Efficiency of exogenous zinc sulfate application reduced fruit drop and improved antioxidant activity of ‘Kinnow’ mandarin fruit

‘ Kinnow’ mandarin (Citrus nobilis L.× Citrus deliciosa T.) is an important marketable fruit of the world. It is mainstay of citrus industry in Pakistan, having great export potential. But out of total production of the country only 10% of the produce meets the international quality standard for export. Pre-harvest fruit drop and poor fruit quality could be associated with various issues including the plant nutrition. Most of the farmers do not pay attention to the supply of micro nutrients which are already deficient in the soil. Furthermore, their mobility within plants is also a question. Zinc (Zn) is amongst those micronutrients which affect the quality and postharvest life of the fruit and its deficiency in Pakistani soils is already reported by many researchers. Therefore, this study was carried out to evaluate the influence of pre-harvest applications of zinc sulfate (ZnSO4; 0, 0.4%, 0.6% or 0.8%) on pre-harvest fruit drop, yield and fruit quality of ‘Kinnow’ mandarin at harvest. The treatments were applied during the month of October i.e. 4 months prior to harvest. The applied Zn sprays had significant effect on yield and quality of the “Kinnow” fruit. Amongst different foliar applications of ZnSO4applied four months before harvest, 0.6% ZnSO4 significantly reduced pre-harvest fruit drop (10.08%) as compared to untreated control trees (46.45%). Similarly, the maximum number of fruits harvested per tree (627), fruit weight (192.9 g), juice percentage (42.2%), total soluble solids (9.5 °Brix), ascorbic acid content (35.5 mg 100 g-1) and sugar contents (17.4) were also found significantly higher with 0.6% ZnSO4 treatment as compared to rest of treatments and control. Foliar application of 0.6% ZnSO4 also significantly improved total antioxidants (TAO) and total phenolic contents (TPC) in fruit. In conclusion, foliar spray of ZnSO4 (0.6%) four months prior to harvest reduced pre-harvest fruit drop, increase yield with improved quality of ‘Kinnow’ mandarin fruit.

Standardization of stage wise water requirement in drip irrigated Kinnow mandarin orchards under sub-tropical conditions

An experiment on drip irrigation scheduling based on pan evaporation replenishment was conducted in Kinnow orchard at Punjab Agricultural University, Ludhiana during 2010-2018. Year was divided into six stages (stage 1 to stage VI) including two months in each stage. First treatment included irrigation scheduling with 30 and 40% ER, treatment two with 40 and 60% ER, treatment three with 60 and 80% ER, alternatively during stages I to VI. However, fourth and fifth treatments had irrigation with 80% ER and 30% ER, respectively, in all the stages. Maximum daily open pan evaporation (9.15 mm) was recorded in May and minimum (1.19 mm) was recorded in January. The water requirement varied from 2.8 liters day-1 tree-1 in stage-I to 58.3 liters day-1 tree-1 in stage-III. Linear increase in vegetative and reproductive growth was observed with increase in irrigation water. Polynomial relationship studies indicated the increase in water quantity applied to Kinnow with increase in temperature subject to the prevailing relative humidity. Similarly, volumes of water applied increased with increased mean evaporation. The study concluded that drip irrigation scheduling with 60 to 80% ER alternatively, starting from January to December save significant amount of water, without affecting yield and quality of Kinnow under subtropical conditions.

Climate variables effect on fruiting pattern of Kinnow mandarin (Citrus nobilis Lour × C. deliciosa Tenora) grown at different agro-climatic regions

Kinnow orchards grown in different agro-ecological regions of Punjab, Pakistan, namely Sargodha, Toba Tek Singh (TTS) and Vehari districts, were selected to assess the effect of climate variables on fruit-bearing patterns. Experiment was laid out in RCBD while selecting identical features Kinnow plants and labeled twigs at analogous canopy positions in all three sites. Temperature was reported higher in TTS and Vehari areas, while relative humidity in Sargodha accounted for different levels of agrometeorological indices by computing more variations in warm districts. Climate variables influenced fruit-bearing habits and vegetative growth trend in all three flushes while recording heavy fruit-bearing plants during on-year and light fruit-bearing in off-year at Vehari. Similarly, three vegetative flushes were recorded unevenly in all three sites due to different fruit-bearing patterns induced by climate variables. Harvesting pattern of orchards began earlier in Sargodha, where maximum orchards were harvested before new flowering to add evenness to fruiting habits during on & off-years. In warm conditions, fruit ripening arrived in the peak of winter and mostly domestic market-driven harvesting resulted in late start of fruit picking with more erratic fruit-bearing habits. Both physiological and pathological fruit drops have been significantly affected by climate variables with a higher degree of physiological drop in warm regions and pathological effects in the humid conditions of Sargodha on heavy fruit-bearing plants. Fruit yield and grading quality were also affected in both seasons by showing more asymmetrical trend in yield and fruit grading in warm areas of TTS and Vehari due to an irregular fruiting pattern compared to Sargodha. From now on, the climate variables of the three sites directly influenced the fruiting patterns, vegetative flushes, fruit drops, yields and grades of Kinnow mandarin.

