Host response of maize to root infection of Macrophomina phaseolina varies depending on maize variety groups

Abstract

Macrophomina phaseolina is a soilborne fungus inducing yield losses up to 50% in maize (Zea mays L.), but little is known about its pathogenicity on the root system of maize. This study aimed to examine host (maize) - pathogen (M. phaseolina) interaction by considering root infection of M. phaseolina and four agronomic characteristics (plant height, root dry weight, grain weight and biomass) of maize. In this respect, seven maize varieties that belong to different maize variety groups [dent corn (Zea mays var. indentata), sweet corn (Zea mays var. saccharata), popcorn (Zea mays var. everta) and flint corn (Zea mays var. indurata)] were used as host plants. The experiments were conducted using soil inoculation technique in a greenhouse in two consecutive years. As a result, soil inoculation of M. phaseolina caused distinctive rottings on primary, crown and lateral roots and lower stems of the inoculated plants. M. phaseolina caused reductions, 36.39, 47.06, 49.57 and 47.11%, in plant height, root dry weight, grain weight and biomass of the tested maize varieties, respectively. Mean reductions in all the examined agronomic characteristics of the maize varietes were ranked from the highest to the lowest one as follows: popcorn, sweet corn, flint corn and dent corn, respectively. Disease scores significantly (P < 0.01) and positively correlated with the reductions in the examined agronomic characteristics. Based on the root infections, four reaction types (susceptible, moderately susceptible, resistant and moderately resistant) were detected among the maize variety groups. The results not only contribute to understanding of maize - M. phaseolina interaction but also reveal new knowledge for epidemiology of the pathogen in maize as well. To the best of our knowledge, this is the first study classifying reactions of maize varieties that belong to the different variety groups (dent corn, sweet corn, popcorn and flint corn) to root infection of M. phaseolina.