Phomopsis Seed Decay of Soybean

Abstract

Phomopsis seed decay (PSD) of soybean, Glycine max (L.) Merrill, is the major cause of poor seed quality in most soybean-growing countries (Sinclair, 1993). The disease is caused primarily by the fungal pathogen, Phomopsis longicolla, along with other Phomopsis and Diaporthe spp. PSD severely affects soybean seed quality due to reduction in seed viability and oil content, alteration of seed composition, and increased frequencies of moldy and/or split beans (Hepperly & Sinclair, 1978; Rupe and Ferriss, 1986; Rupe 1990; Wrather at al., 2004). Hot and humid environmental conditions, especially during the period from the pod fill through harvest stages, favor pathogen growth and disease development (Balducchi & McGee, 1987; Hartman et al., 1999). PSD has resulted in significant economic losses (Baird et al., 2001; Hepperly and Sinclair, 1978). Losses on a worldwide basis were approximately 0.19 million metric tons (MMT) in 1994 (Kulik & Sinclair, 1999). Effects of PSD on yields in the United States from 1996 to 2007 ranged from 0.38 to 0.43 MMT (Wrather & Koenning, 2009). In 2009, due to the prevalence of hot and humid environmental conditions from pod fill to harvest in the southern United States, PSD caused over 12 million bushels of yield losses in 16 states (Koenning, 2010).