New grass hybrid provides feed, fuel

Versatility is always a commendable attribute and Texas A&M University’s Russ Jessup is developing a new grass plant that can be used for both forage or as a biofuel. The grass breeder crossed pearl millet with napiergrass to create a sterile hybrid. “It’s similar to seedless watermelons or seedless grapes in the sense that the new grass, which we’re calling PMN, doesn’t produce seed,” says Jessup.

Pearl millet, a grain crop native to Africa, and napiergrass, used in Africa as a cut-and-carry hay or silage crop, both provide good forage quality and stress tolerance. The millet is an annual and has two sets of chromosomes, while napiergrass is a perennial and has four sets of chromosomes. Because they are close cousins, the plants can be crossed and the result is a sterile, perennial hybrid with three sets of chromosomes that doesn’t set seed.

“The seed for PMN is collected from the pearl millet parent,” explains Jessup. “Pearl millet is a prolific seed producer so seed production costs are relatively low.”

Expanded adaptation

With both parents being adapted to the semi-arid regions of Africa, it’s no surprise that PMN is highly efficient at utilizing available water and nutrients. The new plant shines in drought and hot conditions. In fact, it’s cold tolerance that limits PMN’s adaptation range.

“Currently, our hybrids are suitable for USDA’s 8b plant hardiness zone,” says Jessup. This area encompasses central Texas and east into the coastal areas of the Carolinas. Production can also go west of Texas across southern Arizona and up the coastal regions of California, Oregon and Washington. “Our goal is to extend adaptation,” explains Jessup. “We have some hybrids that look like they will be able to move at least one zone north.”

Many advantages

PMN has a larger seed than other high-biomass perennial grasses. Additionally, its hybrid seed production approaches that of forage sorghum. One of the best characteristics of the plant is its sterility; this means growers will not need to worry about the plant becoming invasive and spreading to areas where it’s not wanted.

The napiergrass parent gives PMN high protein content. It ranges from 10 to 18 percent, depending on input level. With adequate nitrogen fertilization, it touts one of the highest leaf protein concentrations among perennial grasses. PMN can also produce four to five times the amount of protein per unit of water compared to alfalfa and is more water-use efficient. Jessup reports that neutral detergent fiber (NDF) values range from 55 to 65 percent, with NDF digestibility of 45 to 55 percent.

“PMN can be cut multiple times per season, typically every 45 to 60 days, but as short as 30 days under high management,” says Jessup. In tropical regions where there is no risk of frost, cutting heights can be 4 inches. In temperate regions, Jessup suggests 8 inches in summer and 12 inches during fall. This allows sufficient reserves to be maintained to allow the plant to overwinter. To date, no grazing studies have been done with PMN.

PMN possesses a wide natural range of carbohydrate composition. This makes it possible to develop hybrids specifically designed for forage use or for biofuel conversion. “We also think PMN offers potential for bio-based co-products such as bioplastics and biosilica,” says Jessup.

Because of its heat and drought tolerance, Jessup believes PMN is suitable for planting on large areas of marginal or abandoned grasslands that exist across the Southern states.

Commercialization

There are several components of Jessup’s breeding program that are ongoing. In addition to developing improved PMN hybrids for commercial use, he is also making improvements to the pearl millet and napiergrass parents. Already, Jessup has developed a pearl millet with profuse tillering that can be used for biomass production rather than seed or grain.

Jessup’s goal in the short term is to release an improved pearl millet parent and at least two improved napiergrasses in the next 12 months. The first planned PMN hybrid release is scheduled for early 2017.

If you want to learn and see more of Jessup and his new hybrid, Texas A&M AgriLife has produced a video that can be viewed on the internet at bit.ly/TAM-PMN.

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