Avaliação da transmissibilidade de Fitoplasmas e Spiroplasmas via sementes de milho

Seeds generally have a great potential for spreading diseases over long and short distances, infecting hitherto areas free from specific phytopathogens. Corn seeds are responsible for the spread of diseases in their cultivation, but for Corn Stunt Spiroplasm and Maize Bushy Stunt, which are currently challenging the profitable success of the crop, seed transmission is meager studied. Its main transmission route is the vector insect Dalbulus maidis (corn leafhopper) and the organisms responsible for corn stunt are bacteria from Mollicutes class, which distinguish from the others by the absence of cell wall. Spiroplasma kunkelii is responsible for Corn Stunt Spiroplasm and phytoplasma is responsible for Maize Bushy Stunt. These phytopathogens colonize the maize plant’s phloem affecting directly on the production’s decline. Thus, the goal was to evaluate the transmission of Corn Stunt through corn seeds. The work was conducted at IFMG-campus Bambuí from March to July, in 2019, following Completely Randomized Design in factorial scheme (4 cultivar and 2 experimental stations). Twenty-four maize plants, 12 plants under field conditions and 12 under protected environment from the vector insect have been studied in order to evaluate the symptoms of Corn Stunt from possibly infected seeds. Throughout the productive cycle, the sanitary conditions of the plants were observed. By the end of the experiment, 139 days after sowing, data were collected: amount of grain rows per ear and ear length. The conclusion was that for ear length and number of rows of grains per ear the cultivar SHS 7990 PRO2 and field environment differ statistically from the other cultivars and local, respectively. It was also concluded that for the conditions under which the experiment was conducted, the corn seeds did not transmit corn stunt, once they did not show characteristic leaf symptoms.