The Role of Rhizobia in Peanut Drought Resistance


Auburn University

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Southeast (GA, FL, AL)

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Drought stress is one of the major environmental factors affecting peanut productivity; its effect can be economically devastating when occurring at critical growth stages. Breeding drought­tolerant and high-yielding peanut varieties will help mitigate the drought impact. Rhizobia are soil bacteria that can form symbiosis with legumes and result in the fixation of atmospheric N2, thereby reducing or eliminating the need for N fertilization. Our on-going study showed that drought stress negatively affected symbiotic N2 fixation in peanut and the impact of middle­season dro??ght was greater than that oflate season. In spite of the observed negative impact, some high-yielding, drought-tolerant genotypes can obtain more N from N2 fixation than others. In this project, we seek to understand the role that rhizobia play in peanut drought resistance. We conducted greenhouse experiments using three peanut genotypes (two drought-tolerant and one drought-susceptible), subjected to middle-season and late-season drought treatments. A total of 87 bacterial isolates were obtained from root nodules, 15% (13 isolates) of which were positive for ACC deaminase activity. The 13 ACC deaminase positive strains were identified by 16S rRNA gene sequencing and further characterized phenotypically. Three of the 13 ACC­deaminase positive isolates were able to nodulate peanut plants. We are in the process of further characterizing these three isolates and generating ACC-deaminase deficient mutants to determine the role of rhizobia in peanut drought resistance. 

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