Micronutrients affect induced resistance in watermelon against Fusarium oxysporum f. sp. niveum and Meloidogyne incognita infection

Authors: KASMITA, KARKI - University Of Georgia; COOLONG, TIIM - University Of Georgia; MANDAL, MIHIR - Claflin University; Kousik, Chandrasekar - Shaker; GITAITIS, RONM - University Of Georgia; HAJIHASSANI, ABOLFAZL - University Of Georgia; DUTTA, BHABESH - University Of Georgia

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/28/2022
Publication Date: 9/30/2022
Citation: Kasmita, K., Coolong, T., Mandal, M., Kousik, C.S., Gitaitis, R., Hajihassani, A., Dutta, B. 2022. Micronutrients affect induced resistance in watermelon against Fusarium oxysporum f. sp. niveum and Meloidogyne incognita infection. Plant Disease. 10:796. https://doi.org/10.3390/pathogens10070796.
DOI: https://doi.org/10.3390/pathogens10070796

Interpretive Summary: Watermelon is an important vegetable crop grown in 44 states in the U.S.A. Many diseases and pests attack watermelon seedlings and plants and reduce their yield resulting in monetary loss for growers. One such disease, known as Fusarium wilt can infect watermelon plants and cause death of plants resulting in yield reduction in the field. Another problem that can also reduce watermelon yields is galling on watermelon roots caused by root knot nematode. Both these problems are present in the soil in the southeastern U.S.A. where watermelons are grown and routinely result in yield losses. Micronutrients present in the soil also affect the development of diseases caused by various soil-borne plant pathogens. Varying levels of micronutrients in the growing medium (iron, Magnesium and Zinc) differently affected the way watermelon plants responded to infection by Fusarium wilt and root knot nematodes. The information from this study can be used by private and public sector researchers in their studies. This information will also be useful for crop consultants and extension agents when advising growers about micronutrients.

Technical Abstract: Fusarium oxysporum f. sp. niveum (FON) and southern root-knot nematode (RKN, Meloidogyne incognita) are devastating soil-borne pathogens of cultivated watermelon in the southeastern United States. The effects of controlled, micronutrient applications [iron (Fe), manganese (Mn) and zinc (Zn)] via hydroponics on induced resistance (IR) genes [salicylic acid (SA) pathway genes (PR1, PR5, and NPR1) and jasmonic acid (JA) pathway genes (VSP, PDF, and LOX)] in watermelon seedling was investigated. Plants were treated with micronutrients (Fe, Mn and Zn) at higher (3X) and lower levels (0.5X) of the standard-dose in Steiner solution (X= standard dose) for 7-days and the expression levels of the induced resistance genes were evaluated. A sub-set of micronutrient-treated plants was later inoculated with either FON or RKN or both and they were re-evaluated at 3-day post-inoculation for the genes mentioned above. In two?? independent trials, it was observed that induced resistance genes were not up-regulated with any of the micronutrient treatments at 7-day post-treatment. However, upon pathogen inoculation (FON or RKN or both), both SA and JA genes were activated and the expression levels varied considerably with different micronutrient treatments at 3-day post-inoculation (equivalent to 11-day post micronutrient treatments). For genes in the JA pathway, PDF was up-regulated in high Fe treated plants upon FON inoculation, whereas VSP was up-regulated in low Mn treated plants upon RKN inoculation. For genes in the SA pathway, PR1 was up-regulated in plants treated with low Zn only following co-inoculation with both FON and RKN. These observations suggest that soil micronutrients play an essential role in the induction of resistance via. SA and JA pathways against soil-borne pathogens.