Reduced Plant Dry Weight Research Articles

Hydrogen Sulfide and 5‐Aminolevulinic Acid Synergistically Enhance Drought Tolerance in Tomato (Solanum lycopersicum L.)

ABSTRACTEnhancing crop drought tolerance is crucial for food security amid climate change. This study examines how 5‐aminolevulinic acid (ALA) and hydrogen sulfide (H2S) can improve drought resilience in tomato plants, which are essential for sustainable food production. Drought stress was induced using 12% PEG‐6000. Plants were pre‐treated with 25 mg L−1 ALA and 0.1 mg L−1 hypotaurine (HT), followed by 0.2 mM sodium hydrosulfide (NaHS) treatment to assess the effects on plant physiological effects over 10 days. Drought stress reduced plant dry weight, chlorophylls (a and b), Fv/Fm, leaf water potential, and relative water content, while increasing glycine betaine (GB) and proline levels. Additionally, drought stress elevated NADPH oxidase (NOX) and glycolate oxidase (GOX) activities, inducing oxidative stress and membrane damage. ALA and NaHS enhanced plant growth, photosynthesis, proline, GB, ALA content, ATP synthase, and ATPase activities, while mitigating NOX and GOX activities, thereby reducing and H2O2 radicals. ALA alone boosted L‐DES activity, promoting H2S accumulation. However, ALA + HT reduced H2S levels, compromising ALA's efficacy. NaHS with ALA + HT reinstated positive effects by restoring H2S levels. Biochemical assays confirmed ALA and NaHS promoted H2S accumulation, bolstering antioxidants, mitigating lipid peroxidation, suggesting their drought resilience potential in tomatoes.

Winter Cereal Reactions to Common Root Rot and Crown Rot Pathogens in the Field

In Australia, Fusarium pseudograminearum and F. culmorum are the two main fungi causing crown rot, while Bipolaris sorokiniana is the causal agent of common root rot. Fusarium graminearum is typically linked with Fusarium head blight; however, it has been associated with crown rot in Australia and other parts of the world. This study investigated the reactions of single cultivars of barley, bread wheat, durum wheat, oat, and triticale to inoculation with strains of F. pseudograminearum, F. culmorum, F. graminearum and B. sorokiniana in field trials across two seasons. Fusarium pseudograminearum and F. culmorum caused greater visual discolouration than F. graminearum and B. sorokiniana on both stems and sub crown internodes of all hosts. Fusarum pseudograminearum caused the greatest reduction in plant dry weight across hosts in both years. Durum wheat (cv. Hyperno) barley (cv. Grimmett), bread wheat (cv. Livingston) and triticale (cv. Endeavour) observed significantly high levels of visual discolouration on stems when inoculated with F. pseudograminearum, while oat (cv. Genie) exhibited the least visual discolouration. Despite variation in the visual discolouration, the DNA of all pathogens were detected in all cultivars. This research further highlights the complicated nature of the pathogen × strain × cultivar × environment interaction, which remains a challenge in breeding for genetic resistance. The specific infection of each fungus and the host responses in these field trials improves our understanding of disease development and its importance in cropping systems.

Tolerance of ‘Camarosa’ Strawberry (Fragaria ×ananassa Duch.) to Extra-label Use of Single and Tank Mix Preemergence Herbicides in Annual Hill Plasticulture

