Optimizing protocols to evaluate brown rot (Monilinia laxa) susceptibility in peach and nectarine fruits

Abstract

9This study assessed and optimized an in vivo method to evaluate the levels of 10 susceptibility/resistance in fruit from the EEAD-CSIC peach germplasm to an isolate of 11 Monilinia laxa (Aderhold & Ruhland) Honey from peach. A total of four commercial 12 cultivars and six genotypes, descendants of three families, of peach [Prunus persica (L.) 13 88inoculation. 89Using the available methods, longer periods are required for obtaining the source of 90 inoculum and the amount and purity of inoculum are not assured. Moreover, an easy 91 5 inoculation system would help to screen large populations and controlled environment 92 would be preferable to avoid cross contamination. We have modified the existing protocols 93 by shortening the inoculum production and also ensuring the accurate supply of inoculum. 94The objective of this study, therefore, was to have an evaluation method, by optimizing the 95 available protocols, to screen tolerance to brown rot by Monilinia spp. in peach germplasm. 96 We have evaluated brown rot tolerance on Monilinia laxa ex situ inoculated peach fruit by 97 measuring brown rot incidence (%), lesion diameter (mm) and colonization extent (mm). In 98 the Spanish peach collection at the EEAD-CSIC, screening for resistance to brown rot has 99 shown that local germplasm accessions are susceptible although slight differences can be 100 found.

Peach Brown Rot: Still in Search of an Ideal Management Option

“…Walter et al [46] adopted the assessment for lesion development, spore production, storage performance, and cuticle thickness and firmness in screening apricot fruits for resistance to brown rot caused by Monilinia spp. Many advantages exist in support of the ex situ over the in situ method: the manipulation of the fruit is easier, the inoculum load is centrally placed on the fruit cheeks, randomly including mature and immature sides [48], and the pathogenic factors, such as lesion and fungi colonization, are adequately evaluated on each inoculated fruit. Furthermore, the ex situ methodology facilitates the post-inoculation evaluation of qualities such as firmness and soluble solid contents (SSC).…”

“…In addition, the ex situ method enables the washing and disinfection of the fruits, making them pure and uncontaminated for screening against targeted pathogens. However, the artificial inoculation on unwounded fruits, though found to be a reliable method in evaluating brown rot resistance ex situ [8,48], was reported to be not only lengthy and laborious but also affected by season and year variability [20,161].…”

“…(position in classification: Sclerotiniaceae, Helotiales, Leotiomycetidae, Leotiomycetes, Pezizomycotina, Ascomycota) [42]. The species of Monilinia are among the major causal organisms of brown rot disease in various orchard tree crops including: (a) Stone fruits [4,40,41,43,44], such as apricots [45,46], peaches [5,8,47,48], nectarines [48], cherries [49], and plums [45]; (b) Almonds [50] occasionally; and (c) Some pome fruits [51,52], such as pears [51], apples [53], and quinces [54].…”

“…Monilinia fructigena (Honey), Monilinia fructicola (G. Winter) [5] and Monilinia polystroma (G. Leeuwen) [48,55] are other important species. The disease is highly destructive for peaches from fruit formation to storage, but additional losses are caused by the blighting of flowers and twigs.…”

“…Screening for BR resistance in germplasm collections is a very time-and effort-consuming task [40]. Notwithstanding, different methodologies and varying protocols have continued to be assayed in breeding programs to evaluate the genetic resistance of stone fruit crops to fungi [40,48,163,164].…”