The experiments described were designed to investigate the way in which high temperatures (30°C and above) affected the survival and infectivity of spores of Glomus intraradices formulated as the commercial inoculum NutriLink TM. Infection of mung bean (Vigna radiata) occurred most rapidly at 30°C compared with either 22 ° or 38°C, although the final percentage of the root length infected (6 weeks) was similar at all three temperatures. Early rapid infection led to greater plant growth of this species at 30 °. In cashew (Anacardium occidentale) no infection occurred at 38°C and this was associated with low plant growth, compared with the other temperatures at which infection reached 40-60% after 4 months. In both species differences in root temperature were associated with marked differences in the morphology and growth of the root systems, with poor root growth at 38°C.Spores of G. intraradices retained infectivity with respect to mung bean for up to 6 weeks in moist fallow soil, although maximum infectivity was observed in soil without a fallow period. The effects of temperature on germination of spores buried in filter paper sandwiches in soil were consistent with the data for infection and growth. Germination was most rapid and reached the highest percentage at 3 weeks at 30°C. Lowest germination was attained at 38°C. We conclude that G. intraradices can retain its infectivity in moist soil at high temperatures, but that the extent to which the plants become infected and hence their response, depends not only on this but also on host factors such as root growth.

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 Nutrilink� (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.