Effective Pollination Period and Parentage Effect on Pollen Tube Growth in Apple.

Stefan Roeder,Sara Serra,Stefano Musacchi

doi:10.3390/plants10081618

Abstract

Flower receptivity is a limiting factor for the fertilization of several tree fruit. The effective pollination period (EPP) can be used to determine flower longevity and identify limiting factors by assessing stigmatic receptivity, pollen tube growth rate, and ovule longevity. EPPs were determined for three apple cultivars under natural field conditions in Washington State in 2019 and 2020. In addition, a greenhouse study, performed under semi-controlled conditions, evaluated the influence of six maternal parents on the pollen tube growth performance of six pollen sources. The duration of the stigmatic receptivity ranged from 6.3 to 8.1 days, depending on the cultivar and year—pollen tubes required between 5.5 and 7.0 days from the stigma to reach the ovules. Ovule longevity of non-pollinated flowers varied between 8.2 and 11.3 days. Combinations of these factors resulted in EPPs ranging from 3.0 days for ‘Rubinstar’ to 5.6 days for ‘Olsentwo Gala’ in the present experimental conditions. The greenhouse study revealed that parentage affected pollen tube growth performance. Importantly, a significant interaction between maternal and paternal factors indicated that the performance of different pollen sources depended on the maternal parent and that general recommendations on pollination need to account for the maternal parent.

Highlights

Pollination and fertilization are two key processes that impact fruit set and quality of apple (Malus domestica Borkh.) [1,2,3]
Self-incompatibility is caused by a genetic GSI system, which is exhibited in sweet cherry (Prunus avium L.), and pear (Pyrus communis L.) [5] and controlled by multi-allelic genes on a single S-locus [6]
Previous reports investigating the pollen tube growth performance of some crabapple cultivars at different temperatures have already indicated that performance depends on both maternal and paternal effects [8]

Summary

Introduction

Pollination and fertilization are two key processes that impact fruit set and quality of apple (Malus domestica Borkh.) [1,2,3]. Several plant, pollinator, and environmental factors can act alone or in combination to limit fruit set by reducing pollination and fertilization success during the flowering period. Most apple cultivars are self-incompatible and require cross-pollination with genetic compatible and viable pollen to fertilize the ovules [5]. Sufficient cross-pollination with compatible pollen is a key requirement for fertilization [5]. Previous reports investigating the pollen tube growth performance of some crabapple cultivars at different temperatures have already indicated that performance depends on both maternal and paternal effects [8]. Later reports have further highlighted the importance of selecting suitable pollinizers for effective pollen tube growth under natural conditions [9]

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Conclusion