Cercospora zeina is the causal agent of grey leaf spot disease of maize in southern Africa

Abstract

The aim of our study was to identify the causal agent of grey leaf spot disease of maize in southern Africa. Single-conidial cultures were recovered from maize leaves with typical disease symptoms sampled from several fields in South Africa, Zambia and Zimbabwe. Morphology, cultural characteristics, and a PCR-based test using Cercospora zeae-maydis and C. zeina-specific primer sets identified all single-conidial cultures as C. zeina. In addition, sequence alignment of DNA fragments of the internal transcribed spacer region (ITS1, ITS2, and the 5.8S gene) and elongation factor 1-α grouped all cultures in the same clade as the C. zeina ex-type culture CBS 118820. To by-pass cultivation of the slow-growing fungus, a rapid method to isolate DNA directly from lesions was successfully applied for PCR identification of C. zeina with speciesspecific ITS and histone primers. Koch's postulates were fulfilled for C. zeina by artificially inoculating maize plants in a greenhouse, re-isolating conidia emerging from lesions and verifying pathogen identity with molecular techniques. These results provide evidence that confirms the presence of C. zeina and absence of C. zeae-maydis in commercial maize plantations in southern Africa.

Infection process in resistant and susceptible maize (Zea mays L.) genotypes to Cercospora zeae-maydis (type II)

“…African and US group type II populations were co-specific with limited variability and type II species grew much slower and did not produce any toxins in culture. Crous et al (2006) and Meisel et al (2009) reclassified group type II as distinct species now called Cercospora zeina endemic in African countries. Okori et al (2003) confirmed the widespread presence of type II biotypes in East Africa (Kenya, Uganda, and Rwanda) and indicated that gene flow was high among African populations of C. zeaemaydis.…”

Quantitative phenotyping of grey leaf spot disease in maize using real-time PCR

“…CPC 12062 were obtained from the culture collection of the Centraalbureau voor Schimmelcultures, Utrecht, The Netherlands. The C. zeina cultures CMW 25463, CMW 25467, CMW 25445, CMW 25442, CMW 25459, CMW 25465, CMW 25462, CMW 25454, CMW 25452 and CMW 25466 are described in Meisel et al 2009. Fungal cultures were grown on V8 medium (800 ml of distilled water, 200 ml of V8 juice, 15 g of agar, and 2 g of CaCO 3 ) in the dark at 25°C.…”

“…Leaf samples were taken 15 weeks after planting from nine individual plants from each line that were positioned randomly within a field site situated in Kwazulu-Natal Province, South Africa. Grey leaf spot disease is prevalent in this region, and therefore the plants were exposed to a natural inoculum of C. zeina (Meisel et al, 2009). A 12 cm length of the leaf immediately above the lowest cob from each plant was marked with a permanent black marker pen.…”

“…Depending on the geographic region, GLS disease of maize can be either caused by Cercospora zeaemaydis (formerly known as C. zeae-maydis Group I), which has been found throughout various areas of the U.S.A., Canada, Mexico and Brazil, or Cercospora zeina (formerly known as C. zeae-maydis Group II), which has been reported in the Eastern maize growing states of the U.S.A., Brazil and sub-Saharan Africa (Wang et al 1998, Dunkle and Levy 2000, Goodwin et al 2001, Zhu et al 2002, Okori et al 2003, Shim and Dunkle 2005, Crous et al 2006, Brunelli et al 2008, Meisel et al 2009). Characteristics and dimensions of conidia and conidiophores produced on infected plants or nutrient media were found to be unreliable criteria for taxonomic differentiation of C. zeae-maydis and C. zeina (Wang et al 1998).…”

Regulation of Pathogenesis by Light in Cercospora zeae-maydis: An Updated Perspective

“…Later, the two groups were determined to be taxonomically distinct species; Group I retained the species name of C. zeaemaydis, whereas Group II was designated C. zeina (Crous et al, 2006). Interestingly, C. zeina appears to be the predominant (if not exclusive) gray leaf spot pathogen in Africa (Dunkle and Levy, 2000;Meisel et al, 2009). Both fungi causes distinctive rectangular lesions delineated by major veins of the leaf, and the disease derives its name from the grayish appearance of lesions when masses of conidia are produced on erumpent conidiophores emerging from stomata.…”