Abstract:
Objective To clarify the effects of citrus Huanglongbing (HLB) pathogen on agronomic characteristic and fruit quality of Citrus maxima (Burm.) Merr. cv. Shatian Yu.
Method Changes in pathogenic symptom of leaves, fruit external and internal qualities as well as sensory qualities of C. maxima after infected by HLB were studied by field investigation and laboratory test. The effects of bacterial concentration and tree age on disease development process were investigated.
Result After C. maxima grafted with HLB-infected scions, when pathogen concentrations remained relatively low (Ct>28), HLB symptoms were not evident with slight mottled yellow old leaves, slight uniform yellow new leaves and normal shooting. Compared with healthy plants, leaf symptom, fruit yield, and all fruit quality indexes ofC. maxima infected by HLB pathogen at the concentration of 28<Ct<32 had no significant changes. With the increase of HLB affection,C. maxima infected by HLB pathogen at the concentration of Ct<26 showed typical mottled yellow leaves, total yield per plant and fruit number per plant decreased significantly, fruits were smaller and lighter with variable color. The percentage of edible fruit and juice extraction rate, soluble solid content, sweetness, plumpness and overall flavor significantly decreased, while acidity and odor degree significantly increased. The fruit lost edible value.
Conclusion The disease progress of HLB-infected C. maxima is slow, but the economic value of plant is seriously affected with the increase of morbidity degree. This study provides a scientific basis for evaluating the effect of HLB on C. maxima fruit quality and offers theoretical supports for analyzing the HLB tolerance mechanism of grapefruit plants.
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