Phenotypic and genotypic structure of Phytophthora infestans populations on tomato and potato in the North of Thailand in 2000–2002

A total of 80 single–lesion isolates of Phytophthora infestans were collected from tomatoes and potatoes in several locations in Chiang Mai and Tak provinces in 2000–2002. These isolates were analyzed for mating type, metalaxyl sensitivity, mitochondrial DNA (mtDNA) haplotype RFLP pattern as determined by probe RG57, and for microsatellite markers. All isolates were A1 mating type. Isolates from tomato were usually sensitive to metalaxyl, but isolates from potato were usually resistant to metalaxyl. With one exception, all tomato isolates were related to the US-1 clonal lineage. With two exceptions, all potato isolates were related to two European lineages. In these two provinces, the populations of P. infestans on tomatoes are clearly different from those on potatoes.     

Pheromone Research and Development in Israel 1975–2015

The review describes the history of pheromone research in Israel in 1975–2015. The research focused on sex pheromones of moths that were important agricultural pests. Identification, synthesis and field application of sex pheromones was performed. Synthetic procedures of several known sex pheromones were developed. Monitoring and control of key pest moths was evaluated. The interactions of pheromone components of closely related species were studied in field and laboratory experiments. The sex pheromones of three scale insects, two mealybug species and Matsucoccus josephi were studied. New syntheses were developed and the pheromones were implemented in pest management. Structure activity relationship of the pheromonal and kairomonal of the M. josephi pheromone was investigated. Different pherotypes of P. ficus were identified and evaluated. The aggregation pheromone of sap beetles in combination with food baits was evaluated. The aggregation pheromone of the almond bark beetle was identified and a stereospecific synthesis of its enantiomers was developed. Monitoring the pest in stone fruit orchards was implemented. The activity of the pheromone biosynthesis activating neuropeptide (PBAN) was studied in Helicoverpa armigera and Heliothis peltigera. The ligation technique was used to assess the effect of PBAN on the production of female and male pheromones. A structure-activity relationship study of PBAN indicated that shorter peptides display activity as the full length PBAN. A series of linear and cyclic peptide analogs was prepared, resulting in the discovery of a lead antagonist. The research and development activity facilitated the intensive integration of pheromones in the pest management regimes in Israeli agriculture.     

Efficacy and dose–response relationship in biocontrol of Fusarium disease in maize by Streptomyces spp.

Two isolates of Streptomyces spp. DAUFPE 11470 and DAUFPE 14632 were evaluated to determine the antagonist–pathogen inoculum concentration relationship under greenhouse conditions. Pathogen and antagonist concentration, significantly (P < 0.05) affected development of Fusarium disease in maize with a significant interaction between pathogen and antagonist concentration. Dose–response relationship also differed significantly (P < 0.05) between the two isolates, but both isolates demonstrated effective control of Fusarium disease, regardless of pathogen concentration. The isolate DAUFPE 11470 provided the most effective control. The lowest value for disease incidence occurred at low pathogen (10³ chlamydospore g⁻¹ soil) and high antagonist concentration (10⁶ cfu ml⁻¹) for both isolates. The disease incidence for control plants ranged from 19% to 76%. However, in relation to control the lowest disease reduction occurred at low pathogen (10³ chlamydospore g⁻¹ soil) and high antagonist concentrations (10⁶ cfu ml⁻¹). These reductions were 10.6% and 13% for DAUFPE 14632 and DAUFPE 11470, respectively. The highest disease reductions, in relation to control plants, occurred at high pathogen (10⁶ chlamydospore g⁻¹ soil) and antagonist (10⁶ cfu ml⁻¹) concentrations for both isolates. These values were 55% and 62.2% for DAUFPE 14632 and DAUFPE 11470, respectively. The chlamydospore germination of Fusarium moniliforme was affected by glucose addition, antagonist isolates and type of inoculum. The lowest chlamydospore germination was observed with bacterial suspensions of the isolates, for all glucose additions. The results suggested that both Streptomyces spp. isolates were effective at different doses as biocontrol agents against F. moniliforme. Also, there was evidence for at least two mechanisms of biocontrol and that apparently, both isolates showed the same mechanisms of biocontrol action related to production of bioactive compounds and competition for carbon. Further studies will be developed to improve the level and effectiveness of control by these isolates.     

