Creasing in sweet orange: role of cobalt sulfate

Creasing is known as a physiological disorder in sweet oranges. In the current study cobalt sulfate (CoSO₄) an ethylene inhibitor with different concentrations such as 0,125, 250 and 500 mg L^‑1 was sprayed at various stages of the fruit development. These stages were; fruit set (FS), golf ball (GB) or color break (CB) to alleviate creasing as well as to promote textural properties of sweet orange fruit in ‘Washington Navel’ and ‘Lane Late’. At fruit ripening 35-fruit/replication were collected randomly from tree to check the creasing and fruit rind characteristics. Creasing was significantly reduced, when higher concentration of CoSO₄ (500 mg L^‑1) was sprayed at GB (29.29 and 34.29%) stage than control (51.34 and 57.14%) in ‘Washington Navel’ sweet orange during 2011 and 2012, while, similar findings were noticed in ‘Lane Late’. Similarly, FS stage was more effective stage for CoSO₄ (500 mg L^‑1) spray application which improved the fruit rind strength (47.72 and 64.05 N) in both cultivars, respectively. However, the rind hardness (25.75 N) was higher by spraying at CB in ‘Lane Late’. It is concluded from the current study that the exogenous spray applications of CoSO₄ significantly mitigate the incidence of creasing and improve textural properties of ‘Washington Navel’ and ‘Lane Late’ fruit.