Citrus Production and Protection from Pests and Diseases

A special issue of Agronomy (ISSN 2073-4395). This special issue belongs to the section "Horticultural and Floricultural Crops".

Deadline for manuscript submissions: closed (15 November 2021) | Viewed by 29132

Special Issue Editors

U.S. Department Agriculture, Agricultural Research Service, U.S. Horticultural Research Laboratory, 2001 South Rock Road, Fort Pierce, FL, USA
Interests: gene targeting; RNAi; cell culture; insect pathology; insect vectors
Special Issues, Collections and Topics in MDPI journals
University of Florida Institute of Food and Agricultural Sciences, Gainesville, USA
Interests: plant pathology; bioinformatics; evolution; effector biology
Southwest Florida Research and Education Center, University of Florida 2685 SR 29 North, Immokalee, FL 34142, USA
Interests: entomology; biology; ecology; IPM; biological control
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Strategies to manage pathogens and pests of citrus fruit trees are now based on a broad variety of products, from chemicals, biopesticides, phytochemicals, synthetic nucleotides, and peptides to natural beneficial organisms, predators, parasitoids, pollinators, and microbes (virus, bacteria, fungi, yeast). Emergent biotechnologies, using genetics, have also increased the options that can be incorporated into citrus breeding strategies to produce trees with increased resistance to disease pathogens, environmental stressors, and pests.

Based on the above, we would like to pursue these subjects through a Special Issue of the journal Agronomy entitled “Citrus Production and Protection from Pests and Diseases”.

In this regard, papers on the following indicative topics are welcome:

  • Chemicals: natural, synthesized, characterization, mode of action, and biochemistry;
  • Pesticides: Insecticides, miticides, nematicides, growth and/or reproduction inhibitors, repellents, oviposition deterrents, ‘attract and kill’ or ‘push-pull’ strategies, delivery systems, cost–benefit analyses;
  • Microbicides: viricides, bactericides, fungicides, modes of action, delivery, cost–benefit analyses;
  • Biological control agents: arthropods, microbes, pulsed release, augmented, modified;
  • Production practices: nutrition, soil health, breeding, new varieties;
  • Risks and benefits associated with emerging, novel technologies;
  • Reviews, regulatory and legislation issues related to emerging technologies;

We are looking forward to receiving submissions on these interesting topics, with expectations to stimulate further research on sustainable citrus production.

Dr. Wayne B. Hunter
Dr. Liliana M. Cano
Prof. Jawwad A. Qureshi
Guest Editors

Manuscript Submission Information

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Keywords

  • Emerging
  • Liberibacter
  • Genomics
  • Management
  • Sustainable
  • Food Security
  • Pathogens
  • Diagnostics

Published Papers (12 papers)

