Preharvest Fruit Drop in Huanglongbing-affected ‘Valencia’ Sweet Orange

Tang, Lisa; Chhajed, Shweta; Vashisth, Tripti

doi:10.21273/jashs04625-18

Cited by 35 publications

(37 citation statements)

References 53 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Fruit drop is a major concern in HLB-affected trees (Albrigo and Stover, 2015). The preharvest fruit drop increases as the HLB symptoms increase and canopy density decreases (Tang et al, 2019). Similarly, in this study, a negative correlation between canopy volume and fruit drop was observed for the first 2 years of the study (Table 1).…”

Section: Discussionsupporting

confidence: 82%

Assessment of Pruning and Controlled-release Fertilizer to Rejuvenate Huanglongbing-affected Sweet Orange

Vashisth

Livingston

2019

hortte

Self Cite

View full text Add to dashboard Cite

Previous research has shown that Huanglongbing {HLB [causal agent Candidatus Liberibacter asiaticus (CLas)]}-affected sweet orange (Citrus sinensis) trees have a reduced root-to-shoot ratio, potentially due to the high rate of root death. The diminished root system cannot support the existing aboveground canopy and a cycle of imbalance begins. As a result, the tree enters into a continuous carbohydrate stress cycle and, eventually, the tree declines. Therefore, the goal of this study was to evaluate pruning as a strategy to adjust the root-to-shoot ratio to improve growth and productivity of HLB-affected trees. In Jan. 2015, a 3-year trial was initiated on a 14-year-old grove of ‘Hamlin’ sweet orange on Swingle citrumelo (Citrus paradisi × Poncirus trifoliate) rootstock that was symptomatic of HLB and produced less than 180 lb of fruit per tree. The four pruning treatments were as follows: 1) 0% pruning (no canopy removal), 2) 25% pruning (canopy removed), 3) 50% pruning (canopy removed), and 4) 80% pruning (canopy removed). In a split-plot design, two sources of fertilizer were evaluated in combination with the pruning: 1) conventional fertilizer [CNV (dry granular)] applied at 200 lb/acre nitrogen (N) in five split applications per year, and 2) controlled-release fertilizer (CRF) applied at 150 lb/acre N, split in three applications per year. Within each pruning treatment, half of the trees received CNV and the other half received CRF. The fertilizer treatments were applied in each of the 3 years; however, pruning was performed only once in the beginning of the experiment. The trees that were pruned produced new vegetative growth that looked healthy with no visual HLB symptoms (initially); however, the trees remained positive for CLas throughout the study as determined by quantitative real-time polymerase chain reaction. The 80% pruned trees grew vigorously over the course of 3 years but remained significantly smaller in canopy than control trees (0% pruning) for both CRF and CNV treatments. The 25% and 50% pruned tree canopies grew back and were similar in canopy size as 0% pruning (control) treatment by the end of year 2. At the end of the study, the use of CRF on 25% pruned trees resulted in a significantly higher leaf area index as compared with trees receiving CNV. A significant positive linear correlation was observed between canopy volume and root density; the root density decreased with intensive pruning. A significant positive correlation was also observed between canopy volume and yield, and a negative correlation between canopy volume and fruit drop. There were no significant increases in yield resulting from any pruning or fertilization treatments compared with controls (0% pruning). However, with the use of CRF, the amount of N and frequency of application were reduced. Overall, our results indicate that pruning did not improve the productivity of HLB-affected trees over the course of 3 years. Therefore, severe pruning is not a viable option to rejuvenate the HLB-affected trees.

show abstract

Section: Discussionsupporting

confidence: 82%

Assessment of Pruning and Controlled-release Fertilizer to Rejuvenate Huanglongbing-affected Sweet Orange

Vashisth

Livingston

2019

hortte

Self Cite

View full text Add to dashboard Cite

show abstract

“…The significant reduction of pre-harvest fruit drop by trunk-injected SAR inducers at 0.25 g/tree (Table 3) might be attributed to their suppressive effects on Las population growth in HLB diseased citrus trees. Excessive pre-harvest fruit drop, usually happening three to 4 months prior to harvest, is positively correlated with HLB disease severity (Tang et al 2019). 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).…”

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

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

“…Huanglongbing (HLB) is a disease of citrus causing economic loss to the citrus industry around the world (Bové, 2006; Singerman and Useche, 2016). Its causal agent, Candidatus Liberibacter asiaticus ( C Las), vectored by the Asian citrus psyllid (ACP; Diaphorina citri Kuwayama), is a phloem-limited bacterium which affects phloem dysfunction leading to starch accumulation in leaves and loss of sink growth (Achor et al, 2020; Bové, 2006), as well as eventual development of thin canopies (Tang et al, 2019).…”

Section: Introductionmentioning

confidence: 99%

“…Due to the specificity of the leaf level measurements (light levels, angle of radiation incidence, leaf position within the canopy), leaf-level data is difficult to extrapolate to the whole canopy. Because, HLB induces reductions in canopy density (Tang et al 2019), larger scale measures may be more indicative of changes in carbon assimilation than leaf-level measures.…”

Section: Introductionmentioning

confidence: 99%

Citrus photosynthesis and morphology acclimate to phloem-affecting huanglongbing disease at the leaf and shoot levels

Keeley

Rowland

Vincent

2021

Preprint

View full text Add to dashboard Cite

Huanglongbing (HLB) is a phloem-affecting disease of citrus that reduces growth and has impacted citrus production in most global production regions. HLB is caused by a phloem-limited bacterium (Candidatus Liberibacter asiaticus; CLas). By inhibiting phloem function, HLB stunts sink growth, including reducing production of new shoots and leaves, and induces hyperaccumulation of foliar starch. Despite evidence that HLB induces feedback inhibition of photosynthesis by reducing foliar carbohydrate export, its effects on net CO2 assimilation (Anet) have not been reported. In this work we assessed the relationship of bacterial distribution within the foliage, foliar starch accumulation, and Anet. Because HLB impacts canopy morphology, we developed a chamber to measure whole shoot Anet, and tested the effects of HLB at both leaf and shoot levels. Starch accumulation was correlated with bacterial population, and starch was negatively correlated with Anet at the leaf but not at the shoot level. Starch increased between the uninfected group and the shortest duration of infection, then decreased progressively with increasing length of infection. HLB infection reduced Anet at the leaf level, but increased it at the whole shoot level. We attribute this enhancement of whole shoot Anet to the increased contribution of stem photosynthesis due to the altered shoot morphology induced by the disease. Despite the increased photosynthetic efficiency, total carbon fixation per shoot decreased because shoot size and leaf area were reduced. Overall, our results indicate a localized relationship of CLas distribution with negative impacts on foliar carbohydrate export and photosynthesis. Additionally, starch accumulation and Anet acclimate over time at the shoot level to the localized impacts of the disease. Stems contribute important proportions of whole shoot Anet, and these contributions are likely increased by the morphological acclimation induced by HLB. This study highlights the importance of temporal and spatial scale in assessing photosynthesis.

show abstract

Preharvest Fruit Drop in Huanglongbing-affected ‘Valencia’ Sweet Orange

Cited by 35 publications

References 53 publications

Assessment of Pruning and Controlled-release Fertilizer to Rejuvenate Huanglongbing-affected Sweet Orange

Assessment of Pruning and Controlled-release Fertilizer to Rejuvenate Huanglongbing-affected Sweet Orange

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

Citrus photosynthesis and morphology acclimate to phloem-affecting huanglongbing disease at the leaf and shoot levels

Contact Info

Product

Resources

About