- HUANGLONGBING: DEVASTATING DISEASE OF CITRUS 317
C.Clean Nursery Stock
D.Therapeutic Approaches to Maintain Productivity
1 .Enhanced Nutrition and Systemic Acquired Resistance
2 .Effects of pH and Carbonates
3 .Thermal Therapy
4 .Antimicrobial Compounds
5 .Citrus Types/Cultivars with Reduced Susceptibility to HLB
V.HLB EFFECTS ON FLAVOR AND POSTHARVEST QUALITY
A.Implications of HLB Impacts on Fruit and Juice Quality
1 .Impact of HLB on Orange Fruit/Juice Flavor
2 .Impact of HLB on Orange Fruit/Juice Aroma
B.The Dilemma of Bitterness Perception in HLB-affected Juice
C.Management of Off-flavor for the Orange Juice Industry
D.Future Work
VI.CONCLUSIONS
Literature Cited
I. INTRODUCTION TO CITRUS
Citrus products are generally appreciated for their desirable flavors, fra-
grances, and colors along with their healthful attributes. Citrus fruit and
juice products constitute an important part of human diet. To under-
stand the importance of a devastating disease that is affecting citrus
around the world, it is necessary to understand some basic facts about
this popular fruit.
From the time citrus was first recognized as a delicious fruit with pos-
itive nutritional qualities, it has been moved about the globe. The cen-
ter of origin for citrus is believed to be Southeast Asia (Liu et al. 2012).
Historical records and genetic analyses suggest that there are three true
species in the genusCitrus: citron (C. medica), mandarin (C. reticulata),
and pummelo (C. grandis) (Moore 2001). All commercial citrus types,
for example, sweet orange (C. sinensis), grapefruit (C. paradisi), man-
darin, lemon (C. limon), lime (C. aurantifolia), and cultivars thereof,
for example, “Valencia” sweet orange, “Star Ruby” grapefruit, “Clemen-
tine” mandarin, “Lisbon” lemon, “Persian” lime, and “Minneola” tan-
gelo are interspecific hybrids or mutations of citrus types and belong
to the genusCitrus. Poncirus trifoliatais a sexually compatible, close
relative of citrus and has been a parent in rootstock breeding programs.
SeveralCitrus×P. trifoliatahybrids are commercially important as root-
stocks (Soost and Roose 1996).
The citron reached the West in antiquity and other citrus, particu-
larly lemon and sour orange (Citrus aurantium), moved from Asia to
the Mediterranean along trade routes and eventually reached the Amer-
icas via Spanish explorers. Sweet orange was the last major citrus fruit