Effect of Various Rootstocks on Tree Growth, Fruit Production and Quality of Kinnow Mandarin

Abstract

Citrus industry is very important to the economy of Pakistan. Citrus is commonly grown on rootstocks, which effects on more than twenty parameters of scion cultivars. Modern world is developing and adopting new rootstocks for commercial citrus production by applying conventional and biotechnological breeding tools and have developed many high yielding rootstocks which are tolerant/ resistant to biotic and abiotic stresses. In Pakistan, citrus industry is dependent on two rootstocks; Rough lemon in Punjab and Sour orange in Khyber Pakhtunkhwa provinces. Problems faced by these two rootstocks results in low production, disease infestation and short orchard life. To address these short falls, present research was designed to evaluate eight new rootstocks for their effect on vegetative and reproductive characters of ‘Kinnow mandarin’, which could replace/add to traditionally used rootstocks in Pakistan to overcome gaps in citriculture industry. Present research was carried out at Postgraduate Agricultural Research Station (PARS) University of agriculture Faisalabad during 2017-18. Kinnow mandarin grafted on nine different rootstocks i.e. Rough lemon, Cox mandarin, Fraser hybrid, Troyer citrange, Cleopatra mandarin, Poncirus trifoliata, Benton, C-35 and Carrizo citrange, treating Rough lemon as control. Trees were planted according to square system of orchard layout. Performance of rootstocks was evaluated based on nutrient uptake, growth and fruit production. First experiment was to evaluate the effect of different rootstocks on macro and micronutrients uptake of Kinnow mandarin. Poncirus trifoliata showed the superior behavior by having maximum macronutrients followed by Fraser hybrid, while Troyer citrange showed poor uptake. Second experiment was focused on effect of rootstocks on tree growth, vigor and physiology of Kinnow mandarin, including leaf gas exchange, photosynthetic pigments, carbohydrates and endogenous plant hormones in rootstock and scion parts. Poncirus trifoliata rootstock was excellent for vegetative characters of Kinnow tree and Troyer citrange rootstock was the poorest. Concentration of indole acetic acid, gibberellic acid and zeatin in rootstocks and scion were high in Poncirus trifoliata and low in Troyer citrange. High concentration of abscisic acid was recorded in Troyer citrange. To record the compatibility of rootstock regarding carbohydrates distribution, Poncirus trifoliata excelled again followed by Fraser hybrid. In last experiment effect of rootstocks on production and quality of Kinnow mandarin was studied. Maximum fruit yield and other fruit production parameters were recorded on Poncirus trifoliata followed by Fraser hybrid. Minimum yield was recorded on Troyer citrange rootstock. Fruit quality parameters were the best on Fraser hybrid rootstock. It is concluded from these studies that Poncirus trifoliata and Fraser hybrid were best performing rootstocks in relation to Kinnow. Poor performance of citrange rootstocks i.e., Troyer citrange, Benton citrange and Carrizo citrange was recorded in relation to Kinnow. Poncirus trifoliata and Fraser hybrid may further need to be evaluated against other biotic and abiotic stresses and could prove potential rootstocks for citrus industry of Pakistan besides Rough lemon and Sour orange