Phenotyping Brown Rot Susceptibility in Stone Fruit: A Literature Review with Emphasis on Peach

Abstract

Plant disease phenotyping methodologies can vary considerably among testers and often suffer from shortcomings in their procedures and applications. This has been an important challenge in resistance breeding to brown rot, one of the most severe pre-and postharvest stone fruit diseases caused by Monilinia spp. Literature about methodologies for evaluating stone fruit susceptibility to brown rot is abundant but displays significant variations across the described approaches, limiting the ability to compare results from different studies. This is despite the fact that authors largely agree on the main factors influencing brown rot development, such as Monilinia inocula, environmental conditions, cultivars, fruit stage, and management practices. The present review first discusses ways to control or at least account for major factors affecting brown rot phenotyping studies. The second section describes in detail the different steps of fruit infection assays, comparing different protocols available in the literature with the objective of highlighting best practices and further improvement of phenotyping for brown rot susceptibility. Finally, experimental results from multi-year evaluation trials are also reported, highlighting year-to-year variability and exploring correlations of evaluation outcomes among years and assay types, suggesting that choice of phenotyping methodology must be carefully considered in breeding programs.

Monilinia fructicola intercepted on Prunus spp. imported from Spain into South Africa between 2010 and 2020

“…5,[51][52][53][54][55][56] Post-harvest losses of 80-85% may occur under favourable conditions for brown rot development. 16 In Indiana, the brown rot of apples was discovered on the fruit of 'pristine' apples, causing 50% crop loss in 2015. 57 Other apple growers reported a significant loss of 5-20%.…”

“…58 Brown rot fungal infections can begin early in the growth season on blooms and/or young shoots. 16,59,60 While blossom blight outbreaks may not be severe enough to cause a serious decrease in fruit production, they still pose a risk. 59 At harvest, healthy fruit may be contaminated with spores, which then cause decay in storage and during marketing.…”

“…14 M. fructicola subsists on mummified fruits. 15,16 The yellowish exogenous stromata display the principal symptom on peaches, pears, and apples approximately 15 days after ripening. 15,17 The impact of M. laxa and M. fructigena on fruits is considered minimal compared to that of M. fructicola.…”

“…15,17 The impact of M. laxa and M. fructigena on fruits is considered minimal compared to that of M. fructicola. 16 Studies have indicated that the latter pest is more aggressive and hard to control due to its anastomosis behaviour and sexual recombination. 18 It is also known to contain a tremendous genetic change, making and possessing a higher potential to overcome genetic barriers.…”

Feature Papers in Horticulturae

“…Disease and pest management techniques of horticultural crops have been undergoing major changes in recent years, with the push to create more sustainable production systems. While published studies on the methodologies for evaluating stone fruit susceptibility to brown rot are abundant, Mustafa et al [11] reported that significant variation in the various approaches have limited the ability to compare results from different studies. Thus, they reviewed the literature on phenotyping brown-rot susceptibility in stone fruit, focusing on peach (Prunus persica), and discussed ways to manage major factors affecting brown-rot phenotyping studies.…”