First report of Erysiphe corylacearum Causing Powdery Mildew on Hazelnut in Hungary.

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 Érd. 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 (MN822722), and showed low similarity of 83% and 85% each to P. guttata (AB080558). Pathogenicity tests were accomplished on ten healthy two-year-old plants of C. avellana cv. 'Merveille de Bollwiller' with the two isolates under controlled environment on 25°C, 80% humidity and 16/8 photoperiod. Plants were artificially inoculated by conidial suspension droplets (104/ml). Symptoms appeared after 7-8 days after inoculation and the developing fungus was morphologically identical to the original isolates. Control plants were treated with distilled water, no symptoms were found on them. E. corylacearum was first observed on C. avellana in Turkey in 2013 (Sezer et al. 2017) and was considered as a highly destructive pathogen. It is also known in neighbouring countries, Ukraine (Heluta et al, 2019), Austria (Voglmayr et al. 2020) and Romania (Rosati et al. 2021). To our knowledge, this is the first report of Erysiphe corylacearum in Hungary.

Is "Esterhazy II", an Old Walnut Variety in the Hungarian Gene Bank, the Original Genotype?

The old walnut (Juglans regia L.) genotype called "Esterhazy II" was well-known in the Austro-Hungarian Monarchy before World War II, and it can still be found in the Austrian, German and Swiss backyard gardens today. Unfortunately, nowadays, vegetatively propagated progenies of the original "Esterhazy II" are not available anymore around the world because walnut grafting started later than this genotype had become well-known. Although various accessions with "Esterhazy II"-"blood" are available, it is difficult to determine which one can be considered true or the most similar to the original one. In this paper, phenological and nut morphological characteristics of an "Esterhazy II" specimen planted in a Hungarian gene bank were compared to the varieties "Milotai 10" and "Chandler". Examined characteristics were: budbreak, blossom time, type of dichogamy, ripening time, nut and kernel features. An additional SSR fingerprinting was used to identify identical genotypes and to demonstrate the relatedness of the analyzed "Esterhazy II" genotype to the other Hungarian walnut cultivars. It can be concluded that under the name "Esterhazy II", several different genotypes can be observed. All the checked characteristics except budbreak fitted well with the previous descriptions. Our results confirmed that the examined "Esterhazy II" genotype shows high similarity to the "original" "Esterhazy II" described in the literature.

First Report of Colletotrichum godetiae Causing Anthracnose and Twig Blight on Persian Walnut in Hungary.

Persian walnut (Juglans regia L.) fruit with preharvest anthracnose symptoms, necrotic fruit stalks, and twigs with necrotic buds, and peaks were collected in a Hungarian orchard next to Nágocs, in September 2018. Disease incidence was approximately 15% on a Hungarian bred walnut cultivar 'Milotai 10'. Similar symptoms were found on Persian walnut in other locations (eg. Milota, Érd, Sarród, and Kocs). Acervuli were observed on necrotic lesions on fruit, and twigs with pale orange conidial masses. Conidia were hyaline, unicellular, and fusiform. Morphometric measurements of conidia showed mean length ± SD × width ± SD = 15.9 ± 1.7 × 4.5 ± 0.4 µm, length/width ratio 1:0.3 (n=100). The fungus was isolated from conidial masses on potato dextrose agar (PDA) medium amended with Chlorampenicol (25 mg/L). A total of 12 isolates were obtained as pure cultures by single-spore isolations and incubated at 23°C in dark for 10 days. The colonies were white to gray or grayish-orange on the upper side and with black spots on the reverse side. The isolates showed morphological characteristics of Colletotrichum acutatum in sensu lato (Jayawardena et al. 2016). Molecular analyses were conducted to identify the exact species. Internal transcribed spacer (ITS) region, actin (ACT), and calmodulin (CAL) partial genes were amplified by ITS1F/ITS4R, ACT512F/ACT783R and CAL1/CAL2 primers (White at al. 1990, Carbone and Kohn 1999, O'Donnell et al. 2000). The sequences of ITS region (GenBank Accession Nos: MK367398-99, MK367401-02) showed 100% identity with C. godetiae sequence. Based on ACT gene (GenBank Accession Nos: MK415991-92, MK415994-95) were 100% identity with the deposited C. godetiae type strains from walnut. The obtained sequences of CAL gene (GenBank Accession Nos: MK415998-99, MK416001-02) were same and showed 100% with other C. godetiae sequences from other host plants. The fungus was identified as Colletotrichum godetiae Neerg. Pathogenicity tests were accomplished in the field and under laboratory conditions (25°C on thermostat) on 10 green 'Milotai 10' walnut fruit, and 10 walnut twigs each. Tests were conducted on living trees, collected fruit, and two-year-old twigs by inserting mycelial agar plugs (5 mm in diameter) onto wounded pericarp tissues, which were then wrapped with wet cotton and parafilm. Wounded tissues on 5 fruit and 5 two-year-old twigs were treated with non-colonized PDA plugs as noninoculated controls. After 14 d necrotic lesions 9 to 17 mm in diameter developed on fruit on living trees. Lengths of 12 to 17 mm and width of 7 to 12 mm necrosis was measured on phloem of walnut twigs, and almost two times larger in cambium. No necrosis developed around control wounds. Koch's postulates were fulfilled with the reisolation of the pathogen from symptomatic tissues, isolates were identical morphologically and by sequence analysis of ITS region, ACT, and CAL partial genes to the original isolates. Damm et al. (2012) described two C. godetiae strains associated with walnut, one isolated in Austria and another one of unknown origin. An epidemic event of walnut anthracnose caused by Colletotrichum species mainly C. godetiae was reported in France (Da Lio et al. 2018). The pathogen was isolated from nuts, buds, insects, and stems. To our knowledge, this is the first report of anthracnose of walnut fruit caused by C. godetiae in Hungary. Anthracnose caused by C. godetiae, and previously reported C. fioriniae (Varjas et al. 2019) is becoming an increasing preharvest problem on Persian walnut in Hungary.