IT’S only a matter of time before new disease-resistant apple varieties overtake favourites such as Honeycrisp in popularity, an American apple expert predicts.
Associate professor of hort-iculture Mosbah Kushad of the University of Illinois says for traditional apple cultivars and many newer ones, including Honeycrisp, combating apple scab and other diseases means applying multiple pesticides several times during the growing season.
Apple scab, a fungus, can cause yield losses up to 80 per cent.
“I know everyone wants Honeycrisp, but they’re not-oriously hard to grow,” Kushad says. “There are so many issues in producing the fruit – the tree might produce a lot one year, but none the next; the fruit doesn’t keep well and is susceptible to disease.”
The gene for scab resistance was discovered by a University of Illinois scientist in 1944 and a number of resistant varieties were developed.
Kushad says the early cultivars weren’t particularly good, but more recent ones show a lot of promise.
A new wave of scab-resistant apples has been developed and tested as part of a joint breeding programme with Rutgers Un-iversity and Purdue University. Several cultivars have proven to be as nutritious as older types, but until now, it wasn’t clear whether their quality held up over time.
Kushad looked at a new wave of scab-resistant varieties with
names such as GoldRush, WineCrisp, CrimsonCrisp and Pixie Crunch to see if they retained their quality under standard post-harvest storage practices. They also compared their performance to scab-susceptible Golden Delicious.
The apples were exposed to 1-methylcyclopropene (1-MCP) gas used in the industry to inhibit ethylene production and slow ripening of stored fruit.
Nutritional quality and com-mercial viability were tested after 70 and 140 days of storage.
The eating quality – flesh firmness, sugar content, and acidity – of the new scab-resistant cultivars was as good or better than Golden Delicious before and after storage, the researchers report in a study published in the Journal of Food Quality.
GoldRush and CrimsonCrisp had significantly more anti-oxidant capacity after 140 days. Testing with 1-MCP found CrimsonCrisp showing the most promise for long-term storage.
“The quality of the scab-resistant cultivars is very comparable to standard var-ieties,” Kushad says.
“In terms of nutrition, health benefit, aesthetic, and taste, these apples are competing very well. As an alternative to scab-susceptible types, they will be very attractive, especially for organic growers.”