Morphological, molecular biology and pathological characterization of fungi causes root rot on grapevine

Background
Grapevine is subjected to attack by several of soilborne fungi causing root-rot diseases that lead to limit the production of grapevine.
Objective
This study aimed to investigate the morphological, molecular identification, and pathogenic potential of fungi that causes root-rot disease of grapevine in Egypt.
Materials and methods
Isolation of fungi causing root rot of grapevine plants from the samples of diseased roots of different cultivars, i.e., crimson, superior, and flame seedless. Identification according to characterizations of morphological, cultural, and molecular biology based on internal-transcribed spacer 1 (ITS1). Pathogenicity tests of fungal isolates on grapevine plants under greenhouse conditions. Root-rot incidence, disease severity, and plant growth characteristics were determined.
Results and conclusion
Isolation traits from affected grapevine trees with different grape varieties in Egypt’s El-Nobaria Province, El-Behira Governorate, yielded eighteen isolates of four fungal genera. Fusarium spp. was the most fungal genus highly frequent on all cultivars tested and colonization (100%) on root-rot tissue of superior and flame-seedless cultivars, then (75%) on Crimson cultivar. While Lasiodiplodia spp. was recorded with moderate frequency and high colonization (100%) on rotten tissue of Crimson cultivar followed by (75%) in both flame-seedless and superior cultivars. As opposed to that, fungi of Macrophomina phaseolina followed by Rhizoctonia solani had the least frequency and colonization percentage. Isolates of fungi were identified according to morphological characteristics, cultural, and molecular biology based on internal-transcribed spacer-1 (ITS1) sequencing and conserved in GenBank with accession numbers from (ON037457.1 to ON037474.1). Fungal isolates were varied for causes of root rot on grapevine plants and their reduction effect on the characteristics of growth of flame-seedless cultivar. Fusarium solani isolate (ON037462.1) was the most pathogenic isolate that caused (100%) of root rot, high disease severity, and highly significant reduced grapevine plant growth characteristics followed by isolates of Lasiodiplodia theobromae (ON037474.1). In this respect, a new isolate of fungal species was hosting grapevine plants, i.e., two isolates each of F. chlamydosporum, F. brachygibbosum, one isolate of F. ipomoeae, and one isolate of L. exigua are the new causal pathogens of root-rot disease on grapevine as the first report in Egypt.