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Starchy Staples
Starchy Staples
 Most plants store food reserves in the form
of starch
 Often these reserves are stored in
underground organs
 Some types of roots or modified stems
Starchy Staples
 Potato, sweet potato
and cassava among top
ten crops
 All are tropical in
origin but grown
extensively in
temperate areas today
Starchy Staples
 All propagated asexually
 Highly productive > many tons per acre
 Food insurance against some disasters such as
fire, typhoons, or hail
 High in carbohydrates, mostly starch, but low
in protein and fat
Modified stems
 Variety of functions.
– some specialized for asexual reproduction
– some specialized for food storage
– some for both
 Available for renewed growth upon the
return of favorable weather conditions
 Modified stems, like erect stems, have
recognizable nodes and internodes.
Stolons or runners
 Above ground horizontal stems that produce
buds and roots at the nodes
 These buds develop into new plantlets
 Area can be quickly invaded through this
method of vegetative reproduction
 Underground horizontal stems
 Roots form all along the underside
 Buds found at nodes can give rise to new
 Rhizome may also be a food storage organ
 Enlarged storage tips of a rhizome
 White potato is a tuber
 "Eyes" of the potato are actually buds
located at the nodes, and each bud can give
rise to a new plant
Bulbs and corms
 Modified stems found in monocots
 Bulbs are erect underground stems with
both fleshy and papery leaves - food is
stored in the fleshy leaves -- onions
 Bulbs themselves can multiply
 Corms store food reserves in the stem --no
fleshy leaves -- taro
 Corms can multiply
Storage roots
 Tuberous roots modified fibrous roots that
become fleshy and enlarged with food
reserves -- sweet potato
– can also function in asexual reproduction
 Tap roots are food storing organs for
biennial plants such as carrots, rutabagas,
and turnips
 Solanum tuberosum
 Member of the
family Solanaceae,
Nightshade Family
 Other members are
tomato, eggplant,
pepper, nightshade,
and other poisonous
South American origins
 Archeological evidence shows that 8000
years ago indigenous people living in the
Andes Mts. collected wild potatoes (in what
is now Peru)
 At some point the potato became the staple
food crop for the people in this area
 When the Spanish conquered Peru in the
1530's, the potato was the staple of the Inca
civilization spread over thousands of miles
Introduction to Europe
 Potato introduced to Spain sometime during the
middle to late 16th century
 Potato cultivation slowly spread throughout
Europe - only accepted as a food for humans in
the 18th century
 Lots of misinformation - Other members of the
family known to be poisonous or hallucinogenic
 Tuber is the only part safe to eat; all the above
ground parts are poisonous
Potato in Ireland
 Readily accepted in Ireland
 Established crop as early as 1625
 Dietary staple for the Irish peasant
throughout the 18th and the first half of the
19th century
 Climate and soil ideal for the potato
 Even small plot could feed a family
 Potato was so successful that it led to
population increase - from 1.5 million to 8.5
million between 1760 and 1840
 The poor subsisted on potatoes, some milk,
and only occasionally fish or meat
 Estimates - average adult consumed
between 8 to 12 pounds of potatoes each
Phytophthora infestans
 Fungus causes the disease late blight of
 Fungus attacks and destroys the leaves and
stem causing them to blacken and decay in
a short time and stopping tuber growth
 Tubers are also attacked and rot in the
ground or even later in storage
 In cool wet weather, the fungus can kill a
plant within a week.
Late blight disease in Europe
 First appeared in Europe in 1844
 Accidentally carried with new varieties of
potato from Central or South America
 First appeared in Ireland in August of 1845
Irish potato famine
 Disease struck several times during the
period of 1845 to 1849
 Widespread destruction of the potato crop
led to devastating famines among the Irish
 Over one million died from starvation or
from diseases that followed the famine
 1.5 million Irish emigrated to other areaespecially the United States, resulting in a
25-30% decline of the population
Potato in rest of Europe
 Widely grown in Europe because it was
encouraged by the aristocracy as a cheap
food for the peasants
 By the end of 18th century potato gained
widespread acceptance throughout Europe
 Potato blight devastated the crops in
Europe but effects were not as severe as the
Irish famine since the potato was not the
sole dietary staple
Potato in the United States
 Potato made its appearance in North
America through the European colonies
 There is some doubt as to the exact date of
introduction 1621? or 1719?