Toxicity of insecticides to the tsetse fly,Glossina palpalis palpalis in Nigeria and comparison of tolerances in 1974–1975 and 1979–1982

Abstract

Toxicities o1 12 chemical insecticides to wild‐caught tsetse flies, Glossina palpalis palpalis in Nigeria were measured by topical application. Median lethal doses (as ng per fly) at 48 h after application for older flies, males (females), were: DDT 331 (700), dieldrin 14 (46), endosulfan 8 (15), malathion 193 (273), fenitrothion 47, pirimiphos methyl 31 (45), tetrachlorvinphos 14 (33), sumicidin 28 (58), neopynamin 12 (15), sumithrin 10 (8), permethrin 4.4 (5.9), deltamethrin 0.45 (0.94). Lethality expressed as dose per whole fly can be termed effective toxicity/tolerance and those expressed as dose per weight unit of fly can be termed intrinsic (or true) toxicity/tolerance. Generally, effective tolerance was greater for females than males, especially for older flies. However, intrinsic tolerance was often about equal for the sexes or greater for males. Regardless of sex, effective tolerance increased with increasing fly age and intrinsic tolerance increased during later ageing but not during early ageing. This suggested that protecting mechanisms developed during ageing. Flies fed a few hours before treatment in 1979–1982 were more tolerant of three organochlorines and three organophosphates than flies fed the day before treatment in 1974–1975, probably due to diversion of poisons from sites of action into inert undigested blood. However, results and statistical analysis suggested a slight increase in true tolerance of males to DDT during the intervening years. Continued monitoring of tolerance in the fly populations is recommended.     

Pathotype diversification in the invasive PstS2 clonal lineage of Puccinia striiformis f. sp. tritici causing yellow rust on durum and bread wheat in Lebanon and Syria in 2010–2011

Yellow rust is the major wheat disease in central West Asia and North Africa. Recently, severe epidemics have occurred, with major yield losses in 2010–2011 in Lebanon and Syria. We conducted an extensive field survey, with a collection of 273 samples of Puccinia striiformis f. sp. tritici, to explore the origin of these epidemics. All samples were genotyped with 20 microsatellite markers, and 54 isolates were pathotyped. The population was dominated by the PstS2 lineage, which has spread worldwide since 2000 and displays considerable pathotype diversity (10 pathotypes). The 22 multilocus genotypes (MLGs) detected corresponded to variants of the clonal lineage PstS2, but they differed from the common PstS2 genotype found in the worldwide study conducted between 1981 and 2010. No strong differentiation was observed between Lebanon and Syria. The dominant MLG in Syria was common to both countries. Nine MLGs were found exclusively in the Syrian population and four were restricted to the Lebanese population, including the dominant MLG in Lebanon. The predominant MLG-11 was found in nine pathotypes, at high frequency. The dominant pathotype in Syria was virulent against widely deployed resistance genes (Yr2, Yr6, Yr7, Yr9, Yr25, and Yr27); virulence against Yr3, Yr8, Yr17, and YrSP occurred at various frequencies, but Yr1, Yr4, Yr5, Yr10, Yr15, and Yr32 were effective against all isolates. No host effect was detected. The presence of diverse host populations consisting of landraces and elite varieties, and diverse climatic conditions may account for the unexpectedly high diversity of this clonal population.     

Sediment yield and erosion–deposition distribution characteristics in ephemeral gullies in black soil areas under geocell protection

Investigating the effect of geocells on the erosion and deposition distribution of ephemeral gullies in the black soil area of Northeast China can provide a scientific basis for the allocation of soil and water conservation measures in ephemeral gullies. In this study, an artificial simulated confluence test and stereoscopic photogrammetry were used to analyze the distribution characteristics of erosion and deposition in ephemeral gullies protected by geocells and the effect of different conflue...     

Induction of Chitinase and β-1,3-Endoglucanase Proteins by UV Irradiation and Wounding in Grapefruit Peel Tissue

UV irradiation enhanced the resistance of grapefruit against the development of green mold décay caused byPenicillium digitatum, the main postharvest pathogen of citrus fruit, and significantly inhibited the fungus’ growth at the fruit wound sites. Immunoblotting analysis using specific citrus chitinase and β-1,3-endoglucanase antibodies, showed that UV irradiation, wounding of the fruit, or a combination of these two treatments, induced the accumulation of a 25 kD chitinase protein in the fruit’s peel tissue. On the other hand, UV irradiation or wounding of the fruit alone was unable to induce the accumulation of 39 and 43 kD β-1,3-endoglucanase proteins, but the combination of the two treatments increased these protein levels. It is suggested that both chitinase and β-1,3-endoglucanase may play a role in the UV-induced resistance of grapefruit againstP. digitatum. Contribution from the Agricultural Research Organization, The Volcani Center, Bet Dagan, Israel. No. 403/99. http://www.phytoparasitica.org posting June 3, 1999.     

