Aphid

Accessions of cultivated barley (Hordeum vulgare ssp. vulgare) and its wild progenitor Hordeum vulgare ssp. spontaneum (H. ssp. spont.) were screened for gramine content at the seedling stage. H. ssp. spont. generally had higher gramine concentration compared with cultivated spring barley. Thus gramine concentrations might be raised in modern barley through crossings with selected H. ssp. spont. accessions and repeated back-crossings (BC) of selected offspring to cultivated barley. In the present study, the barley cultivar Lina was used as the recurrent parent. Lina was exceptional among the two-rowed barleys in that it contained moderate levels of gramine, whereas most of the others were very low in gramine. Chromosome-doubled haploid lines (DHs) from the first generation (F1) had a skewed distribution towards higher gramine concentrations and so had the first back-cross generation (BC1F1-DHs). A hairy plant surface, another character proposed to confer resistance to aphids, was al...

The experiment was conducted to study the effectiveness of some insecticides against major sucking pests viz. Jassid, white fly and aphid of okra. The experiment consisted of eight management practices coded from T 1 to T 8 using Randomized Complete Block Design with three replications. At total fruiting stage, minimum fruits infestation was found from T 1 (Admire 200 SL @ 0.5 ml/L of water) (2.7%) while maxi mum from control (19.0%) in number and minimum fruits infestation was (2.5%) whereas maxi mum in T 8 (control) (16.9%) in weight. Tallest plant (227.6 cm), longest fruit (18.69 cm), maxi mum number of fruits (32.6/plant), maximum weight of individual fruit (14.4 g) and yield (8.6 kg/plot and 15.9 ton/ha) was found from T 1 (227.6 cm) while inferior results were found from T 8. Maximum benefit cost ratio (2.9) was found in Admire 200 SL @ 0.5 ml/L of water and minimum benefit cost ratio was recorded from Shobicron 425 EC@ 2 ml/L of water (1.2).

Plant viruses have evolved a wide array of strategies to ensure efficient transfer from one host to the next. Any organism feeding on infected plants and traveling between plants can potentially act as a virus transport device. Such organisms, designated vectors, are found among parasitic fungi, root nematodes and plant-feeding arthropods, particularly insects. Due to their extremely specialized feeding behavior – exploring and sampling all plant tissues, from the epidermis to the phloem and xylem – aphids are by far the most important vectors, transmitting nearly 30% of all plant virus species described to date. Several different interaction patterns have evolved between viruses and aphid vectors and, over the past century, a tremendous number of studies have provided details of the underlying mechanisms. This article presents an overview of the different types of virus-aphid relationships, state-of-the-art knowledge of the molecular processes underlying these interactions, and the remaining black boxes waiting to be opened in the near future.Les virus de plantes ont développé une grande diversité de stratégies pour assurer leur transmission efficace d’un hôte malade vers un nouvel hôte sain. Tout organisme se nourrissant sur une plante infectée, et capable de se déplacer vers d’autres plantes, peut potentiellement transporter des virus. De tels organismes sont dénommés « vecteurs » et se trouvent parmi les champignons phytopathogènes, les nématodes des racines, et les arthropodes, en particulier les insectes. Du fait de leur comportement alimentaire très particulier, explorant et échantillonnant différents tissus végétaux (épiderme, mésophylle et tissus vasculaires), les pucerons sont de loin les vecteurs de virus les plus performants, transmettant près de 30 % des espèces de virus de plantes décrites à ce jour. Plusieurs mécanismes d’interaction virus-puceron très différents ont évolué et, depuis plus d’un siècle, un effort de recherche très important a permis de les décortiquer, au moins pour certaines espèces virales modèles. Cet article présente une synthèse de ces connaissances, les trajets des virus dans leurs pucerons vecteurs, les mécanismes cellulaires et moléculaires de leurs interactions et les grandes inconnues qui persistent et qui devront être élucidées dans les années à venir.

In 2009 a greenhouse experiment was conducted to determine the effects of boron (B) and plant growth-promoting rhizobacteria (PGPR) treatments, applied either alone or in combination, on yield, plant growth, leaf total chlorophyll content, stomatal conductance, membrane leakage, and leaf relative water content of wheat (Triticum aestivum L. cv. Bezostiya) and barley (Hordeum vulgare L. cv. Tokak) plants. Results showed that alone or combined B (0, 1, 3, 6, 9 kg ha−1) and PGPR (Bacillus megaterium M3, Bacillus subtilis OSU142, Azospirillum brasilense Sp245, and Raoultella terrigena) treatments positively affected dry weight and physiological parameters searched in both species. Statistically significant differences were observed between bacterial inoculation and B fertilizer on root and shoot dry weight under non-cold-stress (NCS) and cold-stress (CS) conditions. Leaf total chlorophyll content (LTCC), stomatal conductance (SC), leaf relative water content (LRWC), and membrane leakage (ML) were negatively affected by CS conditions and decreased with reduced temperatures of media, but B and PGPR application alleviate the low-temperature deleterious effect in both species. The greatest SC and LRWC, and the lowest ML, were obtained by 6 kg B ha−1 combined with R. terrigena treatment. The greatest LTCC in both NCS and CS conditions was observed with B. megaterium M3 application alone.

Cross-protection is a natural phenomenon whereby tolerance or resistance of a plant to one virus strain is induced by systemic infection with a second. Eighty years have passed since the phenomenon was first demonstrated by McKinney (1929), who observed that in tobacco plants systemically infected with a “light green strain” of Tobacco mosaic virus (TMV: Genus Tobamovirus), the appearance of yellow symptoms after re inoculation with a TMV “yellow mosaic strain” was repressed. In contrast, a “mild dark green” strain did not repress these yellow symptoms upon challenge. Later Salaman (1933) demonstrated that an avirulent strain of Potato virus X (PVX: Genus Potexvirus) provided protection against superinfection with a virulent strain of PVX in potato. Webb et al. (1952) showed that cross protection against the phloem-limited virus, Potato leafroll virus (PLRV: Genus Polerovirus) could be achieved by infection with the aphid vector and not only by sap inoculation. The first demonstrations of virus-disease control by mild strains were done with Citrus tristeza virus (CTV: Genus Closterovirus) (Grant and Costa, 1951), and Cacao swollen shoot disease (Posnette and Todd, 1955). For many years serological and cross-protection tests were used as routine methods to determine strain interrelationships in plant viruses (Latorre and Flores, 1985). Apparently, cross-protection seemed to be a general phenomenon with viruses for which distinct strains could be found (Fulton, 1986; Sherwood, 1987; Fraser, 1998).