Methyl jasmonate effects on sugarbeet root responses to postharvest dehydration

Authors: FINGER, FERNANDO - Universidade Federal De Vicosa; Eide, John; Dogramaci, Munevver; Fugate, Karen

Submitted to: PeerJ
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/26/2021
Publication Date: 6/17/2021
Citation: Finger, F.L., Eide, J.D., Dogramaci, M., Fugate, K.K. 2021. Methyl jasmonate effects on sugarbeet root responses to postharvest dehydration. PeerJ. 9. Article e11623. https://doi.org/10.7717/peerj.11623.
DOI: https://doi.org/10.7717/peerj.11623

Interpretive Summary: Sugarbeet roots typically dehydrate during storage which decreases their storage life and reduces the amount of sugar that can be extracted from them. Research was conducted to determine whether applying the natural plant compound, methyl jasmonate (MeJA), to freshly harvested roots would reduce the storage losses caused by dehydration since MeJA is known to protect plants from drought during the production season. Dehydration during storage caused roots to lose weight and increased the rate at which they degrade sugar to maintain healthy root tissue. Dehydration also increased the accumulation of the amino acid, proline, which protects plants under dehydrating storage conditions but is likely to reduce sugar recovery during processing. Treating roots with MeJA had only a small effect on improving the quality of dehydrated sugarbeet roots. MeJA reduced the rate at which stored roots degrade sugar to provide energy to maintain root tissue, but the reduction was small and only occurred when roots were severely dehydrated. MeJA also hastened the healing of injuries that were incurred during harvest, but this effect was small and evident only in late stages of wound healing. Other changes in sugarbeet roots caused by dehydration such as root weight loss or proline accumulation were unaffected by MeJA treatment. These results indicate that MeJA applications to harvested roots are unlikely to significantly reduce the negative effects of dehydration on stored sugarbeet roots.

Technical Abstract: Sugarbeet roots are stored under conditions that cause roots to dehydrate, which increases postharvest losses. Although jasmonates can reduce drought stress in intact plants when applied exogenously, their ability to alleviate the effects of dehydration in postharvest sugarbeet roots is unknown. To determine whether jasmonate treatment could mitigate physiological responses to dehydration in postharvest sugarbeet roots, changes in fresh weight, respiration rate, wound healing, leaf regrowth, and proline metabolism were investigated in roots treated with methyl jasmonate (MeJA) or water (controls) and stored for up to eight weeks under dehydrating and non-dehydrating conditions. Dehydrating storage conditions increased root weight loss, respiration rate and proline accumulation, prevented leaf regrowth, and reduced expression of the proline-degrading enzyme, proline dehydrogenase, by 340-fold. Under dehydrating conditions, MeJA reduced respiration, but only in severely dehydrated roots, and hastened wound-healing, but only in late stages of barrier formation. Although MeJA treatment altered expression of genes involved in proline biosynthesis and catabolism, it had no impact on root weight loss, leaf regrowth, or proline accumulation under dehydrating storage conditions. Overall, MeJA was minimally effective in alleviating physiological manifestations of dehydration stress, indicating that postharvest jasmonate applications are unlikely to significantly reduce dehydration-related storage losses in sugarbeet roots.