Cassava is the third most important export crop in Vietnam, and CIAT has had a major impact on the country’s cassava production through nearly three decades of collaboration with Vietnam’s national agricultural research systems. An innovative study of cassava diversity in farmer fields in 2016 that combined standard crop adoption survey methods with DNA fingerprinting revealed that the vast majority of Vietnam’s farmers grow improved varieties developed using CIAT germplasm, and showed that the country’s farmers adopt new varieties more quickly than experts assumed.
While the Vietnamese lowlands are dominated by rice, the local staple, higher land is increasingly dedicated to cassava, 70% of which is converted to starch for export markets at a value of approximately USD1.3-1.5 billion per year. Between 2000 and 2015, the area planted with cassava in Vietnam more than doubled, with approximately 560,000 ha dedicated to the crop in 2015. As the area expanded, yields increased—from approximately 8 t/ha prior to 2000 to 19 t/ha in 2015— thanks to farm mechanization, better agronomic practices and improved varieties.
For a precise assessment of the cassava varieties that Vietnamese farmers are growing, CIAT researchers used a combination of farmer surveys and DNA fingerprinting. CIAT tested this approach with a pilot study in Colombia’s Cauca Department, where researchers collected 436 cassava samples from 305 farms in 19 municipalities. DNA analysis of those samples resulted in the identification of 60 main varietal types and 60 unique genotypes that were not represented in CIAT’s genebank. Researchers determined that only nine of those 120 genotypes were improved varieties, and that only 20 of the 320 farms surveyed (9.22%) were growing them.
Researchers encountered a completely different situation in Vietnam, where more than 3,700 samples of cassava planting material were collected in 82 farming communities scattered across the country’s main cassava production regions. DNA analysis of those samples revealed that 90.62% of the cassava grown in Vietnam is of improved varieties related to CIAT germplasm, and just two varieties, ‘KM94’ and ‘KM419’, cover almost 70% of the country’s cassava farming area.
According to CIAT’s analysis, 31.67% of the cassava area in Vietnam is planted with the variety ‘KM94’, which was developed at Kasestart University, Thailand, from a cross of CIAT germplasm with a local variety. Originally released in Thailand in 1992 as ‘KU50’, the variety was subsequently evaluated in Vietnam, where it was released in 1995 as ‘KM94’. DNA analysis also revealed that 38% of the country’s cassava area is planted with the ‘KM419′, which was developed using CIAT germplasm by a breeding program that partnered CIAT with several Vietnamese institutions. ‘KM419’ was chosen through participatory varietal selection and officially released in 2013.
According to Dung Phuong Le, a research associate with CIAT in Vietnam, she and other researchers were surprised to find that ‘KM419’ was so widely cultivated within just three years of its release, especially since ‘KM94’ was generally assumed to be the most popular variety in Vietnam. She noted that an expert consultation undertaken prior to the DNA analysis estimated that ‘KM94’ occupied approximately 60% of Vietnam’s cassava area.
CIAT scientists attribute the rapid adoption of ‘KM419’ to its high yield (35–45.8 t/ha), high starch content, adaptability, and short duration from planting to harvest. Dung noted that ‘KM419’ is more popular in southern Vietnam, where farms are larger, most farmers sell exclusively to the starch export market, and farmer incomes are higher.
While providing a more accurate assessment of varietal adoption, the DNA analysis revealed widespread confusion among farmers about which varieties they were growing, and alerted scientists at CIAT’s genebank of gaps in their collection. This technology has great potential for improving adoption assessments and the conservation of crop diversity, among other applications.
Photo: Harvesting improved cassava varieties in Dong Nai province, Vietnam. G.Smith/CIAT