Impact of ‘Candidatus Liberibacter solanacearum’ haplotypes on sprout emergence and growth from infected seed tubers

Abstract

‘Candidatus Liberibacter solanacearum’ (Lso), which is transmitted by the potato psyllid (Bactericera cockerelli), is the putative causal agent of potato zebra chip. Two haplotypes of the bacterial agent (A & B) are currently widely detected in US potato production regions. This study was aimed at determining the relative impacts of the two haplotypes on plant emergence and agronomic characteristics of emerged plants. Greenhouse experiments were conducted using tubers infected with known haplotypes (A, B or AB mix), collected from two separate locations. Collected tubers were planted in replicated pots and plant emergence was monitored daily. Thirty-five days after planting, emerged plants were harvested and individual plant biomass, height, stem diameter, and leaf area were determined. For both locations, tubers infected with Lso B had lower plant emergence compared to uninfected controls. However, there was no difference in plant emergence between tubers infected with Lso A and Lso B. Emergence of plants from tubers infected with Lso B was slower compared to that of uninfected tubers but there was no difference in time of plant emergence between tubers infected with Lso A and the uninfected controls. Biomass of plants which emerged from uninfected tubers was greater than that from all Lso-infected tubers, regardless of haplotype, and plants which emerged from tubers infected with Lso A had greater biomass than those from tubers infected with Lso B. Differences in height, stem diameter, and leaf area among emerged plants followed similar patterns for both locations (uninfected control the highest and Lso B the lowest) except those from tubers infected with AB, which were inconsistent.