Rab Nawaz

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.

Climate change has not only exacerbated abiotic stress, but has also rendered external conditions more feasible for pests to spread and infest citrus fruit. Citrus leafminer (Phyllocnistis citrella) is a potential pest that directly feeds the newly sprouted leaves and twigs of all three spring, summer and autumn flushes. Increasing temperatures in spring and autumn, leafminer accrued more heat units or developmental degree days to accelerate the biological stages of its life-cycle, thereby increasing the pressure of infestation. Present work was conducted at three different environmental conditions in Sargodha, Toba Tek Singh (TTS) and Vehari districts of the Punjab province, Pakistan; all three experimental sites were located in different agro-ecological zones. More infestation was recorded in all three flushes at TTS and Vehari than in Sargodha. Overall, more damage was observed due to higher temperatures in TTS and Vehari than in Sargodha. After May–June heat stress, spontaneous vegetative growth continued from July to November, produced newly spouted tender leaves for feeding the leafminer larvae, and was seen more in TTS and Vehari. Leafminer larva prefers to enter young and tender leaves with a maximum entrance in leaves up to 1 cm² in size while observing no entrance above 3 cm² of leaf size. Physiological response of leaves primarily attributed to chlorophyll and carotenoid contents, both of which were recorded lower in the mined leaves, thereby reducing leaf photosynthetic activity. Similarly, lower levels of polyphenols and antioxidant activity were also recorded in the mined leaves. The on-tree age of mined leaves of three vegetative flushes of Kinnow plant was also less counted than non-mined leaves. Climate change has affected vegetative phenology and become feasible for pests due to extemporaneous leaf growth, particularly leafminer, and eventually causes economic loss by supplying low carbohydrates either to hanging fruits or next-season crops.

Background Kinnow orchards were selected in different ecological zones in districts Sargodha, Toba Tek Singh (TTS) and Vehari of the Punjab province, Pakistan. Three biological replicates in block form were applied by using analysis of variance techniques to assess varying agrometeorological indices impact on fruit color‐development and peel composition. Results Fruit samples were randomly collected on each month's end starting from August up to February. Chromameter was used for measuring coloring parameters and its values a*, b*, C* and L* were increased from August till February with a rapid elevation started at color‐break stage, while hue angle (h*) rotated from 120⁰ to 60⁰ of portraying green to yellow shade. An increasing level of chlorophyll contents were noted in August till color‐break at the end of October and then diminished afterwards. Whereas, carotenoids increased rapidly upon yellow tinting peel of Kinnow fruits till fully attained deep orange color at the end of February. Ascorbic acid and total phenolic contents (TPC) showed a decreasing trend whereas anthocyanins and antioxidant activity were increased from August to February, with unchanged flavonoids and flavonols level. Fruit firmness was gradually reduced till color‐break with rapid reduction noted subsequently. Maturity index represented internal ripening directly increased with color‐development. Conclusion Color development has directly influenced on maturity index and both were increased rapidly after color‐break to afterwards. More color development with rapid reduction in chlorophyll, ascorbic acid and TPC level were seen in warm districts namely TTS and Vehari after color‐break stage due to accumulating more agrometeorological indices.

Color development in ‘Feutrell’s early’ fruit was used to determine the time of harvest, when color changes from dark green to fully orange take place during season of peak maturity. Ten fruits from each replication were harvested on visual observation of their skin color, and were subsequently made ready for biochemical analysis of color determination by using Chromameter. Dark green color to light green fruits were ordered in (1–5) order whereas light orange to deep orange were given (6–10) numbering orders. Triplicate determinations of all samples were used for all the laboratory analysis. Fruit-peel chlorophylls were recorded as more in fruits having color dark green which on the other hand, had gradually decreased in orange colored fruits. The carotenoids, however, have showed the opposite trend. Titratable acidity and ascorbic acid were observed as lessened in green coloration fruits, while the pH, total soluble solids (TSS), total dissolved salts (TDS), and sugar values showed an increasing tendency in orange-colored fruits. Values of reducing sugars and antioxidants were noted as decreased in orange colored fruits while anthocyanins were increased in that produce. Nonetheless, phenolic contents, flavonoids and flavonols were not significantly affected in coloration. Dark green to light green fruits possessed more titratable acidity, ascorbic acid, antioxidant as well as phenolic contents, and were more useful from nutritional point of view. Light orange to deep orange colored fruits had more sweetness, palatability, and tastiness to appeal increased consumer’s acceptance.