Morpho-physiological characterization of second generation colchiploids in sweet orange (Citrus sinensis (L.) Osbeck) cv. Mosambi

Induction of tetraploidy in citrus is commonly meant for the development of triploid seedless cultivars as well as resistance against abiotic and biotic stresses. Three-year-old, 20 second-generation colchicine treated (0.05, 0.10, 0.15 and 0.20%) plants (colchiploids), established from the putative tetraploid branches of the first generation colchiploids of sweet orange (Citrus sinensis (L.) Osbeck) cv. Mosambi vegetatively propagated on Jatti khatti rootstock, along with their wild (parent) type, were characterized based on morphological and physiological traits. Plant height and canopy volume were reduced, but stem girth, nodes per shoot and bark: wood increased in the majority of the second-generation colchiploids related to the wild type. Colchiploids also possessed improved flower characteristics in terms of length and width. The stomatal dimensions increased, but stomatal concentration reduced in all the colchiploids. Colchicine treatment also caused significant variations in leaf gas exchange parameters, including photosynthetic rate, intercellular CO2 concentration, leaf net transpiration rates, stomatal conductance, and intrinsic water use efficiency in colchiploids affecting their photosynthetic activities. The solid tetraploids identified on the basis of morpho-physiological characterization can be used in future breeding programmes for the development of triploid seedless citrus cultivars or can be used for the mitigation of biotic and abiotic stresses.