Publications /  Annual Report 1998

Farmers Restore Potato Crops with CIP Collection
The potato collection held in trust by CIP is paying off for Peruvian farmers. Center scientists responded to a call for help broadcast over one of Peru’s most popular stations. The authorities of a remote highland community known as Cochas Paca (Department of Lima) reported losses of their traditional potato varieties to a severe outbreak of the infamous potato disease, late blight. The heavy rains and elevated temperatures brought on by the El Niño phenomenon compounded the problem, increasing the virulence of the disease. Cochas Paca authorities had heard of CIP’s potato genebank, and decided to broadcast a plea for assistance. CIP was able to respond by providing seed of 109 traditional potato cultivars from the same region to restore those lost to the blight. Similar situations arose in two other highland communities: in Racracalla (Department of Junin) farmers received 79 potato cultivars, and in Iscopampa (Department of Huanuco) 51 samples were restored to the community.

New Late Blight–Resistant Clones at CIP
Population B3, the most advanced source of horizontal resistance to late blight under improvement at CIP, has yielded about 60 highly resistant clones with outstanding agronomic characteristics and tuber yields. Resistance to late blight, agronomic traits, and quality (for both fresh table stock and processing) are continually being upgraded at CIP through recurrent selection cycles. Chosen from the first recombination cycle of population B3, the 60 new clones were tested under severe disease conditions in two locations in the Eastern Highlands of Peru. The first site (Comas) is representative of the inter-Andean valley, while the second site (Oxapampa) has characteristics typical of a highland rainforest environment. The CIP clones also withstood the effects of the 1997–98 El Niño phenomenon, which contributed to a higher-than-usual incidence of the disease. The best of these clones produced yields as high as 3.3 kilograms of marketable tubers per square meter 85 days after planting, without fungicide applications. About 30 clones will be used in Farmer Field Schools next season in Peru, and prepared for distribution to national agricultural research institutes following quarantine protocol.

CIP Scientist Develops Training Set for Bacterial Wilt Detection
A CIP pathologist has developed a new set of training materials based on her refined method for detecting Ralstonia solanacearum, the pathogen that causes bacterial wilt or brown rot in potato. The training set includes a video and an instruction manual on use of the post-enrichment NCM-ELISA kit (enzyme-linked immunosorbent assay on nitrocellulose membrane using enriched samples). The training set is available in English, Chinese, and Spanish. Armed with these new materials, CIP scientists have engaged in a series of training activities across Latin America, East Africa, South-East Asia, and China. In 1998 the kits were distributed to 15 developing countries. CIP's ELISA test is done on nitrocellulose membranes rather than microtitre plates, which reduces cost. Another advantage is that the membranes can be stored for several weeks, so samples can be farmed out to labs for testing. The kit can detect all races, biovars, and serotypes of Rs, even in tubers or stems without symptoms (i.e., latent infections). Before testing, tuber extracts must be enriched in a semi-selective broth. This increases sensitivity by almost 1 million, allowing for detection of as few as 10 bacteria per milliliter (rather than the 1–10 million/ml normally required for detection). The improved accuracy of these refined procedures makes it possible to ensure bacterial wilt–free planting materials anywhere in the world—quickly, easily, reliably, and cheaply. The detection kit is also suitable for bacterial wilt epidemiology research and germplasm evaluation.

CIP Technique Helps Detect Potato Yellow Vein
A new technique based on the NASH method helps detect a threat that is emerging in the Andean region: potato yellow vein virus. Evidence of the virus in Peruvian cultivars found in 1998 suggests the virus entered Peru at least one season earlier, probably through import of foreign cultivars. Study and control of the virus is difficult, however, due to a lack of reliable detection technology. CIP virologists are now seeking efficient screening methods to prevent the disease from spreading. Screening samples according to visible virus symptoms is unreliable, since the causal agent is latent in some cultivars, particularly tubers grown in the Andean highlands under cooler conditions. Using dsRNA as a template, CIP scientists have developed a method for detecting the virus. This technique will be used by quarantine laboratories and CIP to ensure that the materials distributed internationally are free of the virus.

Tecia solanivora: Threat to Andean Potatoes
The potato tuber moth, Tecia solanivora, is threatening potato crops in the Andean region, after wreaking havoc in Central America. Despite the heavy use of insecticide in that region—where the pest is believed to have originated—T. solanivora has marched steadily southward to Venezuela, Colombia, and Ecuador. Bracing for the onslaught, Peru has focused its resources on prevention. It has added the pest to its quarantine list and launched a large-scale detection program. Helping with these efforts, CIP has provided pheromone capsules and technical support to SENASA, the national agricultural department that is directing the operation. Together with its research partners, CIP is also working to develop an integrated pest management strategy that would give potato farmers better access to the tools and knowledge needed to fight this pest. Pheromone traps (in farmers fields) and baculovirus (in tuber storage units) have been widely used. And technologies used to control the common tuber moth have been adapted for use against Tecia. In the coming year, CIP will test its transgenic potato varieties (Bt-transformed) to help manage this devastating pest. The most popular variety (Parda pastuza) has been transformed, and is being tested by CIP.

New Virus Problem Strikes Peruvian Potato Crops
A new disease has appeared in potato-growing areas in Southern Peru, a region where more than 50 percent of the country’s total crop is grown. Causing symptoms similar to those of the potato virus Y (severely crinkled leaves and weak, stunted plants) this disease has cut yields by more than 60 percent. Scientists associate its dissemination with feeding patterns of the psyllid insect Russelliana solanicola, which has recently spread into the region. While first attributed to a phytoplasma, recent studies suggest the organism is transmitted by another insect from the Cicadellidae family, Empoasca sp. The fact that phytoplasma diseases occur only in seed production valleys in the highlands further distinguishes this new disease from the phytoplasma group. This new, isometric virus is different (serologically, and in its biochemical properties) to any other potato virus. Using infected samples CIP scientists have described this new virus, SB-26, and have been able to isolate it consistently from symptomatic plants. Research is now focused on identifying the virus and developing specific technology to detect it so that seed production and quarantine programs can prevent its spread. Farmers’ attempts to manage the insect vector with pesticides have proven unsuccessful. In fact, the insect population has increased. Because of the insect vector's high mobility, this virus also presents a great potential threat to other potato-growing regions in South America.