Phomopsis Stem Canker: A Reemerging Threat to Sunflower (Helianthus annuus) in the United States

Abstract

Phomopsis stem canker causes yield reductions on sunflower (Helianthus annuus L.) on several continents, including Australia, Europe, and North America. In the United States, Phomopsis stem canker incidence has increased 16-fold in the Northern Great Plains between 2001 and 2012. Although Diaporthe helianthi was assumed to be the sole causal agent in the United States, a newly described species, D. gulyae, was found to be the primary cause of Phomopsis stem canker in Australia. To determine the identity of Diaporthe spp. causing Phomopsis stem canker in the Northern Great Plains, 275 infected stems were collected between 2010 and 2012. Phylogenetic analyses of sequences of the ribosomal DNA internal transcribed spacer region, elongation factor subunit 1-α, and actin gene regions of representative isolates, in comparison with those of type specimens, confirmed two species (D. helianthi and D. gulyae) in the United States. Differences in aggressiveness between the two species were determined using the stem-wound method in the greenhouse; overall, D. helianthi and D. gulyae did not vary significantly (P≤0.05) in their aggressiveness at 10 and 14 days after inoculation. These findings indicate that both Diaporthe spp. have emerged as sunflower pathogens in the United States, and have implications on the management of this disease.

The current status of species in Diaporthe

“…Host -Helianthus annuus , Mathew et al 2015a. Distribution -Australia , Canada (Mathew et al 2015a), USA (Mathew et al 2015b ). Distribution -Worldwide ).…”

Changes in sunflower breeding over the last fifty years

“…First observed in Serbia in 1980 (Mihaljčević et al, 1980), it can be compared with broomrape in that this disease is most important in Europe and has only recently become a problem in North America (Mathew et al, 2015). Perhaps, for both phomopsis and broomrape, the fact that Southern Russia and Eastern Europe was the first and largest area of cultivated sunflower meant that there was a selective advantage to be able to infect this crop on a large scale.…”

Registration of Oilseed Sunflower Germplasms RHA 485, RHA 486, and HA 487, Selected for Resistance to Phomopsis Stalk Canker and Sclerotinia, in a High‐Yielding and High‐Oil Background

“…Phomopsis, the disease caused by Diaporthe helianthi and other Diaporthe species, is a canker disease that increases lodging and can cause premature ripening, reducing yield (Olson et al, 2017; Talukder et al, 2014; Thompson et al, 2011; Thompson et al, 2015). There was low incidence of this disease in the United States until 2010 when an epidemic occurred across the major sunflower‐growing regions of Minnesota, North Dakota, and South Dakota (Mathew et al, 2015). Sources of host resistance to this disease have been found in European lines by several groups including Talukder and colleagues (2014), who also found a broad‐sense genetic correlation between resistance to Phomopsis and HR.…”