Fecha de publicación: 05/10/2024 Fuente: ISHS (International Society for Horticultural Science) Post date: Saturday 5 October 2024
Author:
ISHS Secretariat

Biennial bearing is not a novel concept for perennial fruit trees. Biennial bearing, or alternate bearing, is characterized by a heavy crop one year (the “on” year), accompanied by little to no crop the following year (the “off” year). While environmental factors such as spring frosts and drought can initiate a biennial bearing cycle in fruit trees, genetics play an important role, with certain cultivars having a greater likelihood of bearing biennially. In apples, ‘Honeycrisp’ is prone to biennial bearing, even when environmental factors remain constant and in good supply. Regenerative buds can make up more than 90% of buds in an “on” year, while in an “off” year, less than 20% of the buds are regenerative. Nonstructural carbohydrates fulfill distinct roles within plants, influencing flower bud initiation and fruit bud formation. Moreover, nitrogen reserves play a key role in fueling spring growth and flowering. In this study, we sought to quantify nonstructural carbohydrate and nitrogen levels of various plant tissues in both “on” and “off” trees of ‘Honeycrisp’ and ‘Gala’. The crop load from each tree was used to distinguish between “on” and “off” trees. Nonstructural carbohydrate levels were higher in trees with a higher crop load in ‘Honeycrisp’, while nitrogen levels were lower in high cropping trees. For ‘Gala’, carbohydrate levels did not vary significantly, but nitrogen levels followed a similar pattern. In 2023, results showed less separation in ‘Honeycrisp’. We theorize that abnormal events in 2022, when leaf senescence did not occur going into winter, could have disrupted carbohydrate and nitrogen translocation patterns in the trees, causing data to become more significant. Crop load was more significant in affecting carbohydrate and nitrogen levels in ‘Honeycrisp’ than ‘Gala’. Carbohydrate and nitrogen levels within trees impact biennial bearing, but the strength and influence of these relationships are currently unclear.
Thiago Campbell won the ISHS Young Minds Award for the best poster presentation at the X International Symposium on Plant Nutrition of Fruit Crops in USA in June 2024.
Thiago Campbell, Washington State University, 1100 N Western AVE, Wenatchee, WA 98801, USA, e-mail: thiago.campbell@wsu.edu
The article is available in Chronica HorticulturaeTags: biennial bearingapplenitrogen storageCategories: Young Minds Award Winners