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Research

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10 pages, 879 KiB  
Article
Association between Temperature and Reproductive Fitness of Diaphorina citri Infected with Candidatus Liberibacter Asiaticus
by Mubasher Hussain, Summyya Bano, Muhammad Qasim, Jing Gao, Steven P. Arthurs, Liande Wang, Dongliang Qiu and Runqian Mao
Agronomy 2022, 12(4), 815; https://doi.org/10.3390/agronomy12040815 - 27 Mar 2022
Cited by 3 | Viewed by 2132
Abstract
Diaphorina citri is a serious insect pest of citrus and an insect vector of Candidatus Liberibacter asiaticus (CLas) that causes Huanglongbing disease (citrus greening). In this study, we investigated the effect of the CLas pathogen on the life history parameters of D. citri [...] Read more.
Diaphorina citri is a serious insect pest of citrus and an insect vector of Candidatus Liberibacter asiaticus (CLas) that causes Huanglongbing disease (citrus greening). In this study, we investigated the effect of the CLas pathogen on the life history parameters of D. citri at different temperature regimes. Our results demonstrated that the survival rate of first to fifth instar CLas-positive and CLas-negative D. citri fluctuate with the change in temperature over the range of 16–35 °C. Meanwhile, the mean developmental time (52.5 d) (d = day(s)) and adult longevity (5.2 d) of the CLas-positive psyllids was longer as compared to CLas-negative psyllids mean developmental time (32.81 d) and adult longevity (3.50 d) at the low- and high-temperature regimes (16 and 35 °C). However, at high temperature regimes, the significant effect of CLas-bacteria on D. citri fecundity was higher than the corresponding non-significant effect on their survivorship when compared to non-vectored psyllids. These results indicate a long-term, stable evolutionary relationship among vector-pathogen and climate change. Full article
(This article belongs to the Special Issue Citrus Production and Protection from Pests and Diseases)
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14 pages, 1224 KiB  
Article
Post-Release Evaluation of Diaphorencyrtus aligarhensis (Hymenoptera: Encyrtidae) and Tamarixia radiata (Hymenoptera: Eulophidae) for Biological Control of Diaphorina citri (Hemiptera: Liviidae) in Urban California, USA
by Ivan Milosavljević, Meghan A. Vankosky, David J. W. Morgan, Christina D. Hoddle, Rachael E. Massie and Mark S. Hoddle
Agronomy 2022, 12(3), 583; https://doi.org/10.3390/agronomy12030583 - 26 Feb 2022
Cited by 4 | Viewed by 1682
Abstract
Diaphorencyrtus aligarhensis (Hymenoptera: Encyrtidae) was first released in California for biological control of Diaphorina citri (Hemiptera: Liviidae) in December 2014. The establishment and parasitism rates of D. aligarhensis, along with those of another introduced species, Tamarixia radiata (Hymenoptera: Eulophidae), first released in [...] Read more.
Diaphorencyrtus aligarhensis (Hymenoptera: Encyrtidae) was first released in California for biological control of Diaphorina citri (Hemiptera: Liviidae) in December 2014. The establishment and parasitism rates of D. aligarhensis, along with those of another introduced species, Tamarixia radiata (Hymenoptera: Eulophidae), first released in 2011, were assessed at 15 D. aligarhensis release and 24 no-release control sites over the period 2016–2018. Study sites with citrus trees that were infested with D. citri eggs, nymphs, and adults, were located in residential areas in southern California that spanned three different climatic zones: coastal, intermediate, and desert interior sites. Parasitism rates of D. aligarhensis were low, averaging 0.62% compared to 21.2% for T. radiata which had spread naturally and established widely through the study area approximately one year earlier. Recoveries of D. aligarhensis at release sites were made eight times in 2016 and 2017. Conversely, T. radiata was recovered consistently at 34 of the 39 sites surveyed. Analyses indicated that parasitism of D. citri nymphs by T. radiata exhibited delayed density-dependence with a 12-month lag associated with reductions of D. citri densities by 50%. Irrespective of the climatic zone, the highest frequency of parasitized D. citri nymphs for T. radiata was recorded during peak periods of citrus flush growth from March through June and October through November each year. The findings reported here suggest that it is unlikely D. aligarhensis has established in California and that competition from T. radiata may, in part, have contributed to establishment failure. Consequently, biological control efforts targeting D. citri in California should focus on T. radiata. Full article
(This article belongs to the Special Issue Citrus Production and Protection from Pests and Diseases)
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12 pages, 3928 KiB  
Article
Pathogenicity of Cordyceps javanica (Hypocreales: Cordycipitaceae) to Diaphorina citri (Hemiptera: Liviidae) Adults, with Ultrastructural Observations on the Fungal Infection Process
by Mubasher Hussain, Pasco B. Avery, Wenchao Zhu, Marco Pitino, Steven P. Arthurs, Liande Wang, Dongliang Qiu and Runqian Mao
Agronomy 2021, 11(12), 2476; https://doi.org/10.3390/agronomy11122476 - 06 Dec 2021
Cited by 3 | Viewed by 3212
Abstract
Entomopathogenic fungi are proposed biological control agents against the Asian citrus psyllid (Diaphorina citri). We quantified the pathogenicity of Cordyceps javanica strain Apopka 97 strain (Cja Apopka 97) (blastospores and conidia) against D. citri using the spray technique. We also [...] Read more.