Relatively few herbicides are registered in Alabama or in the southeastern United States for use in annual hill plasticulture production of strawberries. Acquisition of 24(c) special local needs status for certain herbicides could make more of these chemistries available to the strawberry industry. These herbicides, especially when applied as tank mixes pose potential risks to strawberry plant growth and fruit yield. Special local needs status for these herbicides has been granted for other states, but more evaluation of these products in Alabama soils under plastic mulch is needed. The objective of this study was to assess tank mix applications of preemergence herbicides with different modes of action on plant growth, crop yield, and fruit size of ‘Camarosa’ strawberry. A study was conducted at the Chilton Research and Extension Center in Clanton, AL, in 2018 and 2019. Pendimethalin (3.5 L·ha–1) and S-metolachlor (1.6 L·ha–1) were evaluated for potential phytotoxicity in ‘Camarosa’ strawberry when applied alone or in tank mixes with napropamide (8.6 kg·ha–1), sulfentrazone (0.3 L·ha–1), or terbacil (0.42 L·ha–1) by comparing them to a nontreated control. At 18 weeks after planting, pendimethalin tank mixed with napropamide reduced plant dry weight by 33% compared with the control, but this reduction was not significant. Additionally, tank mixes of pendimethalin with sulfentrazone, napropamide, and terbacil reduced shoot dry weight by 43%, 52%, and 43%, respectively, compared with pendimethalin alone. Pendimethalin + napropamide tank mix reduced relative growth rate by 95% compared with the control between 6 and 18 weeks after planting. All treatments were similar to the control in marketable yield. Differences in plant growth parameters did not appear to affect yield by the end of the experiment. All single applied treatments along with S-metolachlor tank mixed with napropamide and sulfentrazone; pendimethalin tank mixed with sulfentrazone and terbacil appeared to be safe for direct application to strawberry planting beds covered in polyethylene mulch.

Susceptibility of kale cultivars to the wheat bug, Nysius huttoni (Hemiptera: Lygaeidae) in New Zealand

ABSTRACT Seedlings of kale cultivars in New Zealand are highly susceptible to direct feeding by the wheat bug Nysius huttoni (Hemiptera: Lygaeidae), an endemic insect pest. Two assays (choice and no-choice) were conducted to compare the relative susceptibility of seedlings of the six most popular kale cultivars in New Zealand (Kestrel, Gruner, Sovereign, Regal, Corka and Coleor). The earliest occurrence of feeding damage in the choice assay was on cv. Kestrel, significantly earlier than on Corka and Gruner. In the no-choice assay, significantly more wheat bugs were found on Kestrel than on Corka. Damage to Kestrel occurred significantly earlier than on all the other cultivars except Corka. Reduction in plant dry weight was significantly higher on Coleor and Kestrel. These results are important for developing integrated pest management protocols for kale pests.

Ameliorative Effect of Ammonium Sulfate on Salt Tolerance and Ion Homeostasis in Lemon (C. limon) Seedlings

To investigate interaction effects of salinity and nitrogen on growth, mineral composition and salinity tolerance of lemon seedlings, a greenhouse experiment with four sodium chloride concentrations (0, 250, 500 and 1000 mg kg-1 soil) and four nitrogen levels (0, 50, 100, and 200 mg kg-1 soil ammonium sulfate) was carried out. Experiment was conducted in a completely randomized design with three replications. Sodium and chloride ions in plant tissues were increased to toxic levels with increase in salinity which resulted in a significant reduction of plant dry weight. Nitrogen consumption up to 100 mg kg-1 soil increased plant dry weight. As the concentration of sodium chloride was increased, the improvement effect of nitrogen on plant growth was decreased. Although nitrogen had no considerable effect on sodium concentration in root and shoot, it made a decrease in chloride concentration in shoot and an increase in root concentration of this element. Salinity decreased essential nutrients concentration in plant shoot. Therefore, it can be concluded that adverse effect of salinity is to some extent due to reduction of required elements to suboptimal ranges in plant tissues. Nitrogen improved the adverse effects of salinity on plant nutrients by increasing their concentration in plant tissues. Therefore it can be inferred that part of the ameliorative effects of nitrogen on salinity adverse effects is related to the maintenance of essential nutrient concentrations in plant tissues. The results of the present study indicate that nitrogen can be applied in amounts higher than optimal level to reduce the harmful effects of salinity.

