The life cycle of Puccinia digitariae on Digitaria eriantha and Solanum species in South Africa

ABSTRACT

Rust fungi are important plant pathogens and have been extensively studied on crops and other host plants worldwide. This study describes the heterecious life cycle of a rust fungus on Digitaria eriantha (finger grass) and the Solanum species S. lichtensteinii (large yellow bitter apple), S. campylacanthum (bitter apple), and S. melongena (eggplant) in South Africa. Following field observations, inoculation studies involving telial isolates collected from Digitaria plants produced spermogonia and aecia on S. lichtensteinii, S. campylacanthum, and S. melongena. Likewise, inoculation of finger grass with aeciospores collected from the aforementioned Solanum species produced uredinia on D. eriantha. Pennisetum glaucum (pearl millet varieties Milkstar and Okashana, as well as 17 experimental lines) and S. elaeagnifolium (silverleaf nightshade or bitter apple) were resistant to the rust isolates. Morphological descriptions and molecular phylogenetic data confirmed the identity of the rust on Digitaria as P. digitariae, herein reinstated as a species and closely related to P. penicillariae the pearl millet rust, also reinstated. Puccinia digitariae has a macrocyclic, heterecious life cycle in which teliospores overwinter on dormant D. eriantha plants. Aecia sporulate on species of Solanum during spring and early summer to provide inocula that infect new growth of Digitaria.

KEYWORDS:

• Bitter apple
• finger grass
• life cycle
• nightshade
• Pucciniales
• Solanaceae

ACKNOWLEDGMENTS

We thank Mr. Alec Edwards (University of the Free State) for his assistance in collecting S. lichtensteinii specimens; Prof. Dave Berger (University of Pretoria) for providing rust isolate UFS_02; and Prof. Hussein Shimelis (University of KwaZulu-Natal), Dr. Tegwe Soko (Seed-Co), as well as Dr. Nemera Shargie (ARC-Grain Crops Institute) for seed of pearl millet breeding lines.

DISCLOSURE STATEMENT

No potential conflict of interest was reported by the author(s).

SUPPLEMENTARY MATERIAL

Supplemental data for this article can be accessed on the publisher’s Web site.

Additional information

Funding

This study was partially supported by the United States Department of Agriculture (USDA)–National Institute of Food and Agriculture Hatch Project 1010662 to M.C.A. The National Research Foundation (SARChI chair UID 8464) is thanked for funding.