Genetic difference in seed iron content and early responses to iron deficiency in wheat

Wheat plants were grown in nutrient solution with or without 100 micromolar iron (Fe) under controlled environmental conditions. Two wheat genotypes were chosen as two extremes in seed Fe content (Z181 with 1.18 microgram Fe seed(-1) and N85021 with 2.21 microgram Fe seed(-1)) from a field screening-experiment that showed a significant difference in seed Fe contents among 26 wheat cultivars. Under 0 micromolar Fe supply, N85021 showed better seedling vigor, and had greater dry matter production in root and shoot, chlorophyll concentration in fresh fully expanded leaves and Fe uptake in both root and shoot in comparison with Z181. However, there was no significant difference for the two genotypes when 100 micromolar Fe was supplied. For the 0 micromolar Fe treatment, the genotype N85021 with high seed Fe had a higher Fe concentration in plants than Z181. Most of seed Fe was transported into the seedling tissues due to the absence of external Fe supply. The difference in Fe concentration between the two genotypes was greater in roots than shoots. On day 13 after germination, the percentage of Fe translocated from seed to plant was 82% for N85021 and 86% for Z181. The rate of phytosiderophore release was higher for Z181 than N85021 only on day 5 after germination due to Z181 being more sensitive to Fe deficiency stress than N85021. The release of phytosiderophores by N85021 increased sharply with the duration of treatment and surpassed Z181 after day 6. The highest release of phytosiderophores by wheat plants was observed on day 11 for Z181 and day 12 for N85021. Compared with Z181, N85021 exuded a higher amount of phytosiderophores under Fe deficiency till day 17 after treatment. N85021 had higher chlorosis resistance than Z181; this genotypic difference in Fe efficiency between N85021 and Z181 could have resulted from both a higher rate of phytosiderophore release and a higher seed Fe content. The pattern of phytosiderophore release, as an important factor related to tolerance to Fe deficiency was mainly controlled by the genotype, while seed Fe content showed only a modifying effect via changing the dynamics of phytosiderophore release over time. The higher Fe content in seed may also be an important factor related to chlorosis resistance in wheat because it improves the early establishment of seedlings. Sowing high-Fe seed combined with growing Fe-efficient genotypes may be an effective measure to solve the Fe-deficiency-related chlorosis in wheat. Thus, the effect of seed Fe content should be taken into account when comparing genotypes for resistance to Fe deficiency