Nutritional, growth, and reproductive responses of maize (Zea mays L.) to arbuscular mycorrhizal inoculation during and after drought stress at tasselling

The effects of root colonization by the arbuscular mycorrhizal (AM) fungus Glomus intraradices Schenck & Smith on nutritional, growth, and reproductive attributes of two tropical maize cultivars with different sensitivities to drought were studied. Freshly regenerated seeds of selection cycles 0 (cv. C0, drought-sensitive) and 8 (cv. C8, drought-resistant) of the lowland tropical maize population "Tuxpeño sequía" were used in this greenhouse experiment. Maize plants were subjected to drought stress for 3 weeks following tasselling (75–95 days after sowing) and rewatered for the subsequent 5 weeks until harvest. Mycorrhizal (M+) plants had significantly higher uptake of N, P, K, Mg, Mn, and Zn into grain than non-mycorrhizal (M–) plants under drought conditions. AM inoculation also produced significantly greater shoot masses in C0 and C8 regardless of the drought-stress treatment. In the sensitive cultivar C0, drought stress reduced the shoot mass and grain yield by 23% and 55%, respectively, when roots were not colonized, while the reductions were only 12% and 31%, respectively, with mycorrhizal association. In addition, the emergence of tassels and silks was earlier in M+ plants than in M– plants under drought conditions. Mycorrhizal response was more pronounced under both well-watered and drought conditions in C0 than in the C8 cultivar. The overall results suggest that AM inoculation affects host plant nutritional status and growth and thereby alters the reproductive behaviour of maize under drought conditions.