This study characterized resistance in pea lines PI 347295 and PI 378159 to Clover yellow vein virus (ClYVV). Genetic cross experiments showed that a single recessive gene controls resistance in both lines. Conventional mechanical inoculation did not result in infection; however, particle bombardment with infectious plasmid or mechanical inoculation with concentrated viral inocula did cause infection. When ClYVV No. 30 isolate was tagged with a green fluorescent protein (GFP) and used to monitor infection, viral cell-to-cell movement differed in the two pea lines. In PI 347595, ClYVV replicated at a single-cell level, but did not move to neighboring cells, indicating that resistance operated at a cell-to-cell step. In PI 378159, the virus moved to cells around the infection site and reached the leaf veins, but viral movement was slower than that in the susceptible line. The viruses observed around the infection sites and in the veins were then recovered and inoculated again by a conventional mechanical inoculation method onto PI 378159 demonstrating that ClYVV probably had mutated and newly emerged mutant viruses can move to neighboring cells and systemically infect the plants. Tagging the virus with GFP was an efficient tool for characterizing resistance modes. Implications of the two resistance modes are discussed.
Two recessive resistance genes against Clover yellow vein virus (ClYVV), cyv1 and cyv2, have been previously reported. We recently screened resistant peas from a
separate set of pea lines and classified them into two groups according to their distinct resistant modes. We later revealed that one group carries cyv2, encoding eukaryotic
translation initiation factor 4E (eIF4E), in linkage group (LG) VI. We explored the possibility that the resistance gene, tentatively designated non-cyv2, that confers resistance on the other group, was actually cyv1. We found that PI 236493, which
carries cyv1, showed restriction of ClYVV cell-to-cell movement similar to that in non-cyv2 peas including PI 429853. PI 429853 was crossed with susceptible line PI 250438. Mapping of F2 progeny revealed that non-cyv2 was 4 cM from the simple sequence repeat marker AB40, whose loci are close to cyv1, mo, and sbm-2 mapped in
LG II, which mediates resistance to other potyviruses. Moreover, PI 429853 crossed with PI 236493 produced F1 progeny resistant to ClYVV, raising the possibility that
non-cyv2 is allelic to cyv1. Because mo was previously mapped with eIF(iso)4E in LG
II, we examined the possibility that non-cyv2, cyv1, and mo encoded eIF(iso)4E.
However, there was no difference in the nucleotide sequence of the eIF(iso)4E-coding
region between susceptible and resistant pea lines. The eIF(iso)4E gene was
equivalently expressed in both PI 429853 and PI 250438 before and after ClYVV
infection. Our results suggest that these resistance genes are unlikely to encod
The objective of this research was to perform screening of biosurfactant-producing bacteria from Amapaense Amazon soils. Floodplain- and upland-forest soils of three municipalities of the Amapá state were isolated and identified. The isolates were cultured in nutrient broth with olive oil, and their extracts were evaluated according to drop collapse, oil dispersion, emulsification, and surface tension tests. From three hundred and eighteen isolates, the 43 bacteria were selected and identified by 16S rDNA gene sequencing, indicating the presence of three different genera, Serratia, Paenibacillus, and Citrobacter. The extracellular biosurfactant production pointed out the 15 most efficient bacteria that presented high emulsification capacity (E24 > 48%) and stability (less than 10% of drop after 72 h) and great potential to reduce the surface tension (varying from 49.40 to 34.50 mN·m−1). Cluster analysis classified genetically related isolates in different groups, which can be connected to differences in the amount or the sort of biosurfactants. Isolates from Serratia genus presented better emulsification capacity and produced a more significant surface tension drop, indicating a promising potential for biotechnological applications.
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