Japanese Foxtail (Alopecurus japonicus) Management in Wheat in China: Seed Germination, Seedling Emergence, and Response to Herbicide Treatments

AbstractLittle information is published related to seed germination and seedling emergence of Japanese foxtail, a troublesome annual grass weed widely distributed in winter wheat fields in China. Three Japanese foxtail populations were studied under laboratory and greenhouse conditions, to determine the effects of different environmental factors on seed germination or seedling emergence. Chemical control is absolutely necessary in integrated management, and efficacy of POST herbicides against different growth stages of Japanese foxtail was evaluated. Germination rate was 90% or more when temperature ranged from 5 to 25 C, with germination onset shortened as temperature increased. Light was not required for germination to occur. For pH values ranging from 5 to10 there was no effect on seed germination. Japanese foxtail seed germination was sensitive to osmotic stress and completely inhibited at an osmotic potential of -1.1 MPa. The ‘1513’ population of Japanese foxtail demonstrated tolerance to soil salinity, with 98% germination at 80 mM NaCl compared with 25 and 40% germination for populations ‘1532’ and ‘1544’, respectively. High amounts of crop residue (10 t ha−1) suppressed Japanese foxtail emergence 38 to 55%. Germination of seeds placed at 160 C for 5 min was completely inhibited for dry seeds, with a similar effect at 130 C for pre-soaked seeds. Seed burial in the soil from 0 to 4 cm had no effect on seedling emergence, but burial at 7 cm completely inhibited seedling emergence. POST herbicides mesosulfuron-methyl (13.5 g ai ha−1), clodinafop-propargyl (67.5 g ai ha−1), pyroxsulam (13.5 g ai ha−1), pinoxaden (67.5 g ai ha−1) and isoproturon (1125 g ai ha−1) reduced plant dry weight 80% or more when applied at three- to seven-leaf stage, but control declined with application at later growth stages. The information from this study helps to develop an integrated approach to Japanese foxtail management.

Management of Meloidogyne incognita and Macrophomina phaseolina by Graphene Oxide on Lens culinaris

Effect of Graphene oxide (GO) was observed on Meloidogyne incognita and Macrophomina phaseolina and on the growth of lentil in pot experiment. Treatment of plants with 10 ml solution of GO with 125, 250 and 500 ppm concentration caused a significant increase in plant dry weight over control. Inoculation of plants with M. incognita or M. phaseolina caused a significant reduction in plant dry weight over uninoculated control. Treatment of plants with 125, 250 and 500 ppm GO and subsequent inoculation with M. incognita or M. phaseolina caused a significant increase in plant dry weight over plants inoculated without GO pretreatment. Treatment of 500 ppm GO caused a greater increase in plant dry weight of M. incognita or M. phaseolina inoculated plants followed by 250 ppm and 125 ppm. Numbers of nodules per root system were high in plants without pathogen. Inoculation of M. incognita or M. phaseolina caused reduction in nodulation. However, treatment of GO in all the three concentrations had no significant effect on nodulation in plants both with and without pathogens. Treatment of GO resulted in reduced galling, nematode multiplication and root-rot index. Greater reduction in galling, nematode multiplication and root-rot index were observed in plants treated with 500 ppm GO followed by 250 ppm and 125 ppm. Indices were reduced to 4, 3 and 2, respectively, when plants with M. phaseolina were treated with 125, 250 and 500 ppm GO. This study shows that the use of GO is useful for the management of M. incognita and M. phaseolina on lentil.

Excess iron alters the fatty acid composition of chloroplast membrane and decreases the photosynthesis rate: a study in hydroponic pea seedlings

