Morpho-Cultural and Pathogenic Variability of Sclerotinia sclerotiorum Causing White Mold of Common Beans in Temperate Climate

Abstract

The present systematic research on cultural, morphological, and pathogenic variability was carried out on eighty isolates of Sclerotinia sclerotiorum collected from major common bean production belts of North Kashmir. The isolates were found to vary in both cultural and morphological characteristics such as colony color and type, colony diameter, number of days for sclerotia initiation, sclerotia number per plate, sclerotial weight, and size. The colony color ranged between white and off-white with the majority. The colony was of three types, in majority smooth, some fluffy, and a few fluffy-at-center-only. Colony diameter ranged between 15.33 mm and 29 mm after 24 h of incubation. The isolates took 4 to 7 days for initiation of sclerotia and varied in size, weight, and number per plate ranging between 14 and 51.3. The sclerotial arrangement pattern on plates was peripheral, sub peripheral, peripheral, and subperipheral, arranged at the rim and scattered. A total of 22 Mycelial compatibility groups (MCGs) were formed with seven groups constituted by a single isolate. The isolates within MCGs were mostly at par with each other. The six isolates representing six MCGs showed variability in pathogenicity with isolate G04 as the most and B01 as the least virulent. The colony diameter and disease scores were positively correlated. Sclerotia were observed to germinate both myceliogenically and carpogenically under natural temperate conditions of Kashmir. Germplasm screening revealed a single resistant line and eleven partially resistant lines against most virulent isolates.

Population and genome-wide association studies of Sclerotinia sclerotiorum isolates collected from diverse host plants throughout the United States

“…Assessment of isolate lesion formation on sunflower stems revealed a broad range of aggressiveness among the studied isolates and identified isolates that were highly aggressive on one or both sunflower inbred lines used for evaluations. Variation in S. sclerotiorum isolate aggressiveness has been reported previously on numerous crop hosts, including sunflower ( Ekins et al, 2007 ; Otto-Hanson et al, 2011 ; Taylor et al, 2015 ; Denton-Giles et al, 2018 ; Yu et al, 2020 ; Rather et al, 2022 ). We observed only a modest correlation between isolate aggressiveness on the two sunflower inbred lines, consistent with observations of genotype-isolate interactions for S. sclerotiorum isolates evaluated on crop hosts such as soybean, canola, and sunflower ( Davar et al, 2011 ; Ge et al, 2012 ; Willbur et al, 2017 ; Buchwaldt et al, 2022 ).…”

“…Isolates of S. sclerotiorum have been reported to vary considerably in numerous traits related to growth and development as well as pathogenicity. This includes variation in rates of in vitro hyphal growth, pigmentation of mycelia, size and number of sclerotia formed, and aggressiveness in causing lesions on host plants ( Otto-Hanson et al, 2011 ; Attanayake et al, 2012 ; Rather et al, 2022 ). Consequently, a comprehensive understanding of isolate diversity for this pathogen is important to facilitate resistance breeding efforts.…”

Leguminous Seedborne Pathogens: Seed Health and Sustainable Crop Management

“…Furthermore, the disease can involve all parts of the plant, with acropetal development. During the infection, lesions occur on the petioles, branches, and stem, with the final evasion of gray mycelium on all of the organs involved [ 114 ]. In the advanced stages of the disease, the pods appear discolored and are characterized by soft rot.…”

“…In the former, sclerotia germinate, generating apothecia and ascospores that infect the aerial portions of host plants, while, in the second case, sclerotia produce hyphae that can directly infect the tissues. In legumes, the mycelium develops an appressorium able to directly use enzymes or produce mechanical force to penetrate through the stomata [ 114 ]. White mold has been reported as a seedborne pest for common bean and soybean, producing issues in the germination stage.…”

Maleic acid and malonic acid reduced the pathogenicity of Sclerotinia sclerotiorum by inhibiting mycelial growth, sclerotia formation and virulence factors

“…Additionally, a study showed a positive correlation between sclerotinia virulence and colony diameter, but no correlation was found between virulence and the number, size, or weight of sclerotia. (Rather et al 2022). Consequently, the relationship between the sclerotia formation and virulence of S. sclerotiorum needs to be further investigated.…”