Cercospora leaf spot resistance of Crapemyrtle cultivars in Tennessee, USA

Authors: PARAJULI, MADHAV - Tennessee State University; LIYANAPATHIRANAGE, PRABHA - Tennessee State University; Shreckhise, Jacob - Jake; FARE, DONNA - Former ARS Employee; Moore, Benjamin; BAYSAL-GUREL, FULYA - Tennessee State University

Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/1/2022
Publication Date: 12/22/2022
Citation: Parajuli, M., Liyanapathiranage, P., Shreckhise, J.H., Fare, D., Moore, B.T., Baysal-Gurel, F. 2022. Cercospora leaf spot resistance of Crapemyrtle cultivars in Tennessee, USA. HortScience. https://doi.org/10.21273/HORTSCI16913-22.
DOI: https://doi.org/10.21273/HORTSCI16913-22

Interpretive Summary: Crapemyrtle, a top-selling deciduous flowering tree in the U.S., can be severely affected by cercospora leaf spot (CLS) disease which reduces salability of susceptible plants if they are not repeatedly treated with expensive fungicides. USDA-ARS scientists teamed up with Tennessee State University to conduct a three-year evaluation of 38 crapemyrtle cultivars to measure their relative resistance or susceptibility to CLS. The researchers discovered that nearly all cultivars of common crapemyrtle (Lagerstroemia indica) were highly susceptible to CLS, whereas the less frequently cultivated crapemyrtle species, L. fauriei, L. subcostata, and L. limii, were highly resistant. They also found that hybrids of L. indica and L. fauriei, including 'Choctaw', 'Miami', 'Natchez', 'Osage', 'Sara’s Favorite', 'Tonto', 'Tuscarora', and 'Tuskegee', were moderately resistant to CLS. Cercospora leaf spot-resistant species and cultivars identified from this research may be used in crapemyrtle breeding programs to incorporate CLS resistance into new varieties. In addition, growers may use this information to reduce or eliminate fungicide applications for crapemyrtle species and cultivars determined to be CLS-resistant.

Technical Abstract: Crapemyrtle (Lagerstroemia spp.) is a top-selling deciduous flowering tree in the U.S., and its salability is often compromised by cercospora leaf spot disease. To compare cercospora leaf spot resistance, 33 crapemyrtle cultivars belonging to L. indica, L. fauriei, L. Indica × L. fauriei, and L indica x L. fauriei x L. limii and 12 cultivars or unnamed selections belonging to L. indica, L. indica × L. fauriei, L indica × L. fauriei × L. limii, L. limii, and L. subcostata were planted in field plots in 2004 and 2011, respectively. The experiment was a randomized complete block design with three and four replications in the 2004 and 2011 plantings, respectively. Plants were evaluated for cercospora leaf spot disease severity and defoliation using a scale of 0% to 100% foliage affected from Aug. to Oct. of 2015, 2016, and 2017. Area under the disease progress curve (AUDPC) was calculated for the evaluation period of each year. Lagerstroemia fauriei cultivars Fantasy, Kiowa, Townhouse, and Woodlander’s Chocolate Soldier and L. indica × L. fauriei ‘Apalachee’ from the 2004 planting, and the L. subcostata and L. limii selections from the 2011 planting had lowest cercospora leaf spot disease severity ratings, AUDPC, and defoliation. Lagerstroemia indica × L. fauriei cultivars Choctaw, Miami, Natchez, Osage, Sara’s Favorite, Tonto, Tuscarora, and Tuskegee were moderately resistant to cercospora leaf spot, whereas cultivars belonging to L. indica and L. indica × L. fauriei × L. limii were highly susceptible to cercospora leaf spot disease. Results from this research may aid breeders, nursery producers, and landscapers in selecting crapemyrtle species and cultivars with cercospora leaf spot-resistance.