As an essential micronutrient, iron (Fe) is directly involved in several fundamental processes in the photosynthetic cells. However, it is not clear if photosynthetic traits affected by high ferrous level are associated with changes in fatty acid composition in chloroplast membranes. To accomplish this, the effects of excess Fe2+ on the fatty acid composition and the fluidity properties of the chloroplast membrane, photosynthesis rate and the chlorophyll fluorescence were investigated in pea (Pisum sativum L.) seedlings grown hydroponically in nutrient solutions with 100, 200, 400 and 600 µM Fe2+ supplied as FeSO4. Increased fluidity of the chloroplast membranes was found under higher Fe2+ treatments, and this might be attributed to the increase in relative content of unsaturated fatty acids (USFA). Excess Fe2+ decreased the chlorophyll content and the electron transport rate, deactivated reaction center of photosystem II, and declined plant net photosynthetic rate. Finally, the reduced plant dry weight was observed. The results indicate that the effects of excess Fe on photosynthesis and fluidity of chloroplast membrane depend on the stress strength and duration, and the increased fluidity of chloroplast membrane may be critical in maintenance of cellular integrity under excess but not lethiferous Fe2+ treatment.

Comparative effect of Nickel and beta-aminobutiric Acid on some Secondary Metabolits of Echium amoenum

Plants have a wonderful variety of secondary metabolites which may be change due to environmental factors and stress conditions. Considering the importance of Echium amoenum in Iranian traditional medicine, this study aimed to investigate the effect of abiotic stresses on the possibility of further production of secondary metabolites in the plant. In general, according our research findings, beta-aminobutyric acid increased growth indexes. Effect of BABA on secondary metabolites was different. BABA increased plant flavonoids but reduced the tannins. Numerous studies have pointed to the stress effects of this material at high concentrations but the concentrations used in this study increased the plant growth. Nickel in applied concentrations had no significant reduction in plant dry weight but increased the photosynthetic pigments. Ni increased plant flavonoids but reduced the tannins. Nickel and beta-aminobutyric acid at low concentrations, is recommended to use for greater production of secondary metabolites in Echium cultivation.DOI: http://dx.doi.org/10.3126/ijls.v9i5.12687

Response of Processing Tomato to Simulated Bromoxynil Drift Followed by In-Crop Metribuzin Application

Simulated drift rates of bromoxynil followed by an in-crop application of metribuzin were applied to processing tomato in eight field studies conducted from 2008 to 2010 in Ridgetown, Ontario, Canada, to determine if a synergistic interaction occurred due to the cumulative herbicide application. A transient synergistic response was observed 7 d after treatment (DAT) when bromoxynil drift rates of 8.5, 17, and 34 g ai ha−1were followed 3 to 5 d later by metribuzin at 250 g ai ha−1. By 28 DAT, visible injury ratings were additive for 8.5, 17, and 34 g ha−1bromoxynil followed by metribuzin treatments. However, when bromoxynil at 68 g ha−1(20% of field rate) was followed by metribuzin, a synergistic interaction was evident and remained through harvest. Based on Colby's equation there was greater visible injury than expected at 7, 14, and 28 DAT when bromoxynil at 68 g ha−1was followed by metribuzin. A corresponding synergistic reduction of plant dry weight and marketable tomato yield, compared with the nontreated control, was identified. Marketable yields were expected to be 65% of the control according to Colby's equation, but observed yield reductions were 49% when bromoxynil at 68 g ha−1was followed by metribuzin. In general, tomato plants sprayed with metribuzin after bromoxynil drift had greater injury than treatments sprayed with bromoxynil alone.

Interactions of Pectobacterium carotovorum pv. carotovorum, Xanthomonas campestris pv. carotae, and Meloidogyne javanica on the Disease Complex of Carrot

