A BACTERIAL DISEASE OF TURNIP 

 {BRASSICA NAPUS). 



By S. G. JONES, M.Sc. 

 Lecturer in Botany, University College of Wales, Aberystwyth. 



(With Plate ill.) 



Of recent years a disease of root-crops known to farmers in Nortli Wales 

 is one in which the heart or core of the root is converted into a soft 

 putrid mass but which leaves the rind and mature foliage intact. The 

 disease is prone to appear on land treated with lime as a pre%'entive 

 against the roots being attacked by Plasmodiophora hrassicae or when 

 the land has received a heavy dressing of nitrogenous fertiUzers. It is 

 common knowledge that nitrogenous manures have a tendency to force 

 the crop and so produce watery, sappy roots which easily fall prey to 

 disease. Recently it was brought to the writer's notice by one of the 

 County Organizers for Agriculture in Wales that some of the farmers 

 in his area were strongly disinclined to lime the land for root-crops 

 because this treatment was favourable to the appearance of "soft-rot." 

 There is probably some modicum of truth in this contention, for as will 

 be seen below, the writer in the investigation of the present disease 

 found that the organism isolated refused to grow on any media which 

 were not neutral or alkaline. The writer observed and investigated this 

 disease on a crop of white turnips grown on the farm of the I'niversity 

 College of North Wales and the land here had received a dressing of 

 nitrate of soda. A casual glance at the crop did not show anything 

 unusual, in fact judging from the amount of green foliage the crop looked 

 very healthy. Closer examination however showed that the very young 

 leaves at the centre of the crown had been destroyed thus forming a tiny 

 wound into which one could push a probe without obstruction to the 

 depth of some three or four inches. The fully expanded leaves very 

 effectively concealed the wound and the disease seemed evidently con- 

 fined to the internal tissues leaving the foliage and rind quite firm even 

 up to time of harvesting the crop. Indeed the extent of damage was 

 only fully revealed at the time of lifting when the harvester's knife 