Entomopathogenic fungi are proposed biological control agents against the Asian citrus psyllid (Diaphorina citri). We quantified the pathogenicity of Cordyceps javanica strain Apopka 97 strain (Cja Apopka 97) (blastospores and conidia) against D. citri using the spray technique. We also used light and scanning electron microscopy to observe the Cja Apopka 97, infection process against D. citri adults at different stages pre- and post-mortem. Our findings demonstrated that psyllid mortality in the blastospore treatment ranged from 8 to 25% within 24–48 h of exposure, compared to 0% in the conidial and control treatments. However, psyllid mortality rate had reached 100% by 7 days after exposure at a concentration of 107 spores/mL, under both fungal treatments compared to the controls (0%). SEM and light microscopy revealed several stages in in the Cja Apopka 97 infection process of D. citri, including spore adherence and germ tube formation within 24 h post-inoculation, penetration pegs and mycelia growth on wings after 72 h, rupturing of cuticle after 96 h and mycelial mass colonizing host body after 144 h. Our study findings provide basic information on the interaction of entomopathogenic fungi with D. citri which will assist in the understanding of the infection process and the potential roles of entomopathogenic fungi in its management. Full article
(This article belongs to the Special Issue Citrus Production and Protection from Pests and Diseases)
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8 pages, 1742 KiB  
Communication
Investigation of Citrus HLB Symptom Variations Associated with “Candidatus Liberibacter asiaticus” Strains Harboring Different Phages in Southern China
by Minli Bao, Zheng Zheng, Jianchi Chen and Xiaoling Deng
Agronomy 2021, 11(11), 2262; https://doi.org/10.3390/agronomy11112262 - 09 Nov 2021
Cited by 3 | Viewed by 1829
Abstract
Huanglongbing (HLB) is a devastating disease affecting citrus production worldwide. In China, the disease is associated with an unculturable alpha-proteobacterium, “Candidatus Liberibacter asiaticus” (CLas). Phages/prophages of CLas have recently been identified through intensive genomic research. The phage information has facilitated research on [...] Read more.
Huanglongbing (HLB) is a devastating disease affecting citrus production worldwide. In China, the disease is associated with an unculturable alpha-proteobacterium, “Candidatus Liberibacter asiaticus” (CLas). Phages/prophages of CLas have recently been identified through intensive genomic research. The phage information has facilitated research on CLas biology such as population diversity and virulence gene identification. However, little is known about the roles of CLas phages in HLB symptom development. Such research is challenging due to the unculturable nature of CLas and the lack of laboratory strains that carry a single phage. In this study, CLas strains singly carrying Type 1 phage (Type 1 CLas) and Type 2 phage (Type 2 CLas) were identified and maintained in an experimental screenhouse in southern China. The strains were characterized through next-generation sequencing (NGS). Then, each CLas strain was inoculated into seedlings of three different citrus cultivars/species through graft transmission in a screenhouse in Guangdong, China. Symptom developments were recorded. All CLas-infected cultivars showed HLB symptoms in seven months. In cultivar Nianju (Citrus reticulata), Type 1 CLas caused pronounced yellowing symptoms and severe defoliation, whereas Type 2 CLas caused typical Zn-deficiency-like symptoms. In contrast, symptoms from the two CLas strains’ infections on cultivars Shatianyu (C. maxima), and Eureka lemon (Citrus limon) were more difficult to differentiate. Results from this study provide baseline information for future research to investigate the roles of CLas phages in HLB symptom development. Full article
(This article belongs to the Special Issue Citrus Production and Protection from Pests and Diseases)
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17 pages, 2610 KiB  
Article
Genetic Diversity of Tamarixia radiata Populations and Their Associated Endosymbiont Wolbachia Species from China
by Hafiza Javaria Ashraf, Komivi Senyo Akutse, Irum Mukhtar, Luis Carlos Ramos Aguila, Muhammad Qasim, Wenjie Wang, Bamisope Steve Bamisile and Liande Wang
Agronomy 2021, 11(10), 2018; https://doi.org/10.3390/agronomy11102018 - 08 Oct 2021
Cited by 3 | Viewed by 1860
Abstract
Tamarixia radiata is one of the established biocontrol pests against the major Asian citrus psyllid, Diaphorina citri, a vector of Candidatus Liberibacter that is a causal agent of citrus Huanglongbing (HLB) disease. Updated information and regional exploration on biocontrol pests are important [...] Read more.
