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Host-range dynamics of Cochliobolus lunatus: from a biocontrol agent to a severe environmental threat.

Louis B, Waikhom SD, Roy P, Bhardwaj PK, Sharma CK, Singh MW, Talukdar NC - Biomed Res Int (2014)

Bottom Line: A maximum likelihood inference based on GPDH locus separated C. lunatus strains into subclusters and revealed the emergence of unclustered strains.The evolving nutritional requirement of C. lunatus in the last decade is exhibited by the invasion of vertebrates, invertebrates, dicots, and monocots.Our results contribute towards a better understanding of the host-range dynamics of C. lunatus and provide useful implications on the threat posed to the environment when C. lunatus is used as a mycoherbicide.

View Article: PubMed Central - PubMed

Affiliation: Institute of Bioresources and Sustainable Development (IBSD), Takyelpat, Imphal, Manipur 795001, India ; Department of Biotechnology, The University of Burdwan, Golapbag More, West Bengal 713104, India ; Department of Biochemistry, University of Yaoundé I, BP 812, Yaoundé, Cameroon.

ABSTRACT
We undertook an investigation to advance understanding of the host-range dynamics and biocontrol implications of Cochliobolus lunatus in the past decade. Potato (Solanum tuberosum L) farms were routinely surveyed for brown-to-black leaf spot disease caused by C. lunatus. A biphasic gene data set was assembled and databases were mined for reported hosts of C. lunatus in the last decade. The placement of five virulent strains of C. lunatus causing foliar necrosis of potato was studied with microscopic and phylogenetic tools. Analysis of morphology showed intraspecific variations in stromatic tissues among the virulent strains causing foliar necrosis of potato. A maximum likelihood inference based on GPDH locus separated C. lunatus strains into subclusters and revealed the emergence of unclustered strains. The evolving nutritional requirement of C. lunatus in the last decade is exhibited by the invasion of vertebrates, invertebrates, dicots, and monocots. Our results contribute towards a better understanding of the host-range dynamics of C. lunatus and provide useful implications on the threat posed to the environment when C. lunatus is used as a mycoherbicide.

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(a) Agarose gel electrophoresis for PCR products (680 bp) from GPDH locus of Cochliobolus lunatus strains separated on a 2.5% agarose gel. Lane-1 and-7 DNA ladder and lane-2, -3, -4, -5, and -6 are Cochliobolus lunatus strains with DDBJ accessions AB859034, AB859035, AB859036, AB859037, and AB859038, respectively. (b) Molecular phylogenetic analysis by maximum likelihood method based on the TN93 + G + I substitution model [22]; AIC is 2974.83; BIC is 3449.49; the highest log likelihood is −1494.28 and bootstrap values ≥50% from 1000 iterations are shown. Subcluster (IV) contains strains of Cochliobolus lunatus which causes foliar necrosis of potato.
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fig3: (a) Agarose gel electrophoresis for PCR products (680 bp) from GPDH locus of Cochliobolus lunatus strains separated on a 2.5% agarose gel. Lane-1 and-7 DNA ladder and lane-2, -3, -4, -5, and -6 are Cochliobolus lunatus strains with DDBJ accessions AB859034, AB859035, AB859036, AB859037, and AB859038, respectively. (b) Molecular phylogenetic analysis by maximum likelihood method based on the TN93 + G + I substitution model [22]; AIC is 2974.83; BIC is 3449.49; the highest log likelihood is −1494.28 and bootstrap values ≥50% from 1000 iterations are shown. Subcluster (IV) contains strains of Cochliobolus lunatus which causes foliar necrosis of potato.

Mentions: The low bootstrap support (≤61%) generated in rDNA ML tree (Figure 2, (I)) made it difficult to determine whether the five strains of C. lunatus causing brown-to-black spot disease of potato in Burdwan Destrict were identical. It could be that all the strains originated from a common source but colonized in different places following dispersion. This is because C. lunatus abundantly produced conidia that can easily be disseminated by air to distant places. To check if the five isolates were identical or not, we used glyceraldehyde 3-phosphate dehydrogenase (GPDH) locus which had been shown to be effective in resolving Cochliobolus species in phylogenetic inference [6, 15]. Partial GPDH locus (Figure 3(a)) was sequenced, as this is one of the house-keeping genes, taken as reference in yeast and fungal systems. Based on sequence alignment for GPDH locus, a total of 340 SNPs out of 708 sites and 325 sites without polymorphism (45.9%) were found. Based on TN93 + G + I substitution model [22], the rate of base transition–transversion was 4.96 and the nucleotide frequencies were A = 23.73%, T/U = 18.55%, C = 33.52%, and G = 24.20% and the overall heterogeneity among taxa was 0.316. The ML tree based on GPDH locus discriminated the five strains of C. lunatus causing foliar necrosis of potato with strong bootstrap support ≥81% (Figure 3(b), (IV)). The overall mean evolutionary distance of 0.03 was observed between the five strains causing foliar necrosis of potato (Figure 3(b), (IV)) relative to other C. lunatus type isolates (Figure 3(b), (I), (II), and (III)).