Pectobacterium carotovorum pv. carotovorum (Jones 1901) Hauben et al., Xanthomonas campestris pv. carotae (Pammel) Dowson, and Meloidogyne javanica (Treub) Chitwood are often associated with roots of carrot (Daucus carota L.) under field conditions. This study was undertaken to determine relationships between M. javanica, P. carotovorum pv. carotovorum, and X. campestris pv. carotae in the wilt and spot disease complex of carrot and how the order of inoculation of these pathogens affects disease and plant development. Inoculation of M. javanica alone caused a greater reduction in plant dry weight than did P. carotovorum pv. carotovorum and X. campestris pv. carotae. Inoculation of P. carotovorum pv. carotovorum or X. campestris pv. carotae with M. javanica caused a greater reduction in plant dry weight than inoculation of both bacteria together. Inoculation of M. javanica 15 days prior to either bacterial pathogen caused a higher reduction in plant dry weight compared to inoculation of a bacterial pathogen prior to inoculation with nematodes. P. carotovorum pv. carotovorum and X. campestris pv. carotae adversely affected nematode multiplication and galling; the effect of P. carotovorum pv. carotovorum alone was greater than that of X. campestris pv. carotae alone. The greatest reduction in nematode multiplication and galling was when P. carotovorum pv. carotovorum plus X. campestris pv. carotae were inoculated prior to inoculation with M. javanica. Wilting index was 3, on a 5 scale, when P. carotovorum pv. carotovorum was inoculated alone. Bacterial spot index was also 3, on a 5 scale, when X. campestris pv. carotae was inoculated alone. When P. carotovorum pv. carotovorum and X. campestris pv. carotae were inoculated together or inoculated with M. javanica, the indices were 5. Inoculation of M. javanica prior to bacterial pathogens predisposes carrot plants and aggravates the severity of disease.

Arbuscular mycorrhizal fungi: potential biocontrol agents against the damaging root hemiparasite Pedicularis kansuensis?

Spatial expansion of root hemiparasitic Pedicularis kansuensis in Bayanbulak Grassland of Xinjiang Uygur Autonomous Region (China) has caused great loss of herbage yield and has threatened the local livestock industry. Current management practices using manual eradication and chemical control have been proved problematic. Arbuscular mycorrhizal (AM) fungi have been suggested to be potential biocontrol agents against a number of plant pests, but experimental evidence is lacking against weedy P. kansuensis. In this study, we tested the hypothesis that inoculation with AM fungi will cause growth depression in P. kansuensis and reduce its damage to host plants. Based on the confirmation of AM status and host community of the hemiparasite in the field, a pot cultivation experiment was conducted to test the influence of an AM fungus (Glomus mosseae) on growth of P. kansuensis and the parasitized host (Elymus nutans). AM colonization was observed in roots of P. kansuensis, but the levels were much lower than those of its adjacent host species. A negative correlation between AM levels and the numbers of haustoria was detected for the field samples of the hemiparasite. Strong suppression of haustorium formation, a significant reduction in plant dry weight (DW), as well as marked reduction in the survival rate of P. kansuensis after inoculation with AM fungi was observed. In contrast, inoculation with G. mosseae increased root DW and whole plant DW of parasitized host plants. Our findings demonstrated significantly repressive effects of AM fungi on growth performance of P. kansuensis with and without the presence of a host. The potential of AM fungi as biocontrol agents against the damaging hemiparasite was confirmed.

Differences in Flood-Stress Tolerance among Sprout Soybean Cultivars

In this study, the response of 22 soybean cultivar sprouts to flooding stress was investigated. After sprouts were subjected to flooding stress for 10 days at the V4-V5 growth stages, their dry weights were compared. All plants were kept in a greenhouse under natural light conditions, an average daytime temperature of <TEX>$35.6{\pm}5.3^{\circ}C$</TEX> and an average nighttime temperature of <TEX>$18.2{\pm}1.7^{\circ}C$</TEX>. Soybeans were grown in a concrete bed filled with silt loam soil. Subjecting plants to flooding stress resulted in a large reduction in plant dry weight, plant height, number of nodes, and number of leaves. Cultivars differed significantly in their responses to flooding stress, as indicated by these characteristics (p<0.05). Soybean cultivars were classified into three groups based on their degree of flood tolerance: strong, moderate, and weak. Hannamkong, Namhaekong, Sobaegnamulkong, and Sorogkong had strong tolerance for flood conditions. Tawonkong, Pureunkong, Eunhakong, Myeongjunamulkong, Doremikong, Saebyeolkong, Paldokong, Sowonkong, Pungsannamulkong, Dagikong, Dachaekong, and Anpyeongkong had weak tolerance for flood conditions.

