Abstract:
Charcoal rot, incited by Macrophomina phaseolina (Tassi) Goid, is a
serious disease of many crops, inflicting 100 % yield losses in Mung and Mash
bean under dry and hot conditions. Therefore, biology and management of the
disease was studied in 65 isolates of the fungus collected from 14 districts of
Punjab and Khyber Pukhtoon Khwa. Morphologically, the isolates differed
significantly in their growth behaviour, sclerotial size and weight. Sixteen isolates
developed fast growth, 11 were slow and the rest were intermediate. Nine isolates
produced large sized sclerotia, 26 small sized while the left over were intermediate.
Similarly 35 isolates produced high weight of sclerotia, 12 low and the rest were
intermediate in weight. Isolates collected form D.G.Khan, Chakwal and Bhakar
were found to be highly variable. All the isolates differed in variability in
aggressiveness. On the basis of infection, 23 isolates appeared to be highly virulent,
5 were least virulent and the remaining isolates showed intermediate response.
Biological agents, antagonistic plant materials and chemicals were tested against
the disease. All the test antagonists inhibited the growth of M. phaseolina
significantly, maximum of 79.63 % with T. harzianum and minimum of 58.14 %
with T. pseudokoningii over control. Antagonists also affected survival of mung
and mashbean plants significantly which was significantly higher at higher
concentrations of all the antagonists. Survival of mung and mash plants treated with
T. harzianum @ 2 x 10 8 was found maximum (83.33 and 80.0%) and minimum in
case of T. pseudokoningii. Similarly, all the test plants inhibited the growth of M.
phaseolina significantly, maximum in case of Carum lopticum (68.61%) and2
Azadirachta indica (55.68%) the minimum (15.96%) inhibition with Nerium
indicum at 100% concentration. Percentage inhibition was significantly higher at
higher concentrations of all the plants as compared to other concentrations.
Survival of plants was also found to be maximum, where seeds were treated with
C. lopticum (83.33 and 76.66%) and A. indica (80.0 and 73.33%) at 100 %
concentration. Mentha piperita and Foeniculum vulgare showed minimum plant
survival (40 %) of mung and mash respectively. All fungicides inhibited the growth
of M. phaseolina significantly. Maximum efficacy was shown by Benomyl
(83.89%) and Carbendazim (79.11%) while Copperoxychloride showed the
minimum (23.57 %). The mung and mashbean germplasm varied greatly in
reaction to charcoal rot under inoculated conditions. In glass house studies, 14 out
of 100 mungbean accessions appeared to be highly resistant as against 34
accessions under field conditions. In case of Mash only 5 lines out of 100
accessions were found to be highly resistant in pot experiment as against 12
accessions in the field.