Variability in the response of sunflower hybrids or parental lines to iron stress

Abstract

The degree of Fe efficiency of 3 inbred parental lines and 2 hybrids of sunflower was studied using single 11 day old plants that had been growing under iron stress for the preceding 6 days. The pH of the root medium was recorded daily for each plant from the third to the sixth day of the treatment. The Fe³⁺ reducing capacity was then measured by placing the root in a small vessel with 20 ml of nutrient solution plus FeEDTA and Ferrozine and recording the absorbance at 562 run after 7.5 h. The inbred lines were classified as follows: line 89 was Fe inefficient, line 273 was Fe efficient, although some plants showed a low Fe³⁺ reducing capacity, and line 276 segregated for both Fe inefficient and Fe efficient plants. Two hybrids which had shown some chlorotic plants when grown in calcareous soils, developed Fe efficient and Fe inefficient plants in this assay.

The progeny of 2 Fe efficient and 2 Fe inefficient plants was studied as previously described. The results point out that the capacity of the root to lower the pH has higher heritability than the capacity of the plant to reduce Fe³⁺. The low correlation between these characters might indicate that both are controled by different genes or gene systems without any linkage. It should be possible then to obtain homozygous inbred parental lines which are Fe efficient by applying both tests to several generations and selecting in each generation the plants with the highest capacity.

Key words:

• Iron stress
• Fe efficiency
• ferrozine
• plant breeding
• reduction of Fe³⁺
• sunflower