Methyl jasmonate alleviates drought stress in young sugar beet (Beta vulgaris L.) plants

Drought is the major cause of yield and economic loss for the sugar beet crop. Mechanisms to reduce drought stress, however, are lacking as sugar beets are largely produced without irrigation and drought-tolerant varieties are not available. As jasmonates are implicated in plant drought-stress responses, research was conducted to determine whether methyl jasmonate (MeJA) could mitigate drought effects on sugar beet. Fourteen-day-old plants were treated with 0, 0.01, 0.1, 1 or 10 mu M MeJA. Seven days later, half of the plants were drought-stressed by withholding water, while control plants continued to receive water. Drought caused leaf relative water content (RWC), shoot fresh and dry weights, net photosynthetic rate (Pn), transpiration rate (EVAP), stomatal conductance (Gs), water-use efficiency (WUE) and PSII quantum efficiency to decline and substomatal CO2 concentration (Ci) and proline and betaine concentrations to increase. MeJA, at 1 and 10 mu M, reduced moderate and severe drought effects on RWC, Pn, Ci and WUE and altered drought-induced changes in proline accumulation, but had no effect on Gs, EVAP or betaine accumulation. Results indicate that MeJA delayed plant dehydration and protected the photosynthetic apparatus from drought-induced impairment. Exogenous application of MeJA, therefore, alleviates drought stress on young sugar beets and may provide a tool to reduce the economic loss caused by dry conditions during early crop production.