Recent Progress in Enhancing Fungal Disease Resistance in Ornamental Plants

Abstract

Fungal diseases pose a major threat to ornamental plants, with an increasing percentage of pathogen-driven host losses. In ornamental plants, management of the majority of fungal diseases primarily depends upon chemical control methods that are often non-specific. Host basal resistance, which is deficient in many ornamental plants, plays a key role in combating diseases. Despite their economic importance, conventional and molecular breeding approaches in ornamental plants to facilitate disease resistance are lagging, and this is predominantly due to their complex genomes, limited availability of gene pools, and degree of heterozygosity. Although genetic engineering in ornamental plants offers feasible methods to overcome the intrinsic barriers of classical breeding, achievements have mainly been reported only in regard to the modification of floral attributes in ornamentals. The unavailability of transformation protocols and candidate gene resources for several ornamental crops presents an obstacle for tackling the functional studies on disease resistance. Recently, multiomics technologies, in combination with genome editing tools, have provided shortcuts to examine the molecular and genetic regulatory mechanisms underlying fungal disease resistance, ultimately leading to the subsequent advances in the development of novel cultivars with desired fungal disease-resistant traits, in ornamental crops. Although fungal diseases constitute the majority of ornamental plant diseases, a comprehensive overview of this highly important fungal disease resistance seems to be insufficient in the field of ornamental horticulture. Hence, in this review, we highlight the representative mechanisms of the fungal infection-related resistance to pathogens in plants, with a focus on ornamental crops. Recent progress in molecular breeding, genetic engineering strategies, and RNAi technologies, such as HIGS and SIGS for the enhancement of fungal disease resistance in various important ornamental crops, is also described.

Keywords: Alternaria sp.; Botrytis cinerea; Fusarium oxysporum; HIGS (host-induced gene silencing); SIGS (spray-induced gene silencing); breeding technology; fungal diseases; genetic engineering; ornamental plants; resistance mechanisms.

Figure 1

Schematic representation of the various steps involved in the fungal infection process and the general mechanism of the defense response of the host plant machinery to combat the fungal pathogen and to provide resistance.

Figure 2

The comprehensive illustration of different strategies, integrating conventional and advanced breeding technologies to develop novel ornamental cultivars which possess enhanced fungal disease resistance traits.