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July 24, 2009
Source:
AVRDC - The World Vegetable
Center - Newsletter
Dr. Andreas Ebert,
Genebank Manager and Global Theme Leader - Germplasm
Dr. Zhanyong Sun,
Pumpkin Breeder
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Pumpkin, a native crop from the Americas, has struck
roots in places as distant as Taiwan |
Butternut squash, cheese pumpkin,
golden cushaw, winter crookneck squash, winter squash, or simply
pumpkin or squash are common English names for the species
Cucurbita moschata, which is usually grown under tropical
conditions. Other English names such as calabaza, Caribbean
pumpkin, West Indian pumpkin, and Cuban squash give a hint of
the Latin American origin of this species. The fruits are called
calabaza in Mexico, ayote from Guatemala to Costa Rica, auyama
from Panama to Venezuela, zapallo in Ecuador and Peru, and joko
in
Bolivia. Archaeological and linguistic evidence suggest two
centers of origin and domestication: Mesoamerica,
especially Mexico, and South America. The crop spread very early
to other countries, given the existence of cultivated pumpkin by
indigenous groups in Florida in the pre-Colombian era. By the
end of the 19th century, pumpkin was already cultivated in very
distant places from its origin, in countries like India, Java,
Japan, and Angola.
It is not unexpected that genebanks located in the center of
origin and domestication of this crop hold the world largest
collections of this species. Among those are the National
Institute of Forestry, Agriculture, and Livestock
Research (INIFAP) in Mexico and the Tropical Agricultural
Research and Higher Education Center (CATIE) in Costa Rica. With
more than 2600 accessions and subaccessions, CATIE’s Cucurbita
collection is possibly the largest in the world.
AVRDC – The World Vegetable Center was able to boost its pumpkin
collection of roughly 400 accessions of C. moschata with the
import of 90 new accessions from CATIE’s genebank. These
accessions have originated from a number of mostly Latin
American countries: Brazil (1 accession); Colombia (3); Costa
Rica (13); El Salvador (9); Guatemala (30); Honduras (10);
Mexico (11); Netherlands (1); Nicaragua (6), Panama (4), and
Peru (2).
“These introductions provide a better genetic base for future
breeding and selection work at AVRDC, aiming at the development
of disease-resistant new lines,” says Dr. Andreas Ebert, the
Center’s Genebank Manager and Global Theme Leader - Germplasm.
“C. moschata easily hybridizes with other species like C. maxima
(banana squash, giant pumpkin, Hubbard squash) thus offering
great potential for diseaseresistance breeding.” Similar
introductions to Southeast Asia in the recent past already have
led to the development of a promising inbred line in the
Philippines.
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The
Center’s germplasm collection holds more than 450
accessions of pumpkin |
Pumpkin contributes to food
security in tropical Africa and Asia by providing fruits,
leaves, flowers, and seeds for consumption. Pumpkin fruits are
rich in provitamin A, including α- and β- carotenes. The tender
leaves and
shoots are good sources of micronutrients including provitamin A
and minerals calcium, iron, and zinc.
The major threat to stable pumpkin production in Africa and Asia
are virus diseases. Commercial and high performing pumpkin
varieties with multiple virus resistance are not available in
the tropics, as the crop did not receive very much attention
from the private or the public sector. “Therefore, there is a
significant lack of crop improvement efforts,” says Dr. Zhanyong
Sun, cucurbit breeder at the Center’s headquarters. “The
breeding
objective of AVRDC – The World Vegetable Center’s cucurbit
breeding program is to develop pumpkin lines resistant to
multiple diseases for small scale farmers in tropical Africa and
Asia. Our strategy is to introduce the key virus resistance into
our developed inbred lines first, while we screen for new
resistant germplasm on
emerging virus like geminivirus.”
One AVRDC developed pumpkin line has been selected as the most
preferred line for its leaf, fruit flavor and taste in a recent
vBSS pumpkin evaluation trial conducted in Madagascar in 2009
(see AVRDC Newsletter 10 July 2009). This selected line is now
being used in the Center’s virus resistance breeding program for
Zucchini yellow mosaic virus (ZYMV), which is the most
widespread virus in Madagascar. “We hope to have a line with
resistance to ZYMV and the same good taste ready in two years,”
says Dr. Sun.
Another challenge the cucurbit breeding program faces is
geminivirus, a relatively new emerging virus in the tropics.
“Together with the Center’s virologists, we currently also
screen cucurbit accessions for resistance to this virus,” says
the Dr. Sun. “Certainly, the 90 accessions obtained from CATIE’s
genebank will increase our chance to develop multiple virus
resistant pumpkin lines, and increase the chance of identifying
the desirable trait.” |
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