Pomegranate cultivars with diverse origins exhibit strong resistance to anthracnose fruit rot caused by Colletotrichum gloeosporioides, a major disease in southeast United States

Authors: SCHALLER, ALEXANDER - University Of Florida; CHATER, JOHN - University Of Florida; VALLAD, GARY - University Of Florida; Moersfelder, Jeff; Heinitz, Claire; DENG, ZHANAO - University Of Florida

Submitted to: Horticulturae
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/27/2023
Publication Date: 10/3/2023
Citation: Schaller, A., Chater, J., Vallad, G., Moersfelder, J.W., Heinitz, C.C., Deng, Z. 2023. Pomegranate cultivars with diverse origins exhibit strong resistance to anthracnose fruit rot caused by Colletotrichum gloeosporioides, a major disease in southeast United States. Horticulturae. 9(10). Article 1097. https://doi.org/10.3390/horticulturae9101097.
DOI: https://doi.org/10.3390/horticulturae9101097

Interpretive Summary: Colletotrichum spp. is a destructive fungal pathogen that severely affects pomegranate fruit, causing complete rotting of fruit (anthracnose fruit rot) before maturity. As pomegranate gains prominence as an emerging crop in the southeastern United States and its im-portance grows worldwide, identifying sources of resistance to this fungal pathogen is crucial for developing new cultivars with improved resistance to this disease. However, only a limited number of cultivars have been evaluated, with few identified as partially resistant to anthracnose fruit rot. This project aimed to expand the scope of evaluation through a 2-year field study in central Florida, examining 35 cultivars using both artificial and natural inoculation. Subsequently, seven cultivars were selected for further testing by inoculating their detached mature fruit to confirm and quantify observed resistance. The field study classified 35 cultivars into five resistance or susceptibility classes, with five cultivars identified as resistant and one, ‘Azadi’, as strongly resistant, exhibiting re-sistance in both field settings and detached fruit inoculation. These findings represent an important step in developing disease resistance information and can guide future breed-ing efforts for disease-resistant cultivars, an important tool for integrated management of anthracnose fruit rot in pomegranate production.

Technical Abstract: Pomegranate, a pivotal fruit that is well recognized globally and a rapidly emerging crop in the southeastern United States and other subtropical regions, faces a formidable challenge from Colletotrichum spp., a fungal pathogen causing anthracnose fruit rot, which leads to severe to complete premature fruit drop. The development and use of disease-resistant cultivars are considered the most cost-effective and sustainable approach to managing this disease. Identifying sources of resistance is essential for developing new cultivars with improved resistance to this disease. This project aimed to expand the scope of evaluation through a 2-year field study in central Florida, examining fruit from 35 cultivars from diverse origins using both artificial inoculation at the petal dehiscent stage and natural infection. Lesion size on the fruit was measured during the growing season in a field setting. Subsequently, seven cultivars were selected for further testing by inoculating detached mature fruit and measuring lesion size to confirm observed resistance and determine the correlation between resistance observed in planta in the field and on detached fruit in the laboratory. The field study revealed significant genetic differences among pomegranate cultivars in susceptibility to naturally occurring and induced anthracnose fruit rot and classified cultivars into five resistance or susceptibility classes. Five cultivars that originated from different regions of the world, including ‘Azadi’, showed consistent resistance to anthracnose fruit rot in the field. Resistance remained strong on detached mature fruit. A strong positive correlation existed between resistance levels on in-planta fruit and on detached mature fruit, suggesting a possible simple, efficient approach to screening breeding populations for anthracnose fruit rot resistance in pomegranate. These findings represent an important step toward developing new anthracnose-resistant cultivars and understanding and improving disease resistance in this increasingly important fruit crop in the world.