*Corresponding author’s e-mail: romensenjam@yahoo.com

Effect of PGRs combination on pre-harvest fruit drop of Khasi mandarin(Citrus reticulata Blanco.)S. R. Singh*, L. Wangchu, Barun Singh, B. N. Hazarika and A. K. Pandey

College of Horticulture & Forestry,Central Agricultural University, Pasighat-791 102, Arunachal Pradesh, India.Recieved: 25-01-2017 Accepted: 09-03-2017 DOI:10.18805/ijare.v0iOF.7635

ABSTRACTThe synthetic auxin like 2,4-D, 2,4,5-T and NAA were investigated on ten (10) years old tree to study the effect of differentcombinations of PGR on pre-harvest fruit drop at Bodak village under East Siang district of Arunachal Pradesh, Indiaduring the year 2014-2015. Result showed maximum fruit retention in T6 Urea 1% + 2, 4- @ 15ppm (45.4%) followed byT5 NAA@5ppm + 2,4-D@10ppm (44.3%) resulting significantly increased the total number of fruits in (T6) (244.3 fruits/ tree) followed by T5 (241.6 fruits/tree) as compared to control (17.3% fruit retention and 181 fruits/ tree) Hence, thecombination of recommended dose of fertilizer i.e. 400:400:900g NPK/plant/year along with Urea 1% + 2, 4- @ 15ppmfoliar spraying thrice during April, July and September can be used to control the fruit drop in Khasi mandarin.

Key words: Khasi mandarin, PRG, Pre-harvest, Fruit drop, Fruit retention.

INTRODUCTIONCitrus is an important fruit crops which rank third

in and it accounts for 12.5% of the total fruit crop productionin India after banana and mango. Among the citrus, mandarinorange (Citrus reticulata Blanco.) is the most commonamong citrus fruit grown in India. It occupies nearly 50% ofthe total citrus area in India (Anon, 2014). In the NorthEastern region of India (Assam, Arunachal Pradesh, Manipur,Tripura and Meghalaya), a type of mandarin called Khasimandarin occupied an important place among the othervarieties of mandarin orange. It is a loose-skinned orange. Itbelongs to species Citrus reticulata Blanco. It is commonlydesignated as mandarins. Although Khasi mandarins arepopularly grown in N-E states, there are certain importantgrowing belt viz. in Assam (Tinsukia, NC Hills, KarbiAnglong), Tripura (Jampui hill), Meghalaya (East & WestKhasi, Ri-Bhoi, Garo Hills, Jaintia Hills), Manipur(Tamenglong) and Arunachal Pradesh (East Siang and WestSiang) are the main producing zone of this fruit crop.According to different region in Manipur, Mizoram andArunachal Pradesh, it is locally called as Komla and inTripura as Kamla, Meghalaya known as Soh (Hazarika andSingh, 2013). It production is an activity of prime importancefor the Adi tribe economy which are inhibited in East Siangdistrict of Arunachal Pradesh. Today, these fruits are grownin many parts of the world wherever climatic conditionspermit cultivation, especially in Algeria, Australia, China,Greece, India, Israel, Italy, Egypt Japan, Morocco, NewZealand, South America, South Africa, Spain, Turkey, thesouthern States of the USA and the West Indies. In India, it

is mainly grown successfully in all frost – free tropical andsubtropical regions of the country viz. Maharashtra, MadhyaPradesh, Tamil Nadu, Rajasthan, Karnataka, Andhra Pradesh,Punjab and North-Eastern states. In Arunachal Pradesh,which is known for its organic khasi mandarin production isfacing problems of fruit drops just after fruit setting in themonth of March-April, in June-July popularly known as Junedrop and pre-harvest drop in September-October resultingless number of fruits/tree at the harvesting stage. Abscissionof mature fruit before harvest is a problem in many citrusproducing countries. Due to excessive fruit drop the citruscultivation proves unprofitable and the farmers tent to startfalling down the mandarin orchard under East Siangcondition(Fig 1a). To minimize the fruit drop and to increasefell fruit retention, farmers are left no option but to use theintegrated nutrient management along with application ofPGR from fruit setting at three phase of fruit drops.Information regarding application of PGR are still lackingin East Siang district of Arunachal Pradesh. Keeping the viewand considering the need of fruit retention during the bearingperiod and to increase the productivity, the present researchwas initiated to explore the potential of growth regulators inreducing the fruit drop after fruit sets drop for increasingthe production and productivity in khasi mandarin under thePasighat condition of Arunachal Pradesh, India.MATERIALS AND METHODS

