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New Mexico State University

New Mexico State University

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NMSU Scientists Unveil New Nematode Resistant Cayenne

LAS CRUCES -- New Mexico State University's latest chile release is long, red and resistant to a devastating pest called the root-knot nematode, a microscopic worm that attacks the plant's roots.


"We've released a lot of varieties in the past, green, red, paprika, jalapeņo, even some ornamental lines, but this is our very first release of cayenne," said Paul Bosland, a chile breeder with NMSU's Agricultural Experiment Station and the director of NMSU's Chile Pepper Institute.

A healthier cayenne crop is important for New Mexico's producers, since they produced 5,500 tons of cayenne peppers last year, valued at $2.2 million, according to the New Mexico Agricultural Statistics Service in Las Cruces. Known as the 'NuMex Nematador' the new resistant cayenne was six years in the making.

"The particular species we have is the No. 1 most widely distributed root-knot nematode pest in the world," said Stephen Thomas, a NMSU nematologist who led the team that extracted, processed and counted nematode reproduction. "Between 2,000 and 3,000 different species of plants are hosts for this particular nematode. It's in basically every crop that we grow in the Mesilla Valley, with the possible exception of pecans." The parasitic worms, which live in the soil, attack the chile's roots, grow into them and eventually form a knot or gall on the root itself.

The microscopic pest, specifically called the southern root-knot nematode, has squirmed across New Mexico for almost 100 years. Nematodes spread largely from movement of farm equipment from field to field. Basically, the eggs ride along until they infect a new area. "We've seen yield reductions from 30 to 100 percent, depending on the level, temperature and time of infestation," Bosland said. Damage is especially severe in sandy soils, the prime nematode breeding ground.

Prior to the new NMSU variety, producers were left with mostly chemical controls to halt nematodes, frequently fumigating their fields with a powerful spectrum of products called nematicides. But an environmental backlash is pushing many of these potent chemicals off the shelf. "Methyl bromide has been commonly used, but that's going off the market," Bosland said. "And other compounds for controlling nematodes may only be available for a couple years."

Fumigant nematicides cost about $100 per acre, a substantial production cost, he said. By having a resistant cayenne, Bosland hopes to save the grower money, as well as reduce future problems. And, if a producer couples the resistant variety with good weed management, there's a greater likelihood of slowing problems on subsequent crops, where there may not be good nematicide alternatives or resistant varieties.

'NuMex Nematador' was developed from a popular cayenne simply called: 'large red thick'. "It's a standard big-fruited type that makes harvesting easier and seems to work well for the industry," Bosland said. However, in the past it was susceptible to nematodes. "We've taken a variety that's already adapted to New Mexico, and selected for nematode resistance. In a sense you don't lose any of the factors that made it good. In fact you've gained one since it's more resistant."

Yayeh Zewdie, a NMSU post-doctoral agronomy research scientist who worked on the study for years, said the new cayenne's resistance is controlled by a single dominant gene with modifiers. "Because of this, it was relatively easy to transfer the resistant gene to other varieties," he said. Still, years of lab time went into making NuMex Nematador.

The breeding project began in 1996 at the chile laboratory with selection of plants that had both good horticultural and agronomic traits. They were then screened for nematode resistance. They were then screened for nematode resistance. All nematode screening was done at the university's greenhouses, using pasteurized, washed sand, which optimized nematode infection.

Zewdie emphasized that resistance to nematodes doesn't mean immunity or zero egg production. "We have very low levels," he said. For example, a susceptible cayenne will produce more than 100,000 eggs per unit, where the resistant variety produces less than 100. Even though eggs are produced, it's not enough to be concerned. Producers interested in planting the new cayenne variety should contact the New Mexico Crop Improvement Association in Las Cruces for seed, Zewdie said.

Why such a heated fight over such a small pest? The answer is hot sauce. Cayenne mash, which is a fermented mix of cayenne and salt, are the essential ingredient in the nationÃĒs booming hot sauce industry. Every tongue-searing brand of hot sauce, other than Tabasco, which is made from an exclusive chile variety, is likely to carry some of the state's cayennes. "It's a neat thing," Bosland said. "When you buy a bottle of Louisiana hot sauce, New Mexico chile is probably in it."