Pollen grain development is highly sensitive to temperature stress in V itis vinifera

Abstract Background and Aims The grapevine ( V itis vinifera   L .) is often exposed to above optimal temperature in the field. Although genomic analysis has been underway for over a decade, studies on grapevine chromosome behaviour and nuclear topology are scarce. Here, we explore the influence of hot‐water sanitation treatments, involving immersing dormant canes in water at 50° C for 45 min or heat exposure to 42° C for 4 h during reproductive growth, on the dynamics of somatic nuclei and meiotic chromosomes. Methods and Results Chromatin behaviour was analysed by 4′,6‐diamidino‐2‐phenylindole hydrochloride staining, fluorescent in situ hybridisation with various probes, and immunocytochemistry with an antibody against DNA methylated at cytosine residues. Sanitation procedures had no effect on somatic or meiotic chromatin behaviour or nuclear topology. In contrast, although meiosis proceeded normally during exposure to 42° C for 4 h, this heat regime resulted in highly disrupted pollen grains likely due to cell wall fragility and in a significant reduction in pollen viability. Conclusions Grapevine pollen mother cell meiosis is described in detail for the first time. Although hot‐water sanitation treatments had no effect on chromatin behaviour, the range of temperature to which grapevines are often exposed to in the field induces gametophyte malformations associated with decreased pollen viability. Significance of the Study Heat stress during reproductive development disrupts pollen grain development and can therefore have implications on yield. Such knowledge may offer a tool for identification and selection of heat‐tolerant genotypes.