Edited, adapted and commented on by Carlos J. Tapia T. Technical Director for Avium and Content Director for SmartCherry 2020.
Only a few days to go before the arrival of one of the most highly anticipated phenologic states among fruit producers, especially those who are involved in cherry tree production and development in our country’s many climate zones. In it, one can see in a graphic manner the result of all efforts undergone during the previous season’s post-harvest period. Even though the orchard’s productive potential will be observable in detail after 15 to 20 days have passed since full bloom (DAFB), as that’s when the fruit is defined for most varieties. However, in accordance to the latest research carried out by Avium in cultivars. Regina and Kordia this potential might be more certainly apparent 25 to 30 days after full bloom.
From this vantage point, not only will the flower be in view, we will also be able to assess in situ any possible frost damage, even before the flower opens, and also any malformation in the flower that might eventually lead to double fruits that must be discarded at harvest.
The DOUBLE FRUIT, which occurs by the formation of a double pistil at the moment of flower differentiation, is a problem that can seriously affect a production’s profitability and has seen an uptick in orchards located in warmer areas, and thus only increased on account of global warming.
Cherries have traditionally been produced in colder climates, but with the commercial goal of harvesting early – when markets offer better prices – several cherry producers have moved to warmer regions around the world (Micke et al., 1983; Southwick et al., 1991; García-Montiel et al., 2010; Li et al., 2010; Beppu and Kataoka, 2011; James and Measham, 2011).
However, this new situation in production has had consequences for the delivery of a high-standard fruit, and has led to the formation of double fruits, malformed flowers containing pistils as appendages in lieu of anthers (Philp, 1933; Beppu and Kataoka, 1999; Roversi, 2001; Martin, 2008) and fruits with deep sutures, as the carpel’s margins have not fused with the base and remain open (Southwick et al., 1991; Engin et al., 2009).
Formation of double pistils and double fruits.
A plethora of research suggests that high summer temperatures during flower bud differentiation can be to blame for the formation of double pistils, which will result in double fruits the following year (Micke et al., 1983). The formation of double pistils is caused by an abnormal differentiation in the pistil primordium (Philp,1933; Tucker, 1934).
The induction of flower buds and the initial stages of bud development may occur before the harvest (Tufts and Morrow, 1925; Westwood, 1993), and present continuous development for the rest of the season (Guimond et al., 1998). In cherries, the interval between initial flower formation and final reproductive development can vary from 86 to 112 days, depending on the climate and the crop (Faust, 1989). The induction of flower buds takes place via a biochemical signal to change from vegetative state to reproductive state (Faust, 1989), as a result of the balance in gibberellins, auxins, cytokinins and ethylene (Westwood, 1993). Under natural conditions, floral initiation in cherries begins in July (northern hemisphere) and sepals, petals and pistils are sequentially differentiated (Guimond et al., 1998; Engin and Ünal, 2007). Temperatures above 30ºC are critical for the formation of double pistils (Beppu and Kataoka, 1999). High temperatures cause double pistils more severely in buds with differentiated sepals and petal primordia when compared to buds in the early stages of differentiation for flower buds or buds that have already-formed primordia for stamens and pistils (Beppu and Kataoka, 2011), thus suggesting that buds are more sensitive to the induction of an abnormal flower primordium in a transitional differentiation state from sepal to petal. Considerable crop variation for double fruit percentage has been reported between years (Tucker, 1934, 1935; Micke et al., 1983; Beppu, 2000; Engin and Ünal, 2008; Roversi et al., 2008; García-Montiel et al., 2010). Coastal areas that are exposed to cold breezes tend to have fewer double fruits than regions without coastal influence (Southwick et al., 1991).
Double pistil
Flower malformation caused by high temperatures
Variations in duplications within crops
In areas with warm summers, the risk of producing double fruits is high (which consequently reduces marketable fruit) and can limit cherry planting. Manual thinning can be used to selectively remove double fruits, but in some orchards costs are considerable (Patten et al., 1989). Several strategies have been put into play to modify the orchard’s climate and minimize duplication in cherries. These discoveries suggest that crop susceptibility to double fruit formation has a strong genetic influence. Therefore, it might be possible to set up new crops with low double fruit occurrence.
