4. Screening tecniques of air born
diseases
• These diseases are caused by fungi classified
either necrotrophic or biotrophic.
Aerial fungal pathogens that cause diseases
such:
• as grey mould, spot, ascochyta blight,
anthracnose,
• rust, powdery mildew and downy mildew
5. Different screening tecniques:
• FIELD SCREENING
• the varities to be evaluated screened for resistance
may be raised in feild under natural infestation,
either in endemic areas
• By adapting techniques for increasing field
infestation cultural pratices such as closer spacing to
creating the most desirable humid microclimate
within the crop , application of nitrogen and
irrigation.
6. • In case of insects such as plants hopper , flies
etc that have tendency to move at a rapid
speed , fibre glass mesh cages may be kept on
microplot and artificially reared insect
released at a specified number per area.
• For diseases artificial inoculation can be done
• The whole plant population should be
effected uniformly so that plant which escape
infestation is not graded as resistance.
9. • GREEN HOUSE SCREENING:
• The screening of germplasm under glasshouse
conditions
• often allows cultivars to be screened rapidly,
using
• techniques that are easily reproducible and in
some instances
• during periods when environmental conditions
• in the field are not conducive for disease
development.
