Abstract
Abstract Background Huanglongbing (HLB) is a devastating citrus disease. Before callose deposition, the bacterial infection causes oxidative stress, starting cell damage. Humic substances are among the most efficient antioxidants found in nature. Furthermore, it is also previously reported that humic substances can induce a phenylpropanoid metabolism contributing to the production of antimicrobial compounds. It has been noted by technicians and growers in the Brazil's main citrus belt that orchards continuously treated with humic substances can live well with the symptoms of HLB. Methods We treated two young citrus orchards (Citrus sinensis cultivars Baía and Pera) with soluble humic substances (HS) isolated from peat either combined or not with a plant growth-promoting bacteria consortium. The activity of key enzymes related to the response against biotic stresses, such as peroxidase (POX), β-1,3-glucanase (PR) and phenylalanine ammonia-lyase (PAL), as well as the differential transcription level of target genes linked to plant stress response by qRT-PCR was monitored for six months. Results No differences were obtained between sole humic substances and their application combined with plant growth-promoting bacteria, indicating that the microbial consortium had no modulatory effect on HS-treated plants. The treatments promoted the activities of POX, PAL and β-1,3-glucanase, which remained significantly higher concerning the control throughout the evaluation period. In addition, treatments positively regulated the transcription levels of CsPR-7, CsPR-3 and CsPR-11 genes. The experimental data were qualitatively similar to those found in commercial orange orchards treated continuously for 12 and 6 years with humic substances, where the activity and transcription levels were also more significant than for untreated plants. Conclusion Our results indicate that humic substances can trigger immune-mediated responses in plants and they can be used as a natural chemical priming agent to mitigate disease symptoms and contribute to more resilient citrus cultivation. Graphical Abstract
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Claims 5
Claim · model-written summary
Humic substances significantly promoted peroxidase, phenylalanine ammonia-lyase and beta-1,3-glucanase activities in Citrus sinensis cultivars Baía and Pera relative to the control.
- Taxon
- Citrus sinensis
Citrus sinensise0 - Material
- Baía and Perae0
- Treatment
- soluble humic substancese0
- Outcome
- activities of POX, PAL and β-1,3-glucanasee1
- Direction
- promotede1
- Comparator
- the controle1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“We treated two young citrus orchards (Citrus sinensis cultivars Baía and Pera) with soluble humic substances (HS) isolated from peat either combined or not with a plant growth-promoting bacteria consortium”
e1“The treatments promoted the activities of POX, PAL and β-1,3-glucanase, which remained significantly higher concerning the control throughout the evaluation period”
Claim · model-written summary
Humic substance treatments positively regulated transcription of the CsPR-7, CsPR-3 and CsPR-11 genes in Citrus sinensis.
- Taxon
- Citrus sinensisCitrus sinensise0
- Treatment
- soluble humic substancese0
- Gene
- CsPR-7, CsPR-3 and CsPR-11e2
- Outcome
- transcription levelse2
- Direction
- positively regulatede2
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“We treated two young citrus orchards (Citrus sinensis cultivars Baía and Pera) with soluble humic substances (HS) isolated from peat either combined or not with a plant growth-promoting bacteria consortium”
e2“treatments positively regulated the transcription levels of CsPR-7, CsPR-3 and CsPR-11 genes”
Claim · model-written summary
Humic substances raised activity and transcription levels more than in untreated commercial orange orchards.
Verbatim
e3“The experimental data were qualitatively similar to those found in commercial orange orchards treated continuously for 12 and 6 years with humic substances, where the activity and transcription levels were also more significant than for untreated plants”
Claim · model-written summary
Humic substances trigger immune-mediated responses in citrus.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e4“Our results indicate that humic substances can trigger immune-mediated responses in plants and they can be used as a natural chemical priming agent to mitigate disease symptoms and contribute to more resilient citrus cultivation”
Claim · model-written summary
Humic substances can be used as a natural chemical priming agent to mitigate disease symptoms in citrus.
- Outcome
- mitigate disease symptomse4
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e4“Our results indicate that humic substances can trigger immune-mediated responses in plants and they can be used as a natural chemical priming agent to mitigate disease symptoms and contribute to more resilient citrus cultivation”
The same questions in other papers
other · physiology: antioxidant enzymes · Citrus sinensis (sweet orange)Results agree
2 papers in the same direction as this paper
- positive
- positive
Claims are grouped by organism, treatment and what was measured or targeted. A paper counts as positive when any of its claims in the group is positive.