Summary• Although canopy architecture is a prime determinant of forest functioning and productivity, it has received little attention when examining forest responses to rising atmospheric CO 2 concentrations. In this study different characteristics of crown architecture of two Populus species and one hybrid were investigated within a highdensity poplar plantation. A free-air CO 2 enrichment (FACE) facility was used to mimic future elevated CO 2 concentrations.• Canopy depth and branching patterns were studied, and detailed branch characteristics such as branch dimension, inclination, and internodal length were assessed for the three poplar species in the FACE and control treatments.• Effects of elevated CO 2 were restricted to a significantly increased canopy depth and longer internodal lengths after two years of CO 2 enrichment. Additionally, branch dimensions and sylleptic branch numbers were increased by FACE, but responses were variable among growing seasons and species. However, FACE did not affect branch angles of origin and termination.• Crown architecture was modified mainly through a growth stimulation in response to FACE. Nevertheless, important differences among species were observed which may influence future CO 2 responses when competition will become more important.

Succinate dehydrogenase inhibitors (SDHI) fungicides are used to control Asian soybean rust (Phakopsora pachyrhizi) and the SdhC-I86F mutation is related to pathogen resistance. The objective of this study was to determine whether fitness penalties are associated with SDHI resistance (SdhC-I86F mutation) in P. pachyrhizi populations. Moreover, it investigated whether the SdhC-I86F mutation remained stable after the fungus propagation both in the absence and presence of fungicide. The populations used in this study presented mutations for all genes analyzed (Cyp51, Cytb, and SdhC), except for a wild type population (WTSdhC) found with no SdhC-I86F mutation. The frequencies of the SdhC-I86F mutant populations were stable after 36 generations in the absence of fungicide. However, in the case of the WTSdhC population, the SdhC-I86F mutation was further detected after one generation of the fungus in the presence of the SDHI fungicide, according to the results of a detached leaf assay. Three tests were performed to evaluate fitness components and sensitivity to fungicides (EC50). SdhC-I86F mutant populations were more sensitive to osmotic and oxidative stress than the WTSdhC population; however, the sensitivity to UV radiation was similar for both populations. All mutated populations were less sensitive than the WTSdhC when using SDHI (azoxystrobin + benzovindiflupyr), but more sensitive to mancozeb. The presence of fitness penalties, the mutation stability, and the sensitivity to mancozeb presented by the SdhC-I86F mutant populations can be relevant to the management of the disease in the field.

Maize (Zea mays L.) is one of the most important commodities, and Brazil is the second-largest maize exporter country in the world. In April 2019, the period of the second crop maize (safrinha), it was observed black decayed lesions on roots and wilting of some maize plants, causing a "sudden death" in a commercial area in the west of Paraná state, Brazil (Figure 1A-C). Symptomatic root and stalk were collected, and tissues surface disinfected with 70% ethanol for 30 s, 1.5% NaOCl for 1 min and rinsed three times in sterile distilled water, slices of necrotic tissues were transferred to potato dextrose agar (PDA) medium and grown for 7 days at 27 ± 1ºC with a photoperiod of 12 h. Pure cultures were obtained through monosporic isolation. The fungal morphology is alike Gaeumannomyces radicicola, which is a synonym of Phialophora radicicola var. radicicola, Harpophora radicicola, P. zeicola, H. zeicola and G. graminis var. maydis (Hernández-Restrepo et al. 2016). Colonies on PDA showed flat, white to light gray at first (Fig. 1D), turning gray to black with age (Fig. 1E). Colony diameter approximately 5.2 cm on PDA in the dark after 7 days at 27ºC. Conidiophores with slightly thickened wall, mostly branched, varying in dimensions, with a range of 57.5-166.5 (avg. 128.7 μm) × 2.9-5.9 (avg. 4.2 μm) n = 25 (Fig. 1H-J). The conidia showed lunate-shaped with rounded ends, produced successively at the apex of phialide, 3.3–9.7 (avg. 6.6 μm) × 1.5–3.6 μm (avg. 2.5 μm), n = 100 (Fig. 1G-J). Morphological characteristics were comparable to the description of this specie (Cain 1952; Gams 2000; McKeen 1952). The total genomic DNA of a representative isolate, LEMIDPRZm 19-01 was extracted and the partial large subunit (28S nrDNA; LSU), internal transcribed spacer nrDNA including the intervening 5.8S nrDNA (ITS), and part of the largest subunit of the RNA polymerase II gene (RPB1) were amplified and sequenced, as following by Hernández-Restrepo et al. (2016) and Klaubauf et al. (2014). The primers to LSU – NL1 (O’Donnel, 1993) and LR5 (Vilgalys; Hester, 1990); ITS – ITS5 and ITS4 (White et al., 1990); and RPB1 – RPB1F and RPB1R (Klaubauf et al., 2014) were used in this study. The gene sequences of LSU (MT123866), ITS (MT114427), and RPB1 (MT123867) were deposited in GenBank and showed 99.67%, 99.75%, and 100% identity with type material G. radicicola CBS 296.53 (KM484962, KM484845, and KM485061). A multi-locus phylogenetic analysis based on Bayesian Inference showed the isolate LEMIDPRZm 19-01 in the G. radicicola clade (Fig. 2). To confirm pathogenicity, ex vivo assays were performed with mycelial PDA discs of 5 mm from a 7-day-old culture using detached roots (adapted method by Degani et al., 2019), on wounded and unwounded stalk and leaves, each treatment consisted of five replications. PDA discs without fungal were used in negative tissue controls. Pathogenicity tests were also conducted in vivo, two experiments performed: i) the stalk tissue was inoculated by sterilized toothpick grown on PDA with fungal mycelium and the leaves inoculated as ex vivo assay, and toothpick without fungal mycelium was used to stalk negative control, whereas PDA discs without fungal were used in the tested leaves; ii) 6 mycelial PDA discs/500 mL were placed on potato dextrose broth (PDB) media and it remained in agitation for 10 days to obtain a mycelial suspension. Subsequently, the mycelial was crushed to soil infestation, and 50 mL from this suspension were dropped in each 2 L maize pot with soil sterilization 10 days after emergence. Maize pots with soil sterilization without mycelium fungal were used as negative controls. Four replications (maize pots), for each treatment, were used in both tests. Experiments were repeated twice. In the ex vivo assay, all inoculated tissues with and without wounds showed necrotic lesions (Fig. 1K-N). In the first in vivo assay, stalk rot symptoms, including wilting of the inoculated plants causing premature plant death, were observed within 6 days (Fig. 1O-Q). In the second in vivo assay, inoculated plants had inferior growth than compared with plant control. Sixty days after inoculation, the plants were removed from the pots and it was observed a roots degeneration with symptoms of necrosis (Fig. 1R-U). No symptoms were detected in the control treatments and the pathogen was re-isolated from symptomatic tissues confirming Koch’s postulate for all assays. So far, to our knowledge, the pathogen distribution was reported solely in the west area of Paraná state, but it may become a potential threat to Brazilian maize production. Further monitoring is necessary to better understand the epidemiology of this pathogen to address a strategy for disease control. The pathogen has already been detected in Canada, South Africa, and China. To our knowledge, this is the first report of G. radicicola in Brazil, as well as in South America.