Physiological studies in pomegranate varieties differing in fruit crack incidence
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Date
2021
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Punjab Agricultural University, Ludhiana
Abstract
Fruit cracking is a major physiological malady of pomegranate (Punica granatum L.) that limits its productivity. The initiation of fruit cracking was observed initially in July and it continued till September. Among varieties, maximum cracking was observed in variety Jodhpur which was significantly higher than the other varieties, whereas it was minimum (Zero) in Kandhari at the three stages of study. It was observed that the fruits cracked in two patterns, viz diagonal and longitudinal. Cracking that starts from stylar end of fruit and with time extends to equatorial zone was regarded as longitudinal type, whereas the cracking that initiates between the two ends of fruit was diagonal type. Maximum diagonal cracking and longitudinal cracking was observed in variety Ganesh and Jodhpur, respectively. Again no diagonal as well as longitudinal cracking was recorded in Kandhari variety of
pomegranate. During fruit growth, fruit weight, size increased significantly at each stage in all the varieties. The fruit juice quality parameters, viz., the juice content, TSS and juice anthocyanin increased significantly at each stage, whereas titratable acidity, juice antioxidants decreased significantly from July to September. The peel characteristics viz., the peel thickness, anthocyanins, cellulase and polygalactouranse activity increased significantly however antioxidants, phenols, peel moisture content continued declining till fruit maturity. Peel moisture percent and peel percent were high in Jodhpur and significantly low in Kandhari. Antioxidant activity in leaf and juice and phenols and peel thickness were higher in Kandhari, whereas activity of polygalactouranase and cellulase were higher in the peel of Jodhpur. The nitrogen, phosphorus and potassium were analyzed in leaf, peel and aril and low level of potassium was observed in Jodhpur in all the tissues, however nitrogen and phosphorus were higher in Jodhpur. There was a significant positive correlation of fruit cracking with physical parameters of the fruits viz., fruit length, breadth, size, weight, aril percent, peel percent, aril/peel ratio; leaf parameters, viz., phosphorus; fruit juice quality parameters, viz., total soluble solids, juice per cent, phosphorus; and peel characteristics viz., peel moisture percent, phosphorus, cellulase and polygalacturonase activity. A negative significant correlation was established between fruit cracking and leaf parameters, viz., antioxidants, proline content, nitrogen and potassium; fruit juice quality parameters, viz., acidity, anthocyanin, potassium and nitrogen; and peel characteristics viz., anthocyanin, peel thickness, total phenols, potassium and nitrogen. SEM examined the peel of Jodhpur and kandhari variety that reveals, the uniform cellular arrangement with no intercellular spaces and rounded cells in peel surface of Kandhari variety make it resistant to cracking while irregular cell arrangement with intercellular spaces and transversely longitudinal cells leads to high cracking in Jodhpur.
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Gurleen Kaur (2021). Physiological studies in pomegranate varieties differing in fruit crack incidence (Unpublished M.Sc. thesis). Punjab Agricultural University, Ludhiana, Punjab, India.