Endosperm responses to irradiated pollen in apples

Area of Science:

• Plant Cytogenetics
• Radiation Biology
• Horticultural Science

Background:

• Understanding the effects of irradiation on plant reproductive processes is crucial for breeding and genetic studies.
• Pollen quality and its subsequent effects on seed and fruit development are key factors in fruit crop propagation.

Purpose of the Study:

• To investigate the cytological consequences of gamma irradiation on apple (Malus × domestica) pollen.
• To assess the impact of varying irradiation doses on embryo and endosperm development, fruit and seed set, and nuclear behavior within embryo sacs.

Main Methods:

• Pollen from Malus × domestica was subjected to gamma irradiation at doses of 50 and 100 krad.
• The effects on fruit and seed set were quantified.
• Embryo sacs were analyzed for nuclear number, morphology, presence of embryos, and various nuclear abnormalities, including polyploidy, chromosomal bridges, and mitotic disruption.

Main Results:

• Increasing pollen irradiation doses led to reduced fruit and seed set.
• Significant nuclear abnormalities were observed in embryo sacs, including polyploid restitution nuclei, chromosomal bridges, and disrupted mitotic synchrony.
• A high dose (100 krad) induced an 'all-or-nothing' effect, resulting in either aborted embryos/endosperms or relatively normal development. Callus derived from irradiated pollen showed altered genome sizes.

Conclusions:

• Gamma irradiation of pollen induces dose-dependent cytological abnormalities in apple embryo sacs, affecting embryonic and endospermic development.
• The study highlights the sensitivity of reproductive processes in Malus × domestica to radiation, with implications for genetic manipulation and breeding strategies.