AUTHOR=Zhao Jian-Ying , Chen Juan , Hu Zhong-Ting , Li Juan , Fu Hua-Ying , Rott Philippe C. , Gao San-Ji 

TITLE=Genetic and morphological variants of Acidovorax avenae subsp. avenae cause red stripe of sugarcane in China

JOURNAL=Frontiers in Plant Science

VOLUME=14

YEAR=2023

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2023.1127928

DOI=10.3389/fpls.2023.1127928

ISSN=1664-462X

ABSTRACT=<p>Sugarcane (<italic>Saccharum</italic> spp.) is an important cash crop for production of sugar and bioethanol. Red stripe caused by <italic>Acidovorax avenae</italic> subsp. <italic>avenae</italic> (<italic>Aaa</italic>) is a disease that occurs in numerous sugarcane-growing regions worldwide. In this study, 17 strains of <italic>Aaa</italic> were isolated from 13 symptomatic leaf samples in China. Nine of these strains produced white-cream colonies on nutrient agar medium while the other eight produced yellow colonies. In pairwise sequence comparisons of the 16S-23S rRNA internally transcribed spacer (ITS), the 17 strains had 98.4-100% nucleotide identity among each other and 98.2-99.5% identity with the reference strain of <italic>Aaa</italic> (ATCC 19860). Three RFLP patterns based on this ITS sequence were also found among the strains of <italic>Aaa</italic> obtained in this study. Multilocus sequence typing (MLST) based on five housekeeping genes (<italic>ugp</italic>B, <italic>pil</italic>T, <italic>lep</italic>A, <italic>trp</italic>B, and <italic>glt</italic>A) revealed that the strains of <italic>Aaa</italic> from sugarcane in China and a strain of <italic>Aaa</italic> (30179) isolated from sorghum in Brazil formed a unique evolutionary subclade. Twenty-four additional strains of <italic>Aaa</italic> from sugarcane in Argentina and from other crops worldwide were distributed in two other and separate subclades, suggesting that strains of <italic>A. avenae</italic> from sugarcane are clonal populations with local specificities. Two strains of <italic>Aaa</italic> from China (CNGX08 forming white-cream colored colonies and CNGD05 forming yellow colonies) induced severe symptoms of red stripe in sugarcane varieties LC07-150 and ZZ8 but differed based on disease incidence in two separate inoculation experiments. Infected plants also exhibited increased salicylic acid (SA) content and transcript expression of gene <italic>PR-1</italic>, indicating that the SA-mediated signal pathway is involved in the response to infection by <italic>Aaa</italic>. Consequently, red stripe of sugarcane in China is caused by genetically different strains of <italic>Aaa</italic> and at least two morphological variants. The impact of these independent variations on epidemics of red stripe remains to be investigated.</p>