Resistance of Lolium multiflorum/Festuca arundinacea hybrids to some diseases of their parent species

Summary

A Lolium multiflorum/Festuca arundinacea hybrid (amphiploid) and three successive generations from backcrosses to L. multiflorum, together with the two parental populations, were screened for resistance to some diseases that commonly attack either or both of the parent species. Where, as with Rhyncho-sporium secalis, both species were susceptible to infection, the amphiploid was also susceptible. Where one or other of the parents was highly resistant, the amphiploid was equally resistant; this occurred with Puccinia coronata var. lolii, P. coronata var. festucae, Drechslera dictyoides and ryegrass mosaic virus.

Resistance to P. coronata var. lolii persisted largely into the first and second backcross generations, but had disappeared by the third. Similarly, there were equal proportions of plants immune to ryegrass mosaic virus in first and second backcross generations, but none were immune in the third. However, resistance to this virus appeared more complex. Only one third of progeny from the first backcross could not be infected and the remainder showed a broad range of symptoms from only very mild chlorosis to severe chlorosis and necrosis.