Commodity
Perspectives:
The commodities that make up root and tuber crops in the CG
System are cassava (Manihot esculenta), potato (Solanum
tuberosum), sweet potato (Ipomoea batatas), yam (Dioscorea
spp.), edible aroids (Colocasia esculenta and Xanthosoma
spp.), and Andean root and tuber crops (several genera).
Root and tuber crops provide a substantial part of the
world's food supply, and are also an important source of animal feed and
industrial products. On a global basis, approximately 45% of root and tuber
crop production is consumed as food, with the remainder used as animal feed or
for industrial processing for products such as starch, distilled spirits, and a
range of minor products.
The pattern of root and tuber crop utilization varies
considerably among countries. In the developing countries (with the exception
of China and Brazil), relatively small amounts (less than 20%) are fed to
livestock. Most of the remainder is used locally as food. The relatively high
cost of transportation, processing, and storage, as well as the considerable
time needed in food preparation, frequently makes unprocessed root and tuber
crops less attractive to urban consumers.
The consumption of root and tuber crops as food in developed
countries is considerably smaller than it is in developing countries, but their
use as animal feeds is relatively higher. A very small proportion of root and tuber
crop production (approximately 5%) is traded internationally. More than
two-thirds (2/3) of those exports come from developing countries, with
Thailand's cassava exports accounting for more than half (½) of the total.
Apart from cassava, only potatoes are traded internationally in significant
quantities - mainly among developed countries.
There are considerable differences in the agroclimatic
conditions suitable for the production for the different root and tuber crops
studied by the CG System. Cassava is grown across a broad range of agroclimatic
conditions from sea level to 1,800 meters, and from areas with as little as 500
mm of rainfall, to tropical rain forest areas with more than 2,000 mm per year.
Potatoes, on the other hand, are considered to be a high latitude/altitude
crop, originating in the Andes, but now grown in a range of environmental
conditions, from traditional ranges to warmer, drier areas, including irrigated
production in Latin America, Asia, and portions of Africa.
Sweet potato is understood to have originated in the
Americas (as did cassava and potato), and it too is grown over a considerable
range of latitude and elevation (up to 2,500 meters). Conversely, yams have a
relatively narrower range of production, being mainly confined to the tropical
region throughout the world from sea level to 1,400 meters. The main production
of yam is in the savannah region of West Africa, where more than 90% of the
crop is grown. Unlike cassava, potato, and sweet potato, the white and yellow
yam (Dioscorea rotundata and D. cayenensis [esculenta],
respectively) are thought to be indigenous to West Africa, whereas the water
yam (D. alata) is thought to have originated in Southeast Asia.
Most of the cultivated edible aroids are well adapted to
high rainfall (and occasional flooding) and can be cultivated in temperatures
ranging between 16° and 30° C, at elevations up to 1,600 meters.
The lesser-known Andean root and tuber crops, of which there
are more than a dozen, vary considerably in their ranges of adaptation and
tolerance to environmental conditions. They are primarily considered to be
medium-to-higher elevation crops of moderate temperature regimes and water
requirements, and have greater tolerance to frost than do other root and tuber
crops.
According to the TAC Secretariat desk study3,
annual production growth rates to the year 2010 for root and tuber crops are
expected to be positive, with the exception of modest declines in cassava in
Asia (including China; -0.4%) and sweet potato and yams in Northeast and North
Africa (-1.0%). TAC also predicts a decline in area for potato, cassava,
aroids, sweet potato and yam in Asia (including China) over the indicated
period (potato, -4.9%; cassava, -1.3%; aroids, -1.1%; sweet potato and yam,
-0.2%).
3 The panel cautions the reader that
the Desk Study's projections are probably linear, and based on very poor data.
Indicated changes in yield in the TAC Secretariat report are
all positive, with the minor exception of a decrease in yield in Northeast and
North Africa for sweet potato and yam (-0.7%). Significant yield increases are
anticipated for potato in sub-Saharan Africa and Asia (including China),
cassava in sub-Saharan Africa, aroids in Asia (including China), and sweet
potato and yam in sub-Saharan Africa as well as in Asia (including China).
