Tolerance Traits and Dry Matter Partitioning in Five Maize (Zea mays L.) Varieties Subjected to Drought Stress during the Vegetative Phase

Maize ( Zea mays L.) is particularly vulnerable to drought stress due to its high water requirements. The aim of this study is to assess the tolerance to drought stress induced during the vegetative phase in five maize varieties (Samaz, TZPB, Ikenne, TZE and Amen) and to understand the dry matter partitioning involved. The results showed that flowering (male or female) is only slightly affected, delayed by two days in the Ikenne variety and by three days in the Amen variety, but not affected at all in the Samaz, TZPB, and TZE varieties. Under drought stress, all varieties exhibit a relatively small decrease in relative water content of between 2.5 and 15.5%. Osmoregulation remains more efficient in the Ikenne variety, with a high foliar proline accumulation of around 300%. Oxidative stress is moderate overall, with foliar malondialdehyde accumulation approaching 45% in the Samaz and TZPB varieties. Calculation of the drought susceptibility index (DSI) shows that the Ikenne and TZE varieties are tolerant (DSI 1), and the Amen variety is intermediate (DSI = 1). The TZPB, Samaz, Ikenne and Amen varieties prioritise biomass allocation to root growth (soil exploration) and/or above-ground growth (stems and leaves) at the expense of grain formation (reproduction), whereas the TZE variety prioritises reproduction at the expense of vegetative growth. These results could provide promising avenues for selecting varieties more resilient to increasing drought stress.