Climatic and physiological parameters related to the progress and prediction of apple sunburn damage in a neotropical climate

Daño de sol y potencial hídrico de tallo y tejidos del fruto de manzanas (Malus domestica) ‘Brasil Gala’, ‘Cripps Pink’ y ‘Granny Smith’

“…Recent studies examining different irrigation regimes and net types in apple cultivation establish the importance of crop water status on fruit quality (20) . Boini and others (18) , in line with Severino and others (2) , conclude that sun damage is more related to water status than to radiation. On the other hand, the use of nets, whether aiming to reduce sun damage, hail damage or for phytosanitary protection, presents adverse effects on color picking in two-tone cultivars (7) and, depending on the level of shading, it could affect floral induction and the vegetative/reproductive ratio (21) .…”

“…According to FAO (1) , the most common discarding defects in packing lines are due to physiological disorders and mechanical damage to the fruit. In "Granny Smith", physiological disorders in the field and during cold storage have exceeded values of 50% (2) . This damage is visible during fruit ripening and storage and depends on several preharvest factors.…”

“…In neotropical climate conditions, sun damage is frequent. The climatic variability of the region (4) and its connection with the damage determine significant differences between years, both in magnitude and in the timing of damage development (2) . This physiological disorder is a major cause of fruit quality loss in apples before harvest (2) , and the study of management measures for its mitigation is recent (5) .…”

“…Physiological disorders in apples, and, especially, sun damage, have been related to high radiation and temperature values (6)(7) and recently to the water status of the fruit and tree tissues (2) (8)(9) . The effect of individual factors and their existing interrelationships determine a high degree of complexity in the conditions that trigger physiological disorders.…”

“…It has also been noted that the effect of climate factors on sunburn appearance depends on fruitsize. Racsko and Schrader (6) report the onset of damage when the fruits reach 45 mm in diameter (7 or 8 weeks after full bloom), and local studies establish the onset of damage at six weeks after full bloom (2) .…”