Herbarium stories: Pressed plants, a portal to the past, a window into evolution

In a small room tucked inside the International Potato Center’s (CIP in Spanish) biodiversity complex, the faint scent of flowering potato plants lingers. Nimble fingers work to adhere pressed samples of potato, sweetpotato and Andean roots and tubers to acid-free paper. Each new addition not only adds to the CIP Herbarium’s growing collection, it adds to the world’s understanding of root and tuber crops.

Hidden in these pressed flowers, leaves, and stems are the unfolding stories of plant evolution. Each specimen is a faithful witness of the environment in which it grew. As a collection, they provide a treasure trove of information on the breadth of plant diversity and allow scientists to understand how these species have evolved in the face of changing environmental pressures.

The CIP Herbarium houses almost 22,000 accessions. Each one lovingly collected and painstakingly preserved from the most remote corners of the world. Here are some of their stories.

Solanum immite

Country: Peru, Region: Lima, Province: Barranca

District: Lomas de Supe, Altitude: 80 meters, white flowers in sandy soil

Date of collection: September 1959

Collector number: OCH2168

Solanum immite is one of the first Peruvian potato wild relatives described in a written text, Prodromus de Candole Vol. 13 (1):32 by Michael Felix Dunal in 1852. In 1959, Dr. Carlos Ochoa, took a trip to Chancay to collect a sample from the sandy and misty Lomas de Supe, a collection of hills near the coast of Central Peru. Rampant urbanization has since transformed the site were this particular specimen was collected. Maintaining such a specimen helps to keep vital information alive that might otherwise be lost in a rapidly changing world. The CIP herbarium now houses 16 accessions of this species, serving as a record for future researchers.

Solanum acaule Bitter

Country: Peru, Region: Cusco, Province: Espinar

District: Pinti frente Phinaya, Altitude: 4000 meters; along the stretch of road between Yauri-Santo Tomás 30 km from the Santo Domingo Bridge

Collection date: April 1984

Collector number: CPS 0010

Collectors record the coordinates of where they collect plants along with information about the altitude and the environment. This helps researchers know where to gather specimens on future trips and provides vital details about the impact of the environment on any given plant. In order to increase the amount of genetic materials in its collection, the CIP genebank plants seeds from collected materials in greenhouses. At an altitude of 4,000 meters, Solanum acaule, grows close to the ground, almost as if huddling for warmth. Samples grown from seed take on a markedly different appearance.

Solanum acaule

Greenhouse sample

Each plant collected is regenerated by the CIP genebank in order to increase the genetic material of a given population. In the controlled environment of a greenhouse at 3,2000 feet where the temperatures don’t dip close to freezing, the same Solanum acaule stretches out and grows larger leaves. Each accession is also a record of how a plant reacts to its environment. Over time, as scientists collect and record data of the same species in different areas and elevations, they amass visual records of how plants respond to their environment. Taxonomists take great care to observe and register physical changes in a plant that are a product of environmental factors.

Solanum amayanum

Country: Peru, Region: Huancavelica, Province: Tayacaja, near Hayncayojaja on Colcabamba-Huacayojaja route, Altitude: 3000 meters

Collection Date: January 1985

Collector number: C. Ochoa y J. Amaya 15910 Ochoa 15910

While photographs might provide a visual record of how a plant looked at any given time, you can’t access the wealth of information hidden in a plant from a still image. Solanum amayanum is covered with downy fine hair lining the leaves and stem. A herbarium specimen allows a taxonomist to hone in much deeper, to count and measure individual hairs with the help of a microscope. This particular species is named after Jesus Amaya Castillo, who once oversaw CIP’s experimental station in Huancayo. Amaya’s work in recording and preserving specimens proved vital contributions to Dr. Carlos Ochoa’s comprehensive book The Potatoes of South America.

