Iron Use Efficiency in Grain Sorghum Hybrids and Parental Lines

Grain sorghum [Sorghum bicolor (L.) Moench] response to iron stress appears to be somewhat different from other species (e.g. release of less reductant and fewer H+ ions into solution), and, while it is apparently genetically controlled as in other species, it may not be as simply inherited. In this study, three grain sorghum hybrids and their parental lies were screened in nutrient culture in order to make preliminary assessment of heritability of Fe use efficiency, to evaluate the screening technique and to investigate the relationship of P and Fe accumulations to Fe use efficiency in these hybrids and parental lines. The seedlings were grown in a greenhouse on a complete nutrient solution at pH 6.5 until the plants were sufficiently large for experimental use. Subsequently, they were transferred for 7 days to either a modified Hoagland‘s No. 1 or Steinberg‘s solu. tion with Fe, P, ammonium, and nitrate concentrations being vaned. The plants were visually ranked for Fe use efficiency based on Fe deficiency symptoms, P and Fe concentrations in the top two leaves were determined and the pH of the nutrient solutions was monitored. Results obtained from screening the sorghum parental lies and F, hybrids indicated varying degrees of Fe use efficiency. Hybrid ATx 378 X RTx 2536 was classed most efficient in Fe utilization and RTx 7000 was classed most inefficient. Heterosis for Fe efficiency was observed when line ATx 378 was combined with lines RTx 2536, RTx 7000 and RTx 415. However, the efficiency of the two latter hybrids was not as good as ATx 378 X RTx 2536. Parental line RTx 2536 had a higher Fe efficiency ranking than the other three restorer lines. The inheritance of the Fe efficient trait appears to be dominant or overdominant in nature. Chemical analyses in this work, show that a negative, apparently linear, correlation exists between P and Fe concentrations in the top leaves of the sorghums studied.