Tamarixia radiata is one of the established biocontrol pests against the major Asian citrus psyllid, Diaphorina citri, a vector of Candidatus Liberibacter that is a causal agent of citrus Huanglongbing (HLB) disease. Updated information and regional exploration on biocontrol pests are important elements for effective disease management strategies. In this study, the diversity and parasitism rate of T. radiata populations were evaluated. Due to the importance of the host–parasitoid relationship, the presence of Wolbachia as an endosymbiont was also investigated. The parasitism rate of various T. radiata populations from Ecuador and China ranged between 57.27% and 66.32%, respectively, with a non-significant emergence rate and a statistically similar sex ratio. Sequence analysis of ITS and COI from T. radiata populations was consistent with the morphological hypothesis that the collections represent a single species, whereas phylogeny of the wsp gene confirmed the presence of Wolbachia pipientis as an endosymbiont within T. radiata populations. Based on partial COI sequences, the maximum genetic diversity such as total haplotype diversity (Hd = 0.788), nucleotide, diversity (π = 0.2439), and average nucleotide difference (k = 171.844) was also estimated for different T. radiata populations. Furthermore, neutrality tests based on COI sequences indicated an overall contraction in T. radiata populations, whereas an expansion trend was observed in associated W. pipientis strains. This study clearly demonstrated the presence of genetically diverse T. radiata populations that were able to parasitize D. citri effectively, and these can be further explored as promising biocontrol candidates in integrated pest management strategies to solve citriculture economic loss caused by D. citri. Full article
(This article belongs to the Special Issue Citrus Production and Protection from Pests and Diseases)
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14 pages, 7607 KiB  
Article
Laboratory and Field Trials to Identify Sustainable Chemical Control Strategies for Trioza erytreae in European Citrus Orchards
by Miguel A. Dionisio, Estrella Hernández-Suárez, Felipe Siverio, Juan M. Arjona-López, Aurea Hervalejo and Francisco J. Arenas-Arenas
Agronomy 2021, 11(10), 1982; https://doi.org/10.3390/agronomy11101982 - 30 Sep 2021
Cited by 4 | Viewed by 1817
Abstract
Trioza erytreae (Del Guercio) is one of the psyllid insect vectors of the causal agents of huanglongbing. This paper proposes an assessment of the effectiveness of several pesticides with and without a pine oil-based organic adjuvant, in order to contain the spread and [...] Read more.
Trioza erytreae (Del Guercio) is one of the psyllid insect vectors of the causal agents of huanglongbing. This paper proposes an assessment of the effectiveness of several pesticides with and without a pine oil-based organic adjuvant, in order to contain the spread and population of this pest and reduce the side effects on the Tamarixia dryi parasitoid. Five insecticides and their combinations with pine oil were sprayed against T. erytreae on citrus trees under semi-field and field conditions. The effect of the same treatments was assessed on T. dryi under laboratory conditions. All insecticides, except for acetamiprid, increased their effectiveness when combined with pine oil under both conditions. Cyantraniliprole, dimethoate, and their respective combinations with the organic adjuvant showed the highest efficacies against T. erytreae. Under laboratory conditions, dimethoate reported the most negative effect on T. dryi activity whereas cyantraniliprole and its combination with pine oil yielded a low toxicity effect on this parasitoid. Our results recommend the development of an integrated control approach for citrus growers based on an insecticide rotation program, preventing the emergence of pest resistance to one substance. In this sense, other insecticides, such as lambda-cyhalothrin with pine oil adjuvant or acetamiprid, could be considered. Full article
(This article belongs to the Special Issue Citrus Production and Protection from Pests and Diseases)
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11 pages, 1554 KiB  
Article
The Survival and Parasitism Rate of Tamarixia radiata (Hymenoptera: Eulophidae) on Its Host Exposed to Beauveriabassiana (Ascomycota: Hypocreales)
by Luis Carlos Ramos Aguila, Komivi Senyo Akutse, Hafiza Javaria Ashraf, Bamisope Steve Bamisile, Jingyi Lin, Jiawang Dai, Huiting Wang and Liande Wang
Agronomy 2021, 11(8), 1496; https://doi.org/10.3390/agronomy11081496 - 28 Jul 2021
Cited by 3 | Viewed by 1884
Abstract
The effect of the entomopathogenic fungus Beauveria bassiana (BB-12) on the biological characteristics of Tamarixia radiata parasitizing Diaphorina citri was studied under laboratory conditions. Twenty 3rd–5th instar nymphs were exposed to a single already-mated female parasitoid (1 day old) and removed after 24 [...] Read more.
The effect of the entomopathogenic fungus Beauveria bassiana (BB-12) on the biological characteristics of Tamarixia radiata parasitizing Diaphorina citri was studied under laboratory conditions. Twenty 3rd–5th instar nymphs were exposed to a single already-mated female parasitoid (1 day old) and removed after 24 h. Subsequently, the nymphs were sprayed at 1, 24 and 48 h post-exposure with 1 × 108 conidial mL−1 suspension. The percentage of parasitism recorded was 22%, 35% and 41% at 1, 24 and 48 h, respectively. The emergence rate varied between 28%, 51% and 49% at 1, 24 and 48 h, respectively. In a subsequent experiment, nymphs of D. citri were sprayed with 1 × 108 conidial mL−1 suspension and then exposed to T. radiata at 1, 24 and 48 h post-spraying to allow for parasitism to occur. The percentage of parasitism recorded was 18%, 27% and 28% at 1, 24 and 48 h, respectively, significantly lower than the parasitism rate recorded in the control (48%). The percentage of emergence varied between 24%, 44% and 45% at 1, 24 and 48 h, respectively. In both experiments, no significant difference was observed in the pre-adult duration (days) and the sex ratio of F1 generation. Meanwhile, significant differences were observed in the longevity of the F1 generation of females and males of T. radiata in a treatment consisting of spraying the fungal suspension and the control. Overall, the findings of the current study revealed a negative interaction between T. radiata and B. bassiana in controlling D. citri nymphs. This outcome is believed to be a result of the antagonistic effects of B. bassiana on the developmental process of the pre-adult stages of the parasitoid. However, our results also show that with a properly timed application (allowing parasitism to occur over an extended period of time before the application of the fungus), T. radiata could potentially be used in combination with B. bassiana for the successful biological control of D. citri. This should be carried out in order to minimize the potentially negative interactions between these two biological agents. Full article
