Interactions between Magnaporthiopsis maydis and Macrophomina phaseolina, the Causes of Wilt Diseases in Maize and Cotton.

Ofir Degani,Dekel Abraham,Roni Cohen,Shlomit Dor

doi:10.3390/microorganisms8020249

Abstract

Fungal pathogens are a significant threat to crops worldwide. The soil fungus, Magnaporthiopsis maydis, severely affects sensitive maize hybrids by causing the rapid wilting of plants at the maturity stage. Similarly, the soil fungus, Macrophomina phaseolina, develops in a variety of host plants, which leads to rot and plant mortality. The presence of both pathogens together in diseased cotton plants in Israel suggests possible interactions between them. Here, these relationships were tested in a series of experiments accompanied by real-time PCR tracking in maize and cotton. Despite the fact that neither of the pathogens was superior in a growth plate confrontation assay, their co-inoculum had a significant influence under field conditions. In maize sprouts and fully matured plants, infection by both pathogens (compared to inoculation with each of them alone) led to lesser amounts of M. maydis DNA but to increased amounts of M. phaseolina DNA levels. These results were obtained under a restricted water regime, while optimal water irrigation led to less pronounced differences. In water-stressed cotton sprouts, infection with both pathogens led to an increase in DNA amounts of each of the pathogens. Whereas the M. maydis DNA levels in the double infection remain high at the end of the season, a reduction in the amount of M. phaseolina DNA was observed. The double infection caused an increase in growth parameters in maize and cotton and decreased levels of dehydration in maize plants accompanied by an increase in yield production. Dehydration symptoms were minor in cotton under an optimal water supply. However, under a restricted water regime, the double infection abolished the harmful effect of M. phaseolina on the plants’ development and yield. These findings are the first report of interactions between these two pathogens in maize and cotton, and they encourage expanding the study to additional plant hosts and examining the potential involvement of other pathogens.

Highlights

The fungus Magnaporthiopsis maydis is known to severely affect sensitive maize (Zea mays) plants at the maturity stage
This study examined the combined effect of M. maydis and M. phaseolina on the growth and yield of maize and cotton plants grown in pots in an open-air enclosure under field conditions
The results of this assay were compared to the growth rate of each fungus alone under the same conditions in order to estimate the growth inhibition rate caused by the other fungus

Summary

Introduction

The fungus Magnaporthiopsis maydis is known to severely affect sensitive maize (Zea mays) plants at the maturity stage. It has two additional synonyms, Cephalosporium maydis [1] and Harpophora maydis [2]. The disease, commonly known as “late wilt”, is reported so far in about eight countries but is considered the most harmful maize disease in Egypt [3] and Israel [4,5]. The only familiar and confirmed alternative host for M. maydis was Lupinus termis (lupine), which is widely cultivated in Egypt [9]. M. maydis was recently identified in Gossypium hirsutum (Pima cotton, Goliath cv.), Citrullus lanatus (watermelon, Malali cv.), and Setaria viridis (green foxtail) [10]

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