Some of the indicated changes will likely be driven by
consumption demands and production opportunities as a result of technology
yet-to-be-developed for root and tuber crops. Some of these technologies will
no doubt entail food processing technologies and expanded feed markets, as well
as current and new industrial uses for the harvested products of root and tuber
crops.
The TAC Secretariat desk study traces historical changes in
food, feed, and industrial uses of root and tuber crops, by commodity and
region. Patterns indicate significant change is apparently taking place in the
utilization of root and tuber crops, particularly with cassava and sweet potato
in Asia (both in China and elsewhere), and in Asia for potato as both food and
feed crops. The latter trend is primarily in China.
Total root and tuber crop consumption increased for
developing countries (1980-1992) while per capita consumption declined
over the same period, primarily with the exceptions of potato (+0.9%) and yam
(+5.5%). When these patterns are examined regionally by commodity, it is
clearly evident that the total consumption of root and tuber crops is
increasing in Africa with annual rates of change for potato and cassava of
+0.32%, and of yam a surprising +8.5%. Despite these increases in total
consumption, per capita consumption patterns in Africa are lagging,
likely as a consequence of increased population. The striking exception to this
pattern is for yam per capita consumption which in Africa increased
+5.2% over the fourteen-year study period.
With a few notable exceptions, per capita consumption
of root and tuber crops in South America and Asia declined over the period of
the study, with some notable changes. Declining per capita consumption
of sweet potato in South America (-2.7% per annum) was out-paced by the change
in Asia (-5.2 %).
These patterns, derived from a TAC desk study, appear to be
at odds with information provided by the relevant IARCs for their mandated root
and tuber crop commodities. Consider the following points:
·
For the past thirty years (from 1961-63 to 1991-93), potato production in
developing countries grew rapidly. Annual growth was particularly strong in
Asia (+3.9 % annually), and in Africa (+4.2%). Growth in production was
combined with a continuing decline in the use of potato for animal feed in
developed countries. Therefore, the share of global production in developing
countries rose from 10% to 30%. By the early 1990s, developing countries
accounted for 36% of the area planted in potato worldwide, up from 16% at the
beginning of the thirty-year period. These patterns are expected to continue
into the future at a projected rate of +2.7 % per annum in developing
countries, reaching 105 million tons (for 34% of world production) by the year
2000.
· During the same thirty year period, world cassava
production has experienced strong growth, with an annual rate of +2.7%,
although this pace has declined during the past decade to +1.8% per annum
(which does not keep pace with population growth). There are also differential
patterns by region, but, for the most part, increased world production of
cassava during the last decade has been mainly due to an area expansion (+1.7%
annually) rather than increased yields. However, survey data gathered by the
Collaborative Study of Cassava in Africa (COSCA) estimate cassava yields of 12
tons per hectare, as compared with FAO estimates of 8.5 tons. This difference
indicates that yield increases may have been contributing more heavily to
cassava production growth than other reports suggest.
· Processed cassava for human consumption is projected to
play an important role in rural and lower- to medium- income urban populations'
daily energy diets. This will be especially true in Africa, where cassava
continues to play an important role in food security. Future cassava production
levels are projected to be consistent with patterns of the past decade, which
implies that the largest share of additional cassava supplies will continue to
be derived from the African continent. Predicted patterns of cassava production
in Latin America and Asia indicate continued growth of production at modest rates.
· The evolution of cassava from a basic world staple crop to
a diversified end-use carbohydrate source has largely been completed in Asia,
and is underway in Latin America. In Africa, while traditional processing
techniques were integral to the adoption of the crop, agro-industrial
transformation appears only to be in the beginning stages.
· Production growth rates of yams in West and Central Africa,
where they are an important food staple, are surpassed only by rice. For
example, yam production increased by seven million metric tons (20 to 27
million tons) between 1988 and 1993. The demand prospects for yams appear
particularly positive, given expected economic growth and rising household
incomes in the region4.