(This article belongs to the Special Issue Citrus Production and Protection from Pests and Diseases)
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18 pages, 2840 KiB  
Article
Spatial Distribution and Development of Sequential Sampling Plans for Diaphorina citri Kuwayama (Hemiptera: Liviidae)
by Gabriel Díaz-Padilla, J. Isabel López-Arroyo, Rafael A. Guajardo-Panes and Ignacio Sánchez-Cohen
Agronomy 2021, 11(7), 1434; https://doi.org/10.3390/agronomy11071434 - 19 Jul 2021
Cited by 2 | Viewed by 2224
Abstract
Vector control in huanglongbing management has been conducted on a calendar basis resulting in high production costs. We addressed this issue and proposed a sequential sampling plan to support decision making for intervention against Diaphorina citri Kuwayama, which is involved in the transmission [...] Read more.
Vector control in huanglongbing management has been conducted on a calendar basis resulting in high production costs. We addressed this issue and proposed a sequential sampling plan to support decision making for intervention against Diaphorina citri Kuwayama, which is involved in the transmission of the bacteria Candidatus Liberibacter asiaticus, associated with such lethal disease. We analyzed 3,264,660 records from samples gathered from the Mexican trapping program for the monitoring of D. citri; it included weekly inspection of 86,004 yellow sticky traps distributed in the country. Spatial distribution of the insect, estimation of a common k (kc), and sequential sampling plans based on Sequential Probability Ratio Test (SPRT) were determined. Taylor’s power law coefficients were ≥1 indicating aggregation in the spatial distribution of the insect. Common k ranged from 0.0183 to 0.2253 and varied independently of geographic zone or citrus species. We obtained 18 sequential sampling plans, one for each state. In the Average Sample Number (ASN) function, the minimal number of samples to make a decision ranged from 17 to 65. In the Operational Characteristic (OC) function, probabilities for a correct intervention at the threshold of 0.2 D. citri adults/trap in most cases were above 80%. In a field evaluation, the application of sampling plans yielded savings obtained by reduction in the number of interventions for insect control. Full article
(This article belongs to the Special Issue Citrus Production and Protection from Pests and Diseases)
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22 pages, 7058 KiB  
Article
Volume Rate Adjustment for Pesticide Applications against Aonidiella aurantii in Citrus: Validation of CitrusVol in the Growers’ Practice
by Alberto Fonte, Cruz Garcerá, Alejandro Tena and Patricia Chueca
Agronomy 2021, 11(7), 1350; https://doi.org/10.3390/agronomy11071350 - 30 Jun 2021
Cited by 4 | Viewed by 1979
Abstract
Aonidiella aurantii is one of the most damaging armored scales in citrus crops worldwide. To control this pest, high water volume rates are conventionally used. In order to rationalize the pesticide applications in citrus, IVIA developed CitrusVol, a tool that recommends the optimal [...] Read more.
Aonidiella aurantii is one of the most damaging armored scales in citrus crops worldwide. To control this pest, high water volume rates are conventionally used. In order to rationalize the pesticide applications in citrus, IVIA developed CitrusVol, a tool that recommends the optimal volume rate based on the vegetation, the pest or disease and the active ingredient. In this study the objectives were: (i) validate CitrusVol as a tool to adjust the spray volume to control A. aurantii and (ii) quantify its environmental and economical advantages. For this, the spray volume adjusted with CitrusVol was compared with the one conventionally used by farmers in 18 applications in seven orchards during two years. The following parameters were evaluated: (i) spray distribution in the canopy, (ii) A. aurantii males trapped per day, and (iii) number of scales per fruit at harvest. CitrusVol reduced the spray volume and the amount of pesticide by 35% on average. Despite this reduction, a satisfactory spray distribution was achieved, and the volume was found to control the pest in a comparable way to the conventional volume. Moreover, CitrusVol saved per application and on average 31.25 h/100 ha of spray operating time, 241.83 L/100 ha of fuel consumption and consequently, the reduction of emissions of CO2 was 631.18 kg/100 ha. Therefore, CitrusVol allows for efficient, low-input and low-impact pesticide applications. Full article
(This article belongs to the Special Issue Citrus Production and Protection from Pests and Diseases)
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15 pages, 1660 KiB  
Article
Citrus Varieties with Different Tolerance Grades to Tristeza Virus Show Dissimilar Volatile Terpene Profiles