Nutrient addition and disturbance effects on the community composition and assembly in a desert steppe北大核心CSCD

The effects of short-term nutrient additions (NPKμ, 10 g·m- 2) and disturbances on the species diversity, functional traits, soil properties, and community assembly mechanisms of the herbaceous community in the Urat desert steppe were examined. A mixed linear model, principal component analysis, and null model methods were utilized and both disturbance and interaction treatments were found to significantly reduce species richness and β diversity. Short-term nutrient additions significantly reduced soil pH but increased soil electrical conductivity. Six functional traits of the dominant species (i.e. Stipa glareosa, Peganum harmala, Salsola collina, Corispermum mongolicum) and six community-weighted mean significant changes under the disturbance and nutrient addition treatments were identified. The disturbance and nutrient additions promoted the transformation of the dominant species in the community from conservative strategies to acquisitive strategies. The results of the two null models revealed that community assembly under the control tended to be a stochastic process, while the disturbance and interaction treatments tended to be deterministic processes, and that of the nutrient addition treatments tended to be weaker deterministic processes. Plant communities in the desert steppe responded and adapted to the nutrient additions and disturbances through changes in the dominant species and their crucial functional traits. © 2023 Chinese Academy of Sciences. All rights reserved.     

Predation and parasitism on eggs of two pod‐sucking bugs,Nezara viridula and Piezodorus hybneri in soybean

Abstract

Cohorts of newly laid egg masses of two pod‐sucking bugs, Nezara viridula and Piezodorus hybneri (Hemiptera: Pentatomidae), were exposed to naturally occurring predators and parasitoids on soybean in unsprayed fields at four sites in Northern Sumatra. The fate of the young stages was recorded until the late first instar, before the nymphs start to disperse and feed. Partial life tables showed that mortality of N. viridula until the late first instar was 50–87%, of which 18–65% occurred during the egg stage and was mainly caused by predation; 2–26% of the eggs died of parasitism. P. hybneri which was present at only two sites, showed a 73–89% mortality until the late first instar, of which 69–85% was during the egg stage and, again, mainly caused by predation; 15–24% of the eggs died of parasitism. To evaluate the role of individual egg predator species in the field, we conducted hourly observations of exposed egg masses of the two pests. Dolichoderus sp., Solenopsis geminata (Hymenoptera: Formicidae), Paederus sp. (Coleoptera: Staphylinidae) and several gryllids (Orthoptera) were most commonly encountered feeding on the eggs. An index of ‘predation pressure”; was calculated from the densities of predators in the field and from an estimate of their attack rate based on field observations of predator feeding. Two sites with low predator pressures had low predation rates, while the two sites with high predation pressures had considerably higher predation rates. The implications of the findings for IPM training in soybean are discussed.     

Effect of α tocopherol and selenium on antioxidant status, lipid peroxidation and hepatopathy induced by malathion in chicks

The objective of the present study was to investigate the role of α tocopherol and selenium on malathion induced hepatic damage, and antioxidant defense in chicks. The chicks were divided into three groups. First group received malathion 10 mg/kg BW, orally for 60 days, the second group received the same dose of malathion but was supplemented with α tocopherol and selenium for 60 days and the third group served as the control. A compromised antioxidant capacity as evidenced by increased levels of erythrocytic lipid peroxidation and decreased concentration of vitamin E and decreased activity of glutathione peroxidase was observed in chicks following the administration of malathion. An improved antioxidant status was observed in chicks of second group with α tocopherol and selenium supplementation including higher concentration of vitamin E, increased activity of glutathione peroxidase and lower levels of lipid peroxidation. Histopathological studies of liver in the chicks which received malathion exhibited, moderate to severe degenerative and necrotic changes in the hepatocytes. The correlation of decreased antioxidant status of chicks with degenerative changes in liver suggests that lipid peroxidation may be one of the important mechanism in the chronic toxicity of malathion. The results indicate that α tocopherol and selenium were effective in partially alleviating degenerative changes induced by malathion in the liver of chicks by attenuating processes leading to lipid peroxidation.     

