EFFECT OF VESICULAR ARBUSCULAR MYCORRHIZA ON VEGETATIVE GROWTH AND HARVEST INDEX OF CHICKPEA GROWN IN NORTHERN SYRIA

Determination of the contribution by vesicular-arbuscular mycorrhizal fungi (VAMF) to crop growth under field conditions requires the comparison of non-mycorrhizal or 'low mycorrhizal' to 'high mycorrhizal' plants. In the Mediterranean region of northern Syria, chickpea (Cicer arietinum L. cv. ILC 482) plants were grown on a calcareous soil low in NaHCO3-extractable phosphorus (P). The indigenous VAMF population was reduced by the fumigant dazomet. Growth and nutrient uptake of non-inoculated chickpea ('low mycorrhizal') plants were compared to growth and nutrient uptake of VAMF-inoculated ('high mycorrhizal') and P-fertilized chickpea plants. At flowering in 'high mycorrhizal' plants, mycorrhizal root length, total P uptake and shoot biomass were significantly higher than in 'low mycorrhizal' plants. At maturity, however, shoot biomass was similar, and harvest index was higher in 'low mycorrhizal' plants than in 'high mycorrhizal' plants. This negative effect on reproductive growth was related to a more shallow root distribution in the soil profile and a lower root:shoot ratio in the 'high mycorrhizal' plants. Although chickpea had a benefit from the mycorrhiza in terms of P uptake and vegetative growth, high infection with VAMF reduced reproductive growth, most probably due to higher water consumption and thus drought stress under the Mediterranean conditions.