Researchers are studying why some citrus species appear to handle huanglongbing (HLB) better than others. Understanding these differences could help breeders develop more resilient citrus varieties and rootstocks for future production.
A new study compared nine citrus species infected with HLB and identified differences in how the plants respond to the disease, including changes in nutrient levels, stress responses and molecular defense mechanisms.
An article about the research (“Differential responses of Citrus species to huanglongbing infection for physiological, biochemical, nutritional, bio-stress enzymes, and molecular markers”) was published in the journal Scientific Reports. The Indian Council of Agricultural Research conducted the study. The article’s authors are Heiplanmi Rymbai, Amrita Banerjee, Veerendra Kumar Verma, Pankaj Baiswar and Joiedevivreson Mawlein.
Researchers evaluated nine citrus species: sweet orange (Citrus sinensis), mandarin (Citrus reticulata), grapefruit (Citrus paradisi), lemon (Citrus limon), lime (Citrus aurantifolia), pummelo (Citrus maxima), citron (Citrus medica), sour orange (Citrus aurantium) and rough lemon (Citrus jambhiri).
The study found significant differences in how the species responded to HLB infection. Some citrus types showed stronger tolerance characteristics, including better maintenance of nutrient levels and increased activity of antioxidant enzymes that help plants manage infection-related stress.
TOLERANCE RESPONSES
Researchers found that pummelo and citron showed stronger tolerance-related responses, including improved regulation of stress-defense mechanisms. Rough lemon and sour orange also showed characteristics associated with better stress responses. Some commercial citrus types, including sweet orange and mandarin, showed greater physiological disruptions after infection.
NUTRIENT BALANCE
HLB infection affected nutrient balance differently among species. Researchers observed changes in important elements such as nitrogen, phosphorus, potassium and micronutrients. Some species maintained more stable nutrient profiles than others. These differences may help explain why certain citrus relatives can survive or tolerate HLB better than commercial cultivars.
STUDY IMPLICATIONS
The findings do not provide an immediate HLB solution, but they offer valuable information for breeding programs. Citrus relatives with natural tolerance traits could provide genetic resources for developing future rootstocks or scion varieties that perform better in HLB-affected groves.
Because HLB continues to challenge citrus production worldwide, researchers are using every available tool — including genetic diversity within the citrus family — to identify traits that may improve tree survival and productivity.
This research adds another piece to the puzzle of understanding HLB tolerance and highlights why preserving and studying diverse citrus genetics remains important for the future of the industry.
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