Geographical Location and Agro-Ecological Conditions Influence Kinnow Mandarin (Citrus nobilis × Citrus deliciosa) Fruit Quality

摘要

This study evaluated the Kinnow fruit quality in relation to geo-ecological conditions in four main Kinnow producing districts of Punjab Province, Pakistan, including Toba Tek Singh (TTS), Khanewal (KHW), Vehari (VHR) and Sargodha (SGD). At commercial maturity, fruit were harvested from six commercial orchards of each district, and compared for cosmetic (mainly blemishes) and internal fruit quality. Wind+LGFI (a complex of blemishes caused by wind and low grade fungal infection), mites and thrips were recognized as the key causal agents of Kinnow rind blemishes. Fruit harvested from district TTS and SGD exhibited highest proportion of A (13.33 and 10.22%) and grade B (25.79 and 17.77%) fruit respectively. Regarding physical quality attributes, rind smoothness was found significantly higher in fruit from district TTS followed by SGD. Among biochemical characters, SGD was on the top with respect to juice percentage (40.9%), TSS/TA ratio (14.5) and vitamin C content (67 mg/100 mL). TSS was significantly higher in fruit from VHR (11.2 °Brix), while, total sugars (8.4%) were maximum in fruit from TTS. Meteorological data showed that, TTS had lower while district KHW higher mean minimum monthly temperatures during most part of the year. Annual rainfall was higher in SGD, while lower in VHR. Average monthly RH was lower in VHR while higher in SGD. Soil and leaf nutrient analysis of the orchards revealed significantly higher soil potassium content (225.11 mg/kg), and favorable range of pH (7.61), leaf nitrogen (N, 1.98%), phosphorous (P,0.1%), potash (K, 0.61%), calcium (Ca,5.58%) and iron content (Fe, 155.04 mg/kg) in district VHR. Soil pH was lowest while leaf manganese (Mn) contents were significantly higher in SGD. TSS was correlated negatively with rain fall and RH.TSS/TA ratio and vitamin C were also correlated negatively with soil N. Disease incidence were negatively correlated with leaf P contents and positively correlated with rainfall. In conclusion, geolocation and agro ecological conditions have significant impact on Kinnow fruit quality. District VHR and TTS were found to be the potential pockets for obtaining good quality fruit along with district SGD for broadening the export base of Kinnow mandarin.