Virus Diseases of Peanut

Brassica crops are grown worldwide for oil, food and feed purposes, and constitute a significant economic value due to their nutritional, medicinal, bioindustrial, biocontrol and crop rotation properties. Insect pests cause enormous yield and economic losses in Brassica crop production every year, and are a threat to global agriculture. In order to overcome these insect pests, Brassica species themselves use multiple defence mechanisms, which can be constitutive, inducible, induced, direct or indirect depending upon the insect or the degree of insect attack. Firstly, we give an overview of different Brassica species with the main focus on cultivated brassicas. Secondly, we describe insect pests that attack brassicas. Thirdly, we address multiple defence mechanisms, with the main focus on phytoalexins, sulphur, glucosinolates, the glucosinolate-myrosinase system and their breakdown products. In order to develop pest control strategies, it is important to study the chemical ecology, and insect behaviour. We review studies on oviposition regulation, multitrophic interactions involving feeding and host selection behaviour of parasitoids and predators of herbivores on brassicas. Regarding oviposition and trophic interactions, we outline insect oviposition behaviour, the importance of chemical stimulation, oviposition-deterring pheromones, glucosinolates, isothiocyanates, nitriles, and phytoalexins and their importance towards pest management. Finally, we review brassicas as cover and trap crops, and as biocontrol, biofumigant and biocidal agents against insects and pathogens. Again, we emphasise glucosinolates, their breakdown products, and plant volatile compounds as key components in these processes, which have been considered beneficial in the past and hold great prospects for the future with respect to an integrated pest management.

https://hal.archives-ouvertes.fr/hal-00886509/document

Defence mechanisms of Brassicaceae: implications for plant-insect interactions and potential for integrated pest management. A review

Alternaria blight disease caused by Alternaria brassicae (Berk.) Sacc. has been reported from all the continents of the world affects most cruciferous crops and is one among the important diseases of rapeseedmustard causing severe yield losses with no proven source of transferable resistance in any of the hosts. The pathogen is greatly influenced by weather with the highest disease incidence reported in wet seasons and in areas with relatively high rainfall. A. brassicae can affect host species at all stages of growth, including seed. Symptoms of the disease are characterized by formation of spots on leaves, stem and siliquae. Identification of signal molecules for induced resistance, development of bioformulations and disease forecasting module will enable trigger newer strategies for eco-friendly disease management for providing safer Alternaria blight free production of rapeseed-mustard with improved crop health.

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Alternaria blight: a chronic disease in rapeseed-mustard

Cabbage aphid, Brevicoryne brassicae L., and turnip aphid, Lipahis eyrsimi Kalt., are the regular insect pests of Brassica crops in Southern Punjab, Pakistan. Population development of and losses to yield and yield components due to these two aphid species were examined on late sown crops of Brassica napus L., Brassica juncea L., and Brassica carinata A. Braun under sprayed and unsprayed conditions during 2007-08 at Mulatn. Populations of both the species of aphids were statistically similar on three species of Brassica in unsprayed plots. Losses to yield, plant height, numbers of pods per plant, pod length, numbers of seeds per pod and pod weight were statistically similar across all the three species in untreated plots, those of thousand seeds weight was different . B. napus, B. juncea and B. carinata suffered 75.06, 77.25 and 81.86% losses from aphids in yield where insecticides were not applied. Pod weight, pods per plant and yield per ha., was significantly increased by application of insecticides for all the three species. Due to heavy losses in yield and yield components we recommend insecticide application for reducing losses due to aphids.

Losses in yield and yield components caused by aphids to late sown brassica napus l., brassica juncea l. and brassica carrinata a. braun at multan, punjab (pakistan)

Alternaria brassicae (Berk.) Sacc., a necrotrophic fungus devastating oilseed Brassicacrops in India, causes up to 47% reduction in seed yield. Morphological characteristics of different isolates revealed variation in growth, shape and pigmentation of colony, conidial measurements and number of septa. Conidial length varied from 106.7 to 285.9 µm, width 33.5 to 57.0 µm and beak length 41.4 to 180.0 µm. Number of horizontal septa varied from 3.2 to 8.0 and vertical 0.3 to 1.4. Different synthetic media showed profound variation in mycelial growth of A. brassicae isolates and the poor sporulation indicated that the fungus requires some organic sources of nutrition for better growth and sporulation. The degree of sporulation of A. brassicae isolates is a function of nutrition proved for the first time. Per cent inhibition of mycelial growth showed diverge among A. brassicae isolates, which may be due to the variation towards fungicidal sensitivity among isolates. Pathogen aggressiveness study demonstrated the existence of considerable variation in tolerance ofBrassica species to A. brassicae, which is proved with the location specific disease severity.

	 

	Key words: Variability, Alternaria brassicae, fungicides sensitivity, aggressiveness,Brassica.

Aggressiveness, diversity and distribution of Alternaria brassicae isolates infecting oilseed Brassica in India

Forecasting of Lipaphis erysimi on oilseed Brassicas in India—a case study

Epidemiology and forecasting of Alternaria blight of oilseed Brassica in India - a case study.

Field experiments were conducted during three post rainy (rabi) seasons of 2001-2004 at Bharatpur, New Delhi and Mohanpur to study the effect of sowing dates and cultural environment on accumulation of growing degree-days vis-a-vis occurrence of different phenological events on oilseed Brassica cultivars 'Varuna', 'Rohini', 'Pusa Jaikisan' [Brassica juncea (L.) Czem. and Coss.] and 'Binoy' (B, rapa L. var yellow sarson) sown at seven-day intervals starting from 1 October. October sown crop recorded higher seed yield due to exposure to higher growing degree-days. Variations were also noticed among locations. Equation developed from the study can be used for simulation of phenology and growth of mustard.

Thermal requirement of oilseed Brassica cultivars at different phenological stages under varying environmental conditions

Experiments were laid out at Bharatpur, New Delhi and Kangra with Indian mustard (Brassica juncea) cvs ‘Varuna’ and an important one in the locality sown on 10 dates at weekly intervals. First appearance of white rust disease (Albugo candida) on leaves and pods (staghead formation) of mustard occurred between 36 and 131 days after sowing (d.a.s.), 60 and 123 d.a.s., respectively. Severity of white rust disease on leaves was favoured by >40% afternoon (minimum) relative humidity (RH), >97% morning (maximum) RH and 16–24°C maximum daily temperature. Staghead formation was significantly and positively influenced by 20–29°C maximum daily temperature and further aided by >12°C minimum daily temperature and >97% morning (maximum) RH. Regional and cultivar specific models devised could predict, at a few weeks after sowing, the crop age at which white rust first appeared on the leaves, as staghead, the highest rust severity on leaves, staghead numbers and the crop age at peak rust severity on leaf, highest staghe...

N. V. K. Chakravarthy

Papers

Forecasting of Lipaphis erysimi on oilseed Brassicas in India—a case study

Epidemiology and forecasting of Alternaria blight of oilseed Brassica in India - a case study.

Thermal requirement of oilseed Brassica cultivars at different phenological stages under varying environmental conditions

Epidemiology and development of forecasting models for White rust of Brassica juncea in India