An age-old conundrum is how many beans make five? Well, one for the 21st century is how many peas make two? The answer is surprising, and it’s one, if the ‘pea’ in question is chickpea.
Within 11 weeks of each other, two teams have published draft genome sequences of chickpea (Cicer arietinum). Rajeev Varshney et al. report the approximately 738-Mb draft whole genome (manuscript received 21 September 2012, accepted 21 December 2012), whereas Mukesh Jain et al. document 520 Mb (70%; manuscript received 6 November 2012, accepted 4 March 2013). Questions of whether an incomplete genome draft is a legitimate draft genome aside, these sequences join the ever-growing list of sequenced plant genomes. But why two genomes? Well, the two groups have examined different ‘types’ of chickpea: Varshney et al. have tackled ‘kabuli’, Jain et al. have dissected ‘desi’. And this distinction is important because the two varieties have different properties, e.g. ‘kabuli’ types contain higher amounts of dietary fibre, particularly cellulose and hemicellulose. Additionally, ‘desi’ is cultivated mostly in the Indian subcontinent, Ethiopia, Mexico and Iran, whereas ‘kabuli’ is mainly grown in southern Europe, northern Africa, Afghanistan, Pakistan and Chile). Furthermore, ‘chickpea is the second largest cultivated grain food legume [in the wonderful, but sadly fictional, plant family Fabulaceae] in the world, grown in about 11.5 million hectares mostly by resource poor farmers in the semi-arid tropics. The highly nutritious, drought-tolerant chickpea contributes to income generation and improved livelihoods of smallholder farmers in African countries… and is crucial to the food security in India’. So, given the importance of chickpeas, arguably the more genomes – draft or otherwise, complete or not – the better, not least in helping efforts to develop more drought-tolerant forms.
[If all of this ‘genome tussle’ sounds a little familiar, readers might recall the controversy surrounding the ‘two’ genomes of pigeon pea (Cajanus cajan), which was summarised in this column in April 2012. Arguably, no other genomes have caused so much controversy (unless it’s Henrietta Lacks’!) – Ed.]