M"y, L974 - MSpace at the University of Manitoba

GREY LEAFSPOT (StanphyLium solani and ,9. bol;tgosum) is a major
disease in the lupin growing areas of the United States. It can seri-
ously decrease yíe1ds by defoliaËing the plants, (Edwardson et al. 1963).
The two species of S1;emphyLiun r{ere once described as tl¡ro separate dis-
eases that produced separate syndromes. They T¡/ere named LitËle Leafspot
(5. botryosum) and Grey Leafspot (,9. soLani) (Wells et al. 7956). How-
ever, upon further investigatíon I^Ie11s et al. (1961) found that both 5"
soLaní and ^9. botryosum caused identical symptoms as described by Grey
Leafspot. Therefore they suggested that the name Grey Leafspot be rede-
fined to include the identical symptoms produced by both species.
The Stemphylium Leaf Spot complex attacks only varieties oÍ. L"
angustifoLius, with tr. albus and tr" Luteus being inmune. Wells et al.
(1956) described the symptoms as follows; infections on the leaflets are
circular to oblong,2 to 6 rmr in diarneter, and during the early stages
are brown" 01der lesions have a rose-grey center with a brown margin"
The pathogen causes tissue collapse and lesíons are Ëherefore sunken.
Very few lesions wíll cause the leaflets to abscise, therefore rapid
defoliation afËer initial infection may occur. Lesions can also occur
on the sËem and pods. They are small and circular, or up to 5 cm long
and may encompass the stem or cover Ehe entire pod"
Iniells et al" (L962) found another species of thís pathogen thaË can
parastize L. angustifolius" ^9" Loti can atËack lines that are resistant
to ,9" solani and .9" botz'yosum, but does not seem to be prevalent in the
South Eastern UniËed SËates. ResisËance to Grey Leafspot has been found
in the form of two independenË genes isolated from a naturally occurrÍng
mutant and from wild forms occurring in PorËugal (Forbes eË al. 1957,
L964" L965) "
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