4 The panel notes that projections
for rising incomes in West Africa are arguable.
· In China, where approximately 85% of global sweet potato
production is grown, multiple uses of the crop (e.g., as animal feed as well as
processing of the roots into starch, noodles, and alcohol), have helped to
diversify markets for what was once mostly a directly-consumed food crop. In
other regions, sweet potato use has declined or stagnated over the past thirty
years. There are, however, some exceptions to this general trend. In
sub-Saharan Africa, sweet potato production and area planted has not declined.
Globally, in the poorest developing countries, and particularly in those areas
affected by civil war, sweet potato production area has substantially expanded,
a testament to its attributes as a human food during periods of famine and
suffering.
There are, thus, discrepancies in not only the numerics of
production and consumption of root and tuber crops, but also in the
interpretation of exactly what the numbers mean, and how this information ought
to be used to plan research strategies and set priorities for resource
allocation. The panel took this divergence of opinion as an opportunity to
reassess the strategies and priorities for roots and tubers from an
inter-Centre perspective.
Research
Accomplishments:
To set the stage for assessing strategies and priorities for
root and tuber crops research, the standing panel inventoried CGIAR's
accomplishments in root and tuber research. This provided some interesting
background information that pointed out the very significant contributions that
the CGIAR Centres have made to these crops.
Cassava (IITA)
·
Collaborative studies, through a network (COSCA) in Africa, have examined
varietal needs of farmers and the potentials for production, processing, and
distribution. One anticipated outcome of the studies, namely to improve the
relevance of research on cassava at national and international levels, was
fully realized. For example, the description across several countries and
socio-economic domains of preferred varietal characteristics at farmer,
processor, and consumer levels has had a major input to priority setting in
breeding programs.
· The characterization and integrated control of pests and
diseases of root and tuber crops in Africa has led to a special focus on the
biological control of cassava pests, including a remarkably successful
Africa-wide biological control effort for the cassava mealybug.
· The genetic base of cassava has been expanded through
varietal releases in a number of countries in sub-Saharan Africa. Most of these
cultivars carry resistance to mosaic virus, mealybugs, cassava green mite, and
cassava bacterial blight.
· Successful wide-crossing of cassava with its wild relatives
has been accomplished to acquire genetic resistance to certain pests and
diseases.
· Post-harvest research has solved, to a considerable extent,
the riddle of cyanogenic glycosides in cassava, thus helping to reduce prussic
acid problems in the leaves and roots.
· Assemblage and maintenance of a significant collection of
cassava germplasm of more than 2,000 accessions, consisting mostly of African
farmers' cultivars and some exotic materials from Latin America, including
roughly 200 accessions of wild manihot species from Brazil.
· Diagnostic capability for reliable screening for African
cassava mosaic virus (ACMV) has been developed. This has enabled routine
indexing of elite materials for distribution to NARS, and has facilitated the
international movement of elite ACMV resistant clones to Latin America.
· A better understanding of ACMV etiology and epidemiology
has been achieved, enabling control strategies to be improved in West Africa.
Yam (IITA)
·
The acquisition and maintenance of more than 2,800 accessions of yam comprising
eight cultivated species and several wild relatives, with accompanying
agrobotanical and biochemical characterization.
· The genetic improvement of yam became possible through the
discovery of how to induce flowering, which - for the first time - permitted
conventional plant breeding.
· The elaboration of a minisett technology appropriate for
use by yam growers, which vastly improves the multiplication ratio, and
therefore the supply, of vegetative planting materials. The technique has been
adopted by seed yam producers in West Africa.
· Studies of little known viruses in Dioscorea spp.
and the development of an indexing protocol for D. rotundata has enabled
germplasm distribution regionally and internationally.
· The development of micropropagation techniques for
producing virus-free minitubers which meet quarantine requirements and enable
the routine transfer of elite materials to national programs.
