Aurifilum cerciana W. Wang & S.F. Chen, 2023

Wang, Wen & Chen, ShuaiFei, 2023, Identification and pathogenicity of Aurifilum species (Cryphonectriaceae, Diaporthales) on Terminalia species in Southern China, MycoKeys 98, pp. 37-58 : 37

Aurifilum cerciana W. Wang & S.F. Chen sp. nov.

Fig. 4

Etymology.

the name refers to China Eucalypt Research Centre (CERC), the former institution of the Research Institute of Fast-Growing Trees (RIFT), which served as the identification site for this study on Terminalia trees disease caused by Aurifilum spp.

Stromata.

No ascostromata were observed on inoculated Eucalyptus branch tissue, the conidiomata on the inoculated Eucalyptus branch tissue were superficial to slightly immersed, pulvinate, globose pyriform to various shapes without necks, blight yellow when young, orange to brown when mature (Fig. 4A, B ), unilocular, 46-236 μm (av. 142 μm) diameter (Fig. 4C ). Stromatic tissue prosenchymatous (Fig. 4D ). Stromatic conidiomatal base was 119 - 678 μm (av. 428 μm) high above the level of the bark and 58 - 269 μm (av. 158 μm) wide. Conidiomatal necks absent. Conidiomatal locules unilocular. Conidiophores, hyaline, branched irregularly at the base or above into cylindrical cells, with or without separating septa, (11.2-)23.8-28.6(-70.2) μm (av. 26.2 μm) long, (1.7-)2.3-3.7(-6.5) μm (av. 3 μm) wide (Fig. 4F ). Conidiogenous cells phialidic, cylindrical, without attenuated apices, (0.8-)1.0 - 1.8(-2.6) μm (av. 1.4 μm) wide (Fig. 4F ). Paraphyses or cylindrical sterile cells, occur among conidiophores, up to 99 μm (av. 51.4 μm) long (Fig. 4E ). Conidia hyaline, non-septate, oblong to cylindrical, occasionally allantoid, extend through on opening at stromatal surface as orange droplets, (3.6-)4.3-4.5(-5.7) × (1.5-)1.8(-2.2) (av. 4.4 × 1.8 μm) (Fig. 4G ).

Culture characteristics.

Colonies on MEA are fluffy with an uneven margin, white when young, turning pale luteous to luteous after 10 days, and reverse yellow to orange-white. Optimal growth temperature 35 °C, reaching the edge of the 90 mm plates after 7 days. No growth at 5, 10 °C. After 7 days, colonies at 15, 20, 25, 30, and 35 °C reached 15.8, 45.9, 49, 50.5, and 74.4 mm, respectively.

Substrate.

Bark of Terminalia neotaliala .

Distribution.

Guangdong Province, China.

Additional materials examined.

China, Guangdong Province, Zhanjiang Region, Suixi District, Chating Town (21°16′06.97″N, 110°5′16.8432″E) from branch bark of T. neotaliala tree, 23 May 2019, S. F. Chen & W. Wang, holotype, CSFF2078, HMAS350333, ex-type culture CSF16261 = CGMCC3.20107 ; Guangdong Province, Zhanjiang Region, Suixi District, Diaolou Town (21°15′57.006″N, 110°12′26.5824″E) from twigs of T. mantaly tree, 25 May 2019, S. F. Chen & W. Wang, CSFF2079, HMAS350334, culture CSF16384 = CGMCC3.20108 .

Notes.

Three species were described in the genus Aurifilum , including A. marmelostoma , A. terminali , A. cerciana . Aurifilum cerciana morphologically differs from A. terminali by the absence of conidiomatal necks ( Wang et al. 2020), and differs from A. marmelostoma by longer paraphyses ( Begoude et al. 2010). A. cerciana could also be distinguished from A. terminali and A. marmelostoma by growth characteristics in culture. The optimal growth temperature of A. cerciana is 35 °C, whereas A. terminali grows relatively slowly at this temperature and no growth is observed for A. marmelostoma ( Begoude et al. 2010; Wang et al. 2020).

Pathogenicity tests.

Eight isolates representing the two species of Aurifilum identified in this study were used to inoculate seedlings of two Eucalyptus hybrid genotypes, and branches of T. neotaliala . These include four isolates in A. terminali and A. cerciana , respectively (Table 2 ). Seedling stems or tree branches inoculated with Aurifilum isolates exhibited lesions, whereas the control group only showed wounds without any lesions. (Fig. 5 ). The lesions produced by Aurifilum species on T. neotaliala and Eucalyptus clones CEPT53 were significantly longer than the wounds on the controls (P <0.05), whereas for the Eucalyptus clones CEPT46, the lesions produced by Aurifilum species were not significantly different (Fig. 5 ). The overall data revealed that A. cerciana and A. terminali have similar pathogenicity (Fig. 5 ). The overall data further showed that CEPT53 is more susceptible than CEPT46 to Aurifilum spp. (Fig. 5B ). Yellow or orange fruiting structures and cankers were produced on the bark of inoculated trees within 7 weeks; these structures displayed similar characteristics of conidiomata on the Terminalia trees in the field and the re-isolated fungi from lesions share the same culture morphology with the Aurifilum fungi originally from the Terminalia trees in the nursery. The inoculated Aurifilum fungi were successfully re-isolated from the lesions but not from the control, indicating that the Koch’s postulates had been fulfilled.

Figures

Figure 4. Morphological characteristics of Aurifilum cerciana A, B conidiomata on the bark C longitudinal section through conidioma showing umber stroma D prosenchymatous stromatic tissue of the conidia E paraphyses F conidiophores and conidiogenous cells G conidia H, I colony of A. cerciana on MEA after 7 days at 25 ° C H front I reverse. Scal bars: 200 µm (A); 100 µm (B, C); 10 µm (D, E, F); 5 µm (G); 1 cm (H, I).

Figure 5. Column chart showing average lesion lengths (mm) produced by each isolate of Aurifilum on the branches of T. neotaliala (left) and two Eucalyptus hybrid genotypes (right). Eight isolates of Aurifilum were used. Vertical bars represent the standard error of the means. Different letters above the bars indicate treatments that were statistically significantly different (P = 0.05).