Crop Response to Carryover of Mesotrione Residues in the Field

Two field residue studies were conducted from 2005 to 2007 in Simcoe, Ontario, Canada, to evaluate the effects of mesotrione soil residues on injury, plant dry weight, and yield of sugar beet, cucumber, pea, green bean, and soybean and to verify the potential of reducing a 2-yr field-residue study (conventional residue carryover) to a 1-yr field study (simulated residue-carryover study) by growing these crops in soil treated with reduced rates of mesotrione applied in the same year. There was a significant difference in mesotrione carryover between 2006 and 2007 and differences between years can be explained by differences in soil pH and soil moisture. The conventional and the simulated residue-carryover studies successfully measured mesotrione persistence and rotational crop sensitivity. Both studies showed that sugar beet was the most-sensitive crop with injury, plant dry weight reduction, and yield loss because of mesotrione residues as high as 100%. Green bean was the next most-sensitive crop to mesotrione residues followed by pea, cucumber, and soybean. The simulated residue-carryover study provided a more-rigorous test of rotational crop sensitivity to mesotrione residues than the conventional residue-carryover study, especially at higher rates for the more-sensitive crops. For the other crops, responses to mesotrione residues were similar between the conventional and simulated residue-carryover studies.

Time of Application of &amp;lt;i&amp;gt;S&amp;lt;/i&amp;gt;-Metolachlor Affects Growth, Marketable Yield and Quality of Carrot and Red Beet

Tolerance of carrot and red beet to s-metolachlor at three application timings—pre-emergence to crop (PRE), early postemergence (crop at two to four leaf stage-EPOST), and late postemergence (crop at five to seven leaf stage-LPOST) —was determined from 2008 to 2010. LPOST applications of s-metolachlor reduced carrot above ground plant dry weight, marketable yield and grower payment, but did not affect carrot length. PRE and LPOST applications of s-metolachlor reduced red beet above ground plant dry weight, total marketable yield, yield of No. 2 and No. 3 red beet, and grower payment. Our findings indicate that while carrot may be tolerant to PRE applications of s-metolachlor, applications made after the 5 leaf stage reduced plant dry weight enough to impact marketable yield and grower payment. In red beet, the potential reduction in growth, yield and grade would not justify the utility of a PRE or LPOST applica- tion timing.

Onion and Weed Response to Mustard (Sinapis alba) Seed Meal

Weed control in organic onion production is often difficult and expensive, requiring numerous cultivations and extensive hand weeding. Onion safety and weed control with mustard seed meal (MSM) derived from Sinapis alba was evaluated in greenhouse and field trials. MSM applied at 110, 220, and 440 g m−2 severely injured onions and reduced onion stand by 25% or more when applied from planting to the one-leaf stage of onions in greenhouse trials. MSM derived from mustard cultivars ‘IdaGold’ and ‘AC Pennant’ reduced plant dry weight of redroot pigweed with an effective dose that provided 90% weed control (ED90) of 14.5 and 3.2 g m−2, respectively, in greenhouse trials, whereas the ED90 of MSM from a low-glucosinolate cultivar ‘00RN29D10’ was 128 g m−2, suggesting that glucosinolate content and ionic thiocyanate (SCN−) production contribute to phytotoxicity of MSM. In field trials, weed emergence, onion injury, and onion yield were recorded following single or three sequential applications of MSM from 1.1 to 4.5 MT ha−1 beginning at the two-leaf stage of onions in 2008, 2009, and 2010. By 8 wk after treatment (WAT), onion injury following MSM sequential applications was 10% or less in all 3 yr. Combined over 2008 and 2009, 48 and 68% fewer weeds emerged 3 WAT with MSM at 2.2 and 4.5 MT ha−1, respectively. In 2010, MSM at 2.2 and 4.5 MT ha−1 reduced the number of weeds emerged 4 WAT by 91 and 76%, respectively. MSM treatment did not significantly affect onion yield or size in 2008 and 2009, but in 2010 onion total yield was reduced by 29% by three sequential applications of MSM at 2.2 MT ha−1. MSM has potential to be used as a weed-suppressive amendment in organic production systems, but the risk of crop injury is substantial.