 Confusion in historical records between the
white potato and the sweet potato
 Word potato stems from the Arawak Indian
word batata which actually referred to the
sweet potato
United States today
 U.S. production about 5% of the world total
 Potatoes grown in virtually every state
 Top producing states are Idaho, Washington,
and Maine
 One-third of U.S. harvest consumed fresh
 One-half is processed to make frozen
French fries, potato chips, dehydrated
flakes, and other products including potato
Processed potatoes
 Nothing new - Peruvian people from high in
Andes Mts have made chuno, a freeze-dried
dehydrated potato, for about 2000 years
 Tubers are spread on the ground when a heavy
frost is expected
 Following freezing, the potatoes thaw during the
day and are trampled to get rid of water repeated until completely dried
 Chuno can be stored for several years without
Solanum tuberosum
 Solanum, a large genus with over 2000
 Member of the Solanaceae or nightshade
 Almost 6000 cultivars but most commercial
growers plant a limited number of varieties
 In the U.S, 12 account for 85% of the potato
The potato plant
 Bushy herbaceous annual with an alternate
arrangement of large pinnately compound
leaves - does best in cool climates
 Two types of stems are produced
– ordinary stems with leaves
– underground rhizomes which end in tubers
 Anatomically, the tuber is a modified
version of a dicot stem
Potato cultivation
 Propagated by "seed potatoes" - small
pieces with at least one eye
 Produces plants genetically identical to the
parent and maintains the desired traits
within a cultivar
 Seed potatoes produced by farmers who
specialize in growing only seed potatoes
Asexual reproduction
 Advantages - faster and produces plants
with desired qualities
 Disadvantages - genetically identical plants
share the same susceptibility to adverse
environmental conditions and diseases
– Most of the potatoes in Ireland were genetically
identical - derived from one or two plants
introduced into the country
– A monoculture is always risky
Four familiar cultivars
 Round white is an all purpose potato good for
boiling, baking, or processing into chips, fries,
or flakes
 Russets (Idahos) elongate cylindrical tubers
have a corky russet-colored skin and mealy
texture - excellent baking potatoes and ideal
for French fries
 Round reds and long whites usually sold as
new potatoes - harvested earlier in the growing
season and have a very thin skin
Nutrients in potatoes
 Rich in carbohydrates (about 25% of the
fresh weight); parenchyma cells within the
pith are filled with starch grains.
 Low in proteins (only 2.5%) but good
protein quality
 Fat free - no cholesterol
 Good source of vitamins, minerals, and
fiber (which occur in the periderm)
Return of Late Blight
 Late blight of potato has remained a major
pathogen for both potato and tomato
 Various fungicides developed to control the
 New strains of fungus have recently
evolved that are resistant to the effective
 Late blight once again poses a major threat
for cultivation of potatoes
Sweet potato - Ipomoea batatas
 Storage root
 Vine in the morning
glory family
 Propagated
vegetatively from
 Requires a long,
warm, growing season
 Susceptible to chilling
Discovered by Columbus
 Discovered on first voyage - 1492
 Introduced to Spain on his return,
 About 50 years earlier than the introduction
of the white potato
 Arawak peoples in Caribbean called it
batata corrupted into the word potato
 Originally “potato” was Ipomoea batatas
but Solanum tuberosum later called that
Sweet potato
 Following the introduction Widely grown in
Spain and other Mediterranean countries
 Considered a delicacy in Europe
 Rumored to be an aphrodisiac, a claim that
was later transferred to the white potato
along with the name
Sweet potato
 Native to tropical South America
 Cultivation several thousand years in Peru
 Widely grown as a staple crop in Central America
and tropical South America
 During this same period also cultivated in several
Pacific Islands and New Zealand
 An earlier introduction by early seafaring natives?
or natural dispersal of seeds?