Solanum salasianum

Country: Peru, Region: Huanuco, Province: Pachitea, District: Chaglla, near Tendalpata, Altitude: 2800 meters, between Asia and Monocanca, on the route from Muña to Tambo de vaca

Date of collection: May 1984

Collector number: OCHS 15751

Accession number: CIP 763578

This particular potato wild relative is named after Alberto Salas, a prolific CIP collector of potato, sweetpotato, Andean root and tuber crops, and potato wild relatives. To date, his collection trips number an estimated 300. It is by sheer luck that the date Alberto collected this specimen didn’t end up on his tombstone. On that fateful day, he traveled by horseback into the highlands of Huánuco, and on his return trip, the Santo Domingo River had grown so swollen from rainfall that it swallowed the horse he was riding. With some quick thinking, Alberto transformed the waterproof backpack he used to carry specimens into a flotation device. He struggled against the savage current and made his way to shore just below a small cliff, where he was pulled to safety with the help of a rope. The quickly churning rapids proved no match for his backpack. It not only saved his life, it also kept the collected plant materials dry enough to be added to the Herbarium collection.

Ipomoea sawyerii

Country: Peru

Date of collection: April 1988

Collector number: DLP 3271

Accession number: CIP 470150

Dr. Richard L. Sawyer, CIP founder and first director general, has the honor of having not one but two species named after him: a wild potato relative, Solanum sawyeri, and this sweetpotato wild relative, Ipomoea sawyeri. It was under his guidance that CIP added sweetpotato to its mandate. That decision has helped to transform lives around the world. For the past decade, CIP has used biofortified orange-fleshed sweetpotato to fight vitamin A deficiency – a pernicious form of micronutrient deficiency that can cause blindness and early death– in Sub-Saharan Africa. In 2016, three CIP researchers were honored with the prestigious World Food Prize for that work.

This accession was verified by taxonomist John Wood of Oxford University.

Solanum peloquiniamum

Country: Peru, Region: Ancash, Province: Congoro, District: La Pampa, 1720 meters on the Yuracmarca-Sihuas route

Collection date: March 1979

Collector number: OCH 13222

Accession number: CIP 764924

The herbarium houses a variety of specimens with preferred traits. It contains one of the most complete collections of Solanum section Petota, housing more than 90 percent of the wild and cultivated species from the southern United States to the South of Chile. Solanum peloquiniamum is a potato wild relative of particular importance because it has an adapted trait that allows it to grow where water is scarce. It’s ability to grow in drought like conditions make it particularly useful to plant breeders working to develop improved varieties in the face of climate change. It is named after University of Wisconsin potato geneticist and cytologist Dr. Stan Peloquin.

Ipomoea amnicola (Original)

Country: Bolivia, Region: Santa Cruz/ Santa Cruz-St. Cruz

Collection date: August 1987

Collector number: DLP 2758

Accession number: CIP 470141

The CIP herbarium collection was acquired through donations and scientific explorations over the course of almost 50 years. Original collected specimens such as the wild sweetpotato relative Ipomoea amnicola can be used for DNA samples and to validate scientific information. Taxonomists from across the globe routinely visit the CIP Herbarium. This particular species was validated by renowned taxonomist D. F. Austin on one such trip.

Ipomoea amnicola (San Ramón Field Station)

Greenhouse sample

CIP’s collection is regenerated at field stations and some of those plants are preserved as herbarium specimens to guarantee botanic identity. While the original specimen of Ipomoea amincola above was collected in Santa Cruz, Bolivia, seeds from it were later planted at CIP’s San Ramón field station, where this specimen was pressed. With the passage of time, continued specimen collection and regeneration, scientists can document evolutionary changes of how plants adapt to environmental pressures. These specimens are housed together to provide a quick visual reference of a given plant’s history.

Dr. Carlos Ochoa

Behind every specimen housed in the herbarium is a collector. Over the course of his lifetime, intrepid explorer Dr. Carlos Ochoa collected and described 80 species of potato wild relatives and produced two authoritative books about potato species across the Americas. After a lapse of 31 years, Ochoa retraced his steps to kilometer marker 38 on the Cerro de Pasco-Huanuco highway, where he originally collected a Solanum ambosinum sample OCH1040. Reaching the collection site meant crossing the Huascar River whose water level rose considerably in the time it took him to gather the material he needed.. Much like Alberto Salas, his colleague, Dr. Ochoa almost lost his life trying to reach safety. Unpredictable rivers are just of one of the life-threatening challenges that collectors like Ochoa and Salas have faced over the years.