Seed Priming Induced Heat and Drought Stress Tolerance during Pearl Millet x Napiergrass Establishment.

Most perennial grasses that are candidates for biofuel production are often limited by vegetative propagation, poor establishment because of small seed size, or low biomass production during the establishment year.  Pearl millet x napiergrass hybrids (“PMN”; Pennisetum glaucum [L.] R. Br. x P. purpureum Schumach.), by contrast, are large-seeded feedstocks capable of high biomass production during the first growing season.  Seed priming, a presowing hydration treatment, is often used to improve stand uniformity and emergence outside the optimal temperature range for germination.  Seed priming also can induce abiotic stress tolerance mechanisms that improve growth during and after seedling establishment.  In this study, seeds were primed in a solid matrix using three methods: (a) priming alone, (b) priming plus the demethylating agent 5-azacytidine, and (c) priming followed by foliar application of chitosan.  Investigation of these effects was performed by growing three PMN hybrids in ambient (30C day/25C night), heat (47C/32C), and heat + drought stress (50% irrigation deficit) environments for 12 wk after sowing.  Seedlings were evaluated weekly for morphological development (tiller number, plant number, biomass yield), chlorophyll concentration index (931nm / 653nm transmission ratio), and chlorophyll LED-induced fluorescence via imaging seedlings after dark adaptation using 430 nm and 465 nm bulbs.  Shoot biomass production of primed PMN 12 wk after sowing was > controls in most environment x genotype combinations.  Analyses of biomass yield, chlorophyll concentration index, and chlorophyll autofluorescence data were incorporated into a multinomial logistic regression model and will be discussed.