Sweet Potato (IITA)
· From 1977 to 1988, when IITA passed
responsibility for sweet potato improvement to CIP, a sizeable amount of
breeding stock was developed and distributed as virus-free plantlets to
national programs worldwide. By 1988, at least fifty improved clones, based on
IITA germplasm, had been officially released.
Aroids (IITA)
· A treatment was identified and
refined to induce flowering in the edible aroids, thus removing the bottleneck
to selective hybridization and genetic improvement of this plant group.
General (IITA)
· Partner institutions have been
strengthened for enhanced global and regional scientific participation,
including helping to establish more than twenty national root and tuber crops
research programs in Africa.
Cassava (CIAT)
·
Development of cassava information services as resources for professional
enrichment of cassava scientists.
· Assemblage and maintenance of a world germplasm collection,
representing 80% of the total diversity of cassava, complemented with related
wild species.
· Methods for the in vitro conservation of cassava
germplasm.
· Morphological and biochemical characterization of collected
cassava germplasm.
· Global germplasm conservation and distribution.
· Ecoregional approach to gene pool improvement in cassava.
· Broad-based and durable resistance to major insects, mites,
and pathogens incorporated into cassava gene pools.
· Characterization of the mechanisms of drought tolerance in
cassava.
· Understanding and describing the C3-C4
intermediate biochemical characteristics of cassava photosynthesis.
· Identification of several effective biological control
agents for major pests of cassava.
· Characterization of the post-harvest physiology of cassava
roots.
· Improvement and local adaptation of cassava selections for
food and industrial processing.
· Co-development of cassava drying and processing plants in
Central and South America.
· Research on cassava's best management practices led to an
understanding of how to maintain long-term soil fertility.
Potato (CIP)
·
Development of Integrated Pest Management (IPM) strategies based on biological
control for the Andean potato weevil and the potato tuber moth.
· Diagnostic field kits for the serological and
DNA-hybridization assay of potato tissue to determine virus status - especially
useful in developing countries.
· Development of true potato seed technology, which is now
deployed in a number of countries.
· Development of potato late blight resistant varieties that
are being used in East Africa and portions of South America.
· Identification, cleanup and wide scale distribution of an
Argentinean clone that is now grown on more than 150,000 ha. in China.
· Collaborative development of a highly saturated marker map
of the potato genome and development of specific markers for virus and improved
late blight resistance.
· Establishment of an R-gene-free population with durable
late blight resistance.
· Development of an in vitro assay system for the
conservation of potato germplasm.
· Completion of eight impact studies on CIP's work in
varietal improvement, IPM, seed technologies, etc., identifying returns on
investment ranging from 26-106% per annum.
· The acquisition and maintenance of an extensive collection
of germplasm, comprising wild and weedy species, cultivars, improved varieties,
and important breeding lines.
· Utilization of the "hairy potato" for resistance
to potato insect pests.
· Bacterial wilt disease management strategy now being used
in East Africa and Central America for effective disease control.
· Widespread utilization of CIP-released potato cultivars in
Eastern Africa.
Sweet Potato (CIP)
·
Production of improved sweet potato varieties now widely used in Peru.
· Development of an IPM system for sweet potato weevil that
is now being used commercially in Cuba.
· An impact study of IPM of sweet potato.
· The collection and maintenance of a sweet potato germplasm
bank (6,522 accessions).
· Development of methodologies to induce sweet potato
flowering and seed set for germplasm conservation.
· Development of in vitro storage systems for sweet
potato germplasm.
Lesser-known Andean Root and Tuber Species (CIP)
· Genetic conservation of nine Andean
species of edible roots and tubers that are presently being evaluated for their
agronomic characteristics, nutritional value, and potential for production and
consumption.
The panel notes these achievements in root and tuber crops
research with an appreciation of each individual Centre's success and with a
view to the terms of reference of the Inter-Centre Review that asked for an
evaluation of the opportunities and potential for inter-Centre collaboration.
To undertake this evaluation, the panel gave focus to the similarities and
dissimilarities of root and tuber crops in an attempt to find
points-of-intersection that would permit synergies through inter-Centre
collaboration.