The effect of inoculation of cashew with NutriLink on vesicular arbuscular mycorrhizal infection and plant growth

Abstract

This investigation was initiated to assess whether inoculation of cashew (Anacardium occidentale) seedlings under commercial nursery conditions would result in mycorrhizal development in the root systems and increased growth of the plants. Three experiments were carried out to investigate the effects of different nursery factors on infection and plant growth. These were: use of triple superphosphate, pH of the potting mix (varied by lime additions) and removal of the cotyledons. Inoculation with the commercially available mycorrhizal inoculum NutrilinkÖ (containing spores of Glomus intraradices) resulted in mycorrhiza formation, but the levels of infection were low even in the absence of triple superphosphate addition. The highest infection (55%) was observed in seedlings from which the cotyledons had been removed. Inoculated plants in general grew less well than non-inoculated plants under all conditions. This depression may be the result of changes in pH following inoculation or the result of development of mycorrhizal infection. There were no positive effects of inoculation on nutrient concentrations in the tissues, except that inoculated plants had higher concentrations of K in both leaves and roots. Addition of lime to the potting mix did not significantly affect the extent of infection or the responses of the plants. Cotyledon removal was associated with higher infection and a reduction in the negative effect of inoculation on growth, although plant growth was reduced in inoculated and non-inoculated treatments. It does not appear that inoculation with NutriLink is appropriate in the potting mixes used, particularly as the formulation causes changes in pH of the potting mixes. Other strategies will need to be adopted to optimize potential benefits of mycorrhizas in cashew production.