Comparative study of 'Monilinia fructigena' and 'Monilia polystrom'a on morphological features, RFLP analysis, pathogenicity and histopathology

In this study, we compared cultural, morphological, pathogenic and biological features of Serbian isolates of 'Monilia polystroma' and 'Monilinia fructigena' from apple fruit. Isolates of 'M. polystroma' formed characteristic stromatal plates throughout the cultures unlike 'M. fructigena', while mycelial growth rates were not distinguishable features between species. Conidia of 'M. fructigena' were larger than 'M. polystroma', and both species produced slightly larger conidia on apple fruit than on V8 medium. The existence and morphology of the microconidial state of 'M. polystroma' was described for the first time using light and SEM microscopy. Microconidia were globose (2.19-3.44 μm), similar to 'M. fructigena'. Digestion of polymerase chain reaction (PCR) product of ribosomal ITS1-5.8S-ITS2 region with restriction enzyme HhaI provided a reliable method for specific detection of 'M. polystroma'. In a pathogenicity test, both species produced larger lesions on cv. Golden Delicious, than on cvs. Idared and Granny Smith. On cv. Golden Delicious, the mean lesion size was not significatly different between species, while on cvs. Idared and Granny Smith M. fructigena tended to produce slightly larger lesions compared to M. polystroma. On artificially inoculated apple fruit after 1 and 4 months of incubation, 'M. polystroma', unlike 'M. fructigena', was capable of forming thicker and more compact stromata with complex morphology, which consisted of densely interwoven medullary hyphae covered with a discontinuous layer of melanized hyphal rind cells. The dynamics of stromata formation beneath the host's cuticle also showed differences between two species, where 'M. polystroma' formed this layer after 1 month, while 'M. fructigena' after 4 months of incubation

Comparative study of Monilinia fructigena and Monilia polystroma on morphological features, RFLP analysis, pathogenicity and histopathology

In this study, we compared cultural, morphological, pathogenic and biological features of Serbian isolates of Monilia polystroma and Monilinia fructigena from apple fruit. Isolates of M. polystroma formed characteristic stromatal plates throughout the cultures unlike M. fructigena, while mycelial growth rates were not distinguishable features between species. Conidia of M. fructigena were larger than M. polystroma, and both species produced slightly larger conidia on apple fruit than on V8 medium. The existence and morphology of the microconidial state of M. polystroma was described for the first time using light and SEM microscopy. Microconidia were globose (2.19-3.44 mu m), similar to M. fructigena. Digestion of polymerase chain reaction (PCR) product of ribosomal ITS1-5.8S-ITS2 region with restriction enzyme HhaI provided a reliable method for specific detection of M. polystroma. In a pathogenicity test, both species produced larger lesions on cv. Golden Delicious, than on cvs. Idared and Granny Smith. On cv. Golden Delicious, the mean lesion size was not significatly different between species, while on cvs. Idared and Granny Smith M. fructigena tended to produce slightly larger lesions compared to M. polystroma. On artificially inoculated apple fruit after 1 and 4 months of incubation, M. polystroma, unlike M. fructigena, was capable of forming thicker and more compact stromata with complex morphology, which consisted of densely interwoven medullary hyphae covered with a discontinuous layer of melanized hyphal rind cells. The dynamics of stromata formation beneath the host's cuticle also showed differences between two species, where M. polystroma formed this layer after 1 month, while M. fructigena after 4 months of incubation

Detection of phytoplasmas in watercress and onion plants from Mauritius. Plant Health Progress http://www.plantmanagementnetwork.org/php/elements/sum.aspx?id=9281&photo=5060 September 30.

Different phytoplasmas were detected and identified in watercress and onion plants from Mauritius. Symptoms observed on watercress were purple coloration of leaves, plant stunting, and reduced leaf size. In onion, witches\u2019 broom and virescence were observed in the inflorescence. Disease incidence in watercress ponds ranged from 30 to 70%, while in onion seed production plots, it was around 10%. PCR/RFLP analyses as well as sequencing of 16S ribosomal gene enabled the identification of phytoplasmas belonging to two ribosomal groups, namely stolbur and aster yellows, from the two aforementioned crops

First Report of Fusarium verticillioides Causing Fusariosis on Triticale Grain in Serbia

Triticale (Triticosecale Wittmack) is a cereal crop species developed to combine positive traits of wheat and rye into a single plant (Arendt and Zannini 2013). Due to its high protein content, favorable amino acid composition, and nutritional values higher than maize, triticale is an excellent component for preparing feed for domestic animals (Đekić et al. 2019). In May 2017, discolored spikes of triticale were observed in a field in Zemun Polje, Serbia, with a disease incidence between 15 and 20%. In total, 400 kernels obtained from discolored spikes were surface sterilized with 1% sodium hypochlorite solution for 3 min, then rinsed three times with sterilized water, plated on potato dextrose agar (PDA) at 25°C, and incubated in the dark for 7 days. In total, 15 isolates of genus Fusarium on PDA formed cottony white to greyish-purple colonies with dark yellow to purple-gray reverse and average colonies. Obtained isolates were transferred to carnation leaf agar (CLA) and synthetic nutrition agar (SNA) for a 7-day incubation in the dark at 25°C. Ten isolates formed “rabbit ear” monophialides, which is the main characteristic of Fusarium verticillioides (Sacc.) Nirenberg. Microconidia are formed from monophialids in long chains. Their shape is oval with a flattened base, without septa (4.0 to 18.0 by 1.5 to 4.5 µm). The shape of macroconidia is slightly falcate to almost straight (3.5 to 4.5 by 31 to 58 µm). Chlamydospores are not produced (Leslie and Summerell 2006). The genomic DNA from one F. verticillioides isolate was extracted using the DNeasy Plant Mini kit (Qiagen, Hilden, Germany) according to the manufacturer’s protocol. Molecular identification was confirmed by sequencing the internal transcribed spacer (ITS), translation elongation factor 1α (EF-1α), and RPB2 (O’Donnell et al. 2000). The sequence was deposited in GenBank as MZ664391, MZ666958, and MZ666957. This sequence was compared with the sequences of F. verticillioides strains registered in the GenBank database based on nucleotide similarity. It showed 100% identity to the sequences MT180471.1 (ITS), MN861767.1 (EF-1α), and MT264836.1 (RPB2). Pathogenicity of all isolates was tested on 20 randomly selected triticale spikes in four replicates (Mesterházy et al. 1999). Inoculation was performed when half of the plants reached the flowering stage by spraying with 20 ml of spore suspension (1 × 106 spores/ml from 7-day-old cultures on PDA). F. verticillioides RBG 1603 Q27 was used as a positive control. Inoculated spikes were covered with PVC bags for 48 h. Discolored spikes were observed after 3 weeks of incubation in a greenhouse at 20°C with a photoperiod of 16 and 8 h (light and dark). All inoculated spikes showed symptoms, similar to those from field infections. Control spikes were symptomless. The fungus was reisolated and was morphologically identical to the original isolates, thus completing Koch’s postulates. Based on morphological, molecular, and pathogenic features, the isolated fungus was identified as F. verticillioides. Fusarium spp. infect crop plants worldwide, resulting in yield loss and reduced grain quality due to mycotoxin contamination (Asam et al. 2017). In Serbia, F. verticillioides was isolated from wheat and barley grains (Stanković et al. 2012) and, to the best of our knowledge, this is the first report of F. verticillioides on triticale grain in Serbia