Effect of arbuscular mycorrhizal fungi and phosphorus concentration on plant growth and phenols in micropropagated Aloe vera L. plantlets

The objective of this work was to investigate the effect of two arbuscular mycorrhizal fungi (AMF) and different phosphorus (P) concentrations on growth and phenolic concentration inAloe vera L. plantlets obtained from micropropagation. Plantlets were multiplied in vitro, acclimatized and inoculated with Glomus claroideum or Glomus fasciculatum at three P concentrations, that is, 0.3, 0.6 or 0.9 mM P. After 90 days in ex vitro, plant height, number of leaves, mycorrhization percent, fresh and dry weight, and total phenol, flavonol and flavanone concentrations in leaves was determined. Inoculating A. vera plantlets with G. fasciculatum reduced plant fresh and dry weight compared to the plants inoculated with G. claroideum or left uninoculated. The concentration of flavonols and flavanones increased whenA. vera plantlets were inoculated with both AMF with the largest increase found in G. fasciculatum. Mycorrhization percent decreased with increased P and the concentration of flavanones was lower in plants fertilized with 0.9 mM P than in those with 0.3 or 0.6 mM P. Key words: Flavonols, flavanones, Glomus claroideum, Glomus fasciculatum, total phenol concentration.

Responses of ectomycorrhizal American elm (Ulmus americana) seedlings to salinity and soil compaction

American elm (Ulmus americana) seedlings were either non-inoculated or inoculated with Hebeloma crustuliniforme, Laccaria bicolor and a mixture of the two fungi to study the effects of ectomycorrhizal associations on seedling responses to soil compaction and salinity. The seedlings were grown in the greenhouse in pots containing non-compacted (0.4 g cm−3 bulk density) and compacted (0.6 g cm−3 bulk density) soil and subjected to 60 mM NaCl or 0 mM NaCl (control) treatments for 3 weeks. All three fungal inocula had similar effects on the responses of elm seedlings to soil compaction and salt treatment. In non-compacted soil, ectomycorrhizal fungi reduced plant dry weights, root hydraulic conductance, but did not affect leaf hydraulic conductance and net photosynthesis. When treated with 60 mM NaCl, ectomycorrhizal seedlings had several-fold lower leaf concentrations of Na+ compared with the non-inoculated plants. Soil compaction reduced Na+ leaf concentrations in non-ectomycorrhizal plants and decreased dry weights, gas exchange and root hydraulic conductance. However, in ectomycorrhizal plants, soil compaction had little effect on the leaf Na+ concentrations and on other measured growth and physiological parameters. Our results demonstrated that ECM associations could be highly beneficial to plants growing in sites with compacted soil such as urban areas.

Severity of Verticillium Wilt, Plant Growth, and Spectral Reflectance Indices of Chile Pepper Under Periodic Flooding and No-flooding Conditions

