Ionomic differences between tomato introgression line IL8–3 and its parent cultivar M82 with different trends to the incidence of blossom-end rot

Fruit blossom-end rot (BER) is a serious physiological disorder that can cause significant yield losses in tomato (Solanum lycopersicum). Although many studies have suggested that calcium (Ca) deficiency in tomato fruits is a major factor for BER, its onset mechanism has not been fully elucidated. Ionomics is a high-throughput elemental profiling of living organisms that can be applied to understand how differences in plant's physiological status involving inorganic elements. In this study, we examined ionomic differences between the tomato cultivar M82 and its introgression line IL8–3, which contains a short chromosome segment from its wild relative Solanum pennellii on chromosome 8 of M82, and has a low incidence of fruit BER. Among the essential elements, Ca showed marked different behavior between the two lines. IL8–3 showed preferential Ca partitioning to fruits compared with M82. The slow growth rate and high Ca concentration observed in IL8–3 fruit during the early growth stages may also be responsible for the low BER incidence in this line. Although Ca ions bind to cell wall pectin and membrane phospholipids, and contribute to cell structure stability, these components showed no significant differences between fruits of the two lines. The fruit ionome differed considerably between M82 and IL8–3, and was not affected by available Ca status in the field. The M82 fruit had higher concentrations of many elements such as magnesium, potassium, boron, and sulfur than did IL8–3, and this trend was also observed in rotten fruit. This suggests that the influence of the leaf (source), rather than the fruit (sink), could be involved in the onset mechanism of BER.