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Published Online:10 May 2022https://doi.org/10.1094/PDIS-12-21-2737-PDN
Abstract
The interest in hazelnut (Corylus avellana L.) cultivation has recently increased in Hungary, it
is currently grown on 490 hectares. In August 2021 early powdery mildew symptoms were
observed in a hazelnut plantation, and in a variety collection of the Hungarian University of
Agricultural and Life Sciences in Erd. White patches of mycelium and conidia were observed
on both side of the leaves. In early October abundant chasmothecia were formed. The disease
incidence was 100% on varieties 'Segorbe', and 'Corabel', 70% on 'Ennis', and 30% on the
leaves of 'Istrska dolgoplodna leska' (15 plants per cultivar). Powdery mildew is usually caused
by Phyllactinia guttata, which was present abundantly on the abaxial and sparsely on the
adaxial surface of the observed leaves. However, another fungus co-occurred on the adaxial
surface of the leaves, and rarely occurred on the abaxial surface of the leaves. Its morphology
differed substantially from P. guttata on having smaller chasmothecia, and branched
appendages. The new powdery mildew agent was morphologically described. Mycelium was
hyaline, branched, septate, thin-walled and smooth, 2.5-3.1 μm wide. Conidiophores measured
22 to 61 × 5.1 to 8.5 (average: 44.1 × 6.5) μm (n = 30), the foot cells were erect, cylindrical,
and flexuous. Conidia occurred rarely and were produced single on conidiophores, 19 to 34 ×
15 to 24 μm. Chasmothecia were spherical, 74 to 103 (average: 85) μm in diameter (n = 100),
single or in groups on both sides of each leaf. Appendages 7 to 15 per chasmothecium,
aseptate, straight, sometimes flexuous with a length of 74 to 118 (average: 103) μm (n = 50),
and had 3 to 5 times dichotomous branched apices with curved tips. Each chasmothecium
contained 3 to 5 asci. Ovoid to subglobose asci measured 43 to 65 × 32 to 54 μm (average: 56
× 43) μm (n = 30). Asci contained 4 to 8 ascospores which were hyaline, ellipsoid, measured 17
to 23 × 11 to 20 (mean: 21 × 15) μm (n = 40) in diameter. Morphological identification was
confirmed by molecular analysis of two samples, one from the plantation, and one from the
variety collection. After DNA extraction partial rDNA internal transcribed spacer region (ITS) of
the isolates was amplified using primers ITS1_F and ITS4_R, as previously indicated
(Meparishvili et al. 2019). Obtained sequences were deposited to the GenBank (accession no.
OL744964 and OL744961). BLAST analysis indicated that the two samples were showing 100%
and 97,81% identity to ITS rDNA sequences of Erysiphe corylacearum from Switzerland
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Abstract
The interest in hazelnut (Corylus avellana L.) cultivation has recently increased in Hungary, it
is currently grown on 490 hectares. In August 2021 early powdery mildew symptoms were
observed in a hazelnut plantation, and in a variety collection of the Hungarian University of
Agricultural and Life Sciences in Erd. White patches of mycelium and conidia were observed
on both side of the leaves. In early October abundant chasmothecia were formed. The disease
incidence was 100% on varieties 'Segorbe', and 'Corabel', 70% on 'Ennis', and 30% on the
leaves of 'Istrska dolgoplodna leska' (15 plants per cultivar). Powdery mildew is usually caused
by Phyllactinia guttata, which was present abundantly on the abaxial and sparsely on the
adaxial surface of the observed leaves. However, another fungus co-occurred on the adaxial
surface of the leaves, and rarely occurred on the abaxial surface of the leaves. Its morphology
differed substantially from P. guttata on having smaller chasmothecia, and branched
appendages. The new powdery mildew agent was morphologically described. Mycelium was
hyaline, branched, septate, thin-walled and smooth, 2.5-3.1 μm wide. Conidiophores measured
22 to 61 × 5.1 to 8.5 (average: 44.1 × 6.5) μm (n = 30), the foot cells were erect, cylindrical,
and flexuous. Conidia occurred rarely and were produced single on conidiophores, 19 to 34 ×
15 to 24 μm. Chasmothecia were spherical, 74 to 103 (average: 85) μm in diameter (n = 100),
single or in groups on both sides of each leaf. Appendages 7 to 15 per chasmothecium,
aseptate, straight, sometimes flexuous with a length of 74 to 118 (average: 103) μm (n = 50),
and had 3 to 5 times dichotomous branched apices with curved tips. Each chasmothecium
contained 3 to 5 asci. Ovoid to subglobose asci measured 43 to 65 × 32 to 54 μm (average: 56
× 43) μm (n = 30). Asci contained 4 to 8 ascospores which were hyaline, ellipsoid, measured 17
to 23 × 11 to 20 (mean: 21 × 15) μm (n = 40) in diameter. Morphological identification was
confirmed by molecular analysis of two samples, one from the plantation, and one from the
variety collection. After DNA extraction partial rDNA internal transcribed spacer region (ITS) of
the isolates was amplified using primers ITS1_F and ITS4_R, as previously indicated
(Meparishvili et al. 2019). Obtained sequences were deposited to the GenBank (accession no.
OL744964 and OL744961). BLAST analysis indicated that the two samples were showing 100%
and 97,81% identity to ITS rDNA sequences of Erysiphe corylacearum from Switzerland
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