ARD Biomarkers

This dataset includes data from two experiments, which aimed at the identification and characterization of candidate genes for ARD biomarkers in roots of the ARD sensitive apple rootstock M26. It is a supplement to the research article DOI 10.1371/journal.pone.0238876.

In the first experiment, plants of M26 were grown in a biotest, including untreated and disinfected ARD soil from the three ORDIAmur reference sites Ellerhoop, Heidgraben and Ruthe. Plant shoot length was recorded over a course of eight weeks. After 0, 1, 3 and 7 days, root samples for gene expression analysis were taken. Further root samples for phytoalexin analysis were taken after 3, 7, 10 and 56 days. After 8 weeks, shoot and root fresh and dry masses were determined from the remaining plants to assess ARD severity in the soils. The genes biphenyl synthase 3 (BIS3), biphenyl 4-hydroxylase (B4Hb) and ethylene-responsive transcription factor 1B (ERF1B) were identified for further testing.

In experiment 2, the expression of BIS3, B4Hb and ERF1B was investigated in M26 in response to the stressors heat, high salinity and nutrient starvation, which were applied in peat substrate (heat, salt) or quartz sand (nutrient starvation). Furthermore, grass soil from Heidgraben with no previous apple culture was tested. ARD soil from Heidgraben and peat substrate served as controls. Gene expression was investigated in the roots after 7 and 14 days and phytoalexin contents were analyzed after 14 days. Shoot lengths were recorded weekly and after 8 weeks and fresh and dry masses of shots and roots were taken. A nutrient analysis was conducted with the shoot material to investigate the effects of the nutrient starvation. The second experiment revealed a response of ERF1B to heat stress. All three genes responded to grass soil but to a lesser extent than to ARD soil after two weeks.

Research domain: Plant Breeding

Research question: This study aimed at the identification and characterization biomarkers for apple replant disease (ARD). The first experiment aimed at narrowing down a set of previously identified set of candidate genes by studying their expression in apple roots in a biotest with soil from three ARD sites. These genes were further characterized in the second experiment by studying their expression in response to common unspecific stressors. The identified candidates may serve to improve our understanding of the disease and upon further characterization aid in the breeding of ARD tolerant apple rootstocks.