Vegetative Compatibility and Virulence Diversity of Verticillium dahliae from Okra (Abelmoschus esculentus) Plantations in Turkey and Evaluation of Okra Genotypes for Resistance to Verticillium dahliae
Verticillium dahliae from Okra: Genetic Diversity and Evaluation of Okra Genotypes for Resistance
Forty-four V. dahliae isolates were collected from symptomatic vascular tissues of okra plants each from a different field in eight provinces located in the eastern Mediterranean and western Anatolia regions of Turkey during 2006-2009. Nitrate-nonutilizing (nit) mutants of V. dahliae from okra were used to determine heterokaryosis and genetic relatedness among isolates. All isolates from okra plants were grouped into two vegetative compatibility groups (VCGs) (1 and 2) and three subgroups as 1A (13.6%, 6/44), 2A (20.5%, 9/44) and 2B (65.9%, 29/44) according to international criteria. Pathogenicity tests were performed on a susceptible local okra (A. esculentus) landrace in greenhouse conditions. All isolates from VCG1A and VCG2B induced defoliation (D) and partial defoliation (PD) symptoms, respectively. Other isolates from VCG2A gave rise to typical leaf chlorosis symptoms without defoliation. These data showed that the virulence level of V. dahliae isolates from okra was related to their VCG belongings. Eighteen okra genotypes (landraces) from diverse geographical origins were screened for resistance to VCG2B and VCG1A of V. dahliae. The results indicated that all genotypes were more susceptible to highly virulent VCG1A-D pathotype than to less virulent VCG2B-PD pathotype of V. dahliae. Significant differences were observed among the genotypes; however, none of them exhibited a level of resistance. Only Çorum, Hatay Has and Şanlıurfa genotypes displayed the lowest level of susceptibility or little tolerance to both D and PD pathotypes. VCG2B of PD was prevailing in the surveyed areas and VCG1A of D was the most virulent of the VCGs identified.
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