by Salvatore Guarino, Loredana Abbate, Francesco Mercati, Sergio Fatta Del Bosco, Antonio Motisi, Mokhtar Abdulsattar Arif, Gabriele Cencetti, Eleonora Palagano and Marco Michelozzi
Agronomy 2021, 11(6), 1120; https://doi.org/10.3390/agronomy11061120 - 30 May 2021
Cited by 12 | Viewed by 3868
Abstract
Plants produce considerable amounts of volatile organic compounds (VOCs) with several biological functions, including protection against biotic agents such as viruses and their vectors. In citrus species, these metabolites can be related with their different susceptibility/tolerance toward the Tristeza virus (CTV), one of [...] Read more.
Plants produce considerable amounts of volatile organic compounds (VOCs) with several biological functions, including protection against biotic agents such as viruses and their vectors. In citrus species, these metabolites can be related with their different susceptibility/tolerance toward the Tristeza virus (CTV), one of the main biotic constraints for the citrus industry. The objective of this study was to compare the VOCs pattern from the leaves of a CTV-susceptible citrus variety such as Citrus aurantium and from three CTV-tolerant varieties: Citrus volkameriana, Carrizo citrange, and Forner-Alcaide no. 5. The VOCs emitted were analyzed via the headspace SPME method, while plant metabolites sequestered in the leaves were analyzed by heptane extraction followed by GC-MS. The results indicated that the majority of the VOCs emitted and sequestered in the leaves of the varieties tolerant and susceptible to CTV are constituted mainly by volatile terpenes (VTs) that exhibit strong qualitative/quantitative differences among the profiles of the four citrus species. In detail, the VOC emission indicated different patterns between C. aurantium and C. volkameriana and from both of them in comparison with Forner-Alcaide no. 5 and Carrizo citrange that exhibited more similarities, with the last two characterized by a higher presence of sesquiterpenes. The data obtained from the analysis of the VOCs sequestered in leaf tissues of the CTV-tolerant varieties indicated a higher presence of monoterpenes such as limonene, α-pinene, and p-cymene, known to be the main components of several plant extracts showing deterrent properties toward viruses and insect vectors. As VOC evaluation is a fast and noninvasive measure of phenotypic dynamics, allowing the association of plant phenotypes in accordance to plant disease resistance and/or stress tolerance, the possible implications of such differences in terms of tolerance grade to CTV and/or its related vectors are discussed. Full article
(This article belongs to the Special Issue Citrus Production and Protection from Pests and Diseases)
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14 pages, 961 KiB  
Article
Rootstock Influence on Growth and Mineral Content of Citrus limon and Citrus sinensis cv. Valencia Inoculated with Candidatus Liberibacter Asiaticus
by Criseida Alhelí Sáenz-Pérez, Eduardo Osorio-Hernández, Benigno Estrada-Drouaillet, Sergio Castro-Nava, Rafael Delgado-Martínez, Claudia Magdalena López-Badillo and Raúl Rodríguez-Herrera
Agronomy 2020, 10(10), 1564; https://doi.org/10.3390/agronomy10101564 - 14 Oct 2020
Cited by 3 | Viewed by 2396
Abstract
Huanglongbing (HLB) reduces the growth and development of citrus and induces changes in secondary metabolites such as flavonoids, limonoids, and polyamines. Likewise, infected plants have a deficient absorption of nutrients such as zinc, potassium, manganese, and copper. Therefore, the objective of this study [...] Read more.
Huanglongbing (HLB) reduces the growth and development of citrus and induces changes in secondary metabolites such as flavonoids, limonoids, and polyamines. Likewise, infected plants have a deficient absorption of nutrients such as zinc, potassium, manganese, and copper. Therefore, the objective of this study was to evaluate the influence of different rootstocks on morphology and mineral changes of Citrus limon and Citrus sinensis cv. Valencia plants inoculated with Candidatus Liberibacter asiaticus. In a greenhouse of the Experimental Station-Autonomous University of Tamaulipas, the Candidatus Liberibacter asiaticus bacteria were inoculated to Citrus limon plants (growing on Citrus volkameriana, Citrus macrophylla, and Citrus aurantium rootstocks) and Citrus sinensis cv. Valencia (growing on Citrus volkameriana and Citrus aurantium rootstocks). The experiment was established under a completely randomized design with 45 graft/rootstock repetitions. In each graft/rootstock combination, the plant height and stem diameter were determined using a tape measurer and a Vernier, respectively. In addition, the nutrient content of foliar samples was determined by an X-ray fluorescence spectrometer. In both citrus species, the C. aurantium rootstock promoted a higher concentration of the bacteria. On the other hand, the rootstock that showed the best agronomical results after inoculation with the bacteria was C. volkameriana, presenting the least variation in mineral content and conferring greater plant height (15%) and stem diameter (23%). In contrast, the presence of Ca. Liberibacter asiaticus decreased S content and increased Cu concentration in C. lemon plants. Similarly, plants infected with C. sinensis presented higher Fe content. Finally, in both species, no significant differences were observed for Mn, P, and Zn concentration. Full article
(This article belongs to the Special Issue Citrus Production and Protection from Pests and Diseases)
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Review

