Delayed self-incompatibility causes morphological alterations and crop reduction in 'Ataulfo' mango (Mangifera indica L.)

Poor fruit set, premature fruit drop and excessive nubbin production are causing crop reduction in 'Ataulfo' mango orchards in southeastern Mexico. Fruit set was measured in self- and cross-pollinated Ataulfo mangoes in the field using houseflies (Musca domestica L.) as pollinators and pollen from donor varieties. Pollen tube kinesis was monitored from pollen germination to arrival at the ovule sac following manual self- and cross-pollination. Cross-pollinated inflorescences produced more fruit set than selfed ones. 'Joe Welch' and 'Criollo' varieties were the most efficient pollen donors tested. Seedling germination in Ataulfo mangoes averaged 3% during 2 consecutive years. Pollen tube development in vivo revealed positive contact with the micropyle and normal zygote formation in cross-pollinated flowers. Selfed pollen tubes entered the embryo sac but produced atrophied embryos and aborted or malformed fruit. Seedlessness was not observed although selfed fruitlets contained malformed or necrotic embryos, suggesting delayed self-incompatibility.