No abstract

Bacterial stalk rot of maize caused by Dickeya zeae previously known as E. chrysanthemi pv. zeae have economic importance of reduced crop yield up to 98.8%. The disease is more prevalent in rainy season in India. The bacterium prefers high temperature and moisture for their growth result is plant toppled down within week. The pathogen has wide host range (maize, rice, tomato, chilli and brinjal etc.) which help to pathogen for long survival in soil. The bacterium characterized by biochemical and molecular tactics. In present, Pel gene and rDNA specific primers are frequently used for D. zeae characterization. The pathogen significantly controls under in vitro and in vivo condition via bleaching powder (drenching of 100 ppm) and antibiotics. The present studies generated data on pathogen nomenclature, etiology, epidemiology, host range, pathogen survival, biochemical, physiological and molecular characterization, germplasm evaluation and disease management.

Oilseed brassicas also known as rapeseed-mustard is an important group of oilseed crop in the world. These crops are susceptible to a number of diseases caused by biotic and mesobiotic pathogens. Among various diseases, Alternaria leaf blight also known as Alternaria dark spot is the most destructive disease of oilseed brassicas species in all the continents. This disease is known to be incited by Alternaria brassicae, Alternaria brassicicola and Alternaria raphani singly or by mixed infection. Alternaria leaf spot pathogens are necrotrophs and produces lesions surrounded by chlorotic areas on leaves, stems and siliquae causing reduction in the photosynthetic areas, defoliation, and early induction of senescence. Alternaria blight causes considerable reduction in quantity and quality of harvested brassica products. The Alternaria leaf blight pathogens are seedborne, soilborne and airborne. The pathogens are greatly influenced by weather with the highest disease incidence reported in wet seasons and in areas with relatively high rainfall. The concentration of conidia, age of the host plants, and wetness period on leaves also influence the severity of the disease. This paper reviews the research and development of Alternaria blight in the oilseed brassicas (rapeseed-mustard) during the past years in relation to pathogen taxonomy, biology, epidemiology, host pathogen interaction and management through chemicals, botanicals, biological, cultural, and biotechnological approaches. The paper also attempts to present future outlook and strategy for Alternaria blight of rapeseed-mustard research.

Bacterial stalk rot (BSR) of maize caused by Dickeya zeae is an important disease in northwest region of India. In the current study, eighty maize lines were evaluated for resistance against this disease. Of these, 20 were moderately resistant, 25 were moderately susceptible and the rest were highly susceptible to BSR. Six lines from each set were randomly selected. Activities of three antioxidant enzymes, viz. phenylalanine ammonia lyase (PAL), peroxidase (POX) and polyphenol oxidase (PPO) were analysed from these three sets of maize lines representing different levels of resistance. A trend of elevated activity of PAL, POX and PPO was observed in all the three sets of maize lines. The results showed significantly more activity of these three enzymes in moderately resistant than highly susceptible maize lines. The activity of PAL and PPO peaked after 48 hr and of POX after 72 hr of challenge inoculation by D. zeae in all the maize lines. The activity of these enzymes further correlated negatively with disease development. Our results show that PAL, POX and PPO play an important role in contributing towards resistance in maize against BSR. K E Y W O R D Santioxidant enzymes, bacterial stalk rot, Dickeya zeae, maize, resistance

In a field study carried out at three different locations, the dissipation of spiromesifen on cotton and chili was studied and its DT50, and DT99 were estimated at each location. Spiromesifen was sprayed on chili at 96 and 192 g a.i. ha(-1) and cotton at 120 and 240 g a.i. ha(-1). Samples of chili fruits were drawn at 0, 1, 3, 5, 7, 10, 15, 21, 30 days after treatment and that of cotton seed and lint at first picking and harvest. Soil samples were drawn 30 days after treatment from 0 to 15 and 15 to 30 cm layer. Quantification of residues was done on GC-MS in Selected Ion Monitoring (SIM) mode in mass range 271-274 m/z. The LOQ of this method was found 0.033 microg g(-1), LOD being 0.01 microg g(-1). The DT50 of spiromesifen when applied at recommended doses in chili fruits was found to be 2.18-2.40 days. Ninety-nine percent degradation was found to occur within 14.5-16.3 days after application. Residues of spiromesifen were not detected in cotton seed and lint samples at the first picking. In soil, no residues of spiromesifen were detectable 15 days after treatment.