Post-harvest management of ber (Ziziphus mauritiana Lamk) fruit rot (Alternaria alternata Fr. Keissler) using Trichoderma species, fungicides and their combinations

Isolates of Trichoderma species from hot arid regions, fungicides and their combinations were evaluated for the management of ber fruit rot at post-harvest stage. Out of 16 isolates of Trichoderma species, six isolates checked growth of mycelia of Alternaria alternata by more than 55%. A distinct variation in the inherent level of resistance in these six isolates was recorded against 13 common fungicides. None of the Trichoderma species grew in PDA amended with carbendazim even at a very low concentration. In contrast, 100 per cent radial growth was observed in Trichoderma citrinoviride isolate T.c-CIAH224 in the presence of copper oxychloride (250 μg g−1) and mancozeb (100 μg g−1) in PDA medium. Isolate T.v-CIAH240 was antagonistic against A. alternata and tolerant to most of the fungicides tested. This isolate was highly compatible with chlorothalonil, dinocap and wettable sulphur even at 1000 μg g−1 and produced yellowish instead of normal green coloured conidia. Isolate of Trichoderma koningii – T.k-CIAH176, T. citrinoviride – T.c-CIAH224 and those of Trichoderma viride – T.v-CIAH181 and T.v-CIAH240 with inherent tolerance to some of the fungicides have shown better efficacy to suppress the fruit rot pathogen in dual cultures. However isolate T.v-CIAH240 was significantly superior in vitro in the suppression (71%) of the A. alternata through mycoparasitism and apparent secretion of secondary metabolites in the growth medium. Mycoparasitism and competition with the fruit rot pathogen were the mode of action in the majority of the isolates. The growth of A. alternata was completely inhibited in PDA amended with dinocap, propiconazole and tridemorph irrespective of the concentrations. In experiments in vivo, isolate T.v-CIAH240 was significantly effective (75% PEDC- Per cent Efficiency of Disease Control) against post-harvest infection by A. alternata followed by T.v-SBI48 (62 PEDC) and T.v-CIAH149 (44 PEDC). Among the individual fungicide treatments, dinocap and copper oxychloride (50 μg g−1) resulted in 52 PEDC. However, dinocap caused a scorching effect and a foul smell in fruits. Fruit rot control efficacy was enhanced to >70% by T.v-CIAH240 with tridemefon, thiophanate methyl, mancozeb or alcidine at 50 μg g−1 and to >80% with 100 μg g−1 of thiophanate methyl, chlorothalonil, mancozeb and alcidine in ber fruits (cv. Gola). There was a non-significant latent infection caused by isolates T.k-CIAH176, T.c-CIAH224 (T. citrinoviride) and T.v-CIAH240. Such a latent infection was completely suppressed by low concentrations of fungicides when used in combination with T.v-CIAH240. The possible hypothesis involved in management of A. alternata in ber fruits at post-harvest stages using fungicides, Trichoderma species and their combinations is discussed.