Response of growth regulators on flower induction, fruit yield and quality of litchi 'Shahi'

Abstract

'Shahi' litchi is known for its unique fragrance and high demanding fruits, not only in Bihar but throughout the whole of India. In the juvenile stage (7-14 years tree age), litchi plants shows erratic and irregular bearing behavior due to continuous growth flushes and the farmers suffer for such a long period in order to get regular fruiting. Since 2006, through National Horticulture Board and State Horticulture Mission, more than 15,000 ha area has been brought under cultivation and orchards older than 4 years were in majority and were the target group. An experiment was conducted at NRC Litchi farm to induce the flowering in litchi through growth regulators in 8-9 years old litchi orchards (junior bearing stage), consecutively for 2 years comprising of 12 treatments of four PGR's, i.e., GA3 (25, 50, 75 ppm), Ethrel (100, 150 ppm), NAA (15, 25, 40 ppm), MH (15, 20, 25 ppm) and control (water spray) with three replications. Three sprayings of NAA, Ethrel, MH along with control and two spraying of GA3 were applied at pre-flowering stage from the 1st week of October with a 30-days interval while the 3rd spraying of GA3 was given after fruit set. Data revealed that PGRs treated plants showed comparatively lesser twig length, number of leaflet per twig, twig length and twig diameter ratio, leaflet and twig diameter ratio and more twig diameter, emergence of pure panicle and fruit yield than control. Plants treated with Ethrel at 100 and 150 ppm, expressed significantly higher number of pure panicle emergence (86.67 and 91.67%, respectively) and fruit yield (53.33 and 52.50 kg plant-1, respectively) than other treatments. Relationship of pure panicle with fruit yield showed positive and moderately strong correlation (r=0.71, R2=0.51). PGRs treated plant expressed more fruit weight, pulp recovery and higher TSS than control.