THE DETERMINATION OF THE REACTION OF BARLEY VARIETIES TO LOOSE SMUT

The inoculation of barley with loose smut ( Ustilago nuda ) using various techniques has given results which do not reflect the known behaviour of varieties under natural conditions. No consistent results have been obtained, but all the varieties thus inoculated could become infected. No variety therefore possessed true physiological resistance and in the field some must escape infection. The inoculation techniques obviously overcame this escape.
A method has been devised which, with the varieties used, has reflected their behaviour in the field. Drops of coloured water or spore suspension are allowed to fall from a height on to ears at anthesis. Grains on the ears of varieties which do not become infected in the field do not become coloured or infected (depending on the drops used), while grains of varieties susceptible in the field do become coloured or infected. This is due to the glumes of the former group of varieties remaining closed, and so preventing access of smut spores under natural conditions.