New insight in Huanglongbing-associated mature fruit drop in citrus and its link to oxidative stress

Tang, Lisa; Vashisth, Tripti

doi:10.1016/j.scienta.2020.109246

Cited by 24 publications

(18 citation statements)

References 86 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Earlier work has speculated that altered balance among the plant hormones abscisic acid, auxin, ethylene, and jasmonic acid caused by Las infection played a critical role in increasing preharvest fruit drop in HLB disease trees (Martinelli et al 2012;Nehela et al 2018). Most recently, the oxidative stress induced by Las infection was suggested to result in cell wall modification, causing cell separation, and eventually promote pre-harvest fruit drop in infected plants (Tang and Vashisth 2020). Furthermore, it was proposed that the HLB-tolerant 'LB8-9' mandarin might have an advanced antioxidant system to mitigate the pathogeninduced oxidative stress, thereby contributing to its significantly decreased pre-harvest fruit drop relative to the HLB-susceptible Hamlin sweet orange (Tang and Vashisth 2020).…”

Section: Discussionmentioning

confidence: 99%

“…Most recently, the oxidative stress induced by Las infection was suggested to result in cell wall modification, causing cell separation, and eventually promote pre-harvest fruit drop in infected plants (Tang and Vashisth 2020). Furthermore, it was proposed that the HLB-tolerant 'LB8-9' mandarin might have an advanced antioxidant system to mitigate the pathogeninduced oxidative stress, thereby contributing to its significantly decreased pre-harvest fruit drop relative to the HLB-susceptible Hamlin sweet orange (Tang and Vashisth 2020). Whether the SAR inducers tested in this study improve the antioxidant system to mitigate the Las infection-induced pre-harvest fruit drop needs to be investigated.…”

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

Evaluation of the control effect of SAR inducers against citrus Huanglongbing applied by foliar spray, soil drench or trunk injection

Kolbasov

Pang

et al. 2021

Phytopathol Res

View full text Add to dashboard Cite

Huanglongbing (HLB) or greening disease, associated with the bacterial pathogen Candidatus Liberibacter asiaticus (Las), is currently the most devastating citrus disease worldwide and no cure is available. Inducers of systemic acquired resistance (SAR) are effective and sustainable to combat various plant diseases. In this study, the SAR inducers acibenzolar-S-methyl (ASM), imidacloprid (IMI), 2,6-dichloroisonicotinic acid (INA), and salicylic acid (SA), applied individually by foliar spray, soil drench or trunk injection at various rates and frequencies, were evaluated for control of HLB in a 3-year field trial with mature Hamlin sweet orange trees in central Florida, USA in the 2016, 2017, and 2018 crop seasons. Six foliar sprays, six soil applications, and three trunk injections of ASM, IMI, INA, or SA per year were conducted with the untreated as a negative control. HLB disease severity, Las titers, pre-harvest fruit drop, yield and fruit quality were investigated for the treatments. By the end of the 2018 season, all trunk injection treatments at 0.25 g/tree and foliar sprays of INA or SA (but not ASM or IMI) at 0.5 g/tree significantly reduced disease severity, Las population, and fruit drop, and increased fruit yield; whereas all foliar spray treatments at 0.25 g/tree, trunk injection treatments at 0.125 g/tree, and soil drench treatments at 0.25 or 0.5 g/tree did not provide effective control of HLB. Additionally, all trunk injection treatments at 0.25 g/tree had shown a significant decrease in fruit drop and increase of fruit yield starting from 2016 after 1 year of applications, whereas foliar sprays of INA or SA at 0.5 g/tree exhibited similar effects at 2018 after 3 years of applications. None of the SAR inducer treatments had significant effect on fruit quality. Economic analysis suggested that the trunk injection treatments at 0.25 g/tree might produce financial benefits. Overall, this study presents useful information for management of citrus HLB with SAR inducers.

show abstract

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Evaluation of the control effect of SAR inducers against citrus Huanglongbing applied by foliar spray, soil drench or trunk injection

Kolbasov

Pang

et al. 2021

Phytopathol Res

View full text Add to dashboard Cite

show abstract

“…HLB-affected trees go through excessive oxidative stress as a result of infection. The tree then undergoes a significant number of processes to suppress or sequester ROS and counteract the effects of oxidative stress (Martinelli et al, 2012;Tang and Vashisth, 2020). Hence, it is likely that in these reactions micronutrients are used at a higher rate to mitigate disease effects; this implies that the fertilization practices should change for HLBaffected trees compared with healthy trees.…”

Section: Discussionmentioning

confidence: 99%

Nutrient Uptake in Huanglongbing-affected Sweet Orange: Transcriptomic and Physiological Analysis

