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A B Zacaroni - One of the best experts on this subject based on the ideXlab platform.
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bacterial leaf spot of radicchio cichorium intybus is caused by xanthomonas hortorum
Plant Disease, 2012Co-Authors: A B Zacaroni, S T Koike, R M De Souza, Carolee T BullAbstract:Radicchio (Cichorium intybus) is ranked 22 among crops in Monterey County, California, with a Farm Gate Value of $19,531,000 (3). Beginning in 2002, a leaf spot disease of radicchio was observed in Monterey County. The disease began as small lesions and in some cases coalesced into larger, irregular spots. Lesions were maroon to dark brown; in some cases, the margins of brown lesions became dark maroon with aging. Each leaf spot was observable from both adaxial and abaxial leaf surfaces. Symptoms primarily occurred on the outer foliage of the heads, though on occasion the head cap leaf could develop lesions. Disease incidence in the first year resulted in up to 10% unharvested radicchio because of cap leaf infections or reduced head size if outer wrapper leaves were all removed; outbreaks in subsequent seasons were more limited. Bacteria forming yellow mucoid colonies were isolated from surface disinfested symptomatic tissue that was macerated and streaked onto sucrose peptone agar medium. Bacteria were gram negative, did not fluoresce on King's Medium B, and used esculin as a carbon source but used none of the other 48 carbon sources tested using the API 50 CH test strip. Nine isolates from symptomatic radicchio had the same DNA fragment banding pattern generated by repetitive extragenic palindromic sequence polymerase chain reactions (rep-PCR) using the BOXA1R primer. Amplicons of rpoD, dnaK, fyuA, and gyrB for multilocus sequence typing (MLST) were generated using a modification of the scheme developed by Young et al. (4) and sequenced by a commercial laboratory. Concatenated sequences of the four genes from the radicchio isolates were compared to the sequences available in the Plant Associated and Environmental Microbes Database (1). The genetic distance between the nine isolates from radicchio and pathotypes of Xanthomonas hortorum were 0.03 or less and MLST analysis indicated that radicchio isolates were members of the species X. hortorum (2). To complete Koch's postulates, freshly grown cultures were suspended in phosphate buffer and adjusted to approximately 5 × 108 CFU/ml. The inoculum was sprayed onto the undersides of leaves of 40-day-old radicchio plants (C. intybus cv. Leonardo). Plants were incubated at 100% humidity for 48 h and then moved to a greenhouse. Plants sprayed with buffer served as negative controls. For each of the two experiments conducted, there were three and six single-plant replicates per treatment. The buffer treated plants did not develop symptoms but the plants treated with isolates from radicchio developed leaf spots similar to those observed in the field with symptoms beginning to be visible after 5 days. The bacteria isolated from symptomatic tissue on inoculated plants were identical to the original strains when compared with rep-PCR, thus completing Koch's postulates. Results from the two experiments were similar. To our knowledge, this is the first report of X. hortorum causing a leaf spot disease on radicchio. The disease continues to occur sporadically on radicchio grown in coastal California. References: (1) Almeida et al. Phytopathology 100:208, 2010. (2) Bull et al. Phytopathology 101:847, 2011. (3) Lauritzen, Monterey County Crop Report, 2010; (4) Young et al. Syst. Appl. Microbiol. 31:366, 2008.
S T Koike - One of the best experts on this subject based on the ideXlab platform.
