Amaranthus tricolor: eat your greens (and reds and purples)

Droughts and high temperatures across Europe this summer are causing our leafy green vegetables to wilt. With the threat of food shortages and against a background of climate change, the hunt is on for tasty alternative crops that can withstand more extreme climates and help to provide a healthy and nutritionally balanced diet. Currently we rely on the three major crops, maize, wheat and rice for up to 60% of our daily calories. However, there is an increasing interest in underutilized and orphan crops to provide alternative food sources and diversity our diet away from the reliance on major crops.

Amaranthus tricolor, commonly known as vegetable amaranth is an underutilized leafy vegetable crop, and a great source of vitamins, minerals and amino acids. If you haven’t heard of it you may have heard of its close relative, the attractive annual garden flower Love Lies Bleeding (A. caudatus). It is mainly cultivated in Africa and South Asia, in warm temperate and tropical regions. It is popular with subsistence farmers because of its low production cost, fast growing season, and tolerance to heat, drought and poor soils. It is the only C4 photosynthetic vegetable crop, and is therefore very water use efficient. Vegetable amaranth is a very versatile crop; you can eat the leaves, stems and in many cases the seeds, although it must be cooked before eating, as it has a high level of oxalates. The leaves come in many shapes and colours with pigmentation ranging from pale to dark green, red to purple and even variegated. This genetically diverse species is a relatively untapped resource for abiotic stress and nutritional quality traits, and is a treasure trove for the plant geneticist. Vegetable amaranth has had relatively little attention compared to other underutilized crops such as quinoa and grain amaranth but it is now gaining more attention.

I am interested in how vegetable amaranth responds to drought stress and what different mechanisms it uses to conserve water. Researching drought stress is challenging as large numbers of plants need to be screened, requiring a lot of space, and they have to be grown to full size to assess the impact of drought on yield. Surrogate traits for drought tolerance are a useful way of quickly and cheaply assessing a large number of accessions for drought tolerance. At Liverpool John Moores University, together with The University of Nottingham, Malaysia Campus and CFF we have been studying the genetic diversity of vegetable amaranth for drought tolerance and are developing rapid drought screening protocols based on surrogate traits such as proline content, net transpiration rate and transpiration efficiency. There is no genome sequence available for vegetable amaranth to investigate genetic diversity so we have used a technology known as DArT. This technique can produce single nucleotide polymorphic (SNP) molecular markers, without needing any existing genome sequence information. We have used these SNP markers to genotype A.tricolor plants and associate these genetic markers with drought tolerance and nutritional quality traits. The publishing of a draft genome of the closely related grain amaranth A. hypochondriacus by Clouse et al., (2016) has been a useful complement to our work. Using this approach, we are studying the phenotypic and genetic characteristics of a large number of drought-tolerant amaranth accessions and hope to produce interesting parent lines for future breeding programs.