Brassica amendments and summer irrigation for the control of Macrophomina phaseolina and Fusarium oxysporum f. sp. cumini in hot arid region

The combined effect of Brassica amendments (mustard oil–cake or mustard residue at 2.5 tons ha-1) and summer irrigation was tested for survival of Macrophomina phaseolina and Fusarium oxysporum f. sp. cumini and on the severity of dry root rot on clusterbean in the rainy season and on wilt of cumin in the subsequent winter season in the same field. Seed coating with a Bacillus sp., an antagonist bacterium against M. phaseolina, was also integrated with pod residues to improve control of dry root rot. The soil temperature of amended soil after one summer irrigation in June ranged from 38–44°C at 15-cm depth. These temperatures were 0.5–5°C higher than those recorded in unamended soil for the same period and 6–16°C higher when amendments were incorporated in July. A single summer irrigation led to a significant reduction in viable propagules of M. phaseolina, Fusarium oxysporum f. sp. cumini, plant mortality due to dry root rot in clusterbean and incidence of wilt on cumin from Brassica amendments, as compared with the application of amendments in July. A seed coating with Bacillus sp. alone was also effective, but integration with residues did not improve control of dry root rot. In general, amended soil held more soil moisture than unamended soil. These findings have a potential value for irrigated pockets in the hot arid zone of India as well as for many countries with the appropriate climatic conditions

Relative Efficacy of On-Farm Weeds as Soil-Amendement for Managing Dry Root Rot of Clusterbean in an Arid Environment

The effectiveness of certain on-farm weeds as soil amendments was ascertained against Macrophomina phaseolina, a soil-borne pathogen causing dry root rot of crops grown under rainfed conditions in arid regions. Population changes in M. phaseolina were determined in soils amended separately with residues (1%, w:w) of Aerva persica, Celosia argentea, Corchorus depressus, Euphorbia hirta, Heliotropium subulatum and Polycarpaea corymbosa, for a period of 90 days. Significant reductions by 90.4–100% in the population of M. phaseolina were achieved with all the weed residues except P. corymbosa. Celosia and Euphorbia residues completely eradicated viable propagules of M. phaseolina. A strong increase (44–61%) in the population of antagonistic actinomycetes was also found in soil amended with Corchorus and Euphorbia. In field tests, soil amended (50 g m2) with Euphorbia, Aerva and Celosia residues significantly reduced dry root rot incidence on clusterbean and also reduced M. phaseolina propagules in the soil. However, dry root rot incidence in Polycarpaea-amended soil (5.8–24.6%) was not significantly different from that in non-amended soil (4.3–25.3%) in both years of the experiment. P. corymbosa also increased the number of propagules of M. phaseolina in the soil. The results demonstrate that dry root rot of rainfed-cultivated annual crops in arid land can be managed with certain weeds as a soil amendment

Cumin wilt management – a review

Cumin (Cuminum cyminum L.) is one of the oldest seed spice and an important production constraint is wilt caused by Fusarium oxysporum f. sp. cumini Prasad and Patel (Foc) and crop losses could be up to 60%. Maximum population of Foc was estimated at 0-5 cm soil depth in the presence of crop, but the population density tended to decline progressively with distance from the surface. Resting structures of the Foc, the chlamydospores, survive in the soil for more than 10 years. The inoculum density in the soil increases with each year of cumin cultivation and is directly proportional to disease incidence in the field. In this review, an effort has been made to compile research findings generated during past four decades on symptomatology, ecology and management strategies. In the absence of resistant sources against Foc, to reduce population of pathogen below the economic threshold level, integration of cultural, chemical and biological control measures is the only effective way to manage this diesease. &nbsp

Combined effects of biosolarization and Brassica amendments on survival of biocontrol agents and inhibition of Fusarium oxysporum

Biocontrol agents (BCAs) added in the soil or applied to the seeds face many abiotic and biotic stress challenges. Only those BCAs that survive under harsh conditions perform well. Improving the survival of BCAs along with inhibiting the biotic stresses imposed by bacterial, fungal, and viral infections has been a major challenge in agriculture, especially in hot-arid climates. The present study aimed to evaluate the individual and combined effects of soil solarization and Brassica amendments on the survival of two biocontrol agents (BCAs), namely Trichoderma harzianum and Aspergillus versicolor, and on the reduction in a cumin wilt pathogen Fusarium oxysporum f. sp. cumini (Foc) in a field experiment conducted for two years under hot-arid climates. BCAs performed well in the solarized pots, it caused the maximum reduction in viable F. oxysporum propagules, significantly higher at 5 cm than at 15 cm of depth. Brassica amendment with BCAs caused a greater decrease in F. oxysporum propagules (95.7 to 96.7%) compared to a combination of BCAs and solarization (91.0 to 95.7%). Combining T. harzianum with A. versicolor increased the survival of T. harzianum, whereas integration with Brassica amendment could only improve the survival of T. harzianum at a depth of 5 cm and not at lower depths. The slightest decrease in A. versicolor population at high soil temperature was estimated when combined with T. harzianum. However, combining A. versicolor with Brassica amendment improved the survival of A. versicolor at high compared to low soil temperatures. Still, elevated soil temperature reduced the viable propagules. These studies demonstrate that both the native BCAs are compatible, and their integration with the Brassica amendment improves their survival and ability to reduce the population of cumin wilt pathogen. Thus, these BCAs with Brassica amendments can survive and perform well under hot-arid climates

Combined Effects of Biosolarization and Brassica Amendments on Survival of Biocontrol Agents and Inhibition of Fusarium oxysporum

Biocontrol agents (BCAs) added in the soil or applied to the seeds face many abiotic and biotic stress challenges. Only those BCAs that survive under harsh conditions perform well. Improving the survival of BCAs along with inhibiting the biotic stresses imposed by bacterial, fungal, and viral infections has been a major challenge in agriculture, especially in hot-arid climates. The present study aimed to evaluate the individual and combined effects of soil solarization and Brassica amendments on the survival of two biocontrol agents (BCAs), namely Trichoderma harzianum and Aspergillus versicolor, and on the reduction in a cumin wilt pathogen Fusarium oxysporum f. sp. cumini (Foc) in a field experiment conducted for two years under hot-arid climates. BCAs performed well in the solarized pots; it caused the maximum reduction in viable F. oxysporum propagules, significantly higher at 5 cm than at 15 cm of depth. Brassica amendment with BCAs caused a greater decrease in F. oxysporum propagules (95.7 to 96.7%) compared to a combination of BCAs and solarization (91.0 to 95.7%). Combining T. harzianum with A. versicolor increased the survival of T. harzianum, whereas integration with Brassica amendment could only improve the survival of T. harzianum at a depth of 5 cm and not at lower depths. The slightest decrease in A. versicolor population at high soil temperature was estimated when combined with T. harzianum. However, combining A. versicolor with Brassica amendment improved the survival of A. versicolor at high compared to low soil temperatures. Still, elevated soil temperature reduced the viable propagules. These studies demonstrate that both the native BCAs are compatible, and their integration with the Brassica amendment improves their survival and ability to reduce the population of cumin wilt pathogen. Thus, these BCAs with Brassica amendments can survive and perform well under hot-arid climates