Ascochyta fabae

The biosynthesis of ascochitine (16), a phytotoxic hexake-tide from the fungus Ascochyta fabae, has been investigated by means of C-labeled acetates and methionine and Relabeled precursors (Ballio, 1981 Stoessl, 1981) (Fig. 5.12). Ascochitine is derived from a single hexaketide precursor with introduction of three methyl groups from methionine via a quinone-methide structure (17) similar to that involved in the biosynthesis of citrinin. The aldehyde (18) and quinone-methide (17) were specifically incorporated. 

Leaf and pod spot (Ascochyta fabae) is probably the most important seed-bome disease of beans although it affects peas as well. Most disease stems from infected seed, but volunteer plants and the movement of tractors and other machinery from crop to crop can also spread it. The testing of seed stocks for Ascochyta is routine. However, modem seed treatments have greatly improved control of this disease. 

Certified seed is advised but if using home-saved seed it should be tested for germination and seed-borne leaf and pod spot (Ascochyta fabae) infection. Low levels of this disease may be treated with thiram. It is recommended that all field bean seed is tested for stem and bulb nematode (Ditylenchus dipsaci) and should not be used for seed if nematodes are present. PGRO offer a testing service. 

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