Uracil and Chloramequat chloride assessed to improve yield and quality of hasta bahar produced sweet orange cv. Sathgudi

Introduction

In India, citrus ranks third in area and production after mango and bananaand plays a vital role in the horticultural economy of the country. According to the Ministry of agriculture and pharmacy welfare (2024-25 advanced estimate), citrus is grown on about 11,20 thousand hectares with an annual production of 14,924. thousand metric tonnes. Sweet orange (Citrus sinensis Swingle) is the second most important citrus crop in India after mandarin and is grown extensively for its pleasing taste, high juice conten tand nutraceutical quality. At present, it occupies 11,29,01 thousand hectares with an annual production of 22,58,020 metric tonnes in Andhra Pradesh (Dept of horticulture,2023-24) Sweet orange is commercially cultivated in Andhra Pradesh, Tamil Nadu, Karnataka, Maharashtra, Punjab, Madhya Pradeshand Assam, with Andhra Pradesh being a leading producer. Within the state, major sweet orange-growing districts are Anantapuramu, Prakasam, YSR Kadapa, Kurnooland Guntur, where the climate and soils are particularly favorable for cultivation (Sable et al., 2022) [13] . Among the different cultivars, 'Sathgudi' is a commercially important variety widely cultivated in Andhra Pradesh and neighboring states. The fruits are medium-sized, nearly round to spherical in shape, with a smooth, moderately thick orange rind. The flesh is strawcolored to orange with 10-12 segments, producing juice of excellent flavor. Because of its high juice content and consumer preference, 'Sathgudi' has become one of the most popular sweet orange cultivars in the region. However, productivity in this variety is often hampered by irregular flowering, poor fruit setand low yields, particularly during the Hasta Bahar season (Ranganna et al., 2017) [12] . Flowering in sweet orange generally occurs in three flushes: Ambe Bahar (January-February), Mrig Bahar (June-July) and Hasta Bahar (September-October). Of these, Hasta Bahar is the most economically important as it results in summer harvests (April-May), when market demand is high and prices are remunerative. Nevertheless, in the southern coastal districts of Andhra Pradesh, inducing flowering during September-October is challenging due to the impact of the North-East monsoon, leading to irregular or poor flowering. This, combined with problems of excessive vegetative growth, shadingand incomplete pollination, reduces productivity and profitability for farmers. Hence, regulating flowering and improving fruit set during Hasta Bahar is of great importance to ensure higher summer yields and better income for growers. Plant Growth Regulators (PGRs) and chemicals have emerged as promising tools to manipulate plant physiology, regulate flowering, improve fruit setand enhance yield and fruit quality. Among these, Cycocel (Chlormequat Chloride), (Cheng et al., 2025) [2] a gibberellin inhibitor, reduces vegetative growth, shortens internodesand promotes flower bud initiation by diverting assimilates towards reproductive structures (Muthupriya et al., 2022) [11] . Mepiquat Chloride, (Fahmy et al., 2023) [3] another antigibberellin compound, reduces excessive vegetative growth, enhances photosynthesis (Hanumatharaya et al., 2022) [5] and helps synchronize flowering (Budensha et al., 2022) [1] . Uracil, though not a conventional PGR, plays an important role in RNA synthesis and cell metabolism, stimulating cell division and floral differentiation. Nitrobenzene functions as a plant energizer, improving photosynthesis, nutrient uptake, floweringand fruit quality. (Kumar et al., 2020) [9] Homobrassinosteroids, (Ghoneem et al., 2024) [4] naturally occurring plant steroids, regulate growth and development while enhancing stress tolerance, floweringand fruit quality even under challenging environmental conditions (Singh et al., 2022) [16] . Reports, including those of (Lakshmi et al., 2014) [10] , have emphasized the importance of these PGRs and chemicals in regulating flowering during Hasta Bahar and thereby improving yield and quality of sweet orange.

Materials and Methods

The experiment was conducted at Citrus Research Station, Tirupathi, on 10 year old sweet orange plants spaced with spacing of 6 X 6 meters. The experiment was carried out during of 2024-2025. The study followed a Two-Factorial Randomized Block Design (FRBD) with 18 treatment combinations (T₁-T₁ 8 ) and two replications, two plants per replication for each treatment In factor one nine levels of plant growth regulators viz., C 1 :CCC @1000ppm, C 2 :CCC @2000ppm, C 3 :Mepiquatchloride@100ppm, C 4 :Mepiquatchloride@200ppm, C 5 :Nitrobenzene@2ml/litre, C 6 :Nitrobenzene @3ml/litre, C 7 :[email protected]/litre, C 8 :Homobrassinosteriods @0.2mg/litre, C 9: Control.

