Reflective Groundcover Improves Fruit Skin Color in ‘Honeycrisp’ Apples Grown under Protective Netting

Abstract

In semiarid apple (Malus domestica) growing regions, high temperatures and excessive solar radiation can increase the risk of sunburn development. Protective netting is increasingly used as a cultural practice under these conditions to mitigate fruit sunburn losses. However, fruit skin color development can be negatively affected under protective nets due to the reduction in light availability. Reflective groundcovers have been previously reported to increase fruit color development, particularly in the inner parts of the tree canopy. Here, we compared two types of reflective groundcover: a woven polyethylene fabric and a film material with a grassed control without reflective material under a protective netting installation that reduced photosynthetically active radiation (PAR) by 17%. The experiment was conducted in a semiarid climate on a 5-year-old ‘Cameron Select Honeycrisp’ apple orchard near Quincy, WA. Light penetration into the canopy was measured with a PAR sensor. At harvest, fruit quality, yield, and size were assessed. The use of reflective groundcover between the rows significantly increased reflected PAR into the lower canopy. Moreover, reflective groundcovers significantly increased the amount of fruit with greater than 25% skin red color compared with the control. Reflective groundcover did not affect fruit weight, yield, and fruit number. The use of reflective groundcover under protective netting can increase light penetration into the canopy, thereby improving fruit skin red coloration in apple.

Combining the Use of Reflective Groundcovers and Aminoethoxyvinylglycine to Assess Effects on Skin Color, Preharvest Drop, and Quality of ‘Honeycrisp’ Apples in the Mid-Atlantic US

“…Horticultural practices, such as the use of reflective groundcovers, are used to enhance the tree canopy light environment [3,14]. The deployment of reflective groundcovers improves the capacity of apple trees to harness sunlight by reflecting the light that would otherwise be absorbed at the ground surface, back into the canopy [2,4,15]. This amplifies the cumulative light reaching the apple fruit surface, particularly fruit located in the lower third and inner part of the canopy [16].…”

“…This amplifies the cumulative light reaching the apple fruit surface, particularly fruit located in the lower third and inner part of the canopy [16]. The deployment of groundcovers around 4 weeks before the anticipated harvest has been reported to increase red skin coloration in apples [3,4,11,12,15,[17][18][19]. Despite its proven ability to enhance apple coloration, research on reflective groundcovers has not been widely conducted under the environmental conditions of the US mid-Atlantic region.…”

The Expression of Key Ethylene and Anthocyanin Biosynthetic Genes of ‘Honeycrisp’ Apples Subjected to the Combined Use of Reflective Groundcovers and Aminoethoxyvinylglycine in the Mid-Atlantic US

“…Anthocyanin concentration has been shown to be significantly impacted by light [ 20 , 21 , 22 ], as well as by ethylene production [ 23 , 24 , 25 , 26 , 27 ], among other factors. In terms of light, the reflective groundcover Extenday has been shown to increase the light that reaches the apple fruit surface [ 4 , 40 , 41 ] and thus enhances the red skin coloration in apples [ 3 , 4 , 28 , 39 , 40 , 43 , 44 , 45 , 46 ], but also to increase the ethylene concentration, thus hastening fruit maturity [ 71 , 72 , 73 ]. In terms of ethylene, the use of AVG has been shown to delay apple ripening rates and to reduce the preharvest fruit drop, a serious problem in ‘Honeycrisp’, which can yield losses up to 50% in the mid-Atlantic by significantly decreasing ethylene production, although it has also been reported to negatively impact apple red skin coloration [ 4 , 24 , 40 , 54 , 63 , 66 , 67 , 70 ].…”

“…Reflective groundcovers are a commercially available cultural practice that have been shown to increase the light that reaches the apple fruit surface via enhancing the light reflection (including ultraviolet radiation) from the orchard floor towards the tree canopy [ 3 , 4 , 28 , 38 , 39 , 40 , 41 , 42 ]. Consequently, the use of reflective groundcovers has been reported to promote red skin coloration in multiple apple cultivars grown under different environmental conditions [ 3 , 4 , 28 , 39 , 40 , 43 , 44 , 45 , 46 ], thus increasing crop value [ 3 ].…”

“…Reflective groundcovers are a commercially available cultural practice that have been shown to increase the light that reaches the apple fruit surface via enhancing the light reflection (including ultraviolet radiation) from the orchard floor towards the tree canopy [ 3 , 4 , 28 , 38 , 39 , 40 , 41 , 42 ]. Consequently, the use of reflective groundcovers has been reported to promote red skin coloration in multiple apple cultivars grown under different environmental conditions [ 3 , 4 , 28 , 39 , 40 , 43 , 44 , 45 , 46 ], thus increasing crop value [ 3 ]. Although earlier studies have documented the effectiveness of reflective groundcovers on enhancing apple red skin coloration, research to evaluate the effect of this practice on the expression of anthocyanin biosynthetic pathway-related genes and the total anthocyanin concentration is scarce and has not been conducted under the environmental conditions of the US mid-Atlantic region.…”