Long term performance of mango varieties on five polyembryonic rootstocks under subtropical conditions: effect on vigour, yield, fruit quality and nutrient acquisition

Abstract

An experiment was conducted to test the hypothesis that uniformity of tree growth, fruit quality and scion physiology are influenced by polyembryonic rootstock, and also deferential vigour behaviour of scion varieties can influence rootstock selection. Hence, the scion growth, fruit yield and quality, leaf gas exchange traits and nutrient content of three mango varieties (two moderate vigorous and one dwarf) grafted on five polyembryonic rootstocks were studied during 2015-2019. Rootstocks ‘K-3’ and ‘Olour’ proved vigorous for scion variety ‘Pusa Arunima’, and ‘Kurakkan’ and ‘Olour’ produced robust trees of ‘Pusa Surya. Rootstocks ‘K-2’ and “K-5’ inhibited vigour in both scion varieties ‘Pusa Arunima’ and ‘Pusa Surya’. For ‘Amrapali’ ‘Kurakkan’ induced more tree height (2.95 m) and canopy volume (87.29 m3), while remaining rootstocks were found to be an equal performer. Though inconsistency in fruiting density was observed, overall, K-2 rootstock has induced fruiting density in ‘Pusa Arunima’ (1.78 fruits m3 canopy volume-1) and ‘Pusa Surya’ (4.36 fruits m3 canopy volume-1), while it was K-5 in case of ‘Amrapali’ (4.10 fruits m3 canopy volume-1). Inconsistent results were also obtained for fruit yield due to rootstocks in all three varieties, in general, ‘Kurakkan’, ‘Olour’ and ‘K-3’ enhanced yield tree-1 in all varieties. Differences in fruit weight, stone weight, pulp stone ratio, total soluble solids (TSS) and acidity was mainly influenced by the mango variety. In two of the three mango varieties, the rootstocks 'K-5' and 'Kurakkan' stimulated higher Vitamin C content. In 'Pusa Arunima' and 'Pusa Surya', 'K-2' stimulated lower intercellular CO2 (Ci), transpiration rate (E) and N, P, K and Ca contents, while in 'Amparali', it stimulated lower photosynthetic rate (A) and N, K and Ca content. On the other hand, leaf P and K also exhibited a higher deviation from the optimum percentage index, while Ca showed lower than optimum in all rootstock scion combinations. Our results indicate that 'K-2' and 'K-5' reduce vertical and lateral growth of all three mango varieties, 'K-3' and 'Kurakkan' rootstocks reduce fruit density, 'K-2' reduces Ci, E, A and leaf nutrient contents, while rootstocks were not capable of modifying fruit quality, except for vitamin C content. Based on results, it could be said that rootstock impacted the scion vigour and fruit yield, but minimal alterations in fruit quality. It could also be inferred that K-2 rootstock imparted dwarfism in ‘Pusa Arunima’ and ‘Pusa Surya’ but failed to modify tree growth in dwarf variety ‘Amrapali’.