PHENOTYPIC-EXPRESSION OF DIFFERENT MAIZE HYBRID GENOTYPES GROWN ON SALINE-SODIC SOIL

Iron deficiency chlorosis (FeDC) in various degrees affects nearly 500,000 ha of com (Zea mays L.) in Nebraska, primarily in the river valleys, but also on eroded uplands. Com hybrids produced from 27 public released and 45 experimental inbreds were grown on a Cozad silt loam, saline-sodic (Typic Haplustolls). This soil is slightly calcareous with average pH of 8.3, organic matter 1.8%, DTPA-iron 2.59 ppm, SAR 1.75, and electrical conductivity (EC) of 1.97 in the top 28 cm. Salinity and sodium increase in the next 28 cm with pH at 8.6, SAR 3.44, and EC 2.12. Under these conditions, corn grain yields ranged from 0 to nearly 7600 kg/ha. Yields of the most tolerant hybrids were still only 60-65% of those hybrids grown on a Cozad silt loam with lower salinity and sodium. Susceptibility to FeDC is very genotype specific with the most extreme case being MO17 by N192 yielding 6400 kg/ha, while MO17 by N195 gave 0 yield. Average yield of the six hybrids made with N139 as a parent was 398 kg/ha. Several other inbreds gave low yield in all hybrids tested. Three hybrids with A634 as a parent averaged 5985 and three with N193 averaged 61 10 kg/ha. The cross A634 by N193 produced 7345 kg/ha. The highest yielding hybrid resulted from a cross of two experimental inbreds selected for tolerance to the saline-sodic conditions. The data from several parent line combinations suggest that at least two major genes are involved in these levels of tolerance. Results show the genetic relationship of tolerance in corn to saline-sodic soils. Enough inbred line differences have now been identified to permit more definitive inheritance studies.