Inconsequential effect of nutritional treatments on huanglongbing control, fruit quality, bacterial titer and disease progress

Gottwald, T. R.; Graham, James H.; Irey, Mike; McCollum, T.G.; Wood, Bruce W.

doi:10.1016/j.cropro.2012.01.004

Cited by 144 publications

(159 citation statements)

References 12 publications

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“…Preharvest fruit drop may result from fruit starvation due to HLB-related phloem impairment (42), the resulting nutritional deficits in the tree, and/or the reduced efficiency in absorbing water due to loss of roots (43). However, these speculations lack confirmation as of yet, and the enhanced nutritional programs adapted by growers to reduce tree disease symptoms have not stopped the fruit drop problems (44). In the last 2 years, the citrus preharvest fruit drop was the most severe ever recorded (45).…”

mentioning

confidence: 99%

High Incidence of Preharvest Colonization of Huanglongbing-Symptomatic Citrus sinensis Fruit by Lasiodiplodia theobromae (Diplodia natalensis) and Exacerbation of Postharvest Fruit Decay by That Fungus

Zhao

Bai

McCollum

et al. 2015

Appl Environ Microbiol

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Huanglongbing (HLB), presumably caused by the bacterium "Candidatus Liberibacter asiaticus," is a devastating citrus disease associated with excessive preharvest fruit drop. Lasiodiplodia theobromae (diplodia) is the causal organism of citrus stem end rot (SER). The pathogen infects citrus fruit under the calyx abscission zone (AZ-C) and is associated with cell wall hydrolytic enzymes similar to plant enzymes involved in abscission. By means of DNA sequencing, diplodia was found in "Ca. Liberibacter asiaticus"-positive juice from HLB-symptomatic fruit (S) but not in "Ca. Liberibacter asiaticus"-negative juice. Therefore, the incidence of diplodia in fruit tissues, the impact on HLB-related postharvest decay, and the implications for HLB-related preharvest fruit drop were investigated in Hamlin and Valencia oranges. Quantitative PCR results (qPCR) revealed a significantly (P < 0.001) greater incidence of diplodia in the AZ-C of HLB-symptomatic (S; "Ca. Liberibacter asiaticus" threshold cycle [C T ] of <30) than in the AZ-C of in asymptomatic (AS; "Ca. Liberibacter asiaticus" C T of >30) fruit. In agreement with the qPCR results, 2 weeks after exposure to ethylene, the incidences of SER in S fruit were 66.7% (Hamlin) and 58.7% (Valencia), whereas for AS fruit the decay rates were 6.7% (Hamlin) and 5.3% (Valencia). Diplodia colonization of S fruit AZ-C was observed by scanning electron microscopy and confirmed by PCR test and morphology of conidia in isolates from the AZ-C after surface sterilization. Diplodia C T values were negatively correlated with ethylene production (R ‫؍‬ ؊0.838 for Hamlin; R ‫؍‬ ؊0.858 for Valencia) in S fruit, and positively correlated with fruit detachment force (R ‫؍‬ 0.855 for Hamlin; R ‫؍‬ 0.850 for Valencia), suggesting that diplodia colonization in AZ-C may exacerbate HLB-associated preharvest fruit drop. C itrus huanglongbing (HLB; also known as citrus greening) is one of the most devastating diseases of citrus and has spread throughout the major citrus-producing regions in Asia, Africa, and the Americas, causing great losses for the citrus industry worldwide (1). HLB is associated with "Candidatus Liberibacter" spp., which are Gram-negative, phloem-limited bacteria (2, 3). The Asian form of HLB is currently present in the United States, and the causal pathogen, bacterium "Candidatus Liberibacter asiaticus," was first confirmed in Southeast Florida in 2005 (1) and now is prevalent in all Florida citrus-growing areas in the state. HLB disease causes substantial economic loss by debilitating the productive capacity and shortening the life span of infected trees, promoting fruit drop and reducing fruit quality (4). Yield reduction can reach 30 to 100%, depending on the proportion of the canopy affected and the age of the trees during inoculation (1, 5).HLB-diseased citrus plants develop a multitude of symptoms. Leaf symptoms include chlorosis, which commonly appears in an asymmetric pattern referred to as "blotchy mottle" (4). Chlorosis may typically appear on a single branch and subse...

