Viability and dissemination of Pantoea ananatis, etiological agent of Maize White Spot disease

Abstract

Maize white spot (MWS) is a disease widely spread in maize production regions in Brazil and causes serious economic damages to the culture. Little is known about the dissemination, growth and development conditions of the MWS causal agent, the bacterium Pantoea ananatis. The objective of this work was to determine the viability of this bacterium, as well as its distribution in the plant. P. ananatis after isolated was stored in both, Nutrient Broth (NB) medium and in mineral oil. For the viability tests, the cultures stored in NB were maintained at 12ºC and –6ºC and the cultures stored in mineral oil were maintained at room temperature. The isolate remained viable for seven months in NB medium at the two temperatures assessed, and four months when stored in mineral oil. The presence of the P. ananatis bacteria was analyzed in, 1) soil samples collected close to rhizosphere, 2) in seeds from plants severely attacked by MWS, 3) foliar segments of healthy plants and 4) the stem of healthy plants. P. ananatis was found surviving epiphytically on the leaf surface and its population increased with plant age, air relative humidity, and decreasing of temperature. This agent was not found neither rhizosphere nor in seeds, but it was isolated in low quantity in maize stem. P. ananatis resides epiphytically on leaves and, due to several factors, may trigger injuries to its host. All epiphytic isolates were characterized in regards to ice nucleation activity, a characteristic of this pathogen.

Atividade De Nucleação De Gelo E Densidade Populacional Do Patógeno Podem Ser Fatores Que Contribuem Para O Progresso Da Doença Mancha Branca Do Milho

“…Essa desorganização celular nas lesões da MBM foi demonstrada anteriormente por Bomfeti et al (2008) por microscopia óptica e eletrônica. Escanferla et al (2018) também encontraram P. ananatis INA+ sobrevivendo epifiticamente na folha de milho e observaram um aumento gradual na sua população com a idade da planta. Em cultivares susceptíveis, o aumento da população de P. ananatis, associado com a umidade relativa do ar e quedas de temperatura, são determinantes para o aparecimento das lesões (WYSMIERSKI;REAL;PACCOLA-MEIRELLES, 2006).…”

“…Todos os isolados epifíticos aqui estudados catalisaram a formação de gelo, em concordância com os estudos de Sauer et al (2014) e Escanferla et al (2018), confirmando que o processo de produção de gelo por esse agente etiológico somente ocorre quando a população bacteriana se encontra em nível mais elevado.…”

“…O agente etiológico da doença foi identificado como Pantoea ananatis (PACCOLA-MEIRELLES et al, 2001;GONÇAL-VES et al, 2013). P. ananatis foi descrita por Serrano (1928) A bactéria reside epifiticamente nas folhas de milho (ESCANFERLA et al, 2018) e pode alcançar os espaços intercelulares da epiderme foliar através de aberturas naturais como estômatos ou injúrias foliares (BOMFETI et al, 2008). Segundo Sauer et al (2014) e Sauer et al (2015), este patógeno tem a capacidade de induzir a formação de cristais de gelo em temperaturas onde normalmente isto não ocorreria, nucleação de gelo (ice nucleation activity -INA) (MAKI et al, 1974), que pode levar à formação de lesões foliares (ROMEIRO, 2001) e consequentemente promover danos importantes economicamente (KAWAHARA, 2002).…”

Efficiency in nitrogen management using conventional and transgenic technology in the cultivation of maize

“…National production of the grain in the 2017/18 crop showed an average yield of more than 5.5 t ha -1 (Companhia Nacional de Abastecimento [CONAB], 2018), mainly due to the use of a high technological level regarding the use of hybrids and intensive crop management. However, national productivity is still below the potential productivity, that can reach 16 to 18 t ha -1 (Sangoi et al, 2011;Sauer, et al, 2015;Santos, Bizzarri, Barbosa, & Zucareli, 2017;Escanferla, Wysmierski, Meirelles, & Paccola-Meirelles, 2018;Rosa et al, 2019).…”

Multi‐parental QTL mapping of resistance to white spot of maize (Zea mays) in southern Brazil and relationship to QTLs of other foliar diseases

“…In advanced disease stages, lesions may coalescence and appear irregularly on dead tissue (Bomfeti et al, 2008;Gonçalves et al, 2013;Lanza et al, 2013;Paccola-Meirelles et al, 2001). P. ananatis occurs in America, Europe and South Africa (Alippi & L opez, 2010;Carson et al, 2005;Derera et al, 2007;Krawczyk et al, 2010;Paccola-Meirelles et al, 2001;Pérez-y-Terr on et al, 2009), but currently MWS is economically important only in South America (De Rossi et al, 2017;Escanferla et al, 2018). In Brazil, the third biggest maize producer in the world (FAO, 2020), MWS is an endemic major disease being present across all growing regions and favoured by high humidity and moderate temperatures (Escanferla et al, 2018;Paccola-Meirelles et al, 2002).…”