, Volume 67, Issue 4, pp 293-305

Synthesis of heterokaryons and parasexual reaction in Fusarium species

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Summary

Evidence of heterokaryosis in a single hypha and genetic recombination through the parasexual reaction have been demonstrated in a crossing between Fusarium oxysporum f. sp. callistephi and F. redolens. Intraspecific crossings produced only prototrophic colonies. Formation of stable diploid conidia could not be detected. Analysis of hyphae from 15 sectors from interspecific crossings found to be homokaryotic and showed either prototrophic colonies or other recombinants. The following reaction types were detected during the analysis: 1 $$\begin{gathered} \left. \begin{gathered} {\text{ Mutant }}R{\text{ }}79{\text{ }}aden^ - ,lys^ + ,{\text{W}},{\text{ purple red}} \hfill \\ {\text{ }}A{\text{ }}74{\text{ }}aden^ + ,lys^ - ,{\text{ C, white }} \hfill \\ \end{gathered} \right\}{\text{ Mating partners}} \hfill \\ \operatorname{Re} {\text{combinants: A }}aden^ + ,{\text{ }}lys^ + ,{\text{ W slow growing}} \hfill \\ {\text{ B }}aden^ + ,{\text{ }}lys^ + ,{\text{ W, fast growing}} \hfill \\ {\text{ C }}aden^ + ,{\text{ }}lys^ + ,{\text{ W, purle red}} \hfill \\ {\text{ D }}lys^ - ,{\text{ }}meth^ - {\text{, W, lysine - methionine diauxotroph}} \hfill \\ {\text{ E }}lys^ - ,{\text{ }}meth^ - {\text{, C, lysine - methionine diauxotroph}} \hfill \\ {\text{ F }}lys^ - ,{\text{ }}aden^ + ,{\text{ W, lysine auxotroph}} \hfill \\ {\text{ G }}lys^ - ,{\text{ }}aden^ + ,{\text{ C, lysine auxotroph}} \hfill \\ {\text{ }}\left. \begin{gathered} {\text{Mutant }}R{\text{ 4 }}aden^ - ,lys^ + ,{\text{ W, white}} \hfill \\ {\text{ }}A{\text{ 74 }}aden^ + ,lys^ - ,{\text{ C, white}} \hfill \\ \end{gathered} \right\}{\text{ Mating partners}} \hfill \\ {\text{ Recombinant: A }}aden^{\text{ + }} ,lys^ - ,{\text{W}}. \hfill \\ \end{gathered} $$

The relatively high frequency of recombination in the nuclei through haploidization and mitotic crossing-over indicates a close affinity between the two species.