The present investigations were carried out at theat Bodak village under East Siang district of ArunachalPradesh during the year 2014 to study the effect of differentcombinations of PGR on pre-harvest fruit drop. The average

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altitude of the sites of the experiment are about 155 m MSLand represent a typical subtropical zone with short cool,dry and windy winter, a hot summer and a heavy monsoonseason. Study site represents a subtropical, hot and humidclimate; in the lower valleys, summer temperatures in June,July, and August typically rise to about 30oC, while wintertemperatures in December, January, and February usuallydrops to 13°C. Annual rainfall in the state averages about130 inches (3,300 mm), mostly between April and September.

Details of the eight treatments are T1: NAA@5ppmT2: 2, 4, 5-T @ 5ppm T3: 2,4-D@10ppm T4: NAA@5ppm +2,4,5-T@5ppm T5: NAA@5ppm + 2,4-D@10ppm T6: Urea0.5% + 2, 4- @ 10ppm T 7: NAA@5ppm+2,4-D@10ppm+2,4,5-T@5ppm and T8: Control. The PGR weresprayed at three stages after fruit setting at April, July andSeptember months respectively(Fig 1b). The fruit retentionwas evaluated by counting the average fruit retention /branches before spraying at April month as initial reading(equal average fruits number/tree) and counted it averagefruits/branches at July to observe after June drop, Septemberbefore spraying for pre-harvest fruit drop and at Novemberto observe fruit retention/branch(Fig 1c). Finally, the numberof fruits/tree at harvesting stage (Nov) was counted for eachtreatment for the evaluation for better fruit retention/tree andevaluated its fruit quality parameters. Every treated plantwas supplemented with 450:450:900g N: P: K/plant/year in

two split doses. First split dose of the recommended dose offertilizer of total P and K fertilizers along with half of nitrogenfertilizer was applied in one time at March-April along witha light irrigation after fruit setting and the remaining half ofthe recommended dose of nitrogen is applied during June-July. Before the fruit drop was anticipated to begin, all thefruit on the ground under the trees were removed. Fruit dropwas counted regularly and dropped fruit were removed. Atthe time of counting, dropped fruit were classified as soundor unsounded. Sound fruit had no visible signs of injury orinfection and unsound fruit had visible injury or pathologicalinfection which we assumed induced abscission. Under eastSiang district of Arunachal Pradesh, monsoon starts fromMarch-April upto Sept-Oct and fertilizers are mainly appliedduring this period. The statistical analysis of the data on themean values of individual characters was analyzed using MState software.RESULTS AND DISCUSSIONSYield and fruit retention parameter

The effect of different combination of PGR showedsignificant influence in the fruit retention/tree resulting betteryield(Fig. 1d)as compared to control (Table 1). It was observedthat the maximum fruit retention was recorded (T6 ) in Urea0.5% + 2, 4- @ 10ppm (244.34 fruits/tree) followed by (T5)NAA@5ppm + 2,4-D@10ppm (241.67 fruits/tree) whereas thelowest fruit retention/tree was recorded in control i.e.