 Thor Heyerdahl's traveled from Peru to Polynesia
in the reed raft Kon Tiki in 1947
Sweet potato today
 Significant crop throughout the tropics and
expanded to warm temperate regions
 Used as livestock feed as well as an
important food staple
 China dominates the world's production
 Important in several African countries
 In the United States primarily grown in the
South often called “yams”
 Rich in carbohydrates and certain vitamins
and minerals  Especially good sources Vitamin A and C
 Some of the carbohydrates are present in the
form of sugar
 About 50% more calories than white
potatoes but slightly less protein
Cassava - Manihot esculenta
 Tuberous root - member of the spurge
family (Euphorbiaceae)
 Many names: manioc, tapioca, yuca
 Vital food for millions in the tropics
 Ranks fourth as a source of calories for
humans in tropical countries
 Tapioca pudding only familar cassava
product in US.
Origin and spread of cassava
 Origins in South America, probably Brazil;
 May have been independently domesticated
in Central America
 Well established crop in the New World
tropics long before the arrival of the
Cultivation today
 Brazil leading producer in South America
 Portuguese introduced cassava into West
Africa in the 16th century
 Extensively cultivated in Africa today
 Asia, especially Thailand and Indonesia,
closely follows Africa in annual production
with South America a distant third
 Tall shrub with numerous tuberous roots that are
similar in appearance to sweet potatoes but usually
much larger
 Propagated by stem cuttings - none of the
root is used
 Growth is fairly rapid and little care is
needed following planting
 Can also be cultivated from seed which can
be a source of new genetic varieties
 Roots harvested from 8 mos to 2 years
Environmental tolerance
 Tolerant to a wide range of moisture and
soil conditions
 From hot lowerlands to cool highlands
 Requires well drained soils to prevent root
 Tolerate extended dry periods ( up to 6 mos)
 Resistant to many insects and fungal
 Once harvested, roots subject to rapid decay
and must be dried or processed by 24 hrs
 Sweet or bitter varieties based on the
concentration of poisonous hydrocyanic
acid (HCN)
 If not removed, this toxin can cause death
by cyanide poisoning
Cyanogenic glycosides
 The HCN is liberated by the action of
enzymes upon cyanogenic glycosides
present in cassava
 Distinction between the sweet and bitter
varieties is the concentration of the toxins
 Environmental conditions are known to
influence the production of cyanogenic
Removing the toxins
 Sweet varieties with low HCN levels can be
eaten with little preparation; peeling
followed by boiling, steaming, or frying
 Bitter varieties must undergo extensive
preparation to detoxify before eating
 Traditional methods of treating the peeled
bitter roots vary and include drying,
soaking, boiling, grating, draining, and
fermenting, or combinations
Traditional preparation
 In South America, the traditional
preparation produces a meal called farinha
 Peeled roots are grated and squeezed
through a long cylindrical woven basket
known as a tipiti
 One end of the tipiti is tied to a tree while
the other end is tied to a pole which is used
to stretch the tipiti, thereby expressing juice
from the grated pulp
Cassava Bread
 Grated cassava meal is
used to prepare a flat
 Starch is the main
nutrient approximately 30% of
the fresh weight
 Very low in protein
(1% or less) and
 Can result in
kwashiorkor - among
peoples who rely on
cassava exclusively
Other uses of cassava
 Asia and the Americas also used for animal
feed and for commercial starch production
 Cassava starch has many applications in the
food, textile, paper, and pharmaceuticals
 Tapioca pudding made by cooking tapioca
pearls with milk, eggs, sugar, and vanilla
 The pearls are partly gelatinized cassava
starch made by heating moist cassava flour
in shallow pans
Yams - Dioscorea spp.