Shahzad¹,

ChangPin²,

Schumann³

et al. 2020

J. Amer. Soc. Hort. Sci.

Self Cite

View full text Add to dashboard Cite

Since the advent of Huanglongbing [HLB (Candidatus Liberibacter asiaticus)] in Florida, several preliminary reports have emerged about the positive effects of mineral nutrition on the performance of HLB-affected citrus (Citrus sp.) trees. HLB-affected trees are known to undergo significant feeder root loss. Therefore, studies have focused on foliar nutrient application instead of soil-applied nutrients speculating that the HLB-affected trees root systems may not be competent in nutrient uptake. Some studies also suggest that HLB-affected trees benefit from micronutrients at higher than the recommended rates; however, the results are often inconclusive and inconsistent. To address this, the goal of the present study was to evaluate the nutrient uptake efficiency and the quantitative and qualitative differences in nutrient uptake of HLB-affected trees. HLB-affected and healthy sweet orange (Citrus sinensis) trees were grown in a 100% hydroponic system with Hoagland solution for 8 weeks. The trees were deprived of any fertilization for 6 months before the transfer of trees to the hydroponic solution. Altogether, the four treatments studied in the hydroponic system were healthy trees fertilized (HLY-F) and not fertilized (HLY-NF), and HLB-affected trees fertilized (HLB-F) and not fertilized (HLB-NF). HLY-F and HLY-NF trees were found to have similar levels of leaf nutrients except for N, which was found to be low in nonfertilized trees (HLY and HLB). Both HLB-F and HLB-NF trees had lower levels of Ca, Mg, and S compared with HLY trees. In addition, HLB-NF trees had significantly lower levels of micronutrients Mn, Zn, and Fe, compared with HLY-NF trees. The hydroponic solution analysis showed that HLB-F and HLY-F trees had similar uptake of all the nutrients. Considering that HLB-affected trees have a lower root-to-shoot ratio than healthy trees, nutrient uptake efficiency per kilogram of root tissue was significantly higher in HLB trees compared with HLY trees. Under nutrient-deficient conditions (day 0) only nine genes were differentially expressed in HLB roots compared with HLY roots. On the other hand, when fertilizer was supplied for ≈1 week, ≈2300 genes were differentially expressed in HLB-F roots compared with HLY-F roots. A large number of differentially expressed genes in HLB-F were related to ion transport, root growth and development, anatomic changes, cell death, and apoptosis compared with HLY-F trees. Overall, anatomic and transcriptomic analyses revealed that HLB-affected roots undergo remarkable changes on transitioning from no nutrients to a nutrient solution, possibly facilitating a high uptake of nutrients. Our results suggest the roots of HLB-affected trees are highly efficient in nutrient uptake; however, a small root mass is a major limitation in nutrient uptake. Certain micronutrients and secondary macronutrients are also metabolized (possibly involved in tree defense or oxidative stress response) at a higher rate in HLB-affected trees than healthy trees. Therefore, a constant supply of fertilizer at a slightly higher rate than what is recommended for micronutrients and secondary macronutrients would be beneficial for managing HLB-affected trees.

show abstract

“…Trees upregulate antioxidant defenses to reduce the damaging effects of ROS (Apel and Hirt, 2004). Similarly, HLB-affected trees are known to accumulate ROS and undergo oxidative stress on infection and symptom development (Martinelli et al, 2013;Tang and Vashisth, 2020). Studies of HLB-affected trees have shown that key processes such as cell defense, transport, photosynthesis, carbohydrate metabolism, hormone biosynthesis, metabolism, and signal transduction are affected due to the disease (Albrecht and Bowman, 2008).…”

Section: Discussionmentioning

confidence: 99%

Effect of Irrigation Water pH on the Performance of Healthy and Huanglongbing-affected Citrus

Ghimire¹,

Kadyampakeni²,

Vashisth³

2020

J. Amer. Soc. Hort. Sci.

Self Cite

View full text Add to dashboard Cite

Huanglongbing [HLB (Candidatus Liberibacter asiaticus)] is one of the most devastating diseases in citrus (Citrus sp.). Field observations in Florida have shown that citrus groves with high soil and irrigation water pH decline rapidly under HLB-prevalent conditions. It is worth noting that irrigation water pH has always been high in Florida; however, neither tree decline nor low productivity under such conditions has been an issue for citrus before HLB. Therefore, there is a need to determine if HLB increases citrus tree sensitivity to high-pH irrigation water. The objective of this research was to evaluate the molecular and physiological responses of healthy and HLB-affected citrus trees irrigated with water at pH levels of 5.8, 7.0, and 8.0. The results demonstrated that soil pH is positively correlated with irrigation water pH. Overall, regardless of disease occurrence, tree performance decreased as pH increased. HLB-affected trees at pH 8.0 had the greatest mortality (40%) and leaf drop (87%) and the lowest height growth (<1%) and leaf biomass (0.1 g). In contrast, HLB-affected trees at pH 5.8 had the lowest mortality (0%) and leaf drop (16%) and the greatest height growth (6.6%) and leaf biomass (5.5 g). Growth and survival data indicate that high pH had a less negative impact on healthy trees than HLB-affected trees, and that HLB symptoms were exacerbated at pH 8.0 compared with pH 5.8. A transcriptomic analysis of root tissue conducted at the end of the experiment further suggested that HLB-affected trees at pH 5.8 were actively detoxing stress-induced radicals and had increased growth and developmental processes with the downregulation of jasmonic acid biosynthesis compared with healthy trees. This implies that at pH 5.8, HLB-affected trees were under less stress than healthy trees. Compared with healthy trees, HLB-affected trees at pH 8.0 resulted in upregulated immune system processes, defense responses, and cell death; no processes were significantly downregulated in HLB-affected trees compared with healthy trees at pH 8.0. Physiological and molecular observations suggest an interaction between HLB and irrigation water pH whereby HLB symptoms are exacerbated in response to high irrigation water pH.

show abstract

New insight in Huanglongbing-associated mature fruit drop in citrus and its link to oxidative stress

Cited by 24 publications

References 86 publications

Evaluation of the control effect of SAR inducers against citrus Huanglongbing applied by foliar spray, soil drench or trunk injection

Evaluation of the control effect of SAR inducers against citrus Huanglongbing applied by foliar spray, soil drench or trunk injection

Nutrient Uptake in Huanglongbing-affected Sweet Orange: Transcriptomic and Physiological Analysis

Effect of Irrigation Water pH on the Performance of Healthy and Huanglongbing-affected Citrus

Contact Info

Product

Resources

About