Reactions of Glycines species and other legumes to Septoria glycines

Abstract

Thirteen genera representing 30 legume species, two weed species (Abutilon theophrasti and Cynanchum laeve), and five cultivars of soybean were inoculated with Septoria glycines in the field and/or greenhouse. Of these, 29 legume species and A. theophrasti had leaf symptoms. Only Cicer arietinum was symptomless under field and greenhouse inoculations. C. laeve was found to be infected in its natural state in the field, but symptoms could not be reproduced when it was inoculated in the greenhouse. Leaf symptoms on the legume species and A. theophrasti were separated into three types. All Glycine spp. except one accession of G. tabacina (PI440994) had lesions typical of soybean brown spot. Ten legume species with green cotyledons had small lesions. Six legume species and A. theophrasti had atypical symptoms. Incubated leaf samples from inoculated field and greenhouse-grown plants were used to count pycnidia with cirrhi. Species with small lesions and atypical symptoms had fewer pycnidia with cirrhi than those plants with typical brown spot lesions. Septoria was isolated from leaf lesions of field-grown noninoculated A. theophrasti and C. laeve plants. These isolates were similar in culture to an isolate of S. glycines from soybean and, like the soybean isolate, caused typical brown spot lesions on soybeans and A. theophrasti.