Host-range dynamics of Cochliobolus lunatus: from a biocontrol agent to a severe environmental threat.

Louis B, Waikhom SD, Roy P, Bhardwaj PK, Sharma CK, Singh MW, Talukdar NC - Biomed Res Int (2014)

(a) Agarose gel electrophoresis for PCR products (680 bp) from GPDH locus of Cochliobolus lunatus strains separated on a 2.5% agarose gel. Lane-1 and-7 DNA ladder and lane-2, -3, -4, -5, and -6 are Cochliobolus lunatus strains with DDBJ accessions AB859034, AB859035, AB859036, AB859037, and AB859038, respectively. (b) Molecular phylogenetic analysis by maximum likelihood method based on the TN93 + G + I substitution model [22]; AIC is 2974.83; BIC is 3449.49; the highest log likelihood is −1494.28 and bootstrap values ≥50% from 1000 iterations are shown. Subcluster (IV) contains strains of Cochliobolus lunatus which causes foliar necrosis of potato.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4060766&req=5

fig3: (a) Agarose gel electrophoresis for PCR products (680 bp) from GPDH locus of Cochliobolus lunatus strains separated on a 2.5% agarose gel. Lane-1 and-7 DNA ladder and lane-2, -3, -4, -5, and -6 are Cochliobolus lunatus strains with DDBJ accessions AB859034, AB859035, AB859036, AB859037, and AB859038, respectively. (b) Molecular phylogenetic analysis by maximum likelihood method based on the TN93 + G + I substitution model [22]; AIC is 2974.83; BIC is 3449.49; the highest log likelihood is −1494.28 and bootstrap values ≥50% from 1000 iterations are shown. Subcluster (IV) contains strains of Cochliobolus lunatus which causes foliar necrosis of potato.
Mentions: The low bootstrap support (≤61%) generated in rDNA ML tree (Figure 2, (I)) made it difficult to determine whether the five strains of C. lunatus causing brown-to-black spot disease of potato in Burdwan Destrict were identical. It could be that all the strains originated from a common source but colonized in different places following dispersion. This is because C. lunatus abundantly produced conidia that can easily be disseminated by air to distant places. To check if the five isolates were identical or not, we used glyceraldehyde 3-phosphate dehydrogenase (GPDH) locus which had been shown to be effective in resolving Cochliobolus species in phylogenetic inference [6, 15]. Partial GPDH locus (Figure 3(a)) was sequenced, as this is one of the house-keeping genes, taken as reference in yeast and fungal systems. Based on sequence alignment for GPDH locus, a total of 340 SNPs out of 708 sites and 325 sites without polymorphism (45.9%) were found. Based on TN93 + G + I substitution model [22], the rate of base transition–transversion was 4.96 and the nucleotide frequencies were A = 23.73%, T/U = 18.55%, C = 33.52%, and G = 24.20% and the overall heterogeneity among taxa was 0.316. The ML tree based on GPDH locus discriminated the five strains of C. lunatus causing foliar necrosis of potato with strong bootstrap support ≥81% (Figure 3(b), (IV)). The overall mean evolutionary distance of 0.03 was observed between the five strains causing foliar necrosis of potato (Figure 3(b), (IV)) relative to other C. lunatus type isolates (Figure 3(b), (I), (II), and (III)).

Bottom Line: A maximum likelihood inference based on GPDH locus separated C. lunatus strains into subclusters and revealed the emergence of unclustered strains.The evolving nutritional requirement of C. lunatus in the last decade is exhibited by the invasion of vertebrates, invertebrates, dicots, and monocots.Our results contribute towards a better understanding of the host-range dynamics of C. lunatus and provide useful implications on the threat posed to the environment when C. lunatus is used as a mycoherbicide.

View Article: PubMed Central - PubMed

Affiliation: Institute of Bioresources and Sustainable Development (IBSD), Takyelpat, Imphal, Manipur 795001, India ; Department of Biotechnology, The University of Burdwan, Golapbag More, West Bengal 713104, India ; Department of Biochemistry, University of Yaoundé I, BP 812, Yaoundé, Cameroon.

ABSTRACT
We undertook an investigation to advance understanding of the host-range dynamics and biocontrol implications of Cochliobolus lunatus in the past decade. Potato (Solanum tuberosum L) farms were routinely surveyed for brown-to-black leaf spot disease caused by C. lunatus. A biphasic gene data set was assembled and databases were mined for reported hosts of C. lunatus in the last decade. The placement of five virulent strains of C. lunatus causing foliar necrosis of potato was studied with microscopic and phylogenetic tools. Analysis of morphology showed intraspecific variations in stromatic tissues among the virulent strains causing foliar necrosis of potato. A maximum likelihood inference based on GPDH locus separated C. lunatus strains into subclusters and revealed the emergence of unclustered strains. The evolving nutritional requirement of C. lunatus in the last decade is exhibited by the invasion of vertebrates, invertebrates, dicots, and monocots. Our results contribute towards a better understanding of the host-range dynamics of C. lunatus and provide useful implications on the threat posed to the environment when C. lunatus is used as a mycoherbicide.

Show MeSH
Related in: MedlinePlus