Effect of pattern and severity of moisture deficit stress on stalk rot incidence in Sorghum I. Use of line source irrigation technique, and the effect of time of inoculation uri icon

abstract

  • Water deficit occurring after flowering in sorghum (Sorghum bicolor (L.) Moench) predisposes the crop to stalk rot, mainly due to infection by the charcoal rot causal fungus Macrophomina phaseolina (Tassi) Goid., resulting in lodging. The line source (LS) sprinkler irrigation technique which produces a gradient of water deficit stress due to decreasing amount of water supply with increasing distance from the sprinkler line was used to study the relationships between applied water levels, time of inoculation and the degree of charcoal rot incidence.Grain yields were reduced in proportion to the deficit in water supply along the gradient, whereas the incidence of charcoal rot increased. Inoculation with the fungus increased the incidence of disease when natural incidence was low. Sorghum was more susceptible to disease during the later stages of grain filling than during the period immediately after flowering. The rows of plants farthest from the LS, which received the least irrigation, showed disease incidence earlier than those nearest, which were better watered. This was apparent for each of the three different, but highly correlated, parameters of disease spread: percentage of soft stalks; number of nodes crossed; and the length of fungal spread (cm). It is concluded that the LS is an effective method to study the quantitative relationship between severity of water stress and the degree of charcoal rot incidence during rainfree dry seasons

publication date

  • 1987
  • 1987