Revista Brasileira de Milho e Sorgo (Dec 2005)
ALTERATIONS IN SOLUBLE SUGAR LEVELS, AND PROTEINS CONCENTRATION IN MAIZE CULTIVARS INOCULATED BY MOLLICUTES
Abstract
Maize diseases caused by mollicutes (Phytoplasma and Spiroplasma) areimportant for the crop because its high incidence causes losses in grain production. Plants phloem are infected by mollicutes, which may alter sugar synthesis and proteins levels.The objective of this study was to verify the mollicutes effect on total soluble sugar andproteins synthesis in two maize cultivars. The experiment was carried out in pots of 30Kg, with soil previously analyzed and fertilized. After thinning two plants were left perpot. The experimental design was a fully randomized 3 x 2 factorial with 6 replications;being 3 inoculations (phytoplasma, spiroplasma and healthy plants) and 2 cultivars (Dina766 and BR 201). Thirty days after inoculating maize plants, it was analyzed theparameters: leaf temperature, relative humidity, stomatal resistance and transpiration. Atmilky growth stage the maize plants were harvested and cut into 3 parts, in order toanalyze total soluble sugars, nutrients and dry matter accumulation. The internode belowmain ear and the flag leaf were sampled to determine the peroxidase activity and proteincontent, respectively. The other plant was left up to end of the crop cycle in order toevaluate ear number, grain and ear weight and grain dry matter. The analysis of variancefor all characteristics evaluated did not show significance on interactions of genotypes xinoculation. Some parameters resulted in significance for genotypes, inoculation or forboth. Soluble sugars, dry matter, peroxidase activity and protein were similar in bothgenotypes and inoculations. Stomatal resistance was higher in Dina 766 and in maizeplants inoculated by phytoplasma. Ear number was higher in plants inoculated bymollicutes than in healthy plants. Ear and grain weights were higher in healthy plantsand in the ones infected by phytoplasma, when compared to the ones infected byspiroplasma. Nutrient concentration and the amounts taken up were similar , except forP and Zn. The mollicutes interfered neither on soluble sugar synthesis nor on proteincontent. However, the yield data suggested a higher susceptibility to the Spiroplasmarather than to the Phytoplasma.
