Increasing interest in woody biomass as a source of biofuel feedstock necessitates the use of marginal lands, rather than fertile croplands, for their production. The extensive network of land disturbed by surface mining in Appalachia represents a significant potential resource for this use. However, these areas are often plagued by edaphic stressors that inhibit successful establishment of woody plants. In particular, the exposure of acid-producing overburden to weathering processes during mining or reclamation activities creates acidic soil conditions that promote the availability of phytotoxic aluminum (Al). Therefore, a screening experiment was conducted in an effort to identify Al tolerant genotypes of a commonly grown woody biomass crop, Salix spp., that can be established on former mined lands affected by Al toxicity for potential woody biomass production. Stem cuttings of sixteen genotypes of Salix spp. were grown using a hydroponic nutrient film technique and exposed to four concentrations of Al (0, 100, 200, and 400 µM). Growth metrics and tolerance indices (growth under all µM Al/mean growth at 0 µM Al for each genotype x 100) were used to assess performance of each genotype under varying levels of Al.
Results/Conclusions
The effect of Al on root and shoot growth depended on the genotype, indicating significant variation in response to Al among the tested genotypes. For all genotypes, Al decreased plant root mass by 39%, 46%, and 73% in the 100, 200, and 400 µM treatments, respectively. Root biomass tolerance index at 200 µM Al ranged from 16.7 to 83.3, reflecting broad genetic variation. Among all genotypes, Al reduced shoot growth by 30% at 100 µM Al and 53% at 400 µM Al. Taken in concert, analyses of growth and Al tolerance metrics identify Salix spp. genotypes ‘Fabius’ and ‘Oneida’ as tolerant to Al, and genotypes ‘Preble’ and ‘Fish Creek’ as Al intolerant. Results of this screening experiment provide fundamental knowledge for mine land reclamation practitioners and bioenergy plantation managers regarding Al toxicity response of an important woody biomass species. Further analysis of these genotypes will help to identify the physiological and genetic underpinnings of Al tolerance in Salix spp. in an effort to maximize potential use of this woody biomass crop on derelict lands affected by Al toxicity.