Lecture 15 - Citrus Flashcards
family of citrus
Rutaceae
citrus classification 3 main progenitor species
C. medica (citron)
c. maxima (pomelo)
c. reticulata (mandarin)
origin of citrus
southeast asia
best growing conditions of citrus
24-27 C (best at lower temp)
what is peel colour of citrus related to
temp - low temp brings out orange color
leaf morphology of citrus
petiole (winged or not) and leaflets
distinct scent of crushed young leaves
citrus flower parts are in sets of ___
five
citrus fruit is a berry called ______
hesperidum
how many citrus flowers actually set fruit
1-5%
how are citrus able to produce seedless fruit
parthenocarpy
weakly parthenocarpic
only a few fruit is produced without pollination
moderately parthenocarpic
fair crop is produced without pollin
strongly parthenocarpic
sets good crop without pollination
nuclear embryony
embryos form from nuclear tissue. Means most embryos are vegetative, not zygotic (clones)
does citrus have nuclear embryos
yes
implications of nucellar embryony
essential trait in rootstock (enable true -to-type propagation from seeds)
impedes progress in breeding
propagation of citrus
done through scion and rootstock (got from seed or cuttings. seed works better)
why use rootstock for citrus propagation
avoids juvenility (produces fruit faster)
necessary for plants without seeds
optimizes tree and root health
important rootstock attributes
anchorage, abiotic and biotic stress tolerance
compatibility with scions
what are the progenitors of sweet orange
pomelo and mandarin
t/f: sweet orange is not poly embryonic
f
scientific name of sweet orange
citrus sinensis
4 types of sweet orange
sugar/acidless orange
pigmented/blood orange
navel orange
common orange
current classification of mandarin
type 1, type 2a, type 2b, type 3
type 1 mandarin
pure with no interspecific admixture
type 2a mandarin
early-admixture containing small amount of pomelo alleles
type 2b mandarin
early-admixture containing additional pomelo alleles
type 3 mandarin
late-admixture with additional pomelo introgressions in type 2, and further crossed with sweet orange
what are the progenitors of grapefruit
pomelo and sweet orange
scientific name of grapefruit
citrus paradisi
2 groups of grapefruit
white fleshed
pigmented
T/F: pomelo is monoembryonic
t
2 groups of pomelo
white-fleshed
pigmented
what are the progenitors of lemon
citron and sour orange
what is lemon highly sensitive to
cold
are lemon seeds mono or polyembryonic
polyembryonic
what are the progenitors of limes
citron and c. micrantha
type of limes
small-fruited lime
large-fruited lime
what is kumquat (citrus japonica)
small oranges that are eaten whole. Peel is sweet, flesh is sour/tart
what determines fruit flavor in citrus
sugar:acid ratio determines flavor
acid and sugar in balance =
good flavor
high acid/low sugar =
sour flavor
high sugar/no acid =
no flavor
factors affecting sugar:acid ratio in citrus
genetic
climate
agronomic
macronutrient deficiencies in citrus
excess nitrogen = excess vigor, promote vegetative growth instead of flowering
low nitrogen = yellow leaves, promotes extensive flowering
low phosphorus = hollow core, thicker rind
low potassium = smaller fruit
grapefruits and pomelo will develop ____ rinds in cooler temps or under phosphorus deficiency
thicker
grapefruits and pomelo will take ____ months to sweeten up
14-16
Major challenges of growing citrus
freezing
citrus canker
citrus greening/yellow dragon disease
cultural practices to protect citrus from freezing
sprinkler irrigation through microsprinklers
clean, hard-packed soil surface
covered trunks
biggest problem disease in citrus
HLB/citrus greening