Table 2: Quality parameter of Khasi mandarin under different PGRs

Treatment TSS o Brix Reducing sugar Acidity Vitamin C Total sugar Shelf life(%) (%) (mg/100g) (%) (No. of days under-

-room temperature)

T1 11.40 4.20 0.96 34.50 7.50 7.60T2 12.00 4.30 0.80 38.60 7.60 7.60T3 11.50 3.90 0.80 35.20 7.20 7.60T4 12.00 4.30 0.90 36.20 7.10 8.30T5 12.00 4.00 0.80 34.40 7.50 7.30T6 11.80 3.80 0.80 35.50 7.10 7.30T7 11.70 3.70 0.90 34.00 7.20 7.30T8 12.00 4.20 0.90 34.30 7.00 7.60SEM 1.26 0.43 0.11 3.65 0.75 0.80CD @5% 4.43 1.50 0.39 12.81 2.66 2.84

Table 1: Physical parameter of Khasi mandarin under different PGRs

Treatment Fruit wt. Fruit breadth Frt. length Peel wt. Pulp wt. No. of Seed wt. Juice / fruit(g) (cm) (cm) (g) (g) seeds/frt. (g) (ml)

T1 121.00 4.93 6.33 24.33 96.6 7.33 0.17 32.66T2 114.00 4.73 6.23 24.66 89.3 8.33 0.16 32.00T3 124.00 4.83 6.26 23.66 100.3 7.33 0.15 36.00T4 119.00 4.60 6.08 23.00 96.00 8.33 0.14 33.66T5 118.60 4.90 6.36 24.66 93.60 8.00 0.15 32.66T6 115.33 4.63 6.20 23.33 92.00 7.66 0.15 34.66T7 110.00 4.53 6.30 22.33 87.60 8.66 0.15 34.66T8 110.33 4.50 6.06 23.33 87.00 7.66 0.15 33.33SEM 12.90 0.66 0.47 2.43 10.31 0.96 0.01 3.80CD @5% 45.20 2.34 1.65 8.54 36.13 3.37 0.05 13.33

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(a) Heavy fruit drops in control plant (b) Spraying of different PGR combination

(c)Tagging of selected branches for fruit counting (d) Better fruit retention in the bearing tree

Fig. 1

recommended fertilizer only (T8) (181.00/tree) resultingmaximum fruit retention percentage in T6 (50.97%) followedby T5 (50.60%) as compared to control (17.30). Stewartand Hield (1950) reported that the fall of mature fruit wascharacterized mainly by alterations in the cellular walls inthe zone abscission, localized at the peduncle, and that themain action of plant growth regulators in the fall of ripefruit was that of reducing the weakening of the cellular wallmaterial in this region, reducing the fall of fruit. NAApresented the same positive effect on the layer of abscission.This dependence of abscission relative to the endogenouscontent of auxins has been proven by exogenous applicationsof 2,4-D or NAA. These findings are in conformity with thefindings of Amiri et al., (2012). The trees which were treatedwith urea 1% was found to be vigorous growth tree canopywhich might photosynthate better as compared to othertreatments with the help of sunlight. Similar report wasreported by Lodhi and Rashid (1980) that the urea had littleeffect on percentage fruit set and increased leaf N and shoot

growth, especially at the higher rate on Kinnow. Besides,Malik et al. (2000) also reported that the maximum numberof fruits and yield per tree were found in trees that received1.5and 0.4% urea and zinc sulphate spray, respectively. Ascorbicacid content in fruits, however, decreased with increasingconcentration of urea and zinc sulphate in Kinnow. Further,El-Kobbia et al. (2011) also revealed that the foliar spraysof urea at pea or marble stage significantly increasedvegetative growth and help in the fruit retention due to betterphotosynthetic activity. Monselise and Goren (1978)reported that the spraying of auxins prevented the droppingof fruit by maintaining the cells at the zone of abscision,preventing the synthesis of hydrolitic enzymes, such ascellulase, which decomposed the cell walls. PGR applicationduring fruiting period and the supplementation ofrecommended dose of fertilizer after fruiting perhaps resultedin better fruit retention resulting better yield as compared tocontrol. Besides, Anthony et al. (2001) also reported thatthe treatment of NAA reduced drop by 31% to 88% comparedto untreated control.

