First Report of Bacterial Leaf Streak in Sweet Corn Caused by Pantoea ananatis in Southeast China

Abstract

Sweet corn (Zea mays convar. saccharata var. rugosa) is a popular vegetable crop in southeast China. During the spring seasons of 2018-2021, a serious outbreak of bacterial leaf streak was observed in sweet corn variety Yuetian28 in the field in Guangzhou, Guangdong Province. The disease incidence was 50%-70%. Infected leaves initially displayed long, chlorotic streaks parallel to veins at the V5-V6 stage, and then turned white or brown and dried out over the course of disease development. In severe infections, leaf lesion coalesced to form large irregular blight areas (Fig. S1A). To investigate this disease, we collected 0.5 cm2 samples of infected leaves from four plants after surface sterilization and rinsed them three times with sterile distilled water. We placed all leaf samples on nutrient agar (NA) medium and incubated them at 28℃ for 48 hours. Bright-yellowish colonies were observed near the edges of the samples. We picked the colonies and re-streaked them onto NA medium three times to obtain pure cultures. Four isolates, GZ2201, GZ2202, GZ2203, and GZ2204, were selected for further study. All isolates were gram-negative rods and were negative for oxidase, urease, nitrate reductase reactions, and gelatin liquefaction. They were positive for catalase, citrate utilization, indole production, and the Voges-Proskauer test. We sequenced the 16S rDNA, rpoB, leuS, and gyrB sequences using previously reported primers (Brady et al. 2008) and deposited the sequences in GenBank (accession nos. ON740665 to ON740668 for 16S rDNA; ON755167 to ON755170 for rpoB; ON755171 to ON755174 for leuS; and OP227136 to OP227139 for gyrB). The sequences share >98% identity with sequences from Pantoea ananatis type strain LMG2665 (GenBank JFZU01) indicating that the causal pathogen of bacteria leaf streak of sweet corn is P. ananatis (Fig. S1B). Phylogenetic analysis of gyrB, leuS, and rpoB concatenated sequence showed that the four isolates clustered with P. ananatis (Fig S2). To test the pathogenicity of the isolates of P. ananatis on the sweet corn variety Yuetian28, we inoculated plants at the V3 stage by syringe infiltration of bacterial suspension (108 CFU/ml) (Kini et al. 2020) or sterile distilled water as a negative control. Inoculated plants were placed in a growth chamber at 28 ℃, 60% relative humidity, 16-h/8-h light-dark cycle. After 7 days of incubation, chlorotic streaks resembling the original symptoms developed on inoculated plants (Fig. S1D), while control plants remained symptomless (Fig. S1C). We successfully re-isolated bacteria from the inoculated plants and confirmed their identity by sequencing of 16S rDNA, rpoB, leuS, and gyrB. P. ananatis was previously reported to cause leaf spot disease in maize grown in Argentina, Ecuador, and China (Alippi et al. 2010; Toaza et al. 2021; Cui et al. 2022). To our knowledge, this is the first report of P. ananatis causing leaf streak in sweet corn in southeast China. Further research on P. ananatis management is needed to help control disease spread.

Microbiota of maize kernels as influenced by Aspergillus flavus infection in susceptible and resistant inbreds

“…The only species of Pantoea with a high abundance was P. ananatis, having the highest total relative abundance (19.3%) of all bacteria present, and was the most abundant within each maize genotype (Supplementary Table S2). This species has been reported to negatively impact maize growth by causing diseases such as leaf spot (Paccola-Meirelles et al, 2001), brown stalk rot (Goszczynska et al, 2007) and leaf streak (Zhang et al, 2023). Its abundance was greatly impacted by K49 treatment in a maize genotype-dependent manner.…”

Rapid detection of virulence-related genes by multiplex PCR in five pathogenic bacteria of mulberry bacterial wilt

“…It was first identified as a pathogen of pineapple fruit rot in Philippines in 1928 [56]. It was found to cause bacterial brown rot of maize [56], center and bulb rot of onions [2], wilt and collapse of eucalyptus [12], bacterial leaf streaking of sweet corn [85], and bacterial diseases of rice [78]. Evidence from these reports, therefore, shows that P. ananatis, ECC, KpSC, KoC and RSSC can cause bacterial diseases in a wide range of plant hosts.…”