ABSTRACT
Necrotrophic fungal pathogens are known to produce host-specific=host-selective and host-nonspecific phytotoxins. Pyrenophora tritici-repentis, the causal agent of tan spot of wheat
(Ptr ToxA toxin) (Martinez et al., 2004; Manning et al., 2004; Manning and Ciuffetti, 2005;
Sarma et al., 2005), Pyrenophora teres, the net-blotch pathogen of barley (aspergillomarasmine)
(Friis et al., 1991), Mycosphaerella zeae-maydis, the corn yellow leaf blight pathogen (PM-
toxin) (Yun et al., 1998), Cochliobolus victoriae, the oat leaf blight pathogen (victorin) (Churchill
et al., 1995), and Cochliobolus carbonum, the corn leaf blight pathogen (HC-toxin) (Pitkin et al.,
2000) are known to produce host-specific toxins. Helminthosporium maydis T strain, the maize
pathogen, produces HMT-toxin, a host-specific one (Turgeon et al., 1995). Helminthosporium
oryzae, the rice brown spot pathogen, produces a host-specific toxin (Vidhyasekaran et al., 1986).
H. oryzae produces several nonspecific toxins including ophiobolin A, 6-epiophibolin A,
anhydroophiobolin A, 6-epianhydroophiobolin A, and ophiobolin 1 (Xiao et al., 1991).Bipolaris
zeicola, the pathogen of maize and rice, produces BZR-toxin (Xiao et al., 1992). Helminthos-
porium sacchari, the sugarcane pathogen, produces a host-specific toxin (HS-toxin) (Livingston
and Scheffer, 1984). Exserohilum turcicum, the corn leaf blight pathogen, produces a peptide
toxin (Bashan et al., 1995).
