Potassium phosphite reduction of Candidatus Liberibacter spp. population on leaves of Ponkan tangerines tree with huanglongbing

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.

Rootstock Influence on Growth and Mineral Content of Citrus limon and Citrus sinensis cv. Valencia Inoculated with Candidatus Liberibacter Asiaticus

“…On the contrary, in other investigations, it has been observed that Citrus sinensis cv. Navelina has a higher Ca content when infected with HLB [48]. The literature mentions that citrus fruits infected with HLB can present Ca deficiencies because bacteria use this mineral for their growth [49].…”

“…This mechanism occurs across the plasma membrane via permeable ion channels [39]. In addition, calcium strengthens cell walls and provides greater protection against pathogens, which is one of the reasons why symptomatic fruits with HLB are harder and have a thicker shell [48,52].…”

Phenolic Extract from Olive Leaves as a Promising Endotherapeutic Treatment against Xylella fastidiosa in Naturally Infected Olea europaea (var. europaea) Trees

“…KP values resulted significantly higher than those of the untreated trees, while no relevant differences were found in comparison with G, which, in turn, presented significant differences with T only for LAD values and only at a 95% confidence level. The behavior of the trees treated with potassium phosphite alone can be traced back to its booster effect on plant growth, even if antibacterial effects on populations of Candidatus liberibacter [ 76 ] and Streptomyces scabies [ 77 ] have been described. The percentage increase varied from 20.19 (PE3), to 10.77 (KP), to 6.72 (G), to 2.46% (T) for LAI and from 9.25 (PE3), to 8.29 (KP), to 6.51 (G), to 0.26% (T) for LAD.…”