Development of alternative, chemical‐free approaches for control of postharvest fungi on a commercial scale has become a challenge for plant pathologists in recent years. Although there are several established techniques such as heat that are used as postharvest treatments, they often have disadvantages, including alteration of food quality due to physiological responses to the treatment, or environmental pollution. A promising new postharvest treatment is cold plasma, which is a gas‐derived mix of atoms, excited molecules and charged particles. Cold plasma has no known adverse effects on fresh produce or the environment. It is an established technology in the medical field and has been demonstrated to successfully control bacterial pathogens that cause food safety issues. This review focuses on the potential of cold plasma technology for postharvest disease control, especially those caused by fungi. An overview of plasma generation systems is provided, and in vivo and in vitro research is reviewed to consider benefits, limitations and research gaps in the context of cold plasma as a potential method for controlling postharvest fungal pathogens. Finally, recommendations are provided for the application of this technology in commercial facilities.

This study investigated the use of cold plasma to reduce the in vitro growth of two postharvest fungal plant pathogens, Colletotrichum alienum and C. fioriniae, isolated from avocados. Cold plasma (CP) was used to treat pure cultures and conidial suspensions of both pathogens, for 180 or 360 s, in either open or sealed environments from varying distances. In an open environment, the 360 s treatment at a distance of 5 cm reduced the colony growth of freshly inoculated cultures to less than 2 mm/day compared to the control of more than 8 mm/day, and treatment of conidial suspensions resulted in almost 100% reduction of conidial germination. In the same environment, the 180 s CP treatment did not significantly reduce the colony growth of fresh or actively growing cultures, but did suppress the germination of conidia by up to 80%. In a sealed environment, the 360 s CP treatment also effectively reduced the growth of freshly inoculated cultures, with no growth for some isolates. Production of reactive oxygen and nitrogen species was observed during treatment, and these may have contributed to the reduction in growth and germination. These results demonstrate the potential of CP for the control of two Colletotrichum species.

Cold plasma, an ionized gas produced by applying an electrical current to air, can be used to produce plasma‐activated water (PAW), which has excellent antimicrobial properties. In this study PAW was applied to conidia of Colletotrichum alienum to investigate its impact on conidial germination in vitro. PAW was produced by treating tap, deionized, or distilled water with cold plasma for 30 or 60 min to produce PAW30 or PAW60, each of which was then incubated for up to 24 hr with a conidial suspension of C. alienum in a ratio of 1:1, 1:2, or 1:3 (conidial suspension:PAW), and the percentage germination measured. The greatest reduction in germination occurred when conidia were incubated with PAW60 produced from deionized water or distilled water, for all ratios. For PAW30, deionized water was the most effective for all three ratios, and on this basis, deionized water was selected for all further experiments. PAW produced from smaller volumes of water and at shorter distances from the cold plasma source was more effective at reducing germination. Treatment of conidia with acidified water was not as effective as PAW at inhibiting germination. Nitrates and nitrites were present in the PAW in varying concentrations and may have contributed to the inhibition of germination. PAW retained activity and reduced germination even after storage for 15 days. These findings demonstrate the potential of PAW as a novel treatment for postharvest fungal pathogens.

The experiment was conducted at the field laboratory of the Department of Genetics and Plant Breeding, Bangabandhu Sheikh Mujibur Rahman Agricultural University, Gazipur during November 2008 to March 2009 to estimate the genetic diversity of exotic and local onion. Ten genotypes of onion were evaluated for 16 characters in a randomized complete block design to study the genetic divergence through multivariate analysis. Ten genotypes formed three clusters. Cluster III contained maximum number of five genotypes. Cluster I and II contained three and two genotypes, respectively. The inter cluster distance was larger than the intra cluster distances. The inter cluster distance was maximum between the cluster II and III (6.336) and minimum between the cluster I and II (3.876). The intra cluster distance in the entire three clusters was more or less low, indicating that genotypes within the same cluster were closely related. Considering clustered distance and cluster mean, the intra cluster distance revealed that the genotypes Indian big (G1) and Patnai pink (G5) from the cluster II and genotypes Taherpuri, Indian medium (G1), Big single bulb (G7), Big double bulb (G8), Small single bulb (G9) and Small double bulb (G10) from the cluster III may be selected as parents for future breeding program.The Agriculturists 2015; 13(1) 26-34

An experiment was conducted at Microbiology Laboratory of Plant Pathology Department, Bangabandhu Sheikh Mujibur Rahman Agricultural University (BSMRAU) during 2007 to determine the virulence and variation in symptom development by Fusarium oxysporum f. sp. phaseoli isolates at different growth stages such as emergence and early vegetative stage, branching and rapid vegetative growth stage and early flowering stage of Bush bean, and in-vitro control of the pathogen with the selected fungicides. Eight isolates of this pathogen were collected from different pathology laboratory of BARI, BAU and BSMRAU. IS3 isolate collected from Bushbean seeds were found most virulent in pathogenicity test such as pre-emergence mortality, root rot, root lesion, leaf yellowing and wilting when this isolate was inoculated at different growth stages of bush bean. Four fungicides such as Vitavax, Rovral, Cupravit and Aimcozim were evaluated invitro to test the efficacy against isolate IS3. Aimcozim at different concentration (50-400 ppm) was found most effective in in-vitro evaluation.

Biological control through habitat management leads to sustainable insect pest control. Different types of land composition such as multiple landscapes, patchiness of landscapes enhance the natural enemies which ultimately lead to control of insect pest. Plant characteristics such as flower shape, flower color and blooming period ensures excess food for natural enemies like nectar and pollen. Moreover, some agricultural practices such as tillage, crop rotation, and intercropping influence the natural enemies especially parasitoid and predators. Consequently, they increase longevity and fecundity of parasitoid and predator that help to control insect pest. One of the most important recently used methods is push-pull which consists of semiochemicals called Herbivore-Induced Plant Volatiles (HIPVs). This compound has been used to prevent pest and attract natural enemies.

Previous studies demonstrated that a reduction in germination of Colletotrichum alienum conidia could be achieved following treatment with cold plasma (CP) or incubation with plasma‐activated water (PAW). In this study, the mode of action of CP and PAW on C. alienum conidia was explored using transmission electron microscopy. Following treatment of the conidia, noticeable ultrastructural changes were observed, including cell wall maceration, disorganization of the cytoplasm and vacuole, and changes to the nuclei and mitochondria. Disorganization of the cytoplasm was exhibited by 85% of conidia after CP or PAW treatment. Also, 85% of conidia were observed with disorganized vacuoles after 6 min of CP treatment and 65% after 3 hr incubation in PAW. Further, 45% or more conidia had modified cell walls after PAW incubation or CP treatment. Deformation of conidia was observed in 23% of conidia after PAW incubation. These ultrastructural changes are a likely reason for the reduced germination of C. alienum conidia following CP or PAW treatment.