In factor two levels uracil combination of viz., levels: U 0: without uracil, U 1: with uracil @ 50 ppm. Yield parameters included number of fruits per shoot, number of fruits per tree, fruit yield (kg/tree), fruit weight (g) and quality parameters are TSS (˚Brix), Titratable acidity (%), Ascorbic acid (mg/100 ml), Juice (%), Total sugars (%), Reducing sugars (%), Non-reducing sugars (%), TSS: Acid ratio and Shelf life (days).

Results and Discussion

Significant differences in number of fruits per shoot were observed among plant growth regulators and flower inducing chemicals and uracil. Maximum number of fruits per shoot was recorded in (T 10 ) C 1 U 1 -CCC @ 1000ppm and uracil @50ppm resulted 12.61 fruits when compared with (T 9 ) C 9 U 0 -Control and without uracil 5.29 fruits and followed by(T 11 ) C 2 U 1 -CCC@2000 ppm with uracil @50ppm is represented in Table 1. These findings align with Salomon et al., 1981 [14] , where CCC improved fruit set and compact fruit set and compact growth habit in citrus. Hussain et al., 2017 [6] , where uracil @ 25 ppm have increased the number of fruit per shoot. Table 1. represents that number of fruits per tree was significant were observed among plant growth regulators, flower inducing chemicals and uracil. Maximum number fruits per tree was in (T 10 ) C 1 U 1 -CCC @ 1000ppm and uracil @50ppm resulted 378.30 fruits when compared with (T 9 ) C 9 U 0 -Control and without uracil 158.70 fruits and followed by (T 11 ) C 2 U 1 -CCC@2000ppm and uracil @ 50 ppm. Similar findings Hussain et al., 2017 [6] , where uracil @ 25 ppm have increased the number of fruits per tree. Ranganna et al., 2017 [12] , where CCC@ 1000 ppm + GA 3 +KNO 3 gave highest fruit number in sweet orange. Significant differences in fruit weight (g) was observed among plant growth regulators flower inducing chemicals and uracil. Highest fruit weight was in (T 10 ) C 1 U 1 -CCC @ 1000ppm and uracil @50ppm observed is 159.85gwhen compared with (T 9 ) C 9 U 0 -Control and without uracil of 130.25 g and followed by (T 11 ) C 2 U 1 -CCC@2000ppm and uracil @ 50 ppm was in presented in the Table 1. The study conduted by Sable et al.,2022 [13] , CCC's treated fruits showed highest fruit weight. Hussain et al., 2017 [6] , where uracil @ 25 ppm have higher fruit weight. Table 1. represents that fruit yield was significant were observed among plant growth regulators flower inducing chemicals and uracil. Maximum fruit yield was in (T 10 ) C 1 U 1 -CCC @ 1000ppm and uracil @50ppm resulted 60.48kg when compare with the (T 9 ) C 9 U 0 -Control and without uracil 20.67 kg and followed by (T 11 ) C 2 U 1 -CCC@2000ppm and uracil @ 50 ppm. Field trails conducted by Hussain et al., 2017 [6] , where uracil @ 25 ppm and with CCC@ 1000ppm show maximum fruit yield. Significant data wise differences in shelf life was observed among plant growth regulators flower inducing chemicals and uracil. maximum shelf life was in (T 10 ) C 1 U 1 -CCC @ 1000ppm and uracil @50ppm observed is 21.72 days when compare with the shelf life displayed in 14.53 days (T 9 ) C 9 U 0 -Control and without uracil and on par with (T 11 ) C 2 U 1 -CCC@2000ppm and uracil @ 50 ppm was in presented in the Table 2. Study conducted by Salomon et al.,1982, CCC's treated fruits showed maximum shelf life. Hussain et al., 2017 [6] , where uracil @ 25 ppm have better storability. Table 2. represents that TSS was significant were observed among plant growth regulators flower inducing chemicals and uracil. Maximum TSS was in (T 10 ) C 1 U 1 -CCC @ 1000ppm and uracil @50ppm resulted 12.40˚B when we comapre with (T 9 ) C 9 U 0 -Control and without uracil 8.95 ˚B. and followed by (T 11 ) C 2 U 1 -CCC@2000ppm and uracil @ 50 ppm. Field experiment conducted by Hussain et al., 2017 [6] , where uracil @ 25 ppm and with show maximum TSS.

