Natural Variation for Nutrient Use and Remobilization Efficiencies in Switchgrass

Abstract

Nutrient management in biomass production systems serves to maximize yield and minimize production costs and environmental impact. Loss of soil nutrients with harvested biomass can be reduced by the judicious choice of genotype and harvest time. Sustainable production of switchgrass for biofuel will depend, in part, on breeding of varieties that are conservative in their use of soil nutrients to produce biomass. To aid such breeding programs, we assessed the natural variation in nutrient-use and remobilization efficiencies of 31 accessions of Panicum virgatum by measuring the concentration of 20 elements (N, and Cd) in shoots of field-grown plants harvested at two different stages of development. Significant differences between accessions were found for elemental composition at maturity and after senescence. The concentration of several elements (N, P, K, and Rb) decreased in the shoots of all accessions during senescence, although the efficiency of remobilization ranged from 20% to 61% for N, 31% to 65% for P, 25% for 84% for K, and 33% to 84% for Rb. The accessions/cultivars with the greatest nutrient-use efficiency (smallest loss of nutrient per unit biomass) were BN-14668-65, Kanlow, Caddo from the point of view of N content, and Kanlow, Cave-in-Rock, and Blackwell from the point of view of P content in senescent shoots. Finally, differences in elemental composition between upland and lowland ecotypes were also found. The information presented here will help to guide future breeding programs and nutrient management practices.

PvNAC1 and PvNAC2 Are Associated with Leaf Senescence and Nitrogen Use Efficiency in Switchgrass

“…Remobilization of N from aboveground to belowground organs in switchgrass is a natural process that occurs during shoot senescence in autumn, which helps to conserve nitrogen in the plant for regrowth of the shoot in spring. There is substantial variation in N remobilization efficiency during shoot senescence between switchgrass ecotypes, which could be harnessed in breeding programs to conserve N [5]. The results presented here point to roles of PvNAC1 and PvNAC2 in leaf senescence in switchgrass and to the possibility of using these TFs to improve plant NUE.…”

“…Successful development of switchgrass for biofuel production will depend, in part, on agricultural sustainability including nutrient conservation in the soil-plant system [1,5]. Like other perennial grasses, switchgrass plants remobilize a portion of some nutrients, including N, P, and K, from shoots to roots during yearly senescence [5].…”

“…Like other perennial grasses, switchgrass plants remobilize a portion of some nutrients, including N, P, and K, from shoots to roots during yearly senescence [5]. Nonetheless, substantial amounts of soil nutrients are removed with the harvested shoot biomass.…”

“…In perennial grasses like switchgrass, nutrients in leaves are remobilized during yearly senescence not only to the inflorescence for seed production but also to the root system for storage and later reuse. There is natural variation among switchgrass accessions for nitrogen remobilization efficiency, with a range of 20-61 % remobilization from shoots recorded in one set of experiments [5]. Nothing is known about the genetic regulation of nutrient remobilization in switchgrass and other perennial grasses at present.…”

All Washed Out? Foliar Nutrient Resorption and Leaching in Senescing Switchgrass

“…When grown for bioenergy, these grasses can provide a high-yielding feedstock for solid and liquid fuel applications [3,4]. A sustainability advantage of perennial grasses is their capacity to recycle and store mineral nutrients and carbohydrates over dormant periods (e.g., winter or dry seasons), thus making for a nutrient efficient, lowinput, bioenergy crop [5][6][7].…”