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Title: Seasonal Progress of Phomopsis Longicolla and its Relationship to Seed Quality in the Early Soybean Production System of the MidSouthern USA

Author
item Mengistu, Alemu
item Boykin, Deborah
item HEATHERLY, LARRY - ARS-RETIRED

Submitted to: Phytopathology
Publication Type: Abstract Only
Publication Acceptance Date: 3/17/2006
Publication Date: 7/29/2006
Citation: Mengistu, A., Boykin, D.L., Heatherly, L.G. 2006. Seasonal Progress of Phomopsis Longicolla and its Relationship to Seed Quality in the Early Soybean Production System of the MidSouthern USA. Phytopathology. 96:S78

Interpretive Summary:

Technical Abstract: The seasonal progress of Phomopsis longicolla was measured for two growing seasons in plots that were either nonirrigated or irrigated at VC through R6 and R1 through R6. Disease was assessed based on isolation frequency from leaves, stems, roots and pods during the season, and from seed at harvest. Isolations made from the vegetative parts and seeds and seed weight and yield were correlated with each other. Phomopsis longicolla was consistently recovered from leaves, stems, roots and pods during the growing season. P. longicolla was isolated from leaves, stems and roots 3 weeks after planting. Recovery of the pathogen from leaves and stems increased as the crop developed in advance of pod infection. P. longicolla recovery from roots was much lower in all irrigation regimes. There were no differences among the irrigation regimes in the recovery of P. longicolla from the vegetative parts and the roots. However, the recovery of P. longicolla from seeds was strongly associated with irrigation regimes. Plants in irrigated plots had more P. longicolla than nonirrigated plants plots and maturity groups (MG) 3, 4, and 5 had more P. longicolla than MG 2. Recovery of P. longicolla from pods was highly correlated with percent P. longicolla recovery from seeds in all years. P. longicolla from seed was negatively correlated with percent seed germination, while seed health rating, a measure of poor seed quality, was positively correlated with P. longicolla recovery from seeds and pods in all years. The level of seed infection by P. longicolla is more environmentally dependent than the infection of the vegetative plant parts.