Screening of rhizobacteria against Fusarium oxysporum f. sp melongenae, the causal agent of wilt disease of eggplant

Rhizosphere isolates of Bacillus and Pseudomonas species isolated from the roots of eggplants (Solanum melongena L.) were collected in eggplant cultivated areas in various geographical districts of Turkey. Isolates were evaluated for siderophore, protease and cyanide production along with the cell wall degrading enzyme production as well as phosphate solubilizing and nitrogen fixing capacities. The isolates showing good performance were tested against Fusarium oxysporum f. sp. melongenae, a highly destructive fungal agent for eggplants, for the antagonistic activities. The isolates designated as 11-4, 13-1, 56K-3, 65A-3, 67A-2, 76A-1, 85A-2, 10a, 318b, 346a, 379c, 007-1, 007-4, and 048-2 were found promising in inhibition of F. oxysporum f. sp. melongenae in vitro conditions. The isolates differing in their antagonistic responses to F. oxysporum f. sp. melongenae would be identified in species level. Also, the best performing isolates for the reduction of disease severity and increased plant growth would be further evaluated via more biochemical parameters such as indole acetic acid production (IAA) and total antioxidant status (TAS)

INDUCED SYSTEMIC RESISTANCE AGAINST FUSARIUM WILT OF TOMATO BY RHIZOBACTERIAL ISOLATES

Plant growth-promoting rhizobacteria (PGPR) include bacteria in the soil rhizosphere that promote plant growth and development through a wide variety of mechanisms. In this study, potential effects of three rhizobacteria Bacillus subtilis (57-2), B. mojavensis (36-1) and B. pseudomycoides (80-1) isolated from tomato rhizosphere on induction of resistance to Fusarium oxysporum f. sp. lycopersici (Fol) were examined through biochemical and histological analyses. These PGPR isolates significantly reduced Fusarium wilt incidence up to 70%. However, the combination of isolates was found either less or not effective in suppressing the disease severity when compared to those of application by the individual isolates. The induction of peroxidase (PDX, EC 1.11.1.7) and catalase (CAT, 1.11.1.6) enzymes was found to be significantly higher in treatment groups than in comparison with the control group. Present biochemical study revealed that three Bacillus spp. resulted in great accumulation of proline and key defense enzymes (PDX and CAT). In situ studies also demonstrated that hydrogen peroxide (H2O2) accumulation and the callose deposition at reaction sites as a response to the pathogen attack reached to maximum level, 24 h after pathogen inoculation. The present findings revealed that PGPR isolates could be effectively used for the biocontrol of Fol through enhancing disease resistance responses of tomato plants

Türkiye'de Açık Tarla Patlıcan Yetiştiriciliğinde Fusarium Solgunluk Hastalığının Yaygınlığı ve İzolatların Virülenslikleri

Fusarium solgunluk hastalığı (Fusarium oxysporum Schlecht. f. sp. melongenae) patlıcan yetiştiriciliğinde ekonomik olarak verim kayıplarına neden olmaktadır. Bu çalışmada, açık tarla patlıcan yetiştiriciliğinin yaygın olduğu Akdeniz Bölgesi'nde Antalya, Mersin ve Hatay, Ege Bölgesi'nde İzmir, Manisa, Muğla ve Aydın, Marmara Bölgesi'nde Bursa, Karadeniz Bölgesi'nde Samsun, Güney Doğu Anadolu Bölgesi'nde Şanlıurfa ve Diyarbakır illerinde 2010 ve 2011 yıllarında, patlıcan yetiştiriciliği yapılan tarlalarda Fusarium solgunluk hastalığının yaygınlık oranı ve hastalık şiddeti tespit edilmiştir. Her iki sörvey yılında en yüksek hastalık yaygınlık oranı yaklaşık % 50 değeri ile Hatay ve Bursa illerinde belirlenmiştir. Bu illeri Antalya, Samsun ve Mersin illeri izlemiştir. En düşük hastalık yaygınlık oranı ise Diyarbakır ilinde saptanmıştır. Makroskobik, mikroskobik incelemeler ve patojenisite denemeleri sonucunda simptomatolojik olarak toplam 381 izolat, Fusarium oxysporum f. sp. melongenae (Fomg) olarak saptanmıştır. Ülkemiz genelinde elde edilen Fomg izolatlarının yüzde hastalık şiddeti değerleri üzerinden virülenslik grupları belirlenmiş, bu izolatlardan 122'si yüksek virülens (% 90-100), 175'i virülens (% 80-89), 62'si orta virülens (% 70-79) ve 22'si düşük virülens (% 60-69) olarak değerlendirilmiştir

Genetic variability among breeding lines and cultivars of eggplant against Fusarium oxysporum f. sp melongenae from Turkey

Seventy isolates of Fusarium oxysporum (Schlechtend: Fr.) f. sp. melongenae Matuo and Ishigami (Fomg), the causal agent of eggplant Fusarium wilt, were tested for their interaction with different lines and cultivars to determine whether there was race-specific interaction. Also, a total of 13 cultivars were tested under greenhouse conditions to evaluate the presence of resistance to Fusarium wilt. The disease severity (%) and the area under disease progress curve (AUDPC) for each of the Fomg isolates were calculated by scale values. Results showed that neither of the resistant lines (LS1934 and LS2436) exhibited wilting symptoms, whereas susceptible local cultivars (cvs. 'Kemer' and 'Hadrian') displayed severe disease symptoms. There was no significant variation in the virulence, indicating the occurrence of a race or races among 70 Fomg isolates tested on resistant lines and susceptible cultivars. This may indicate a genetically homogeneous population structure of Fomg in Turkey

ISOLATION AND CHARACTERIZATION OF RHIZOSPHERIC BACTERIA FOR BIOCONTROL OF TOMATO BACTERIAL SPECK DISEASE AGENT PSEUDOMONAS SYRINGAE PV. TOMATO

Bacterial speck of tomato, caused by Pseudomonas syringae pv. tomato (Pst), continues to be a problem for greenhouse production in the Mediterranean region of Turkey. Effective and augmentative control methods are still in need as for the numerous bacterial plant diseases. In this study, 524 bacteria were isolated from the vicinity of root area of tomato plants from 120 different locations in Adana and Mersin provinces of Turkey. The isolates were characterized and evaluated for their biocontrol potential against Pst. Cultural characteristics were determined on the basis of appearance of colonies developed on King's B media. Isolates having pectolytic activities and causing hypersensitive reaction in tobacco plants were eliminated due to possible pathogenic characteristics. Out of isolated rhizobacteria, 325 of them were found to have nitrogen fixing capacity, 11 of them were able to solubilize phosphorus, and 4 of them induced indole acetic acid (IAA) activity. Forty eight isolates showed antagonistic effect against Pst in vitro. Only 39 isolates out of 48 had siderophore effects. Rest of the isolates had more than one characteristics. The promising isolates on the basis of above parameters are planned to test in field and greenhouse conditions for the ability to reduce the impact of bacterial speck disease and to remediate the polluted soils such as saline and heavy metal contaminated soils