<i>Alternaria</i> spp. Associated with Leaf Blight of Maize in Heilongjiang Province, China

Abstract

Maize (<i>Zea mays</i> L.) is a major economic crop worldwide. Maize can be infected by <i>Alternaria</i> species causing leaf blight that can result in significant economic losses. In this study, 168 <i>Alternaria</i> isolates recovered from symptomatic maize leaves were identified based on morphological characteristics, pathogenicity, and multilocus sequence analyses of the genes glyceraldehyde-3-phosphate dehydrogenase (<i>GAPDH</i>), the internal transcribed spacer of ribosomal DNA (rDNA ITS), the RNA polymerase II second largest subunit (<i>RPB2</i>), and histone3 (<i>HIS3</i>). Maize isolates grouped to four <i>Alternaria</i> species including <i>Alternaria tenuissima</i>, <i>A</i>. <i>alternata</i>, <i>A</i>. <i>burnsii</i>, and <i>Alternaria</i> sp. Notably, <i>A</i>. <i>tenuissima</i> (71.4%) was the most prevalent of the four isolated species, followed by <i>A</i>. <i>alternata</i> (21.5%), <i>Alternaria</i> sp. (4.1%), and <i>A</i>. <i>burnsii</i> (3.0%). Pathogenicity tests showed that all four <i>Alternaria</i> species could produce elliptic to nearly round, or strip, lesions on leaves of maize, gray-white to dry white in the lesion centers and reddish-brown at the edges. The average disease incidence (58.47%) and average disease index (63.55) of maize leaves inoculated with <i>A</i>. <i>alternata</i> were significantly higher than levels resulting from <i>A</i>. <i>tenuissima</i> (55.28% and 58.49), <i>Alternaria</i> sp. (55.34% and 58.75), and <i>A</i>. <i>burnsii</i> (56% and 55). Haplotype analyses indicated that there were 14 haplotypes of <i>A</i>. <i>tenuissima</i> and five haplotypes of <i>A</i>. <i>alternata</i> in Heilongjiang Province and suggested the occurrence of a population expansion. Results of the study showed that <i>Alternaria</i> species associated with maize leaf blight in Heilongjiang Province are more diverse than those that have been previously reported. This is the first report globally of <i>A</i>. <i>tenuissima</i>, <i>A</i>. <i>burnsii</i>, and an unclassified <i>Alternaria</i> species as causal agents of leaf blight on maize.