Abstract - Crop Physiology
Some Effects of the Physiological State of Pigeonpeas on the Incidence of the Wilt Disease
Tropical Grain Legumes Bulletin, (1978), 11, 24-5
ABSTRACT:
The symptoms of the pigeonpea wilt (causal
fungus: Pusarium udum) generally appear during the reproductive
phase, particularly while pod-filling is taking place (Mundkur,
1935).
In an off-season crop planted in December 1974
we observed that while there was a high incidence of wilt during the
pod-filling phase of untreated plants, almost all the plants where
pod development had been prevented by the removal of flowers
remained healthy.
Conversely, we found that the incidence of the
disease increased when the plants were defoliated during the
reproductive phase. In an experiment carried out on medium- duration
cultivars grown during the normal season (planted in June 1975)
leaves were removed at the time flowering began, and subsequent
defoliations were made as new leaves were produced. Different
degrees of defoliation were employed: 33% (one leaf out of three
removed), 50% (alternate leaves removed), 67% (two leaves out of
three removed), 75% (three leaves out of four) and 100% (all leaves
removed). We found that, in general, the incidence of the wilt
increased with the severity of defoliation.
A second experiment was carried out on
medium-duration plants (56 lines in the breeders' plots) which had
been ratooned at the time of the harvest of the first flush of pods.
These plants regenerated new branches and entered into a second
reproductive phase, during which (on March 1 1976) one row of plants
of each line was completely defoliated and another row was left as a
control. Two months later the plants were scored for wilt. Of the
controls, 16 out of 380 plants (4%) had wilted whereas 174 out of
360 defoliated plants (48%) had wilted.
Defoliation of plants in the ICRISAT
patholigists' wilt-sick plot has also been found to lead to an
increase in the incidence of the wilt disease.