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11 pages, 616 KiB  
Review
A Review on the Role of Silicon Treatment in Biotic Stress Mitigation and Citrus Production
by Mireille Asanzi Mvondo-She, Auges Gatabazi, Mark Delmege Laing and Ashwell Rungano Ndhlala
Agronomy 2021, 11(11), 2198; https://doi.org/10.3390/agronomy11112198 - 30 Oct 2021
Cited by 5 | Viewed by 2499
Abstract
This paper reviews the threat of citrus pathogens during citrus production, with a focus on two pre-harvest diseases, citrus leaf spot, caused by Alternaria alternata (Fr.) Keissl. (1912) and brown rot, caused by Phytophthora citrophthora (R.E. Sm. and E.H. Sm.) Leonian, (1906) as [...] Read more.
This paper reviews the threat of citrus pathogens during citrus production, with a focus on two pre-harvest diseases, citrus leaf spot, caused by Alternaria alternata (Fr.) Keissl. (1912) and brown rot, caused by Phytophthora citrophthora (R.E. Sm. and E.H. Sm.) Leonian, (1906) as well as green and blue mold post-harvest disease, caused by Penicillium digitatum (Pers.) Sacc. and P. italicum Wehmer, (1894), respectively. Furthermore, it reviews the role of soluble silicon, Si nutrition in biotic stress mitigation and potential mitigation mechanisms. Previous studies on the use of Si fertilizers have focused on high accumulator Si crops. These have demonstrated the potential of Si to reduce the occurrence of biotic stresses, which takes place through both physical and biochemical mechanisms. However, few studies have demonstrated the potential of Si to mitigate biotic stress in citrus, or the mechanisms involved. There is a clear need for studies on the impact of Si on various stress biochemical pathways in plants generally, and specifically for citrus due to the huge loss caused by pre- and post-harvest pathogens. This will assist in deepening our understanding of the pathophysiology which is essential to develop resistant cultivars. Full article
(This article belongs to the Special Issue Citrus Production and Protection from Pests and Diseases)
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