Characterization of Fusariumsambucinum isolates associated with potato dry rot and evaluation of cultivar susceptibility and fungicides

Abstract

and Salas, 2001). The disease occurs in warehouses. 1 Dry rot disease affects both tubers in the warehouse and seed tuber parts in the field economically (Wharton et al., 2007). The disease begins primarily on the tubers in the form of dark and sunken superficial spots. In tuber flesh, necrotic areas are observed in colors ranging from light brown to black (Figure 1). When the rot progresses, gaps form in the tuber and tuber surface wrinkles.The disease reduces yield, seed quality and marketable product. It causes product losses directly or indirectly. Most tuber infections consist of wounds that appear during planting, mechanical harvesting or classification by size before storage. It is estimated that the crop losses due to dry rot range from 6 to 25%, and during long-term storage, 60% of qualitative tubers can be affected by dry Abstract: Potato dry rot disease (Fusarium spp.) is one of the most important fungal storage rots on potato tubers after harvesting. The aims of this study were to identify the Fusarium species that cause dry rot in potato storages, evaluate the most virulent Fusarium species in vitro and in vivo for fungicide sensitivity and determine the susceptibility of the cultivars. In this context, as a result of surveys carried out in potato storages of Ödemiş and Torbalı counties in İzmir province in 2015-2016; Fusarium species obtained from diseased potato tubers were identified as Fusarium sambucinum, F. oxysporum, F. avenaceum and F. equiseti, using morphological and molecular methods. The most virulent species was determined according to the pathogenicity tests. To determine the susceptibility to disease, 13 potato cultivars, commonly stored in the region throughout the working period, were tested against the most virulent Fusarium species. The pathogenicity tests showed variation between the rank order of susceptibility of the cultivars to the most virulent pathogen. Fungicide sensitivity tests have been conducted with the most susceptible among these cultivars. There are not any plant protection products licensed against this disease in Turkey. On fungicide sensitivity tests, fludioxonil, flutolanil, thiophanate methyl, imazalil, fludioxonil + sedaxane, fluxapyroxad and tolclophos-methyl + thiram efficacy were investigated on the mycelial growth of F. sambucinum. In vitro assays; fludioxonil, fludioxonil + sedaxane and imazalil were the most effective fungicides preventing mycelial growth of the pathogen. In addition to chemicals that are effective in vitro tests, efficacy of Bacillus subtilis QST 713 strain 1.34%, Pseudomonas fluorescens strain Pf1 1.5% and 42% carboxylic acid were also evaluated. In vivo tests were conducted with Russet Burbank, Lady Olympia, Granola cultivars and fungicides were applied in two different methods including before and after inoculation. Results of this study indicated that the treatments with fludioxonil + sedaxane had the highest efficacy and treatments before inoculation was more effective.

Spécies Diversity and Physiological Characterization of Fusarium spp. Isolates Causing Potato (Solanum tuberosum L.) Fusariosis (Far-North, Cameroon)

“…This percentage shows that Fusarium head blight is a cosmopolitan fungal disease that significantly affects the potato crop in the Far North Region, Cameroon. These results are in agreement with the work of [13,14] who reported that in Great Britain, the national average incidence of affected tubers was as high as 1.4% and 50-100%. Furthermore, [15] also showed that more than 50% of tubers are infected by Fusarium in Michigan; it is 43.7% in the Oued Tafna region of Algeria [34].…”

“…In addition, F. oxysporium, F avenaceum, F. equiseti, and F. solani have been recorded on potato by [17,24]. In Africa, Fusarium sambicum, F. oxysporium, predominate in Egypt [14]. The results of the morphological characterization of the colonies of the isolates grown on PPA, PCA, PSA and PDA culture media revealed that the majority of the colonies had a white colour, a regular growth, a cottony aspect on the different culture media with a relief varying from Flat to Domed.…”

“…The identification of the species was based on the identification keys as defined by [30,12,14,6] this was done by comparing the symptoms on different organs (leaves and tubers) in the field and the microscopic structures in the laboratory.…”

“…In addition, F. oxysporium, F avenaceum, F. acuminatum, F. equiseti, F. sulphureum and F. solani have been recorded on potato [17,24]. In Africa, Fusarium sambicum, F. oxysporium, F. verticillioides and F. incarnatum predominate in Egypt [14]. To the best of our knowledge, no study has revealed the specific diversity of fungi of the genus Fusarium in Cameroon in general and in the Far North Region in particular.…”

“…In almost all potato production areas, Fusarium head blight appears to be the most important foliar and post-harvest disease causing the highest yield losses estimated at more than 25% per year [12,13,14]. Various studies have also shown that the severity of diseases caused by Fusarium varies from 6 to 25% and even 60% in some cases [12,14]. In Great Britain, the national average incidence of affected tubers could be as high as 1.4% and 50-100% of tubers are attacked [13].…”