Verticillium wilt, caused by Verticillium dahliae, is an economically important disease on chile pepper (Capsicum annuum L.), which is grown primarily under furrow and drip irrigation in New Mexico. Field observations by producers indicate that Verticillium wilt is more prevalent on chile pepper grown under drip irrigation than under furrow irrigation. To test these observations, chile pepper plants at the six- to eight-leaf stage inoculated or noninoculated with V. dahliae were subjected to either periodic flooding or no-flooding conditions in the greenhouse. Plants under periodic flooding were subjected to three events of 7 day flooding and two events of no flooding over a period of 5 weeks. Differences among treatments were assessed using disease severity, plant dry weight, and spectral reflectance-based physiological indices such as moisture stress index (MSI), chlorophyll-based difference index, water band index, and photochemical reflectance index (PRI). There was a significant interaction between flooding and inoculation with respect to disease severity (P &lt; 0.003). In plants inoculated with V. dahliae and subjected to periodic flooding, the relative treatment effect (RTE) based on disease severity was increased from 40% to 130% relative to noninoculated plants subjected to no flooding. However, under conditions of no flooding, RTE increased by ≈200% to 286% when plants were inoculated with V. dahliae relative to noninoculated plants. In general, periodic flooding and inoculation with V. dahliae were accompanied by a decrease in plant dry weight as well as in the level of spectral reflectance-based physiological indices. In noninoculated plants subjected to periodic flooding, plant dry weight was reduced by ≈45% to 50% relative to noninoculated plants subjected to no flooding. In plants inoculated with V. dahliae and subjected to periodic flooding, reduction in plant dry weight was ≈46% to 60% relative to noninoculated plants subjected to no flooding. Under conditions of no flooding, plant dry weight was reduced by ≈33% to 52% when plants were inoculated with V. dahliae relative to noninoculated plants. Of all the spectral reflectance-based physiological indices, PRI was the most affected by flooding and inoculation. For noninoculated plants, the mean area under the curve for PRI (AUC-PRI) was decreased by ≈90% under periodic flooding relative to no flooding. In plants inoculated with V. dahliae and subjected to periodic flooding, reduction in AUC-PRI was ≈93% relative to noninoculated plants subjected to no flooding. Under conditions of no flooding, AUC-PRI was reduced by ≈93% when plants were inoculated with V. dahliae relative to noninoculated plants. These results showed that chile pepper growth and physiology were affected similarly by flooding and inoculation with V. dahliae. However, severity of Verticillium wilt was greater under no-flooding than under periodic flooding conditions.

Glyphosate-Resistant and -Susceptible Soybean (Glycine max) and Canola (Brassica napus) Dose Response and Metabolism Relationships with Glyphosate

Experiments were conducted to determine (1) dose response of glyphosate-resistant (GR) and -susceptible (non-GR) soybean [Glycine max (L.) Merr.] and canola (Brassica napus L.) to glyphosate, (2) if differential metabolism of glyphosate to aminomethyl phosphonic acid (AMPA) is the underlying mechanism for differential resistance to glyphosate among GR soybean varieties, and (3) the extent of metabolism of glyphosate to AMPA in GR canola and to correlate metabolism to injury from AMPA. GR50 (glyphosate dose required to cause a 50% reduction in plant dry weight) values for GR (Asgrow 4603RR) and non-GR (HBKC 5025) soybean were 22.8 kg ae ha-1 and 0.47 kg ha-1, respectively, with GR soybean exhibiting a 49-fold level of resistance to glyphosate as compared to non-GR soybean. Differential reduction in chlorophyll by glyphosate was observed between GR soybean varieties, but there were no differences in shoot fresh weight reduction. No significant differences were found between GR varieties in metabolism of glyphosate to AMPA, and in shikimate levels. These results indicate that GR soybean varieties were able to outgrow the initial injury from glyphosate, which was previously caused at least in part by AMPA. GR50 values for GR (Hyola 514RR) and non-GR (Hyola 440) canola were 14.1 and 0.30 kg ha-1, respectively, with GR canola exhibiting a 47-fold level of resistance to glyphosate when compared to non-GR canola. Glyphosate did not cause reduction in chlorophyll content and shoot fresh weight in GR canola, unlike GR soybean. Less glyphosate (per unit leaf weight) was recovered in glyphosate-treated GR canola as compared to glyphosate-treated GR soybean. External application of AMPA caused similar injury in both GR and non-GR canola. The presence of a bacterial glyphosate oxidoreductase gene in GR canola contributes to breakdown of glyphosate to AMPA. However, the AMPA from glyphosate breakdown could have been metabolized to nonphytotoxic metabolites before causing injury to GR canola. Injury in GR and non-GR canola from exogenous application of AMPA was similar.