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confidence: 99%

High Incidence of Preharvest Colonization of Huanglongbing-Symptomatic Citrus sinensis Fruit by Lasiodiplodia theobromae (Diplodia natalensis) and Exacerbation of Postharvest Fruit Decay by That Fungus

Zhao

Bai

McCollum

et al. 2015

Appl Environ Microbiol

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“…In the first 3 years no effects were detected of the nutrient plus salicylic acid treatments on the Las content in the trees or on yield (Stansly et al 2011). In another replicated (but shorter-term) experiment no differences were observed in tree health, fruit quality and production, or Las titre between trees treated with a nutritional program (plus or minus phosphite) and a control treatment (Gottwald et al 2012). Additionally, application of micro nutrients, phosphite and salicylic acid was compared to regular nutrient management in several commercial blocks, but no differences in disease development or yield were observed.…”

Section: Introductionmentioning

confidence: 81%

“…In particular, micronutrients combined with salicylic acid and/or phosphite have been applied, often as foliar sprays, to maintain the productive capacity of HLB infected trees (Ahmad et al 2011;Masaoka et al 2011;Razi et al 2011). The effectiveness of these treatments has been controversial (Gottwald et al 2012), but balanced nutrition likely slows down tree decline due to HLB, considering the occurrence of healthy looking trees many years after Las infection was demonstrated (field observations by the authors). Asymptomatic infection has been noticed in several organically managed groves, despite infestation by Las-positive psyllids (Halbert, unpublished;Shen et al 2013).…”

Section: Introductionmentioning

confidence: 96%

Relation between plant nutrition, hormones, insecticide applications, bacterial endophytes, and Candidatus Liberibacter Ct values in citrus trees infected with Huanglongbing

et al. 2013

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Intensive insecticide and nutrient management have been attempted worldwide to reduce citrus huanglongbing (HLB) symptom development and yield loss. However, effects of insecticide and nutrient applications on HLB have been poorly understood. Leaf nutrients, jasmonic and salicylic acid contents, cycle threshold (Ct) values of Ca. Liberibacter asiaticus (Las), and community structure of endophytic α-proteobacteria were evaluated after insecticide treatment, 'nutrition' treatment (including systemic resistance inducing agents), or both in comparison with a control in a two-factor field experiment in 2008-2012. Leaf N, Mn, Zn and B significantly increased whilst Cu decreased after nutrient applications. Salicylic acid significantly increased in old leaves treated with insecticides, nutrients or both, and in young leaves treated with nutrients only. The jasmonic acid concentration was highest after the nutrition treatment in both old and young leaves. Ct values of Las and leaf area and weight significantly increased after long-term nutrient applications in 2011 and/or 2012. Redundancy analysis of the endophytic α-proteobacteria community structure indicated that the communities were mainly separated according to nutrient applications, which were positively associated with Ct values of Las and Ca, Mn, Zn, B, Mg, and Fe contents in leaf samples collected in 2012. Thus, effects of insecticides on HLB were significant in the early 2-year period whilst nutrients had significant effects on Las content and leaf size and weight after at least 3 years of application.

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“…Gottwald et al ( 2012 ) revealed that ENPs conducted in the US state of Florida do not sustain the tree health, yield, or fruit quality of HLB-infected plants. Similar fi ndings were reported by Razi et al ( 2011 ), who showed no relationship between nutritional defi ciency status and HLB incidence in citrus and, in addition, that Zn occurred at signifi cantly higher levels in HLB-infected trees, even though ENPs lead to minor improvements in HLB-infected trees.…”

Section: Enhanced Nutritional Programmes For Disease Suppression and mentioning

confidence: 97%

Enhanced Nutritional Programme: An Innovative Approach to Controlling Plant Diseases in the Tropics

Ahmad

Ismail

2016

Plant, Soil and Microbes

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Inconsequential effect of nutritional treatments on huanglongbing control, fruit quality, bacterial titer and disease progress

Cited by 144 publications

References 12 publications

High Incidence of Preharvest Colonization of Huanglongbing-Symptomatic Citrus sinensis Fruit by Lasiodiplodia theobromae (Diplodia natalensis) and Exacerbation of Postharvest Fruit Decay by That Fungus

High Incidence of Preharvest Colonization of Huanglongbing-Symptomatic Citrus sinensis Fruit by Lasiodiplodia theobromae (Diplodia natalensis) and Exacerbation of Postharvest Fruit Decay by That Fungus

Relation between plant nutrition, hormones, insecticide applications, bacterial endophytes, and Candidatus Liberibacter Ct values in citrus trees infected with Huanglongbing

Enhanced Nutritional Programme: An Innovative Approach to Controlling Plant Diseases in the Tropics

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