ARS | Publication request: Soybean seed composition as affected by drought and Phomopsis in phomopsis susceptible and resistant genotypes

Submitted to: Journal of Crop Improvement
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 18, 2011
Publication Date: May 30, 2012
Citation: Bellaloui, N., Mengistu, A., Fisher, D.K., Abel, C.A. 2012. Soybean seed composition as affected by drought and Phomopsis in phomopsis susceptible and resistant genotypes. Journal of Crop Improvement. 26:428-453.

Interpretive Summary: The Early Soybean Production System in the midsouth showed yield benefit under irrigated and non-irrigated conditions. However, declines in seed quality in the Early Soybean Production System due to phomposis seed decay, which is primarily caused by Phomopsis longicolla, have been a major concern. The objective of this research was to evaluate susceptible, moderately resistant, and resistant soybean genotypes to phomopsis for seed composition components (seed protein, oil, fatty acids, sugars, and minerals) in maturity group 3 and 5. The experiment was conducted in the field for two years at Stoneville, Mississippi. The results showed that there was no consistent trend in seed composition components between moderately resistant, resistant, and susceptible genotypes in maturity group 3 under irrigated conditions. Under non-irrigated conditions, however, protein and oleic acid (desirable fatty acid) were higher and linoleic and linolenic acids (undesirable fatty acids) were lower in susceptible genotypes than in moderately resistant or resistant genotypes. Under irrigated and non-irrigated conditions, maturity group 5 genotypes had higher seed protein, oil, and oleic acid and lower linoleic and linolenic in moderately resistant and resistant genotypes than in susceptible genotypes. Generally, seed sucrose, raffinose, and stachyose were higher in resistant genotypes than in moderately or susceptible genotypes. Seed concentrations of calcium, potassium, boron, manganese, zinc, and copper were higher in moderately resistant and resistant genotypes than in susceptible genotypes, especially under irrigated conditions. This research demonstrated that seed protein, oil, and sugars were affected by phomopsis under irrigated and non-irrigated conditions. The effect of phomopsis and irrigation on seed protein, oils, and sugars depended on the genotype and maturity. The higher levels of calcium, potassium, boron, manganese, zinc, and copper in seed of resistant genotypes suggest that these minerals may be associated with phomopsis infection. This research provides breeders with valuable information to select for seed composition traits under stress environments of drought and diseases.

Technical Abstract: Limited research has been done on the effect of phomopsis on seed composition in the Early Soybean Production System (ESPS). The objective of this research was to evaluate the effect of phomopsis on seed protein, oil, fatty acid, sugars, and minerals in phomopsis susceptible, moderately resistant, and resistant soybean genotypes grown under irrigated (I) and non-Irrigated (NI) conditions in ESPS. A field experiment was conducted in 2003 and 2005. Two susceptible genotypes (S), two moderately resistant genotypes (M), and two resistant genotypes (R) of maturity group (MG) III and V were grown in Stoneville, MS. Seed protein, oil, fatty acids, and sugars were evaluated in seed harvested at maturity (matured harvesting, MH) and 15 days after maturity (delayed harvesting, DH). The results showed that there was no consistent trend in seed composition components between M, R, and S genotypes in MG III at MH or DH under I conditions. In NI, however, protein and oleic acid were higher and linoleic and linolenic acids were lower in S than in M or R in seed at DH. For MG V genotypes, seed protein, oil, and oleic acid were higher and linoleic and linolenic were lower in M and R than in S under I and NI conditions at MH and DH. In MG III genotypes, seed sucrose, raffinose, and stachyose was higher in M and R than in S genotypes under I conditions at MH only. Under I or NI conditions, seed sucrose, raffinose, and stachyose were higher in R than in M or in S in MG V in 2003 and 2005 at MH or DH. In MG III, seed concentrations of Ca, K, B, Mn, Zn, and Cu were higher in M and R than in S genotypes in I environment at DH and in NI at MH and DH. In MG V, seed concentrations of K, Ca, B, Mn, Cu, Zn were higher in M and R than in S under I or NI and at MH or DH. Seed ratios of 15N/14N or 13C/12C were altered more in S compared with M and R genotypes at MH under I and NI conditions, indicating nitrogen and carbon metabolism pathway alteration by phomopsis infection. This research demonstrated that seed composition components were altered by phomopsis and the degree of alteration depended on the level of resistance of the genotype and maturity group. This research provides breeders with valuable information to select for seed composition traits under stress environments of drought and diseases.