Easily Extractable Glomalin-Related Soil Protein as Foliar Spray Improves Nutritional Qualities of Late Ripening Sweet Oranges

Lu-Lu Meng,Qiang-Sheng Wu,Ying-Ning Zou,Anoop Kumar Srivastava,Sheng-Min Liang,Kamil Kuča,Abeer Hashem,Yan Li,Elsayed Fathi Abd_Allah,Chun-Yan Liu

doi:10.3390/horticulturae7080228

Abstract

The role of arbuscular mycorrhizal fungi in sweet oranges is well known, but the function of their secondary metabolite, especially the easily extractable glomalin-related soil protein (EE-GRSP), an active fraction of glomalin, is still unclear. The proposed study aimed to analyze the field response of foliar application of exogenous EE-GRSP on tree mycorrhizal development and fruit quality of two sweet orange (Citrus sinensis L. Osbeck) varieties viz., Lane Late Navel (LLN) and Rohde Red Valencia (RRV). Application of EE-GRSP significantly increased the root mycorrhizal colonization and soil mycorrhizal hyphal length in both the sweet orange varieties. The external quality of fruits (fruit weight, polar diameter, and equatorial diameter) also improved in response to foliar application of EE-GRSP in both sweet orange varieties. However, EE-GRSP treatment showed no change in fruit soluble solid content, while it increased the Vc content, solids-acid ratio, fructose, glucose, and sucrose content of sarcocarp in the two sweet oranges varieties. The LLN variety treated with EE-GRSP recorded significantly higher N, P, K, Fe, and Si content of sarcocarp as a mark of nutritional quality, while the RRV variety treated with EE-GRSP displayed a higher concentration of nutrients like Cu, Fe, Si, and Zn in the sarcocarp as compared with the corresponding non-treated control. To the best of our knowledge, this is the first report regarding the improvement in fruit quality of late-ripening sweet oranges (especially LLN) in response to foliar application of EE-GRSP as another potential biostimulant.

Highlights

Citrus is an evergreen commercially grown tree with worldwide and substantial trade and tariffs
Glomus intraradices improved the phenolic acid content of fruits, such as gallic, p-coumaric, ferulic, and ellagic acid [26]. These results showed a positive benefit of Arbuscular mycorrhizal fungi (AMF) on fruit quality
Both Lane Late Navel (LLN) and Rohde Red Valencia (RRV) varieties were colonized by indigenous AMF

Summary

Introduction

Citrus is an evergreen commercially grown tree with worldwide and substantial trade and tariffs. Arbuscular mycorrhizal fungi (AMF), are a kind of beneficial soil microorganisms that inhabit the rhizosphere of citrus trees [1,2] and colonize the root cells of the host plant, thereby, establishing a mutualistic relationship [3]. Earlier studies have shown that AMF inoculation improved plant growth and nutrient acquisition of potted trifoliate orange and fruit quality of Ponkan mandarin in the field through developed mycorrhizal extraradical hyphae and improved root hairs [4,5,6]. Another feature of AMF is to enhance drought

Methods

Results

Conclusion