Mucor Species in Orchard Soil – Population Dynamics and Pathogenicity on Pear Fruit

Strains of Mucor piriformis were isolated from orchard soils and from packinghouse dump-tank waters. Pathogen propagules were not found in fruit sample washings. M. piriformis was the most prevalent of the Mucor isolates, only one of 67 isolates was a different Mucor sp., possibly M. racemosus. The population of the pathogen propagules fluctuated in an annual cyclic pattern, declining in warm months and increasing after harvest. The viability of sporangiospores was markedly affected by rain. There was a good correlation (r=0.88) between the number of recovered propagules in the soil and the amount of rainfall. M. piriformis isolates caused decay on pear at 0°C after 14 days.     

The effect of α-hexachlorocyclohexane on liver growth in intact and adrenalectomized rats

α-Hexachlorocyclohexane was administered as a single oral dose (100 mg/kg body wt) to both intact and adrenalectomized male Sprague-Dawley rats. In the intact rats there was a peak in [³H]thymidine incorporation into DNA at 30 hr and an increase in relative liver weight (liver weight/body wt × 100) which peaked at 60 hr post α-HCH dose. However, in α-HCH-dosed adrenalectomized rats [³H]thymidine incorporation into DNA remained elevated throughout the study period and relative liver weight was not significantly increased. In corticosterone-supplemented α-HCH-dosed Adx rats, [³H]thymidine incorporation into DNA was significantly reduced and RLW was increased comparable to that seen in intact animals. These results suggest that α-HCH-induced liver growth is mediated by corticosterone.     

Genotype × environment interactions in symptom development and yield of cassava genotypes with artificial and natural cassava bacterial blight infections

Thirty-seven cassava genotypes from Benin, including advanced breeding lines, were tested for their reaction to bacterial blight in the forest–savanna transition, wet savanna and dry savanna zones of Benin. Sixteen genotypes were repeated in 12 environments. In year 1998, genotypes RB92164, RB92022, TMS30572, BEN86004, RB92033 and Dangbo2, and in year 2000, genotypes RB92202, RB92151, RB92132 and TMS30572 were resistant in one ecozone. Among the more resistant genotypes, CAP94030, BEN86040, RB89509, RB92132 and TMS30572 showed low interaction across environments and were most stable in disease reaction. Ten genotypes were classified as high yielding across environments. Among the more resistant group of genotypes, only TMS30572 and RB89509 were high yielding, with RB89509 being unstable in yield across environments. Selection of genotypes proved reliable only after artificial inoculation. Comparing environments, artificially inoculated treatments in the wet savanna zone and in the forest–savanna transition zone with stable high symptom severity proved most suitable for screening of genotypes, while the wet savanna zone with low natural infection in year 1998 was suitable for production of propagation material, and the site in the dry savanna zone with natural infection in year 1998 was the best environment for cassava production. The correlation between disease severity and root yield was significant only for the non-inoculated treatment in the dry savanna zone in year 2000 (R = –0.58), but not in any other environment. Among the 37 genotypes tested, several genotypes can be recommended to farmers in specific ecozones, and genotype TMS30572 revealed as relatively stable in disease resistance and in high yield across ecozones.     

β-Tubulins in Gibberella zeae: their characterization and contribution to carbendazim resistance

BACKGROUND: Fusarium head blight caused by Gibberella zeae is an important disease of wheat and barley because it reduces grain yield and quality and results in the contamination of grain with mycotoxins. Recent studies have shown that carbendazim resistance in field strains of G. zeae is not caused by mutation of the β‐tubulin gene (β₁tub), which is the case with other filamentous fungi, but that fungicide resistance is greatly increased by deletion of β₁tub. The aim of the present study was to clarify the function of β₁tub and its role in carbendazim resistance in G. zeae by artificial gene operation. RESULTS: Deletion of β₁tub reduced vegetative growth and pathogenicity but increased asexual reproduction in G. zeae. All the mutants were more resistant to carbendazim than parent strains. A three‐dimensional model of β₁tub was constructed, and the possible carbendazim binding site was analysed. CONCLUSION: β₁tub is not an essential gene in G. zeae, but it affects the sensitivity of the fungus to carbendazim. Copyright © 2012 Society of Chemical Industry