Evaluation of a core collection of Brassica oleracea accessions for resistance to Brevicoryne brassicae, the cabbage aphid

A rapid, simple and reliable technique was developed for evaluating Brassica accessions in the glasshouse for resistance to Brevicoryne brassicae, the cabbage aphid. Brassica accessions were grouped into crop types with similar habit and vigour for evaluation. 401 Brassica oleracea accessions, representing the genetic and geographic diversity of the species, were evaluated for resistance to a population of B. brassicae collected originally from HRI, Wellesbourne. Ninety eight accessions were identified as being moderately resistant (grade 3) or partially resistant (grade 4). Re-testing of accessions in the glasshouse identified 12 moderately resistant and 43 partially resistant accessions. The most promising gene pool was kale, where a higher than expected number of resistant accessions were found. Three of the kales were consistently rated as moderately resistant in all tests. In contrast the broccoli gene pool was a poor source of resistance with less (one out of 46) resistant accessions than expected. Eleven of the kales graded 3 were tested in the field in 1995 and resistance to B. brassicae was confirmed. Ten accessions were also tested for resistance to two additional populations of B. brassicae, one from Greece and the other from Portugal. The results provided no evidence of aphid biotype/host specific differences in the resistance of these B. oleracea accessions. This revised version was published online in August 2006 with corrections to the Cover Date.     

THE PATH OF CARBON IN PHOTOSYNTHESIS. XXVII. SUGAR-CONJUGATED PLANT GROWTH REGULATORS ENHANCE GENERAL PRODUCTIVITY

We have found that applications of sugar-conjugated plant growth regulators (SPGRs) by exposures of roots or shoots to millimolar (mM) SPGRs are key to their uptake and transport for enhancement of vegetative productivity of the entire plant as compared to control populations. Initial surveys utilizing foliar applications of identically nutrient-supplemented 0.3 mM cytokinin glycosides, N⁶-benzyladenine glycosides, kinetin glycosides; and a 0.3 mM auxin glycoside, indoxyl-β-D-glucopyranoside (IG) resulted in significant shoot enhancements over controls. Foliar application of 0.3 mM kinetin glucoside resulted in significant root increase above the control. Foliar application of 3 mM to 6 mM IG resulted in enhanced root and shoot growths over controls. Similarly, increases of root and shoot yields over controls were observed as a result of foliar application of 3 mM indoxyl-β-D-glucuronide. Foliar application of 1 mM trans-zeatin-β-D-glucoside was particularly effective, resulting in significant enhancement of root and shoot growth with no phytotoxicity.     

Biopesticide based sustainable pest management for safer production of vegetable legumes and brassicas in Asia and Africa

Vegetables are one of the important crops which could alleviate poverty and malnutrition among the smallholder farmers in tropical Asia and Africa. However, a plethora of pests limit the productivity of these crops, leading to economic losses. Vegetable producers overwhelmingly rely on chemical pesticides in order to reduce pest‐caused economic losses. However, over‐reliance on chemical pesticides poses serious threats to human and environmental health. Hence, biopesticides offer a viable alternative to chemical pesticides in sustainable pest management programs. Baculoviruses such as nucleopolyhedrovirus (NPV) and granulovirus (GV) have been exploited as successful biological pesticides in agriculture, horticulture and forestry. Maruca vitrata multiple nucleocapsid NPV (MaviMNPV) was found to be a unique baculovirus specifically infecting pod borer on food legumes, and it has been successfully developed as a biopesticide in Asia and Africa. Entomopathogenic fungi also offer sustainable pest management options. Several strains of Metarhizium anisopliae and Beauveria bassiana have been tested and developed as biopesticides in Asia and Africa. This review specifically focuses on the discovery and development of entomopathogenic virus and fungi‐based biopesticides against major pests of vegetable legumes and brassicas in Asia and Africa. © 2019 Society of Chemical Industry     

Biofumigation: environmental impacts on the biological activity of diverse pure and plant-derived isothiocyanates

Four pure isothiocyanates (methyl, 2-propenyl, benzyl and 2-phenylethyl isothiocyanate), hydrolysing tissue of two brassicas rich in either 2-propenyl or 2-phenylethyl isothiocyanate, and the methyl isothiocyanate-generating pesticide metam-sodium were tested in vapour exposure tests for biological activity against a model soil insect both in vitro and in the presence of three contrasting soils and under four temperatures from 5 to 20 degrees C. The purpose was to develop an understanding of the factors controlling isothiocyanate release and maintenance in soil in order to identify advantageous attributes to seek in utilising brassicas for isothiocyanate-based biofumigation. Methyl isothiocyanate, structurally the simplest and the most volatile, was the most biologically active isothiocyanate under all conditions. It was less affected by the presence of soil and by lower temperature than the longer-chain aliphatic 2-propenyl isothiocyanate. The activity of the less volatile aromatic isothiocyanates was reduced much more by soil, with a decline up to many thousand-fold in the presence of soil with high organic matter content at lower temperature. Metam-sodium closely reflected the methyl isothiocyanate results. The results indicate that brassicas rich in aliphatic isothiocyanates are more likely to have the potential to exert stronger isothiocyanate-based biofumigation effects than those similarly rich in aromatic isothiocyanates.     

