ISHS Acta Horticulturae 814: XII EUCARPIA Symposium on Fruit Breeding and Genetics
REPRODUCTIVE BIOLOGY OF AVOCADO (PERSEA AMERICANA MILL.) IN SOUTHERN SPAIN |
| Authors: | M.L. Alcaraz, J.I. Hormaza |
| Keywords: | Hass, pollen germination, stigmatic receptivity, temperature, relative humidity |
| Abstract:
Spain is the only European country with a commercial production of avocados, mainly in the coasts of Málaga and Granada. Only a very small fraction of the flowers produced at anthesis in an avocado tree (less than 1%) are able to set fruits and the production is very dependent of the environmental conditions. Consequently, knowledge of avocado reproductive biology is important to increase yield and to design appropriate breeding programs in this species. Avocado is a tropical and subtropical fruit tree that shows protogynous dichogamy. Although the flowers are bisexual, each flower opens twice: first functionally as female (stigmas are receptive), then the flower closes and reopens the next day functionally as male (dehiscence of anthers). The different avocado cultivars are classified by their floral behaviour in two groups: A and B. In type A cultivars, the flowers open in the morning as females and in the afternoon of the following day as males whereas in type B cultivars, the flowers open in the afternoon as females and the following morning as males. The main objective of this work was to determine the changes in the effective pollination period (EPP) due to environmental factors, mainly temperature and relative humidity. Thus, we analyzed the progamic phase, from pollination to fertilization under the environmental conditions of Southern Spain: pollen deposition on the stigmas, pollen germination, pollen tube growth, and pollen tube penetration into the ovule. The response of pollen germination to temperature and humidity has also been evaluated for different genotypes both in vivo and in vitro. The results are discussed in terms of the implications of the environmental conditions on reproductive success and fruit set in avocado to elucidate the limiting factors in production of this species and to design appropriate crosses. | |
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