Usually, if plant breeders do anything at all with wild species, they use them to try to improve the domesticated relative in some way. But in Bajra–Napier Hybrids (BNH), it’s actually the crop that is used to improve a wild (or at least wildish) relative.
That’s more than just a fun fact. BNH are actually pretty important forages in tropical and subtropical livestock systems, though you don’t hear too much about them other than from specialists. I certainly hadn’t, until a recent social media blitz from ICRISAT.
They are made by crossing the crop pearl millet (bajra, Pennisetum glaucum) with the related forage Napier grass (Pennisetum purpureum). This has the effect of combining nicely complementary traits into a highly productive fodder plant.
The best thing about BNH is their high yield of biomass. Under ideal conditions, annual green fodder production can exceed 200–300 tonnes per hectare, which comfortably outperforms other forage grass options. This productivity is due to fast growth, profuse tillering, and efficient nutrient uptake. For smallholder dairy systems, where land is usually at a premium, such a yield advantage translates pretty quickly into higher milk output per area. Also, BNH are perennial, which reduces costs over time, as fields can remain productive for several years with proper care.
And the nutritional profile of the fodder is pretty good. Crude protein is typically 8–14%, depending on management and cutting stage, while digestibility remains ok if the plants are harvested relatively early, before they start getting woody, say at 45–60 day intervals.
BNH are resilient, being tolerant to drought and intermittent water stress, a trait inherited largely from pearl millet, though they also respond well to irrigation and fertilization. That makes them widely suitable, everywhere from low-input rainfed systems to intensive peri-urban dairying.
All that said, there are drawbacks. Perhaps the main one is that BNH are typically sterile, not producing seeds, and therefore have to be propagated vegetatively, through stem cuttings or root splits. This means farmers depend on planting material supply chains that are often weak or informal. Diseases can also be transmitted more easily via vegetative material. Plus high biomass production demands big nutrient inputs, particularly nitrogen, with inadequate fertilization quickly eroding both yield and quality. That can be expensive.
In response, an important recent line of research has focused on developing seed-propagated BNH. Seeds simplify dissemination, reduce transport costs, and mitigate the spread of vegetatively transmitted diseases. They also enable more formal seed sector engagement, including developing new varieties.
Making fertile hybrids is technically tricky. Sterility in the classic hybrids is due to genomic incompatibilities between the parental species, basically their different ploidies, or numbers of chromosomes. So breeding strategies have explored chromosome doubling, intermediate ploidy levels, and backcrossing to restore partial fertility while retaining the desirable forage traits.
This has been reasonably successful, but trade-offs remain: some seed-propagated lines show lower biomass yields or less persistence compared to established clonal hybrids, and ensuring consistent performance across environments is still a work in progress. So it’s good to see ICRISAT and its partner still on the case, hard at work.
LATER: Dr Chris Jones, program leader for feed and forage development at ILRI, who should know, tells me that the currently accepted names for the parents of BNH are Cenchrus americanus (pearl millet) and C. purpureus (Napier grass). Something to do with Cenchrus being nested within Pennisetum evolutionarily speaking, so the best bet was to merge the genera, but under the name Cenchrus because that is the older one.
