Flowering Dogwood Infections with Macrophomina phaseolina

Abstract

<jats:p><jats:italic>Macrophomina phaseolina</jats:italic> was isolated from the crown region and roots of mature flowering dogwood (<jats:italic>Cornus florida</jats:italic> L.) trees in the landscape and nursery plantings. Although this pathogen has been reported in <jats:italic>Cornus</jats:italic> species, its occurrence and impact on <jats:italic>C. florida</jats:italic> has not been reported. Pathogenicity tests were conducted on dogwood seedlings, and all inoculated seedlings developed root necrotic lesions and no small lateral roots, whereas the non-inoculated control seedlings remained disease-free and developed numerous small roots. Seedlings inoculated with <jats:italic>M. phaseolina</jats:italic> exhibited numerous microsclerotia, but non-inoculated seedlings did not. In greenhouse experiments, plants inoculated on the stems near the soil line developed brown canker-like lesions and swellings around the inoculated area. These were not observed on non-inoculated plants.</jats:p>

Evaluation of Biological Agents for Control of Macrophomina Root Rot and Powdery Mildew in Flowering Dogwood (Cornus florida L.)

“…Dogwood seeds for this study were collected from fieldgrown C. florida at Otis Floyd Nursery Research Center experimental farm (Tennessee State University) in McMinnville, TN and vernalized at 4°C to break dormancy. M. phaseolina inoculum, previously isolated from dogwood (Mmbaga et al, 2018), was prepared from 5 d-old cultures grown on potato dextrose agar (PDA). Mycelia was scraped from the PDA into sterilized water and macerated using a sterilized hand-held blender.…”

“…More than 500 plant species are affected across 100 families, including the dogwood family (Farr et al, 1989;Smith and Carvil, 1977). Woody ornamental plants affected by this fungus include pine, douglas fir, and the highly valued ornamental flowering dogwood (Cornus florida) (Barnard and Gilly, 1986;Hodges, 1962;Mmbaga et al, 2018;Rowan, 1971;Seymour, 1969aSeymour, , 1969bSmith and Bega, 1964). Macrophomina phaseolina effects on woody hosts are primarily on seedlings and young plants, causing severe damping-off, especially in stressful environments.…”

“…Macrophomina phaseolina effects on woody hosts are primarily on seedlings and young plants, causing severe damping-off, especially in stressful environments. Recently M. phaseolina was reported to cause cankers in seedlings of flowering dogwood (Mmbaga et al, 2018). The greatest economic impact of M. phaseolina is on agronomic crops, such as soybean, corn, sorghum, sunflower, and cotton, where it is associated with severe crop losses (Khan, 2007;Lotfalinezhad et al, 2013;Su et al, 2000;Wrather, 1995;Wyllie, 1988).…”

“…The greatest economic impact of M. phaseolina is on agronomic crops, such as soybean, corn, sorghum, sunflower, and cotton, where it is associated with severe crop losses (Khan, 2007;Lotfalinezhad et al, 2013;Su et al, 2000;Wrather, 1995;Wyllie, 1988). Although initial isolation of M. phaseolina from dogwood was from plants that were also infected with Erysiphe pulchra (Mmbaga et al, 2018), the impact of compounded infections on plant growth has not been evaluated. Such information would have significant implications on disease management in nursery production systems that have been already devastated by powdery mildew since the disease emerged in early 1990s (Mmbaga, 2000;Windham, 1994).…”

“…A similar phenomenon may occur in dogwoods infected with powdery mildew. Recent studies have shown that M. phaseolina causes stubby roots and reduces root mass in seedlings of flowering dogwoods (Mmbaga et al, 2018). This study was conducted to evaluate the impact of compounded infection from M. phaseolina and E. pulchra on dogwood plant growth; such information would provide a better understanding of factors that may contribute to dogwood decline.…”