Development and characterisation of diagnostic AFLP markers in Prunus persica for its response to peach tree short life syndrome

Abstract

SummaryPeach tree short life (PTSL) is a complex disease syndrome caused by multiple factors, the genetics of which is unknown. Amplified fragment length polymorphism (AFLP) technology and bulked segregant analysis (BSA) were used to identify diagnostic markers for PTSL syndrome in peach rootstocks. Forty-four AFLPs were identified as potential PTSL-response associated markers based on the combined results of BSA and screening 11 PTSL tolerant, two intermediately-susceptible and two highly-susceptible genotypes with 60 polymorphic EcoRI/MseI primer combinations. The use of primer combination EcoRI+AC/MseI+CCC in conjunction with BSA, resulted in the identification of a single amplification product in the bulk DNA from ten susceptible trees that died from PTSL. This AFLP fragment was also detected in the intermediately-susceptible rootstock ‘Lovell’, the highly-susceptible rootstock ‘Nemared’, and in the highly-susceptible rootstock ‘Nemaguard’. This 96 bp AFLP fragment was absent in the DNA bulked from ten tolerant trees and in the PTSL-tolerant parents used in four controlled crosses that segregated for their response to PTSL. Testing this AFLP primer pair on an additional 111 trees that died or survived on a severe PTSL site, revealed the presence of the diagnostic fragment in 18 trees, of which 17 were ‘Lovell’. Death due to PTSL syndrome was observed in 61% of those trees with the AFLP fragment, which was significantly higher (P ≤ 0.05) compared to those that did not have the fragment (17%). Furthermore, the PTSL symptom ratings were significantly higher, and cumulative tree-life was significantly shorter, (P ≤ 0.05) for ‘Lovell’ when compared with 93 genotypes that lacked the AFLP fragment. These results suggest an association of this AFLP marker, called EAC/MCCC1-96, with PTSL-susceptibility. An additional 43 marker candidates, diagnostic for the PTSL-response were also selected.