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Table 3: Fruit retention percentage of Khasi mandarin under different PGRs

Treatment Initial Equal Av. Frt. No./ Av. Frt. No./ Av. Frt. No./ Branch Final Frt. Total No.Frt. No./Branch Branch BranchSeptember, November, Retention % Frt. / Tree

April, 2014 July, 2014 2014 2014 November, 2014T1 30.33 18.00 11.00 9.67 31.80 207.00T2 30.33 19.00 11.00 9.34 30.67 202.34T3 30.33 20.33 10.00 10.00 32.70 209.67T4 30.33 18.66 12.66 11.34 36.80 224.67T5 30.33 22.66 13.34 15.34 50.60 241.67T6 30.33 23.33 13.67 15.67 50.97 244.34T7 30.33 21.00 13.00 12.67 41.60 238.00T8 30.33 15.00 9.00 5.34 17.30 181.00SEM ——— 2.40 1.37 1.34 4.15 23.46CD @5% ——— 8.44 4.84 4.72 14.54 82.19

NB: April month statistic was not analyzed as equal number fruits/tree was counted

Physical parameter and quality parameters of khasimandarin

CONCLUSIONIn summary, it is concluded that the combination

of recommended dose of fertilizer i.e. 400:400:900g NPK/plant/year along with Urea 1% + 2, 4- @ 15ppm foliar spraythrice during April, July and September were effective incontrolling fruit drop in Khasi mandarin under East Siangdistrict of Arunachal Pradesh. Therefore, application ofrecommended dode of fertilizers 400:400:900g NPK/plant/year along with Urea 1% + 2, 4- @ 15ppm foliar sprayingthrice during April, July and September can be recommendedto the mandarin growers to increase the yield andproductivity.ACKNOWLEDGEMENT

The authors like to render gratefulness to theCollege of Horticulture & Forestry, Central AgriculturalUniversity, for funding the research work under the IRPproject scheme.

Analytical investigation with different treatmentsrevealed that TSS was found maximum in T2,T4,T5 and T8(120 Brix) which was significantly at par with T6 (11.80 0Brix) which indicate that the application of PGR does notaffect the fruit quality (Table 2). Same observation was alsoreported by Amiri et al., 2012 in mandarin cv. Satsumamandarin. In case of fruit acidity, maximum acidity (0.96%)was recorded in T1 but others ( T4, T7 & T8) was found to beat par with the T1 which indicate that treatment with PGRdoes not affect its fruit quality. In case of physical parameterslike fruit length maximum was observed in T5 (6.36 cm)followed by T1 (6.33 cm) and minimum in T8 i.e control(6.06 cm). Similarly, fruit breadth was also found maximumin T1 (4.93 cm) followed T5 (4.90 cm) and minimum incontrol T8 (4.50 cm). Other parameters like fruit weightmaximum was observed in T3 (124.00g/fruit) followed byT1 (121.00 g/fruit) and lowest fruit weight in T7 (110.33 g/fruit) which is at par with T8 (110.33g/fruit) which indicatePGR does not affect the physical parameters of the fruit(Table 1). Aranguren et al. (1988), also reported increase oflength and diameter of ‘Valencia’ oranges with pre-harvestapplication of 2,4-D in concentrations of 20 and 25 ppm.Besides, as described by Barros (1992) that the applicationof GA3 alone or with 2,4-D provoked significant increase of

fruit diameter compared to the control. The shelf life of thefruit under the room temperature was found to be non-significant however, without any deterioration of its fruitquality it can kept upto 7-9 days under Pasighat condition.Fungal growth is the major problem in the shelf life of thefruit which shorten its storage period. It is reported that sprayof carbendazim one month before harvest prolong the storageperiod under the room condition (Ladaniya, 1997).

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