Association between plant nutrients, the development of Huanglongbing and abnormal growth symptoms in navel orange

Abstract

Huanglongbing (HLB) causes extensive damage in citrus orchards worldwide. Symptoms include blotchy mottle leaf (BML) and little leaf chlorosis (LLC), and nutrient deficiency usually occurs concurrently. However, the relationship between plant mineral content and infection with Candidatus Liberibacter asiaticus (CLas) is not clearly established.• We sampled 7-month-old autumn shoots with three characteristic phenotypes, asymptomatic leaf (AL), BML and LLC, representing HLB disease progression, and further divided samples into CLas-infected and uninfected based on PCR analysis.• HLB infection decreased transfer coefficients of Mg and K from leaf to phloem tissues through regulation of the transporter genes Cs3g03790.1 and PtrMGT5, increasing the content of leaf Mg and K. HLB infection also decreased leaf Zn, xylem Ca and phloem Ca and Zn content. Leaf Ca, Mg, Zn and B content decreased while leaf K content increased significantly as symptoms progressed from AL to LLC. The transport of P from leaf to phloem tissue, as evaluated by the transfer coefficient, was regulated by the transporter CsiPT2, resulting in irregular levels of leaf P.• Our results provide insights into the nutrient dynamics in Citrus in response to CLas infection and the progression of HLB symptoms.

Bioprospecting Microbiome for Soil and Plant Health Management Amidst Huanglongbing Threat in Citrus: A Review

“…Hence, HLB-associated phloem blockage resulted due to starch-packed sieve pores rather than C Las bacterial aggregates. This work highlights the role of C Las in altering the host gene expression in the development of HLB symptoms ( Kim et al, 2009 ; Dong et al, 2021a ).…”

“…The soil micro-communities frequently help the plant to acquire macro and micronutrients by solubilizing and mobilizing them in addition to a breakdown of organic matter through various complex mechanisms to release the immobilized nutrients ( Srivastava and Malhotra, 2017 ). Particularly, micro-communities also use soil C and N for their growth and energy responses ( Wild et al, 2014 ; Tian et al, 2018 ; Dong et al, 2021a ).…”

“…Declining rock phosphate deposits, energy-intensive N-fertilizer manufacture, and emerging adverse environmental issues due to unscientific use of inorganic fertilizers have sparked interest in developing alternative strategies for plant nutrition to improve better sustainability ( Jacoby et al, 2017 ; Dong et al, 2021b ). Microbes-mediated nutrient conversion is a crucial driver for the growth of the plant, which could be the rate-determining step in the functioning of an agroecosystem ( Schimel and Bennett, 2004 ; Dong et al, 2021a ). Microbiome-plant interactions are driven by fine adjustment between the genetic response of the host and activities of related microbiomes to enable uptake of nutrients ( Srivastava and Singh, 2006 ).…”

“…Numerous micronutrients comprising Zinc (Zn), Iron (Fe), Manganese (Mn), Molybdenum (Mo), and Boron (B) are essentially required for plant growth and development of citrus as they are significantly involved in photosynthesis, water oxidation, respiration, and protection against a variety of oxidative stress damages ( Srivastava and Singh, 2006 ; Srivastava and Malhotra, 2017 ). Despite these, the above micronutrients are not easily available to plants as they are by and large observed in immobilized and complex forms, inaccessible to plants directly ( Dong et al, 2021a ). Soil microbiome performs enormously to solubilize, oxidize, and mobilize these nutrient elements by synthesizing a large number of enzymes, chelators, and organic acids.…”

“…Additionally, micronutrient is reported to elicit systemic acquired resistance in citrus plants acting as elicitors to reduce disease-related injuries and inhibit the development of pathogens, either by knock-down effect or by controlling gene-linked pathogenicity ( Dordas, 2008 ; Spann and Schumann, 2010 ; Gottwald et al, 2012 ; Fones and Preston, 2013 ). Hence, the changes in the composition of phloem sap mainly due to under supply of different micronutrients revealed some useful insights for inactivating the development and sustenance of C Las in the phloem ( Hijaz and Killiny, 2014 ; Hijaz et al, 2016 ; Killiny, 2016 ; Dong et al, 2021a ). Indeed, researches have shown that zinc (Zn) can reduce bacterial infection, followed by manganese (Mn) playing an important role in the synthesis of non-structural carbohydrates, nitrogen metabolism, phenols, and phytoalexin in citrus ( Srivastava et al, 2005 ; Datnoff et al, 2007 ; Bargaz et al, 2018 ; Ray et al, 2020 ).…”