Survey of Fusarium species in an arid environment of Bahrain. VI. Biodiversity of the genus Fusarium in root-soil ecosystem of halophytic date palm (Phoenix dactylifera) community

Qaher A. MANDEEL, Najma AYUB & Jamshaid GUL

en Cryptogamie, Mycologie 26 (4) - Pages 365-404

Published on 30 December 2005

Date palm (Phoenix dactylifera) as an indigenous halophytic tree was selected as a target host to evaluate biodiversity of the genus Fusarium in the north-west transect of the main island of Bahrain.A total of 27 villages were thoroughly surveyed and 81 samples of roots, plant debris and soil were collected from the rhizosphere soil of small, medium and large plants. Soils samples were found mostly saline, high in soluble salts, calcareous, gypsiferous, poor in organic matter and sandy to coarse in texture. Data assessment for recovery of Fusarium species was based on colony identification and plate counts by direct plating of roots, plant debris and soil on selective media.A sum of 2107 isolates, fluctuating between 1 to 345 per sample, were encountered among all transects, plant heights, media and isolation type. Jid Ali village yielded the highest colony counts (162.56). Mean recovery of Fusarium isolates was highest in plant debris (723) followed by roots (540) and lowest in soil samples (410). A gradual increase in colony counts from root samples were observed proportionally related to growth in plant height from small to large. A total of thirteen species were recovered representing eight sections, twelve from roots and six from plant debris and soil samples each. The isolated species were F. avenaceum, F. chlamydosporum, F. equiseti, F. illudens, F. lateritium, F. moniliforme. var. subglutinans, F. oxysporum, F. pallidoroseum, F. poae, F. sambucinum, F. solani, F. sporotrichioides and F. tricinctum. Three species, F. avenaceum, F. illudens, and F. poae are reported for the first time from Bahrain. F. solani and F. oxysporum were the most dominant and frequently encountered species, a finding confirm previously reported data and validated by chi-square contingency analysis. Northern transect resulted in higher species assemblage and isolate counts compared to west and principally isolation from root samples was superior than other isolation types. Analysis of data supported by diversity indices revealed that roots of small plants were the most diverse (0.588) followed by large plant (0.544). Overall, variations related to locations were much greater than differences attributed to isolation type or plant height. Large-medium plants combinations exhibited the highest species similarity composition (0.80) as determined by Sorensen community coefficient. Species richness among samples fluctuated between 2-10 for soil of medium plants and root of small plants. Overall, that predominance of F. solani and F. oxysporum in the rhizosphere of date palm is consistent with the hypothesis that these fungi have broad ecological tolerances and tend to be illustrative of hot arid habitats. The influence of soil biotic factors on Fusarium diversity and spectra is discussed.

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