NH4 fertilization increases susceptibility of sweet basil (Ocimum basilicum L.) to grey mould (Botrytis cinerea) due to decrease in Ca uptake

• Published in: Phytoparasitica 2020-11, Vol.48 (5), p.685-697
• Main Authors: Yermiyahu, U., Halpern, M., Shtienberg, D.
• Format: Article
• Language: English
• Subjects: Agriculture; Biomedical and Life Sciences; Ecology; Life Sciences; Plant Pathology; Plant Sciences
• ISSN: 0334-2123; 1876-7184
• DOI: 10.1007/s12600-020-00832-5

Sweet basil ( Ocimum basilicum L.) is an economically important herbaceous annual plant of the Labiaceae family. One of the main pathogens of sweet basil is grey mould ( Botrytis cinerea ). Previous work showed that susceptibility to grey mould increased with increasing N availability. The purpose of this work is to determine the role N form and Ca in this phenomenon. First, data from previous experiments were reexamined in order to determine whether there was a correlation between shoot Ca and basil plant susceptibility to B. cinerea . Then, basil plants were grown in a complete randomized design with 12 treatments and 5 repetitions in which N concentration, N type, and Ca concentration were varied. Plants were harvested 7 times, and shoot Ca and N were measured. Cuttings and full plants were inoculated with B. cinerea in order to determine their susceptibility to grey mould. We found that increases in N availability only increased the susceptibility of the basil plants to grey mould when the N was provided as a mix of NO 3 and NH 4 , whereas in treatments where N was provided solely as NO 3 , N availability had no effect on plant susceptibility. Furthermore, we found that NH 4 inhibited Ca accumulation, and shoot Ca concentration was negatively correlated to plant susceptibility. Taken together, this shows that N availability per se did not increase basil susceptibility to B. cinerea , rather it was the increase in NH 4 fertilization which caused a reduction in shoot Ca which in turn was responsible for this effect.