INTRODUCTION ‘Kinnow’ mandarin is considered as trademark product of Pakistan citrus industry. This distinction of Kinnow is due to its magnificent aroma, premium taste, high juice contents and nutritional profile like high vitamin C/ascorbic acid contents, rich in sugars, reducing sugars and antioxidants (Memon, 2014). Pakistan produces 2395550 tonnes of citrus annually and total area under citrus cultivation is 192832 (FAO, 2019). The significance of citrus rootstocks for the better productivity of citrus can never be neglected. It is a well- known fact that the availability of suitable and compatible rootstocks is the key to sustained citrus industry. Fruit growers primarily focused on yield and fruit quality to determine their net income. Internal quality parameters of Kinnow such as juice content, color of flesh and peel, total soluble solids, titrable acidity, juice pH are also affected by rootstocks (Wutscher, 1997). Some rootstocks like Sour orange, Rough lemon and RLC-4 manipulated the biochemical characteristics of citrus fruits i.e. total soluble solids (TSS), titratable acidity (TA) and Vitamin C contents of lemon fruits. Differences in quality characteristics were due to different rootstocks (Yonemoto et al. 2005). Previously a lot of researchers has reported that yield and fruit quality of citrus is affected by rootstocks (Qureshi et al., 2021; Ahsen et al., 2019; Smith et al., 2004). It is very essential to understand the rootstock/scion interaction and effects of rootstocks on different scion parameters such as yield and fruit quality for making a profitable citrus fruit cultivation. Various fruit quality attributes of citrus fruits such Pak. J. Agri. Sci., Vol. 58(3), 929-935;2021 ISSN (Print) 0552-9034, ISSN (Online) 2076-0906 DOI: 10.21162/PAKJAS/21.348 http://www.pakjas.com.pk INFLUENCE OF DIFFERENT ROOTSTOCKS ON PHYSICO-CHEMICAL QUALITY ATTRIBUTES OF KINNOW MANDARIN Muhammad Ahsan Qureshi 1 , Muhammad Jafar Jaskani 1,* , Ahmad Sattar Khan 1 , Muhammad Salman Haider 2 , Waqar Shafqat 3 , Muhammad Asif 1 and Asim Mehmood 4 1 Institute of Horticultural Sciences, University of Agriculture Faisalabad, Pakistan; 2 Nanjing Agricultural University, China, 3 University of Florida, Institute of Food and Agricultural Sciences, Horticultural Sciences Department, Indian River Research and Education Center, 2199 South Rock Road, Fort Pierce, FL 34945 . , 4 COMSATS Institute of Information Technology, Pakistan * Corresponding author’s e-mail: jjaskani@uaf.edu.pk Citrus holds the position of top ranked fruit crop of Pakistan in terms of area and production. ‘Kinnow’ (Citrus reticulata Blanco) is considered as the trademark of Pakistan’s citriculture industry and occupies the share of 95% out of total citrus production in Pakistan. But there is an alarming problem of single rootstock culture. Rough lemon (Citrus jambhiri Lush.) has monopolized the citrus industry in Punjab province. Rough lemon is susceptible to phytophthora and waterlogging. There is an absolute need for substitute rootstock for higher yield and improved fruit quality of Kinnow. A rootstock scion interaction research trial was conducted during 2017 to 2019. Kinnow was grafted on eight rootstocks, i.e. Cox mandarin, Fraser hybrid, Troyer citrange, Cleopatra mandarin, Poncirus trifoliata, Benton, C-35 and Carrizo citrange. Experiment was laid out according to Randomized complete block design (RCBD). Each rootstock was considered as single treatment and replicated thrice. Performance of six year old Kinnow trees grafted on different rootstocks was evaluated on the basis of physicochemical quality attributes of fruits. Data was taken for two consecutive years and average was calculated. Results revealed that rootstocks had a significant role in manipulating the morphological and biochemical quality attributes of Kinnow fruits. Kinnow fruits from the trees grafted on Poncirus trifoliata rootstock showed the maximum fruit diameter (84.03 mm), peel weight (28.99 g), rag weight (87.68 g) and individual fruit weight (221.85 g). Poor performance of Troyer citrange regarding morphological quality parameters was observed. Total soluble solid (TSS) (13.76 °Brix), Vitamin C (69.38 mg/100 ml) and Total antioxidants (72.32 % inhibition) in Kinnow juice were maximum on Fraser hybrid. Carbohydrate analysis of Kinnow juice by HPLC method revealed that concentration of sucrose, fructose and glucose was highest in Fraser hybrid rootstock. Poor performance of Troyer citrange and C-35 rootstocks was recorded regarding all biochemical parameters of Kinnow. It is concluded that physicochemical quality of Kinnow is manipulated by different rootstocks. Poncirus trifoliata and Fraser hybrid rootstocks can be used as alternate rootstocks for citrus industry of Pakistan to substitute the traditional rootstocks like rough lemon and sour orange. Keywords: Citrus, citriculture, rootstock interaction, productivity, quality.