Resistance to Brevicoryne brassicae in horticultural brassicas

Summary A wide range of cultivated brassica accessions including broccoli, Brussels sprouts, Chinese cabbage, cauliflower, collard, kale and swede material was tested against the cabbage aphid, Brevicoryne brassicae, at HRI, Wellesbourne in the field and laboratory in both 1992 and 1993. In the field, B. brassicae attack was assessed as the proportion of infested plants and the numbers of aphid colonies present. In the laboratory, aphid performance was measured in terms of the pre-reproductive and reproductive period, population increase, and insect mortality. Interpretation of the data was facilitated by plotting sorted accession means against normal order statistics. This statistical approach indicated the spread of variation amongst the accessions and permitted identification of extremes. Partial levels of antixenosis resistance were discovered in red brassicas. Glossy accessions of cabbage and cauliflower possessed antixenosis and antibiosis resistance that lasted throughout the season of crop growth in the field. Other accessions were shown to withstand aphid attack and therefore possessed tolerance. The laboratory studies provided information on mechanisms of antibiosis resistance. The potential value of the different sources of resistance is discussed.     

Molecular genetics and breeding of vegetable brassicas

Summary Genetic traits relevant to breeding vegetable brassicas are surveyed to determine the effects that recent advances in molecular genetics and molecular marker technology might have on breeding priorties and practices. The problems peculiar to breeding horticultural crops are addressed. The application of DNA restriction fragment length polymorphisms (RFLPs) as an aid to breeding brassicas is discussed and genes amenable to molecular analysis are considered in the light of both experimental and economic factors.     

Biological and molecular characterization of two closely related carlaviruses affecting brassica plants

Carlaviruses are plant-infecting viruses with flexuous filamentous particles of approximately 650 nm in length and a positive single-stranded hexacistronic RNA molecule as the genome. In this study, we analysed 14 samples of brassicas plants, reportedly affected by carlaviruses, that were collected in distant and edaphoclimatic distinct regions in Brazil. The genomes of four viral isolates detected in leaf kale (Brassica oleracea var. acephala) plants displayed the typical genomic organization of carlaviruses, subdivided into two contrasting identity profiles. Isolates T25, T107, and T110 showed a higher sequence identity among them (c.93%) than with T90 (c.67%), which had the highest nucleotide sequence identity (85.2%) with the only documented genomic fragment, approximately 1 kb of the RNA 3′-end, of cole latent virus (CoLV). Identity values among the other three isolates and CoLV were consistently lower than 78.6%. Nucleotide and amino acid sequence identity values of the replicase cistron of the isolates T25 and T90 are below the threshold for species demarcation in the genus Carlavirus. Upon mechanical transmission, these two isolates induced different symptoms in brassicas and solanaceous plants. Overall, data indicated that these viruses belong to two related but distinct species of carlaviruses. While T90 was recognized as an isolate of CoLV, the remaining isolates were considered members of a new tentative carlavirus named Cole mild mosaic virus (CoMMV). Current work provides convincing support for the taxonomic status of the species Cole latent virus, enlarges the known diversity of carlaviruses, and makes available new molecular tools to improve surveys of brassica-infecting viruses.     

Serological variability among European isolates of radish mosaic virus

Serological variability of radish mosaic virus (RaMV) isolates from white mustard, winter turnip rape, Camelina sativa and Chinese cabbage, collected in the Czech Republic and Russia, was studied using antisera against the Czech isolate RaMV1. In contrast to previous studies, reasonable serological differences were found between isolates from different locations and hosts, and even between neighbouring mustard plants in the field. Serological variability of European isolates was confirmed in extended experiments involving an Italian isolate, the American Type Strain (ATS) and its homologous antiserum. The results indicate that, in Europe, RaMV isolates may occur which differ both serologically and in host plant response, but no typical strains can be defined with the methods and isolates employed so far. Camelina sativa is reported as a new host of the virus.     

Isolation of useful variants in alloplasmic crop brassicas in the cytoplasmic background of Erucastrum gallicum

Alloplasmic Brassica juncea was synthesized by repeatedly backcrossing amphidiploid of Erucastrum gallicum × B. juncea with pollen of B. juncea. The E. gallicum cytoplasm was also transferred to B. napus and B. carinata through alloplasmic (E. gallicum) B. juncea. RFLP analyses of organelle DNA confirmed the presence of E. gallicum cytoplasm in all the alloplasmics. The cytoplasm of E. gallicum, though alien, did not induce stable cytoplasmic male sterility in any of the oilseed brassicas. Many useful variants such as early flowering and dwarf phenotypes were isolated in the alloplasmics of B. napus and B. carinata. These morphotypes provide useful genetic variability for the improvement of crop brassicas. This revised version was published online in July 2006 with corrections to the Cover Date.     

Serotypic variation in turnip mosaic virus

A panel of 30 monoclonal antibodies (MAbs) was produced against four isolates of turnip mosaic virus (TuMV). The panel was tested in plate-trapped antigen ELISA tests against 41 TuMV isolates (with different host and geographical origins and of differing pathotypes). The antibodies were also tested against four other potyviruses (bean common mosaic virus, bean common mosaic necrosis virus, lettuce mosaic virus and zucchini yellow mosaic virus). The reactions were assessed quantitatively (using multivariate analysis) and qualitatively (using the standard deviation obtained against healthy leaf material). The MAbs recognized 16–17 TuMV epitopes that were not present in the other potyviruses and a further two potyvirus epitopes. The isolates were grouped into three serotypes. Only one isolate did not fit this grouping. The classification of seven isolates in coat protein amino acid sequence homology groups correlated with serotypes. There was no correlation between serotype and pathotype, or between reactions to individual MAbs and single lines. There was therefore no evidence that the epitopes recognized by the MAbs are elicitors for the resistance genes present in the Brassica napus lines. However, the sensitivity and specificity of the MAbs will be useful for both routine detection of TuMV and fundamental studies on plant–virus interactions.