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bacterial leaf spot of radicchio cichorium intybus is caused by xanthomonas hortorum
Plant Disease, 2012Co-Authors: A B Zacaroni, S T Koike, R M De Souza, Carolee T BullAbstract:Radicchio (Cichorium intybus) is ranked 22 among crops in Monterey County, California, with a Farm Gate Value of $19,531,000 (3). Beginning in 2002, a leaf spot disease of radicchio was observed in Monterey County. The disease began as small lesions and in some cases coalesced into larger, irregular spots. Lesions were maroon to dark brown; in some cases, the margins of brown lesions became dark maroon with aging. Each leaf spot was observable from both adaxial and abaxial leaf surfaces. Symptoms primarily occurred on the outer foliage of the heads, though on occasion the head cap leaf could develop lesions. Disease incidence in the first year resulted in up to 10% unharvested radicchio because of cap leaf infections or reduced head size if outer wrapper leaves were all removed; outbreaks in subsequent seasons were more limited. Bacteria forming yellow mucoid colonies were isolated from surface disinfested symptomatic tissue that was macerated and streaked onto sucrose peptone agar medium. Bacteria were gram negative, did not fluoresce on King's Medium B, and used esculin as a carbon source but used none of the other 48 carbon sources tested using the API 50 CH test strip. Nine isolates from symptomatic radicchio had the same DNA fragment banding pattern generated by repetitive extragenic palindromic sequence polymerase chain reactions (rep-PCR) using the BOXA1R primer. Amplicons of rpoD, dnaK, fyuA, and gyrB for multilocus sequence typing (MLST) were generated using a modification of the scheme developed by Young et al. (4) and sequenced by a commercial laboratory. Concatenated sequences of the four genes from the radicchio isolates were compared to the sequences available in the Plant Associated and Environmental Microbes Database (1). The genetic distance between the nine isolates from radicchio and pathotypes of Xanthomonas hortorum were 0.03 or less and MLST analysis indicated that radicchio isolates were members of the species X. hortorum (2). To complete Koch's postulates, freshly grown cultures were suspended in phosphate buffer and adjusted to approximately 5 × 108 CFU/ml. The inoculum was sprayed onto the undersides of leaves of 40-day-old radicchio plants (C. intybus cv. Leonardo). Plants were incubated at 100% humidity for 48 h and then moved to a greenhouse. Plants sprayed with buffer served as negative controls. For each of the two experiments conducted, there were three and six single-plant replicates per treatment. The buffer treated plants did not develop symptoms but the plants treated with isolates from radicchio developed leaf spots similar to those observed in the field with symptoms beginning to be visible after 5 days. The bacteria isolated from symptomatic tissue on inoculated plants were identical to the original strains when compared with rep-PCR, thus completing Koch's postulates. Results from the two experiments were similar. To our knowledge, this is the first report of X. hortorum causing a leaf spot disease on radicchio. The disease continues to occur sporadically on radicchio grown in coastal California. References: (1) Almeida et al. Phytopathology 100:208, 2010. (2) Bull et al. Phytopathology 101:847, 2011. (3) Lauritzen, Monterey County Crop Report, 2010; (4) Young et al. Syst. Appl. Microbiol. 31:366, 2008.
R M De Souza - One of the best experts on this subject based on the ideXlab platform.
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bacterial leaf spot of radicchio cichorium intybus is caused by xanthomonas hortorum
Plant Disease, 2012Co-Authors: A B Zacaroni, S T Koike, R M De Souza, Carolee T BullAbstract:Radicchio (Cichorium intybus) is ranked 22 among crops in Monterey County, California, with a Farm Gate Value of $19,531,000 (3). Beginning in 2002, a leaf spot disease of radicchio was observed in Monterey County. The disease began as small lesions and in some cases coalesced into larger, irregular spots. Lesions were maroon to dark brown; in some cases, the margins of brown lesions became dark maroon with aging. Each leaf spot was observable from both adaxial and abaxial leaf surfaces. Symptoms primarily occurred on the outer foliage of the heads, though on occasion the head cap leaf could develop lesions. Disease incidence in the first year resulted in up to 10% unharvested radicchio because of cap leaf infections or reduced head size if outer wrapper leaves were all removed; outbreaks in subsequent seasons were more limited. Bacteria forming yellow mucoid colonies were isolated from surface disinfested symptomatic tissue that was macerated and