 True yams - Tuber crop
 Important staples in many areas:
– West Africa, southeast Asia, Pacific Islands, and
Caribbean Islands
 Genus has several hundred species of which
ten are major food sources
 Yams have been cultivated for over 5000
years in tropical Africa.
 Tubers vary from size of potatoes to
massive ones often weighing over 80 lbs
 Prepared in ways similar to potatoes
 20% starch with about 2% protein
 Medically the tubers were an important
source of sapogenins, a type of steroid used
to make human sex hormones and cortisone
Taro - Colocasia esculenta
 Corm (underground storage stem)
 Member of the Araceae or arum family
 Related to and resembles elephant's ears
 Poi - the traditional dish of the native
Hawaiians prepared from taro
 Foods are also wrapped and cooked in the
leaves during a Hawaiian feast or luau
 Corms are steamed, mashed, made into a
dough, and allowed to ferment to prepare
 Taro may also be cooked in ways similar to
potatoes or processed into flour, chips, and
breakfast foods
 Nutritionally - around 25% carbohydrate,
2% protein and very little fat
 Good source of energy
since it’s rich in starch
 Some converted to
sugar as the fruit
 Good source of
Bananas: the starchy fruit
 Important dietary staple for millions in
tropical countries
 Bananas are true fruits
 Starchy plantains are traditionally cooked
and eaten as a vegetable
 Africa leader in plaintain production
 Cultivation of sweet banana greatest in
Central America
Origin and early domestication
 Native to southeast Asia
 Among the first cultivated plants in area
 Polynesians spread the banana throughout
the Pacific islands
 Cultivated in India for at least 2500 years
Spread of banana
 Arabian traders introduced bananas into
parts of Africa about 2000 yrs ago
 Word "banana" comes from West Africa
 Portuguese and Spanish colonizers spread
bananas throughout tropical regions
 Early in the 16th century they were
introduced to the New World
 Became established very early
Early 20th century
 United Fruit Company (and other
companies) developed extensive banana
plantations in Central America along with
corporate-run railroads and steamships
 For 50 yrs United Fruit exerted control over
the economies and governments of several
countries - "banana republics"
 Rise of nationalism starting in the 1950s led
to the decline of United Fruit
Botany of banana
 Produced by various species in the genus
Musa in the Musaceae, the banana family.
 Most cultivars are sterile triploids
 Need tropical climate and constant moisture
 Cultivated for the fruit, the fiber or even the
foliage which is often used to wrap foods
Banana plant
 Often called a tree but large herbaceous
 May be 20 ft or more in height
 "Trunk" not woody but is actually a rosette
of overlapping, tightly packed leaf bases
which arise from an underground corm.
 Large leaves
Fruit production
 Apical meristem converts from vegetative
growth to flowering
 Single monoeocious inflorescence develops
 Flowering stalk contains 5 to 13 groups of
flowers (often called hands or bunches)
 Most groups contain female flowers that
develop parthenocarpic fruit
 Male flowers confined to the end of the
Fruit Production
 Fruit production ends the life of a plant
 New suckers develop from the corm
 Since the fruits are seedless these suckers
are used in vegetative propagation
 Suckers reach maturity in 9 to 12 months
Starchy Staples
 Starchy staples are an important source of
food for people in every area of the world
 These starchy staples as well as many of the
starchy grains are also grown for many nonfood uses as well
Other uses for starch
 Adhesives
– cardboard, paper bags, gums for envelopes and stamps
 Sizings (fillers or coatings)
– manufacture of paper, cloth, thread, and yarn
– strengthen the material, impart a smooth finish, or
prepare the surface for dyes
 Pharmaceutical industry as a binding and coating
 Laundry starch
 Production of sugar-based sweeteners
 The fermentation by yeast produces alcohol
 Modified stems and storage root function as food
reserves, for asexual reproduction, and storage
 Starchy staples include some of the world's
foremost crops and play major roles in the human
 Potato pivotal to developing societies from the
ancient Incas in South America to the preindustrial countries of Europe, especially 19th
century Ireland