Electron Microscope Studies of Heteroduplex DNA from a Deletion Mutant of Bacteriophage phi X-174

A population of double-stranded replicative form of DNA molecules from bacteriophage phi X-174 carrying a deletion of about 9% of the wild-type DNA has been discovered in a sample cultivated under conditions where the phage lysozyme gene is nonessential. The structures of deleted monomers, dimers, and trimers were studied by the electron microscope heteroduplex method. The dimers and trimers are head-to-tail repeats of the deleted monomers. Some interesting examples of the dynamical phenomenon of branch migration in vitro have been observed in heteroduplexes of deleted dimer and trimer strands with undeleted monomer viral strands from the wild-type phage

Predicting the potential distribution in South Korea of two mealybug species (Hemiptera: Pseudococcidae) intercepted on pineapples in quarantine

Dysmicoccus brevipes (Cockerell) and Dysmicoccus neobrevipes Beardsley are major pests of pine­apples, ornamentals, and vegetable crops in many countries around the world. The potential distribution of these mealybug pests into South Korea remains a prime concern because of their high incidence in intercep­tions screened during inspection. Hence, these species prompted a modelling effort to assess their potential risk of introduction. Potential risk maps were developed for these pests with the CLIMEX model based on occurrence records under environmental data. The potential distribution of these pests in South Korea in the 2020s, 2050s and 2090s is projected based on the RCP 8.5 climate change scenario. Results show that D. brevipes and D. neobrevipes have little potential for invasion in the exterior environment of South Korea due to high cold stress. However, for D. brevipes, three locations in Jejudo were predicted to be marginally suit­able for this pest under future climate factors. In that respect, the results of these model predictions could be used to prepare a risk-based surveying program that improves the probability of detecting early D. brevipes and D. neobrevipes populations. The introduction of an exotic species to new geographical areas without their natural enemies has often been followed by large outbreaks in their population and subsequent economic damage to plants (CABI 2023a). Mealy­bugs (Hemiptera: Pseudococcidae) are plant feeders that have a more-or-less cryptic way of life because of their small size and limited mobility (Kondo and Watson 2022a). They are almost always found associated with plants, and are commonly intercepted on imported plant material (PIS 2023). As a result, they can easily be transported to other areas on the plants on which they live. A total of 114 species have been considered as pests in the world (Kondo and Watson 2022b). As of 2005, some 255 exotic scale insect species had become established in the USA; of these, 53 species were mealybugs (Miller et al. 2005). In South Korea, 91 exotic species have been documented from 1910 to 2019; of these, three species are mealybugs (RDA 2019). Numerous kinds of insect pests were intercepted during import inspections at South Korean ports of entry. Mealybugs comprised 16.3% of the 198,086 interceptions from 1996 to 2022 (PIS 2023), of which, Dysmicoccus brevipes (Cockerell) (22.9% of the mealybug interceptions) and Dysmicoccus neobrevipes Beardsley (54.3%) were intercepted most frequently (Table 1). The pink pineapple mealybug (PPM), D. brevipes, was described in 1893 from pineapples in Jamaica. Since then, it has become a major pest of pineapples, ornamental plants and vegetable crops in many other countries in the world where it has spread by the international trade of these goods (García Morales et al. 2016). The grey pineapple mealybug (GPM), D. neobrevipes, is probably native to the Australasian region and was first reported in 1959 from Hawaii. Over the last 60 years, this species has been found in 44 coun­tries on a wide variety of host plants (García Morales et al. 2016)

Effects of nucleon resonances on η\eta photoproduction off the neutron reexamined

We investigate $\eta$ photoproduction off the neutron target, i.e., $\gamma n \to \eta n$, employing an effective Lagrangian method combining with a Regge approach. As a background, we consider nucleon exchange in the $s$-channel diagram and $\rho$- and $\omega$-meson Regge trajectories in the $t$ channel. The role of nucleon resonances given in the Review of Particle Data Group in the range of $W \approx 1500 - 2100$ MeV and the narrow nucleon resonance $N(1685,1/2^+)$ is extensively studied. The numerical results of the total and differential cross sections, double polarization observable $E$, and helicity-dependent cross sections $\sigma_{1/2}$, $\sigma_{3/2}$ are found to be in qualitative agreement with the recent A2 experimental data. The predictions of the beam asymmetry are also given.Comment: 12 pages, 6 figure