2011 Annual Report
1a.Objectives (from AD-416)
1) Determine if differences in mycorrhizal dependence exist in selected US elite sorghum hybrids and African sorghum lines, and determine how this is reflected in their response to low input management (low levels of N and P);
2) Integrate these findings into measures of the growth and production of sorghum crops, grain quality, and evaluation of end-use quality.
1b.Approach (from AD-416)
Our approach will be to.
1)evaluate mycorrhizal dependency of modified sorghum cultivars in controlled greenhouse studies;.
2)determine consequence of reductions in dependency on the symbiosis by assessing: drought tolerance, grain quality (C:N:P) and quantity, biomass production, and root morphology (e.g. root length production) of selected cultivars;.
3)assess drought tolerance, tissue quality, and biomass production of selected cultivars grown with and without the fungal symbiont, under high- and low-input fertilization;.
4)conduct biochemical characterization of sorghum starch and protein; and.
5)evaluate end-use grain quality from each cultivar.
Significant progress has been made on understanding the influence of cultivar selection on arbuscular mycorrhizal (AM) dependence of sorghum crops. Our first year greenhouse study assessed the role of AM symbiosis on sorghum biomass production and grain quantity and quality. Modern (modified) and African sorghum cultivars were grown in native low-nutrient prairie soil and treated with low- and high-fertilization (N and P). Half of the sorghum plants were treated with fungicide to suppress the AM symbiosis.
When grown in native low-nutrient prairie soil, African cultivars produced as much as three-fold greater biomass and grain production than modern cultivars.
Fertilization of native low-nutrient soil (control pots) increased vegetative biomass and grain production only in modern cultivars. These cultivars required fertilization to attain the biomass production of African cultivars grown in native soils not receiving fertilizer inputs. However, fertilization of native soils did not further increase biomass production of African cultivars.
AM fungi were essential for the growth and reproduction of both modern (modified) and African sorghum cultivars, as fungicide reduced AMF colonization, with a large and significant reduction in plant biomass production and complete lack of reproduction of all sorghum cultivars tested.
Additions of N and P fertilization to fungicide-treated plants compensated for the loss of biomass and grain production in all cultivars. However, the modern cultivars were generally more responsive to fertilization, resulting in larger vegetative biomass and grain production than African cultivars.
Methods used to monitor the progress of the research were emails, phone calls and periodic research meetings.