Sable et al.,2022 [13] , CCC's treated fruits showed highest TSS.Significance differences in titratable acidity (%) was observed among plant growth regulators, flower inducing chemicals and uracil minimum titratable acidity was in (T 10 ) C 1 U 1 -CCC @ 1000ppm and uracil @50ppm observed is 0.45% when compare with the0.76(T 9 ) C 9 U 0 -Control and without uracil and on par with (T 11 ) C 2 U 1 -CCC@2000ppm and uracil @ 50 ppm was in presented in the Table 2. Experiment conducted by Ranganna et al.,2017 [12] , CCC's treated fruits showed lower acidity. Hussain et al., 2017 [6] , where uracil @ 25 ppm have balances sugaracid.Significantly differences in TSS: Acid ratio was observed among plant growth regulators flower inducing chemicals and uracil in Table 4.Maximum TSS: Acid was in (T 10 )C 1 U 1 -CCC @ 1000ppm and uracil @50ppm observed is 31.05 when compare with TSS: Acid displayed in 8.74 (T 9 )C 9 U 0 -Control and without uracil and followed by(T 11 ) C 2 U 1 -CCC@2000ppm and uracil @ 50 ppm was in presented in the Table 3. Sable et al.,1982, reported that the CCC's treated plants favorable TSS: Acid ratio. Hussain et al., 2017 [6] , where uracil @ 25 ppm, where TSS: Acid ratio favored. The Ascorbic acid show significant difference was observed among plant growth regulators flower inducing chemicals and uracil. Maximum ascorbic acid was in (T 10 ) C 1 U 1 -CCC @ 1000ppm and uracil @50ppm resulted 62.10 when compare 35.94 is resulted in (T 9 ) C 9 U 0 -Control and without uracil is with on par with (T 11 ) C 2 U 1 -CCC@2000ppm and uracil @ 50 ppm. Experimental trails said that Ranganna et al.,2017 [12] , CCC's treated fruits showed maximum ascorbic acid content. Shukla et al., 2019 [15] where uracil @ 50 ppm improved ascorbic acid. The Juice % among plant growth regulators, flower enhancing chemicals and uracil is having the significant difference was observed in Table 3. Highest juice 50.05% was in (T 10 ) C 1 U 1 -CCC @ 1000ppm and uracil @50ppmwhen compare with the juice 36.27% is displayed in (T 9 ) C 9 U 0 -Control and without uracil is on par with (T 11 ) C 2 U 1 -CCC@2000ppm and uracil @ 50 ppm. The study trails said that Hussain et al., 2017 [6] , where CCC @1000 ppm and uracil @ 25 ppm have highest juice %. Among plant growth regulators, flower enhancing chemicals and uracil the total sugars shows the significant difference was observed in Table 3. Maximum total sugars was observed in (T 10 ) C 1 U 1 -CCC @ 1000ppm and uracil @ 50ppm (6.43%) when compare with the total sugars 5.37% is displayed in (T 9 ) C 9 U 0 -Control and without uracil. on par with (T 11 ) C 2 U 1 -CCC@ 2000ppm and uracil @ 50 ppm. Findings told that Kaur and kaur (2017)-uracil raised total sugars in guava. Salomon et al., 1981-CCC increased dry matter and sugar content. Reducing sugars have the significant difference among the plant growth regulators, flower inducing chemical and uracil was observed in Table 3. Highest reducing sugar 4.23% was in (T 10 ) C 1 U 1 -CCC @ 1000ppm and uracil @50ppm when compare with the reducing sugars 3.27% is displayed in (T 9 ) C 9 U 0 -Control and without uracil was on par with (T 11 ) C 2 U 1 -CCC@2000ppm and uracil @ 50 ppm. The trails conducted by the Hussain et al., 2017 [6] , where sugar fractions improved. Sabel et al., 2022-CCC treated plants shows improved sugar fractions. Among plant growth regulators, flower inducing chemicals and uracil the non-reducing sugars was observed significant difference in Table 3. Highest non-reducing sugars was 2.32% in (T 10 ) C 1 U 1 -CCC @ 1000ppm and uracil @50ppm when compare with onreducing sugars 1.94% is displayed in (T 9 )C 9 U 0 -Control and without uracil was on par with (T 11 ) C 2 U 1 -CCC@2000ppm and uracil @ 50 ppm. Experimental study said that Hussain et al., 2017 [6] , where showed balanced sugar profile noted. Ranganna et al.,2017 [12] , CCC's treated plants shows balanced sugar fractions.

Conclusion

Among plant growth regulators and flower inducing chemicals and uracil.The treatment combination (T 10 ) C 1 U 1 -CCC @ 1000ppm and uracil @50ppm was the best performer in the both of the yield and quality parameters followed by C 2 U 1 -CCC@2000ppm and uracil @ 50 ppm. hence we conclude that (T 10 ) C 1 U 1 -CCC @ 1000ppm and uracil @50ppm is the best combination treatment among the plant growth regulators and flower inducing chemicals and uracil

Acknowledgement

AcknowledgementI am sincerely grateful to the advisory committee for their valuable guidance and unwavering support throughout my research. I also extend my heartfelt thanks to the Citrus Research Station, Tirupathi, for providing the necessary facilities and resources to complete this project.

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