DIVERSIFICATION OF DEFENSE RESPONSE TO POTATO VIRUS YAMONG ALLOPLASMIC…

DIVERSIFICATION OF DEFENSE RESPONSE TO POTATO VIRUS YAMONG ALLOPLASMIC TOBACCO FORMS– Anna Czubacka, Anna Depta, Teresa Doroszewska

Abstract

Cytoplasmic male sterility is used in plant breeding to obtain forms incapable of self-pollination, which are utilized mainly in breeding of hybrid cultivars. It is based on incompatibility between the cell nucleus and cytoplasm because cytoplasmic male sterile plants are obtained by mutation in the cytoplasmic genome or by substitution of the native cytoplasm with another that of a different species. Alloplasmic forms develop modified, non-functional male generative organs or do not develop them at all. Morphological changes may involve other parts of flow-ers and sometimes a whole plant. An alien cytoplasm may also affect other traits, including resistance to pathogens. In order to determine the effect of alien cytoplasm on tobacco resistance to Potato virus Y (PVY), artificial inoculations with two virus iso-lates differing in virulence were performed. The test included 13 alloplasmic forms of cultivar Zamojska 4 with cytoplasm from Nicotiana wild species and a form with cytoplasm from the mutant obtained within Nicotiana tabacum. Plant resistance was assessed on the basis of disease symptoms and DAS-ELISA immunoenzymatic test results. Differences were observed in the severity and earliness of disease symptoms. Fertile cultivar Zamojska 4 is considered as tolerant to PVY, that is it reacts to infection with mild symptoms like vein clearing and chlorotic spots of the leaves, but not with vein necrosis. In the case of a combination of cell nucleus from cv. Zamojska 4 and cyto-plasm from species N. goodspeedii, N. megalosiphon and N. undulata, alloplasmic forms were not completely resistant, but the level of their tolerance to strong isolate IUNG20 increased compared to that in their male fertile isogenomic counterpart and observed symptoms were delayed. In contrast, tolerance of cms forms with cytoplasm from the species N. eastii, N. occi-dentalis and N. suaveolens was overcome leading to develop-ing severe disease symptoms. Unlike the other cms forms, the form with the cytoplasm of N. tabacum mutant reacted with a development of necrotic symptoms to inoculation with isolate IUNG20, but with delayed mild symptoms when inoculated with the weaker isolate IUNG21. The diversified reaction of different isogenomic alloplasmic forms to viral infection sug-gests that the mechanisms of defense responses depended on the type of cytoplasm.

Keywords: cytoplasmic male sterility, alloplasmic form, Po-tato virus Y, tobacco, Nicotiana