Etiology and Symptoms of Maize Leaf Spot Caused by Bipolaris spp. in Sichuan, China

Abstract

Many species of the genus Bipolaris are important plant pathogens and often cause leaf spot, root rot, and seedling blight in an extremely wide range of hosts around the world. In recent years, maize leaf spot caused by Bipolaris species has frequently occurred with complex symptoms and is becoming increasingly serious in Sichuan Province of China. To investigate the population diversity of Bipolaris spp. and their corresponding symptoms in maize, 747 samples of maize leaf spot were collected from 132 sampling sites in 19 administrative districts of Sichuan Province from 2011 to 2018. Based on morphological characteristics, pathogenicity testing, and phylogenetic analysis of the rDNA internal transcribed spacer (ITS) and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) genes, a total of 1186 Bipolaris isolates were identified as B. maydis, B. zeicola, B. cynodontis, B. oryzae, B. setariae, and B. saccharicola, among which B. maydis and B. zeicola were the dominant pathogenic species, accounting for 57.34% and 42.07% of the isolates, respectively. We found that B. zeicola isolates were mainly distributed in high altitude and cool mountainous areas, while B. maydis was more widely distributed in Sichuan Province. The typical symptoms caused by the Bipolaris species were clearly distinct in maize. The typical symptoms caused by B. maydis were elongated strip lesions, or fusiform, elliptical lesions, and those caused by B. zeicola were narrow linear lesions. Herein, B. saccharicola was first reported on maize and caused subrotund lesions. This study provides useful information for disease diagnosis and management for Bipolaris leaf spot in maize.

Occurrence and characterization of Bipolaris setariae associated with leaf blight of browntop millet (Brachiaria ramosa) in India

“…Concatenated phylogenetic analysis of ITS, GAPDH and LSU gene sequences showed better interspecies differentiation than any individual data set in the current study (Figure 4). Our findings are similar to those of Pham et al., (2015), Bhunjun et al., (2020) and Sun et al., (2020).…”

“…The findings of this research are consistent with those of Alcorn (1988) and Manamgoda et al., (2012). Other distinguished microscopic characters such as conidial length, septation and conidial germination are in accordance with the earlier observations from Manamgoda et al., (2014) and Sun et al., (2020), although B. setariae shares similar morphological characters with B. luttrellii . It differs by producing concolorous conidia and few conidiogenous loci on conidiophore, while B. luttrellii mostly produces darker conidia and end cells with light colour (Manamgoda et al., 2014).…”

“…Traditionally, morphological characteristics have been used to identify Bipolaris species (Pham et al., 2015; Sun et al., 2020). However, researchers have been confused for years between three genera, Cochliobolus , Bipolaris and Curvularia , due to repeated name changes, refinements, and most crucially, similar or intermediate morphological traits between Curvularia and Bipolaris asexual phases (Manamgoda et al., 2012; Sivanesan, 1987).…”

Fungal Species Causing Maize Leaf Blight in Different Agro-Ecologies in India

“…Race 'T' of B. maydis is highly virulent and was reported to cause the devastating 'Southern corn leaf blight' epidemic in the USA during the 1970s, resulting in huge losses due to the extremely susceptible response of Texas Male Sterile maize lines [6,[15][16][17][18]. Although race 'T' has been reported on seeds of Phaseolus mungo, Vigna sinensis, and Paspalum scrobiculatum from India [19], B. maydis race 'O' is the prevalent pathogen of maize in India and elsewhere in the world [4,20,21]. Drechslera maydis (synonym of B. maydis) on maize was reported for the first time in Punjab [22].…”

Identification of Colletotrichum Species Associated with Blueberry Anthracnose in Sichuan, China

“…After culturing on PDA at 28 °C for 5 days, the morphological characteristics of all isolates, including colony, conidia, conidial appressoria and mycelial appressoria, were initially observed. The colony diameter of each isolate from 1 day to 7 days after inoculation was assessed using the cross measurement method [ 41 ]. The size of approximately 30 conidia was measured and recorded.…”