Impact of varying agrometeorological indices on peel color and composition of Kinnow fruit (Citrus nobilis Lour x Citrus deliciosa Tenora) grown at different ecological zones

Abstract

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 120° to 60° 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 content and total phenolic content (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. © 2020 Society of Chemical Industry

Environmental variables influence the developmental stages of the citrus leafminer, infestation level and mined leaves physiological response of Kinnow mandarin

“…Leafminer's individual developmental stages DDs were multiplied with each month's average relative humidity (RHa) for the calculation of HYTUs and expressed as °C day% 30 , 46 , 47 . …”

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

“…Citrus growth ceases below 13 °C 92 by keeping this temperature as threshold when computing growing degree days (GDDs) and other heat units of subtracting base temperature from mean daily temperature 10 , 93 . Vehari region has higher mean daily temperature, followed by TTS and lower was recorded in Sargodha 15 , accordingly GDDs, CHU, mCHU, p Heat unit and n Heat unit were counted in all three districts with leading counts in Vehari and lesser in Sargodha 6 , 12 . More GDDs were counted of citrus fruit in the warm areas of Australia 92 to justify this work of recording additional GDDs at warm district Vehari along with other temperature based heat units such as CHU, mCHU, pHu, nHu.…”

“…However both RH and temperature different regimes decide the extent of diseases, pests and fruit quality of citrus 15 by recording more pest damage in dry conditions and diseases infestation in warm-humid areas to affect fruit quality 11 which has justified the present work of showing more unevenness in fruiting patterns in warm conditions due to more fluctuation in climate variables. Climate variables also influence on citrus external quality features based on color development 6 as well as internal changes in the levels of juice contents, acidity, sugars and polyphenols 12 .…”

“…Climate variables of a particular area decide cropping system as well as agrometeorological/ thermal indices and energy use efficiencies 1 , 2 by showing a fluctuating trend location-wise 3 to count different levels in unalike crop in a specified region 4 . As climate variables of an agro-ecological zones depicts temperature regimes, relative humidity, sunshine duration, solar radiation intensity, precipitation and wind velocity 5 , 6 henceforth, are used to compute thermal indices 7 like growing degree days (GDDs), crop/ citrus heat unit (CHU), modified citrus heat unit (mCHU), hydrothermal units (HYTUs), photothermal index (PTI), photo thermal unit (PTU) and helio thermal unit (HTU) 4 , 8 , 9 . Thermal indices decide citrus fruit phenophases, peel coloration, physico-chemical quality, abiotic & biotic stress, maturity indices as well as grading volume 6 , 10 – 12 , while indirectly fruit-load and net-return 13 , fruit cosmetic outlook 14 , harvesting and marketing 15 as well as consumers penchant 16 .…”

“…As climate variables of an agro-ecological zones depicts temperature regimes, relative humidity, sunshine duration, solar radiation intensity, precipitation and wind velocity 5 , 6 henceforth, are used to compute thermal indices 7 like growing degree days (GDDs), crop/ citrus heat unit (CHU), modified citrus heat unit (mCHU), hydrothermal units (HYTUs), photothermal index (PTI), photo thermal unit (PTU) and helio thermal unit (HTU) 4 , 8 , 9 . Thermal indices decide citrus fruit phenophases, peel coloration, physico-chemical quality, abiotic & biotic stress, maturity indices as well as grading volume 6 , 10 – 12 , while indirectly fruit-load and net-return 13 , fruit cosmetic outlook 14 , harvesting and marketing 15 as well as consumers penchant 16 . More extremes in climate variables are seen in global warming era due to rising temperatures 17 which have increased abiotic and biotic stress 18 while escalating pests pressure 19 in temperate 20 and subtropical zones 21 and showing more unevenness in changing weather conditions 22 to negatively affecting perennial crops, including citrus crop as their slow acclimatization 23 .…”