Genetic diversity and morphological variability of Sclerotinia sclerotiorum isolates of oilseed Brassica in India

Abstract

Sclerotinia stem rot caused by Sclerotinia sclerotiorum (Lib.) de Bary is one of the most serious disease and causes damage to oilseed Brassica. Seventeen geographical isolates of S. sclerotiorum from different geographical locations of India were compared for their growth under artificial culture conditions and the result was validated through random amplified polymorphic DNA (RAPD) markers. Based on the morphological studies, the isolates were grouped into fast growing (SR-01, SR-02, SR-05, SR-16) and intermediate (SR-03, SR-04, SR-07, SR-10 to SR-13, SR-18), though the rest of the isolates showed comparatively a slow mycelial growth rate. In RAPD analysis for their genetic diversity, fifty decamer primers of arbitrary sequences produced 692 scorable amplicons ranging from 180 to 3900 bp in size. Out of these, 385 fractionated fragments were reported polymorphic. As an average, 13-14 unambiguous and reproducible amplified products were generated by single primer (minimum of 4 and maximum of 23 fragments). Hence, the present investigation confirmed the diversity among the different geographical isolates from India.

Morphological and molecular diversity of Sclerotinia sclerotiorum infecting Indian mustard

“…However, Contrary to the present observation, Kumar et al (2016) reported that HSR isolate had dirty white colony colour indicating the presence of two types at the same location for colony colour. Slight variations can occur for colony colour within isolates collected from different hosts as Sharma et al (2013) also found differences in colony colour among the isolates as whitish and dirty white, however, off white and grey white colony colour as observed by them were not found in any of the isolates in the present study. However, Ziman et al (1998) observed a slight variation in colony colour of S. sclerotiorum isolates collected from different hosts, which differentiate from white to brown but the white colour was predominant in most of the isolates.…”

“…Choudhary and Prasad (2012) also observed two types of mycelial growth as fluffy and compact among different isolates. However, Sharma et al (2013) observed three types as scattered, smooth and fluffy mycelial growth among different isolates. The results of Kumar et al (2016) are in agreement with the present study as they have also examined this characteristic in nearly half of the isolates which we have taken afresh from different sites.…”

Genetic Diversity Studies Based on Morphological Variability, Pathogenicity and Molecular Phylogeny of the Sclerotinia sclerotiorum Population From Indian Mustard (Brassica juncea)

“…Mycelial bit touching the stem at 15 cm height was then secured by wrapping the parafilm strip around the stem. Wet cotton swab maintained high humidity during the infection period (Sharma et al, 2013). …”

“…Furthermore, MCGs is another diversity analysis method based on the mycelial compatibility grouping (MCG) has been used in establishing the kinship among S. sclerotiorum isolates from chickpea (Kull et al, 2004; Li et al, 2008). In addition to it, the diversity based on the morphological appearance of sclerotia, mycelial growth, and ascospores formation have also been reported in analyzing the genetic diversity of S. sclerotiorum isolates in previous studies (Li et al, 2008; Sharma et al, 2013). However, polymorphism and genetic diversity of the S. sclerotiorum isolates at the morphological and DNA sequence level has not been comprehensively studied so far especially for the isolates from Brassica species of India.…”

“…In pursuance of basic understanding about pathogenicity, diversity and distribution pattern of the S. sclerotiorum were extensively studied on isolates collected from various host species like chickpea (Mandal and Dubey, 2012), vegetable crops (Choudhary and Prasad, 2012), cumin (Prasad et al, 2017), carnation (Kumar et al, 2015), oilseed Brassica (Sharma et al, 2013), and their identity were established on the basis of morphological features and cultural conditions. However, major variation in the growth characteristics has been reported in the growing collection of S. sclerotiorum isolates even as they belong to the same Sclerotinia species.…”