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ARS Home » Southeast Area » Byron, Georgia » Fruit and Tree Nut Research » Research » Publications at this Location » Publication #346983
Title: Heterokaryosis and diploid formation among Brazilian isolates of Macrophomina phaseolina

Author
item PEREIRA, TAIS - Universidade Estadual De Maringá
item ESQUISSATO, GIOVANA - Universidade Estadual De Maringá
item FRANCO, CLAUDINEIA - Universidade Estadual De Maringá
item ZANNUTO, ALEXANDRE - Universidade Estadual De Maringá
item Bock, Clive
item SOARES, DARTANHA - Non ARS Employee
item NUNES, WILLIAM - University Of Maringa
item MATHIAS, PAULO - University Of Maringa
item DE CASTRO-PRADO, MARIALBA - University Of Maringa

Submitted to: Plant Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/11/2018
Publication Date: 11/6/2018
Citation: Pereira, T.S., Esquissato, G.N., Franco, C.C., Zannuto, A., Bock, C.H., Soares, D.J., Nunes, W.M., Mathias, P.C., De Castro-Prado, M.A. 2018. Heterokaryosis and diploid formation among Brazilian isolates of Macrophomina phaseolina. Plant Pathology. 67:1857-1864.

Interpretive Summary: Heterokaryosis is the term used to describe the association of genetically distinct nuclei in a single hypha of a fungus. It is a process involved in the generation of genetic variation as the distinct nuclei within the hyphae fuse to produce a diploid nucleus, resulting in parasexuality. The ability for heterokaryosis depends on the two isolates’ het (heterokaryon incompatibility) or vic (vegetative incompatibility) loci that determine compatibility. The current study evaluated diversity of vegetative compatibility reactions in isolates of Macrophomina phaseolina derived from different hosts. Complementary mutants of each isolate were obtained and paired in all possible combinations. Isolates were classified in vegetative compatibility groups (VCG) according to their ability to form viable heterokaryons. Ten VCGs were identified, two of them containing 2 isolates, and the remainder containing a single isolate. The results demonstrate the ability of M. phaseolina to form viable heterokaryons and heterozygous diploid nuclei, suggesting that the parasexual cycle may be an alternative source of the genetic variability in this species.

Technical Abstract: Heterokaryosis is the association of genetically distinct nuclei in a common hyphal cytoplasm, and is a process involved in the generation of fungal variation. The fusion of the distinct nuclei within a heterokaryotic hyphae produces a heterozygous diploid nucleus and is a stages in the parasexual cycle. A heterokaryon’s viability depends on the isolates’ het (heterokaryon incompatibility) or vic (vegetative incompatibility) loci. The current study evaluated diversity of vegetative compatibility reactions in isolates of Macrophomina phaseolina derived from different hosts. Complementary nit mutants of each isolate were obtained and paired in all possible combinations. Isolates were classified in vegetative compatibility groups (VCG) according to their ability to form viable heterokaryons. Ten VCGs were identified, two of them containing 2 isolates, and the remainder containing a single isolate. When cultured on basal medium (BM), heterokaryons produced both: a) auxotrophic segregants exhibiting the same phenotype of the paired mutants, and b) a fast-growing sector, characterized as a heterozygous diploid sector, named D653, which showed a nit+ phenotype with a growth rate similar to the original wild isolate. When growing in the presence of benomyl, the haploidizing agent, D653 produced auxotrophic haploid segregants exhibiting the nit phenotypes of the crossed mutants. The results demonstrate for the first time the ability of M. phaseolina isolates to form viable heterokaryons and heterozygous diploid nuclei, suggesting that the parasexual cycle may be an alternative source of the genetic variability in this species.