Morphological, cultural, pathogenic and molecular studies of Alternaria brassicae infecting cauliflower and mustard in India

Abstract

Dark leaf spot (Alternaria brassicae) is one of the important diseases in crucifers causing serious yield and quality loss in production due to the seed borne nature of the pathogen. Variation in morphology and cultural characteristics among 32 representative Indian geographical isolates of Alternaria brassicae, the causal agent of Alternaria blight of cauliflower (Vegetable) rapeseed-mustard (Oil seed), was studied. All the isolates showed high level of variability in vitro in respect of conidial length, width, and number of septa. Conidia of Uttar Pradesh isolate (CaAbU4) were smallest in size with lowest number of septa. Substantial variation was found in mycelial growth, sporulation among these isolates in different nutrient media. All the isolates did not grow and sporulate abundantly on the same nutrient medium. However, Potato Dextrose Agar, Cauliflower (Host) Agar medium and Carrot Potato Agar were good for all the cultures. Variation in mycelial growth, sporulation was also observed. Cluster analysis of data on cultural variability among thirty two A. brassicae isolates found a close relationship among isolates of both origins viz, from Cauliflower and mustard. Isolates from Uttar Pradesh, Delhi, Haryana and West Bengal were found to be more similar to each other whereas the Rajasthan isolates along with Tamil Nadu and Kerala isolate were distantly related to others. All the isolates were pathogenic in nature but not directly related to the cultural and the morphological characteristics. These isolates were further molecularly characterized by using internal transcribed spacer region where all the isolates were found 56% similar to each other and 99% similar to the A. brassicae isolates present in NCBI database.

Variability Among the Isolates of Alternaria Species Causing Blight in Rape-Seed Mustard (Brassica Juncea L.)

“…As far as colony shape and zonation was concerned, isolates Ab 1, Ab 4 , Ab 7 , Ab 11 and Abl 4 had circular shape with no zonation whereas in Ab 2, Ab 10 , Abl 2 and Abl 5 colony shape was circular with zonation (Table 2). These results are in agreement with earlier workers (Meena et al 2005, Patni et al 2005, Kaur et al 2007, Sharma et al 2013.…”

“…Variability studies are important to document the changes occurring in the population and individuals as variability in morphological and physiological traits indicate the existence of different pathotypes. Many reports on the existence of variability among different Alternaria species have been reported by earlier workers (Verma et al 2006, Kaur et al 2007, Kumar et al 2008, Goyal et al 2011, Sharma et al 2013, Singh et al 2015. The present study was conducted to find out the variability in Alternaria brassicae and A. brassicicola.…”

Isolation and Morpho-Molecular Characterization of Alternaria spp. Causing Grey Leaf Blight of Mustard in Different Regions of Bangladesh

“…was observed in SIR isolate (1.00) which was statistically similar to DINAb (1.33). These results are in agreements with earlier workers (Sharma et al, 2013;Pramila et al, 2014;Singh et al, 2016;Singh 2018, Singh andSingh, 2018), who observed morphological variability in different geographical isolates within Alternaria isolates. Khan et al (2007) Kumar et al (2014) and Giri (2013).…”

“…The colour of colonies varies between light brown to black on PDA. Diversity in colony colour, growth, its margin and topography were noticed among the isolates of A. brassicae by different workers (Sharma et al, 2013, Pramila et al, 2014, Singh et al, 2015, Singh et al, 2016, and Singh and Singh, 2018.…”

Pathogenicity of Alternaria Species Causing Tomato Blight in Agro-Ecological Zones of Kirinyaga County in Kenya

“…Microscopic observation revealed variation in the conidia morphology of the pathogen isolates, which is consistent with the findings of Mugao et al [20] where variability of the tomato early blight pathogen in Mwea was reported. Furthermore, the observations on the morphological traits of the conidia are in agreement with other studies where conidia have differed in breadth, length, and beak and have been reported to be straight, slightly curved, muriform or ellipsoid [44][45][46][47][48]. The conidial transverse and longitudinal septa varied ranging from 1 to 6 and from 0 to 2, respectively, which was in tandem with other studies [45,46,47,49].…”