The influence of the progamic phase for fruiting in the apple tree

Abstract

Final fruit production is the result of a number of processes, over which several environmental circumstances interact. But it is often difficult to disentangle the part played by each of these factors in the final crop. The aim of this work is to evaluate the influence of the progamic phase for fruiting in the apple tree. For this purpose we track back the process that goes from flower to fruit, identifying the inflection points where the final crop is reduced. We evaluate early versus late fruit development, pollination versus non-pollination, and the effect of the progamic phase that goes from pollination to fertilization. From flowers to fruits 15 weeks elapsed, but the final fruit set settled 8 weeks after flowering, and the main flower-fruit drop occurred 3-4 weeks after flowering. Differences between dropped fruits and those that remained in the tree emerged earlier, and the onset of fruiting started 7 days after pollination. This time was coincident with the time lapse of the progamic phase. These results show that fruiting gets established well ahead of cropping, but also that the progamic phase is the main determinant of the final fruit set in apple trees.

Fruiting pattern in longan, Dimocarpus longan: from pollination to aril development

“…A similar situation has been observed in apple (Losada & Herrero, ), pear (Herrero & Gascon, ), cherimoya (Lora et al , ) or avocado (Alcaraz et al , ). But, in longan, fruiting does not occur as an immediate response to pollen tube penetration to the ovule, as it may occur in apple (Losada & Herrero, ), but is delayed. This may be related to the fact that, while in apple the fruit is the developing receptacle, in longan the fruit is formed by the aril.…”

“…In other unrelated species adapted to subtropical climates, such as avocado and cherimoya, the pollen tube reached the ovary in 1 day (Alcaraz et al , ; Lora et al , ). Conversely, longer periods have been observed in temperate fruit tree crops such as apple, where the pollen tube reached the ovule 1 week after pollination (Losada & Herrero, ), or even longer in peach (Herrero & Arbeloa, ), plum (Thompson & Liu, ) or cork oak trees (Boavida et al , ). In any case, compared to gymnosperms, a fast pollen tube growth rate resulting in a short progamic phase has been considered a key innovation of angiosperms (Williams, ) although environmental factors, mainly temperature, play a major part in regulating pollen tube kinetics (Sanzol & Herrero, ; Hedhly et al , , ).…”

“…The fruiting pattern in fruit tree species in which the edible part is a developed pericarp or receptacle is well characterised (Westwood, ). The progamic phase, which goes from pollination to fertilisation (Linskens, ; De Graaf et al , ), has proven to play a major role on the establishment of fruit set in most fruit trees such as apricots (Rodrigo & Herrero, ), cherries (Hedhly et al , ), apples (Losada & Herrero, ) or cherimoyas (Lora et al , ). Along the progamic phase, important successive events, such as pollen germination, pollen tube growth in the style and penetration into ovule, take place (Rost et al , ; Linskens, ; Herrero, ; De Graaf et al , ; Williams, ; Mauseth, ).…”

Effect of Pollination by the Osmia Bicornis (syn. O. rufa) Bee on Fruit Set, Seed Set and Yield in Three Apple Cultivars

“…O. rufa) and those exposed to open pollination was similar, whereas very few fruitlets developed in the selfpollination group. Losada & Herrero (2013), Garratt et al (2014b) and Jahed & Hirst (2018), indicate that with handpollination used to ensure the selection of an appropriate pollinizer, the proportion of fruit set to the total number of flowers ranges from 23% to 84%. Fruit setting in open pollination depends on native wild bees' presence, their abundance, species richness, functional group diversity or the use of managed pollinators i.e., honeybee accompanied by bumblebees and mason bees (Brittain et al, 2013;Mallinger & Gratton, 2015;Blitzer et al, 2016;Földesi et al, 2016;Sapir et al, 2017).…”

“…On the other hand, Ladurner et al (2004) demonstrated that fruit set determined on the basis of the number of fruitlets before June fruitlet drop, which is 22% and 31% depending on the season, is considered sufficient to obtain high commercial yields. However, when there is a shortage of pollinators in orchards, open pollination of flowers yields up to 20% of fruit set when the measurement is performed during the first fruitlet thinning, or 15% when the measurement pertains to ripe fruit (Losada & Herrero, 2013;Garratt et al, 2014a;2016). Regardless of the use of the honeybee as a support for little abundant wild pollinators, 11-18% of fruitlets remain on apple trees from three to four weeks after petal drop (Mallinger & Gratton, 2015).…”