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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 cm 2 in size while observing no entrance above 3 cm 2 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.

We have established an efficient protocol for in vitro callogenesis from leaf explants of Troyer citrange (Poncirus trifoliata x Citrus sinensis) and Feutrell's early (C. reticulata x C. sinensis) using modified MS medium enriched with varied concentrations of 2,4-Dichlorophenoxy acetic acid (2,4-D), Naphthalene acetic acid (NAA) and Benzylaminopurine (BAP). Indirect shoot organogenesis was also achieved from leaf derived calli on medium comprising varied concentrations of BAP, Kinetin (KN) and NAA. Best interaction for callus induction was observed by Troyer citrange with modified MS medium containing 0.5 mg L-1 2,4-D, 0.5 mg L-1 NAA and 0.5 mg L-1 BAP, which resulted in 99.66% of leaf segments producing calli within 16.33 days. Morphological differences were also noticed for calli texture and color with different concentrations of 2,4-D, NAA and BAP used. Compact and hard calli were noticed on MS medium with 0.1 mg L-1 NAA and 0.5 mg L-1 BAP however, medium including 1.0 mg L-1 2,4-D, 0.9 mg L-1 NAA and 0.5 mg L-1 BAP resulted in friable and smooth calli by both cultivars. Exuberant shoot regeneration response (65.33%) with an average of 6.2 shoots/calli was recorded on MS medium with 2 mg L-1 BAP and 0.5 mg L-1 NAA by Feutrell's early. Our findings are the pre-requisite for various biotechnological tools like mutation breeding, somaclonal variations, genetic transformation and somatic hybridization which may be helpful in citrus varietal improvement. [ABSTRACT FROM AUTHOR]

• More days were taken in Kinnow fruit during ripening phase at warm conditions as well as more agrometeorological indices were computed in fruit different phenophases. • Prior flowering, fruit-setting and cell division initiated with rapid fruit growth at warm districts of TTS and Vehari as compared to Sargodha. • Fruit peel thickness, size index, volume, diameter and weight were recorded as an increasing level in warm districts whereas fruit specific gravity and firmness were decreased in these districts during ripening process. • Timely color development, more fruit specific gravity and firmness were recorded at Sargodha due low fluctuation in climate variables had yielded exportable superior quality Kinnow fruit. • In climate change scenario, more fluctuating climatic variables were observed at warm conditions which adversely affected Kinnow fruit growth and development and also delayed in color development. Kinnow orchards of uniform age, planting density and vigor were selected in three different ecological zones situated in the districts of Sargodha, Toba Tek Singh (TTS) and Vehari of Pakistan. Climate change has adversely affected plants; particularly perennial fruits cultivated in tropical (banana, mango), subtropical (citrus, olive, grapes) and temperate (apple, apricot, plum) zones owing to their slow adaptability. In this context, the fluctuating effect of agrometeorological indices and energy-use efficiency on Kinnow mandarin's fruit growth and development was evaluated. Each experiment was performed in three biological replicates. Ten fruits were randomly collected at the end of each month (April-December) from a single plant to study fruit growth and development. Similarly, physical fruit parameters were recorded from August to February. More days were passed between fruit-setting till arrival of maturity at Vehari, whereas less number of days was counted in Sargodha. More growing degree days and photothermal index were calculated at Vehari during different phenophases of Kinnow fruit as compared to Sargodha. Hydrothermal units were more recorded in Sargodha than Vehari. More yields were obtained from TTS which had increased energy use efficiency than other two districts. Fruit cell division and cell enlargement stages were commenced afore and had finished earlier in Vehari district, followed by TTS. Fruit diameter, peel and pulp thickness as well as fresh weight were recorded in higher values at TTS and Vehari. Non-significant differences were seen in moisture percentage. More fruit size and shape indices were also recorded in TTS and Vehari. Fruit volume was measured larger at TTS, whereas fruit specific gravity was recorded higher at Sargodha from August to February. More intercellular space was seen in fruit samples collected from Vehari and TTS, which at maturity had reduced fruit firmness. Fruit color was recorded as green in samples from all three districts until the beginning of color-break in October. At the arrival of ripening phase in February, more values of color parameters a, b, C and L were enumerated at Vehari. Hue angle of fruit color was found to be at 1200, depicting green color that was rotated at 600 by portraying deep yellow or orange tinge on Kinnow mandarin. Climate variables have had a substantial effect on fruit growth and development phases as well as physical characteristics. Better physical quality and timely color development of Kinnow fruit was noted at Sargodha due to milder environmental conditions compared to TTS and Vehari. [ABSTRACT FROM AUTHOR]