Microwave-assisted extraction and characterization of pectin from citrus fruit wastes for commercial application

Pectin is an essential hydrocolloid widely used as a gelling, thickening, and stabilizing agent in the food, pharmaceutical, and cosmetic industry. In the present study, an effort has been made to extract pectin from Pomelo (Citrus maxima), Kinnow mandarin (Citrus reticulata) and Citron (Citrus medica) peels with microwave-assisted extraction (MAE) technique using organic citric acid. Pectin extracted with MAE was characterized in terms of yield, ash content, pH, solubility, equivalent weight, methoxyl content, anhydrouronic acid content, and degree of esterification. The extraction conditions had significant effects on physicochemical properties. The results showed that the highest amount of pectin (24.19±0.26%) was obtained from Citrus maxima. Based on DE value all pectins were categorized as low methoxy pectin (LMF). Extracted pectins were highly pure based on AUA content. Structural characterization of extracted pectin from three fruit peels by Fourier Transform Infrared (FT-IR) spectroscopy revealed that pectin has functional groups within the 1740–800 cm-1 spectral region. However, pectin extracted in this study can be used in the manufacturing of low sugar foods such as diet jams and jellies.

Impact of Chitosan and Alginate Based Edible Coating on Shelf Life and Postharvest Quality of Kinnow Mandarin

The Kinnow mandarin (Citrus nobilis x Citrus deliciosa) was highly perishable citrus fruit, after harvest the quality of Kinnow fruits undergoes rapid changes due to the sharpen rate of ripening, respiration and transpiration. Edible coating formulation of chitosan (0.5%, 1%, and 1.5%), alginate (0.5%, 1%, and 1.5%), composite formulation of chitosan and alginate (0.5% chitosan+0.5% alginate & 1% chitosan+0.5% alginate) were evaluated in relation to enhancing and improving shelf life and postharvest quality of Kinnow respectively. Kinnow fruit shelf life efficiency was evaluated on the basis of postharvest quality parameters like weight loss percent, firmness, pH, total soluble solids, total acidity and ascorbic acid from 6th to 24th day during incubation at ambient room temperature (20-25°C). The results signifies that the Kinnow fruit coated with alginate 1% have higher shelf life efficiency up to 24 days; however chitosan 1% coated fruits shown to have higher ascorbic acid retention as compared to untreated Kinnow fruits. The principal component analysis of different quality parameters for studied treatment shows 65.7 % variation in component 1 and 16.6% variation in component 2. PCA plot elucidate that coated fruit samples were high positive values and completely different from untreated samples.

Productivity and water use efficiency of kinnow mandarin (citrus reticulate blanco) as influenced by drip trickle irrigation and hydrogel

An experiment was conducted to find out the effect of drip trickle irrigation and hydrogel with black polyethylene mulch on productivity and water use efficiency of Kinnow mandarin. The two years pooled data revealed that highest available nitrogen, phosphorus and potassium (244, 20 and 164 kgha-1), porosity and maximum water holding capacity (34.5 and 40.9 %) and percent increase height, spread and canopy volume (13.6, 14.8 and 44.5 %), respectively, were obtained with the application of 3 days drip trickle irrigation and 90 g hydrogel with black polyethylene mulch materials of tree. The drip trickle irrigation and hydrogel with black polyethylene mulch produced a significantly (p=0.05) maximum improve in soil moisture content over control treatment. The 3 days drip trickle irrigation and 90 g hydrogel with mulch showed highest fruit yield (9404.7 kg ha-1), length (6.5 cm), weight (116.5 g) and quality of fruit volume (113.9 cc), Juice content (54.1 %) and TSS (13.3 0Brix). The specific gravity and titratable acidity showed reverse trend. The water use efficiency and benefit cost ratio were better in 3 days drip trickle irrigation and 90 g hydrogel with mulch materials of tree.