Naphthaleneacetic acid impairs ovule fertilization and early embryo development in loquat (Eriobotrya japonica Lindl.)

- NAA inhibited pollen grain germination and halted pollen tube growth in loquat.
- Mature but not fertilized ovule and newly fertilized ovule were also sensitive to NAA.
- The effects have been shown both in vivo and in vitro conditions.
- NAA prevents ovule fertilization and fruit set in loquat.
- NAA thinner effect depends on the phenological growth stage at treatment.

By applying 20 mg l−1 of α-naphthaleneacetic acid (NAA) potassium salt to 'Algerie' loquat tree flowers prior to or at anthesis pollen grain germination was signficantly inhibited and pollen tube growth was halted, both in vivo and in vitro conditions, thus ovule fertilization and fruit set were prevented. These effects of NAA are direct since stigmas were not damaged or dried off by the treatment. Mature but not fertilized ovule and newly fertilized ovule were also sensitive to the gametocidal action of the NAA, whereas new developing seeds did not, both in vivo and in vitro conditions as well. According to our results, NAA acts as a chemical thinner of loquat by preventing ovule fertilization and fruit set and by causing ovule/embryo abortion, depending on the phenological growth stage at treatment.