Response of Soybean Iron and Manganese Deficiency

134 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1993.Iron (Fe) and manganese (Mn) deficiency are recurring problems in soybeans (Glycine max (L.) Merr.) grown on high pH, calcareous soils. Although chemical fertilizers have been used to control yield losses associated with these deficiencies, genetic resistance is more reliable and effective. Identification of resistant cultivars requires an understanding of the genetic inheritance for resistance, knowledge of the physiological mechanisms involved with resistance, and the development of reliable screening techniques to identify superior soybean cultivars. Therefore, field and laboratory studies were initiated to enhance present understanding of soybean response to iron and manganese deficiency.Tissue culture was employed to screen soybean genotypes for resistance to iron deficiency chlorosis. A 4MSII medium amended with 10 mM sodium bicarbonate was developed that accurately identified soybean genotypes resistant to iron deficiency. Because of the time constraints associated with this procedure a modified screening technique was developed that used cotyledons as the explant source. Rating of cotyledon color and callus growth provided an accurate indicator of a genotype's response to iron deficiency. A low iron medium was used to demonstrate that a single dominant gene is responsible for resistance to iron deficiency chlorosis at the cellular level. Differences in soybean genotype response to boron, zinc, and manganese deficiency were demonstrated by using a 4MSII medium deficient in one of the above micronutrients.Field studies were used to evaluate soybean response to Mn deficiency. In the first study a highly significant correlation was observed between soybean response to iron and manganese deficiency indicating a similarity in mechanisms associated with resistance to these two micronutrient deficiencies. A genetic study using F$\sb2$ plants and F$\sb{2:3}$ families indicated that multiple genes were required for tolerance to Mn deficiency. Yield studies indicated that Mn deficiency had no affect on soybean yield. However, because previous reports have shown that Mn deficiency affects seed yield it was speculated that factors such as genotype maturity and environmental variation may have influenced the results.U of I OnlyRestricted to the U of I community indefinitely during batch ingest of legacy ETD