . It promotes fruit set in the states of inhibited development. Paclobutrazol plays major role in regulation of excessive vegetative growth, enhancement and advancement of flowering, induction of early bearing, management of alternate bearing, establishment of high density plantation and re-juvenating of old orchards (Saran et al., 2008) [2] . Application of paclobutrazol has been found to promote the vegetative growth, flowering and fruiting of guava, including their number of new shoots per branch and Flowering and fruiting growth.

Materials and Methods

The current study was carried out on ten-year-old guava plants in two consecutive years, 2022 and 2023, at the Department of Fruit Science, Acharya Narendra Deva University of Agriculture and Technology, Narendra Nagar, Kumarganj, Ayodhya (U.P.). The coordinates of the Ayodhya district are 26.47 n latitude, 80.120 e longitude, and 113 m mean sea level. The site is in typical salty, alkaline Indo-Gangetic plains soils. The randomised block design with three replications was used to assess ten different treatment combinations. two weeks of November, the number of shoots on each experimental tree was counted on four chosen branches, one in each direction.

Four tagged branches, one in each direction, were used to measure the shoot length on each experimental tree in December (for the winter season). For the winter months, the average shoot length per branch was computed and reported in centimetres (cm).

Four tagged branches were used to estimate the percentage of fruits set for each season one month after anthesis. The formula provided was used to get the average percentage of fruit set.

Fruit set (%): set fruit of Number ÷ counted flowers Total

For each tree, the number of fruits on four tagged branches was recorded during the second fortnight of July (for the rainy season) and the second fortnight of November (for the winter season).

The average number of fruits per branch was calculated for each season. 6. Fruit yield (kg/tree): At the time of fruit harvesting, the yield per tree was noted and given in kilograms per tree.

Statistical analysis

The data obtained were statistically analyzed in Randomised Block Design (RBD). The significance of treatment effects was tested using F-test and critical differences (CD) at a 5% probability level were calculated for comparison among treatment means. The experimental data were analysed statistically with the analysis of variance method given by Panse and Sukhatme (1985) [1] .

Result and Discussion

The [3] , Brarr (2010) [5] , Arora (1983) [11] , Pandey et al. (2017) [7] and Singh et al. (2018) [8] in guava.

The application of T7 (6gm Paclobutrazol TSLP) had the lowest flower bud initiation (15.70 days) and the highest fruit set (77.40%) and fruit retention (59.00%), respectively. This was followed by the application of T4 (6gm Paclobutrazol RB), which had the lowest flower bud initiation (16.20 days) and the highest fruit set (75.60%) and fruit retention (56.70%) in guava plants. However, the highest flower bud initiation (21.00 days) while minimum fruit set (69.00%) and fruit retention (48.20%) was recorded in the T1-control (Untreated plant). Additionally, the findings support the notion that the application of paclobutrazol influences the timing of flower bud initiation in guava cv. L-49, with certain treatments promoting earlier or delayed flower bud initiation compared to the control. Furthermore, specific treatments resulted in significantly higher or lower fruit set and fruit retention than the control group. These results are consistent with studies by Brarr et al. (2010) [5] , Jain and Dashora (2007) [9] in guava, Pandey et al. (2017) [7] in litchi, and Gaur et al. (2005) [13] in guava.

Fruit yield (kg/ha): It is clear from looking at data on fruit yield kg per plant in Table 4.1 and Fig. 1 that Paclobutrazol had a considerable impact on fruit yield per plant in guava cv. L-49 during the experiment's 2022-2023 years. In a particular year, treatment T7 (6 gm Paclobutrazol TSLP) produced the highest fruit yield per plant, measuring 42.90. In 2022, therapy T4 (42.06 RB) likewise showed equally positive outcomes. However, throughout the year, the control treatment (T1) had the lowest fruit yield per plant, measuring 25.01.

These results are in line with studies on mangos by Bagchi et al. (2008) [10] and Bal, J. S. and G. S. Dhaliwal (2003). They discovered that applying 5.00 g/ha of cultar to the soil along with 20 ppm NAA produced the maximum yield per tree (68.12 kg) and yield per hectare (106.25 q/ha). In the 10-year-old mango variety Langra, the control group had the lowest yield (29.85%). Therefore, the current study's results and those of Bagchi et al. (2008) [10] indicate that Paclobutrazol spraying significantly affects fruit output per plant in guava cv. L-49.

In comparison to the control group, some treatments-such as T7 and T4-produced more fruit.

References

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