1. STARCHY STAPLES Potato, Sweet potato, Cassava
Most of staples popular in Pakistan
Starch food reserves in underground organs (roots or modified stem)
Starch-polymer of glucose molecule
Tropical origin
High in carbohydrates, low in proteins

2. STARCH MOLECULE Amylose poly-(1-4) glucose, a straight chain
Tends to coil up into a helix
Amylopectin is poly(1-4) glucose with branches
Open molecular structure than amylose
Because it has more ends broken more quickly than amylose by amylase enzymes

3. Modified Organs Rhizome underground horizontal stem Food storage organ
Leaves reduced in form of scales on surface of rhizome
Roots adventitious
Buds on nodes give rise to new plants

4. Tubers enlarged storage tip of rhizome
White potato
Eyes are buds that form new plant
Bulbs modified storage organs mostly in monocots
Underground stems with fleshy leaves
Onions, Tulips
New bulbs can develop in the leaves axils

5. White Potatoes Solanum tuberosum associated with Ireland
Established in 1965
Dietry staple food for Irish people
Ideal climate and soil for potato
Small plots of land sufficient to feed a family
Historian link population explosion to presence of reliable food

6. Average adult consumption of potato 4 to 6kg each day
Reliance on potatoes set the disaster: Irish potato famine of
Pathogen Phytophthora infestans cause of late blight of potato
Fungus attacks leaves, blacken them stopping tuber growth
In cool wet weather, fungus kills plant within a week

7. Disease appeared in 1845 in Ireland
Widespread destruction of potato crop
1million people died from starvation
Resulted 20-30% decline of population in Ireland in Ireland in less than a decade
Conflicts between English rulers and Irish people another reason
In history, Ireland a colony of English people and Irish were shamelessly exploited

8. Solanum tuberosum Genus Solanum- cultivated potato
2,000 species in Solanaceae
S. tuberosum 6,000 cultivars
Europe produce 70% of world crop
China second leading producer and next Brazil
Stem of two types
Ordinary foliage bearing stems
Underground rhizome that ends in tubers

9. Anatomically, tuber modified version of dicot stem
Enlarged pith, a ring of vascular bundle, and narrow cortex
Vascular tissue appear black in potato chips
with narrow cortex on outside and large pith within ring
Cool season crop with maximum tuber production ranging under 15to 18C

10. Higher temperature inhibit tuber production
Potato cultivation through propagation by seed potatoes, small tubers or cut pieces containing at least one eye
Seed potatoes cultivation- asexual reproduction producing plants genetically identical to their parents and maintaining desired traits within a cultivar

11. Seed potatoes checked for diseases
Fast method
Disadvantage- Share same susceptibility to adverse environmental conditions
Susceptible to Phytophthora infestans and Colorado potato beetle
Potato beetles became resistant to chemical insecticides used for control

12. Russet
Red
Potatoes Varieties
white

13. Round white used for baking, chips, fires
Russets elongate, cylindrical tubers, excellent for baking purposes, common in Pakistan
Russets potatoes high in starch
Round red and long white relatively new
Good for boiling steaming, roasting

14. Potatoes rich in carbohydrates (25% of fresh weight)
Parenchyma cells within pith filled with starch grains
Vitamin, minerals and fibers in cortex and periderm
Nutritional value enhanced when consumed with skin

15. Sweet Potatoes Ipomoea batatus Storage root in family Convolvulaceae
Habitat vine
Columbus discovered sweet potatoes
Native to South America
China dominating country in production

16. Drier, starchier variety in Northern States
Sweeter, moist, deep orange (Yams) common in South
Rich in carbohydrates, vitamins and minerals
50% more calories than white potatoes
Root source of carotene, vitamin A, C
Thanksgiving diet

17. Bananas Important dietary staple in in tropical countries
Popular dessert, source of starch and potassium
Sweet banana
Tree habitat
Herbaceous with height of 6meters or 20 feet

18. Bananas native to Southeast Asia
Cultivated 2500 years
Genus Musa in Musaceae
Require tropical climate with constant moisture
Cultivated for food, fibre, foliage (natural waxed paper)

19. Banana Tree

20. Plantains Important food in poor countries Planta-sole of foot
Genus Plantago
P. ovata P. afra (Grown in India)
Twice the size of banana
Sour or sweet in taste
Ripe black plantain more sweet than banana

21. Plantains

22. Ten times more B-carotene than banana
Source of vitamin A, C, B6, potassium, iron and magnesium
Helpful in treating ulcers
Green, unripe varieties have enzymes for healing

23. CASSAVA Manihot esculenta Family Euphorbiaceae
Known as Manioc, Yuca, Mandioca
Ranks fourth behind rice, sugar and corn as source of calories in tropical countries
Tall shrub with palmately compound leaves
Can tolerate dry period upto 6 moths

24. CASSAVA
Roots
Cassava plant

25. Varieties may be sweet or bitter
Hydrocyanic acid (HCN)
If not removed, toxin may cause death by cyanide poisoning
HCN liberate through enzymatic actions cyanogenic glycosides
Sweet and bitter varieties differ only on cyanide content
Environmental conditions influence cyanide production

26. Sweet variety can be bitter under different condition
Traditional methods for treating bitter ones varies
May include drying, soaking, boiling, draining
Processed to make flour
In Indonesia, peeled roots sliced, dried in sun, allows HCN to diffuse
Resulting chips called gaplek

27. Stored for long period of time or ground into flour
Breads, cakes, cookies, noodles
Starch rich (30% of fresh weight)
Protein content is being improved through cassava breeding programmes
Roots also contain calcium, vitamin B and C
Being used for Bioethanol

28. Recommended Links