Abstract
The objective of this work was to evaluate the population variation dynamics of Candidatus Liberibacter spp. under phosphite applications. The 'Ponkan' tangerines (Citrus reticulata Blanco cv. Ponkan) with symptoms and a high degree of huanglongbing (HLB) severity were used for the test. 'Ponkan' tangerine plants were treated with potassium phosphite leaf applications at a dose of 2.5 L ha-1. Applications frequency was intervals of 25 days with a total of two applications. There was variation in bacterium Candidatus Liberibacter spp. population, depending on the application of phosphite. Phosphites have an indirect action on pathogens control, stimulating the formation of phytoalexins, a natural self-defense substance of plants. Indirect effects of these products were reported in citrus seedlings presenting symptoms of phosphorus deficiency, which when treated with foliar applications of potassium phosphite overcame these symptoms, restoring plant growth. Candidatus Liberibacter spp. population in 'Ponkan' (Citrus reticulata Blanco cv. Ponkan) leaves was reduced and the phosphorus and potassium contents increased with 2.5 L ha-1 of potassium phosphite by means of leaf application. Key words: Citrus reticulata, leaf nutrition, huanglongbing, phosphorus, potassium.
Highlights
Citrus crops are an important activity worldwide with special relevance for Brazilian economy
Indirect effects of these products were reported in citrus seedlings presenting symptoms of phosphorus deficiency, which when treated with foliar applications of potassium phosphite overcame these symptoms, restoring plant growth
Ponkan) leaves was reduced and the phosphorus and potassium contents increased with 2.5 L ha-1 of potassium phosphite by means of leaf application
Summary
Citrus crops are an important activity worldwide with special relevance for Brazilian economy. Citrus crop expansion is attributed to the emergence of new varieties and to the development of cultivars more adapted to cultivated ecosystems (Lopes et al, 2011). Citrus crops are distributed in all regions of Brazil, but with a notable concentration in the Southeast region, especially in São Paulo State, whose orchards are mainly based on sweet orange trees, followed by tangerines and acid lime trees (Cunha Sobrinho et al, 2013). It is important to alert that citrus activity is threatened by the occurrence of the most destructive disease in the world, which is pointed out as the protagonist of the decline of the world citrus cultivation
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