Page Banner

United States Department of Agriculture

Agricultural Research Service

Research Project: SOYBEAN DISEASE AND PEST MANAGEMENT

Location: Soybean/maize Germplasm, Pathology, and Genetics Research

Title: Comparison of field, greenhouse, and detached-leaf evaluations of soybean germplasm for resistance to Phakopsora pachyrhizi

Authors
item Twixeyimna, Mathias - INT.INSTITUTE NIGERIA
item Ojiambo, Peter - INT.INSTITUTE NIGERIA
item Ikotun, Tom - INT.INSTITUTE NIGERIA
item Paul, Chandra - UNIV OF ILLINOIS
item Hartman, Glen
item Bandyopadhyay, Ranajit - INT.INSTITUTE NIGERIA

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 20, 2007
Publication Date: September 20, 2007
Citation: Twixeyimna, M., Ojiambo, P., Ikotun, T., Paul, C., Hartman, G.L., Bandyopadhyay, R. 2007. Comparison of field, greenhouse, and detached leaf evaluations of soybean germplasm for resistance to Phakopsora pachyrhizi. Plant Disease. 91(9):1161-1169.

Interpretive Summary: Soybean accessions and breeding lines were evaluated for resistance to soybean rust caused by the fungus Phakopsora pachyrhizi. Evaluations were conducted in replicated experiments in growth chambers using detached leaves, and under greenhouse and field conditions. There were significant differences among genotypes in their response to P. pachyrhizi infection in the detached leaf, greenhouse and field evaluations. Three accessions had very low levels of disease compared to the susceptible checks and all other genotypes. Detached leaf, greenhouse and field results were comparable, and there were significant correlations between detached leaf and greenhouse (absolute and between detached leaf and field resistance across genotypes). The overall results show the utility of detached leaf assay for screening soybean for rust resistance. This information is important to soybean pathologists, breeders and others that are interested in host-pathogen interactions.

Technical Abstract: Fourteen soybean accessions and breeding lines were evaluated for resistance to soybean rust caused by the fungus Phakopsora pachyrhizi. Evaluations were conducted in replicated experiments in growth chambers using detached leaves, and under greenhouse and field conditions. In growth chamber experiments, inoculation of detached leaves with 1 million spores per ml resulted in a significantly (P<0.0001) higher total number of pustules and spores per unit leaf area than inoculations with lower spore concentrations. Amending agar medium with plant hormones significantly (P<0.0001) aided retention of green leaf color in detached leaves. Leaf pieces on a medium containing 10 mg/l kinetin had 5% chlorosis at 18 days after plating compared to leaf pieces on media amended with all other plant hormones, which had higher levels of chlorosis. Leaf age significantly affected number of pustules (P=0.0146)and number of spores per pustule (P=0.0088) and 3- to 4-week old leaves had a higher number of pustules and number of spores per pustule, compared to leaves that were either 1- to 2- or 5- to 6-weeks old. In detached leaf and greenhouse screening, plants were evaluated for days to lesion six appearance, days to pustule formation, days to pustule eruption, lesion number, lesion diameter, lesion type, number of pustules and spores per pustule in 1 square centimenter leaf area. Plants were also evaluated for diseased leaf area (in greenhouse and field screening) and sporulation (in field screening) at growth stage R6. There were significant (P<0.0001) differences among genotypes in their response to P. pachyrhizi infection in the detached leaf, greenhouse and field evaluations. Accessions PI 594538A, PI 417089A and UG-5 had very low levels of disease compared to the susceptible checks and all other genotypes. Detached leaf, greenhouse and field results were comparable, and there were significant correlations between detached leaf and greenhouse (absolute r=0.79; P<0.0001) and between detached leaf and field resistance (absolute r=0.83 P<0.0001) across genotypes. The overall results show the utility of detached leaf assay for screening soybean for rust resistance.

Last Modified: 7/23/2014
Footer Content Back to Top of Page