EFFECT OF FOLIAR SPRAY OF ZINC SULPHATE AND CALCIUM CARBONATE ON FRUIT QUALITY OF KINNOW MANDARIN (Citrus reticulata BLANCO)

Abstract

Citrus belongs to family Rutaceae in kingdom Plantae. Pakistan is significant for its production in large scale and worldwide distribution. It has economically remunerative and highly valued fruits, with distinct taste and beneficial values. Juice is soothing, refreshing and delightful (Ahmed et al., 2007). Nutrients are usually quickly available by plants as foliar spray than soil application. Foliar spray of micronutrients is 7-21 times extra effective than applied in soil. ZnSO4 plays an important role in increasing the production by improving the fruit quality and reduce fruit drop. Foliar application of 4 to 12 kg/ha zinc (ZnSO4) gave beneficial effect on chemical and physical attributes of fruits, but the lowest application of Zn indicated the better flavor and juice contents, total sugar and vitamin-C (Altaf and Khan, 2008). Fruit weight, TSS, diameter, ascorbic acid and juice fraction are best obtained at the rate of 0.06% Zn in the form of foliar spray on Kagzi lime (Ashraf et al., 2012). Basically, Zn acts as a metal activator for numerous enzymes, including RNA polymerase carbonic anhydrase, super oxidase dismutase and alcohol dehydrogenase. Zn deficiency limits RNA synthesis, resulting in reduced protein synthesis. It is involved in tryptophan biosynthesis a pre-cursor of auxin (IAA). Zn holds significance importance as imparting sustainability in production/productivity by reducing the fruit drop and granulation. Zinc sprayed at the rate of 0.3-0.8% on 13 years old mango trees at bloom stage gave great enhancement in TSS, total sugars and fruit weight. Foliar application of zinc effect on fruit quality and yield of mango, and increase TSS in fruits and decreased the alternate bearing in Valencia orange and mandarins (Tariq et al., 2007). Calcium plays significant role in sustaining fruits quality, preserving fruit firmness, proliferation of vitamin C, decreased breakdown of storage rotting and reduction in browning of apple. It also defends from membrane disorganization and protects apparent-free space of tissue generally related with senescence and sustains the protein manufacturing capability of cell. Calcium increases the mechanical power of cell wall because it is the main component of cell wall as calcium pectate in plants which play significant role in establishment of pedicel attachment to proximal of fruit thus resulted in reduced fruit drop (Guardiola and Garcia, 2000). Commercially preharvest spray of calcium delays senescence and increase consumer acceptance with less damaging effect during fruit storage (Lester and Grusak, 2004). Smaller amount of calcium carbonate has been effectively used to decrease softening in fresh fruit. High level of calcium contents in fruit may sustain membrane permeability and decrease the process of ripening during storage and it also increase fruit retention because it stimulate the development of lignin and cellulose and stimulate translocation and formation of carbohydrates (Aguayo et al., 2008). The present study was to investigate the preharvest foliar application of zinc sulphate and calcium J. Glob. Innov. Agric. Soc. Sci., 2019, 7(4):157-161. ISSN (Online): 2311-3839; ISSN (Print): 2312-5225 DOI: :https://doi.org/10.22194/JGIASS/7.875 http://www.jgiass.com