Effects of ambient temperatures on floral initiation in Australian mango (Mangifera indica L.) selections

Abstract This study aimed to find the relationship between ambient temperatures and flower initiation in six mango cultivars grown in the Northern Territory, Australia. Shoot length and type (floral/vegetative) were measured on a weekly or fortnightly basis for six months on trees that were tip-pruned during the growing season. Generalised linear regression was used to model the relationship between shoot ontogenesis (i.e., floral/vegetative) in response to ambient temperature. The minimum and maximum daily temperatures were assessed for their impact on shoot type. Bud length and temperature integration period at induction were assessed to determine their effect on floral response. Low minimum temperatures were required for flower initiation, but low maximum temperatures were a better descriptor of floral response. Some terminals that did not flower early in the trial, but instead grew vegetatively, produced a second growth that was floral shortly after. The period between reaching the maximum vegetative flush length and visible floral growth ranged from ten to 63 days depending upon the cultivar. Floral response to temperature varied among cultivars, with ‘Calypso®’, ‘Kensington Pride’, and ‘NMBP 1201’ having the greatest tolerance to high temperatures, followed by ‘Honey Gold’, ‘NMBP 1243’, and ‘NMBP 4069’. This work suggests that some cultivars are better adapted to flowering during warmer conditions, which would be an advantage under projected climate change. Extending our understanding of mango reproductive biology to describe the climatic limits for fruit set and crop development will provide more efficient tools for exploring the broader genetic resource and improve management strategies in order to adapt this valuable crop to future growing conditions.