Friesia X, 4-5

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toms on thirteen Triticum species and cultivars but were pathogenic
to all of twelve H ordeum species and cultivars. Similarly isolates from
wheat, also collected from different geographic areas in Denmark,
were non-pathogenic on all of the species and cultiva rs of Hor deum
tested but attacked all species and cultivars of Tr iti cum tested.
The re sults from these infect ion experiments, to gether wit h t he
data by W E BER (1922) and JOHNSON (1947), clearly show that iso lates
of Leptosphaeria nodorum from barley and wheat are st ri kingly differe
nt in pathogenecity on these two host genera.
Since L. nodorum isolates from barley and wheat closely resemble
each other in both morphological characteristics and growt h behaviour
but differ in pathogenecity on barley and wheat, it is suggest ed that
t he L . nodorum att acking barley should be regarded as a f or m a
speci alis of L eptosphaer i a nodorum M ULL E R.
DESCRIPTION
L ept osphaer ia nodorum MULLER f. sp. hordei f. sp. nov.
In H ordeo vulgari) praesertim in laminis et vaginis foliorum, minus
perfecte in glumis et paleis spicularum. Loci laesi foliorum 1-2 cm
longitudine, ovales vel lenticulares, colore rufo vel griseo, pycnidia
ferentes. Pycnidia tempore aestatis serae saepe peritheciis secuta.
Pycnidia subepidermalia, globosa, ostiolis circularibus subpapillatis,
primo translucida, postea fusca, 78-182 Il. Pycnosporae cylindricae,
extremo rotundatae, hyalinae, 1-3 (plerumque 3) septis, 17-28 X
2.8-4.0 Il. Perithecia subepidermalia, globosa, ostiolis breviter papillatis,
fusca vel nigra, 100-240 Il diametro. Asci cylindrici vel clavati,
bitunicati, 8-spori s, 51-80 X 9-12 Il. Ascosporae biseriatim collocatae,
rectae vel subcurvatae, 3-septatae, constrictae prope septa, saepe cellula
secunda ab apice paulo crassiore, subfuscae, 19-28 X 4.4-5.6 Il .
Stadium imperfectum: Septoria nodorum (BERK.) BERK. & BR.
f. sp. hordei f. sp. nov.
Leptosphaeria nodorum MULLER f. sp. hordei f. sp. nov.
On leaf lamina and sheaths of barley (Hordeum vulgare ) ) les s
pronounced on glumes and awns. Lesions on leaves 1-2 cm long, oval
or lens shaped, redbrown to grey, bearing pycnidia. Pycnidia often
followed by perithecia in late summer. Pycnidia subepidermal, globose
with a circular, slightly papillate ostiole, at first translucent, later