streaked onto sucrose peptone agar medium. Bacteria were gram negative, did not fluoresce on King's Medium B, and used esculin as a carbon source but used none of the other 48 carbon sources tested using the API 50 CH test strip. Nine isolates from symptomatic radicchio had the same DNA fragment banding pattern generated by repetitive extragenic palindromic sequence polymerase chain reactions (rep-PCR) using the BOXA1R primer. Amplicons of rpoD, dnaK, fyuA, and gyrB for multilocus sequence typing (MLST) were generated using a modification of the scheme developed by Young et al. (4) and sequenced by a commercial laboratory. Concatenated sequences of the four genes from the radicchio isolates were compared to the sequences available in the Plant Associated and Environmental Microbes Database (1). The genetic distance between the nine isolates from radicchio and pathotypes of Xanthomonas hortorum were 0.03 or less and MLST analysis indicated that radicchio isolates were members of the species X. hortorum (2). To complete Koch's postulates, freshly grown cultures were suspended in phosphate buffer and adjusted to approximately 5 × 108 CFU/ml. The inoculum was sprayed onto the undersides of leaves of 40-day-old radicchio plants (C. intybus cv. Leonardo). Plants were incubated at 100% humidity for 48 h and then moved to a greenhouse. Plants sprayed with buffer served as negative controls. For each of the two experiments conducted, there were three and six single-plant replicates per treatment. The buffer treated plants did not develop symptoms but the plants treated with isolates from radicchio developed leaf spots similar to those observed in the field with symptoms beginning to be visible after 5 days. The bacteria isolated from symptomatic tissue on inoculated plants were identical to the original strains when compared with rep-PCR, thus completing Koch's postulates. Results from the two experiments were similar. To our knowledge, this is the first report of X. hortorum causing a leaf spot disease on radicchio. The disease continues to occur sporadically on radicchio grown in coastal California. References: (1) Almeida et al. Phytopathology 100:208, 2010. (2) Bull et al. Phytopathology 101:847, 2011. (3) Lauritzen, Monterey County Crop Report, 2010; (4) Young et al. Syst. Appl. Microbiol. 31:366, 2008.
M Fidelibus - One of the best experts on this subject based on the ideXlab platform.
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effect of biostimulants micronutrients hydroxy propanoic acid cytokinins and humic acid as a transplant dip and plant spray on onions
Proceedings of the 35th Annual Meeting of the Plant Growth Regulation Society of America San Francisco California USA 3-7 August 2008., 2008Co-Authors: G Boyhan, R Torrance, M FidelibusAbstract:A variety of products were tested as growth stimulants on short-day onions in the Vidalia growing region of southeastern Georgia over several years. These included 2-hydroxypropanoic acid, humic acid, cytokinin, and seaweed extracts. These products whether applied as a foliar spray or as a transplant dip did not have any affect on onion growth, yield, or graded size. In one year cytokinins (foliar or soil Triggrr) and humic acid, seaweed extracts & micronutrients (Super Shot 40 & Super PGA VII Plus) had a higher percent marketable onions after 4.5 months of controlled atmosphere (CA) (3% O2, 5% CO2, 34 deg. F.) storage compared to the untreated check. The 2-hydroxypropanoic acid treatment did not, however, differ for CA storage from the check of plain water with surfactant. These growth stimulants have been reported to have positive effects on many plants including onions in some cases, but without consistent results from one study to the next or from one year to the next these products are of marginal usefulness in onion production. INTRODUCTION Onions are an important crop in southeast Georgia where they are grown under the Vidalia trade name. Vidalia onions are short-day mild flavored sweet onions with a Farm Gate Value over $130 million in 2006 (Boatright and McKissick, 2007). Several chemical products have been marketed to onion growers with claims of increasing bulb size and yield. These include 2-hydroxypropanoic acid (Propel, Entek Corp., Brea, Calif.), 0.012% cytokinin foliar formulation (Foliar Triggrr, Westbridge Inc., Vista, Calif.) or 0.004% cytokinin soil formulation (Soil Triggrr, Westbridge Inc., Vista, Calif.), and 10% humic acids solution (Super Shot-40, CropChem, Decatur, Ill.) in combination with 4% humic acids, seaweed extracts, and micronutrient solutions (Super PGA VII Plus, CropChem, Decatur, Ill.). More recently Kelpak has been offered as having growth promoting properties in onions. This product is processed from freshly harvested seaweed (Ecklonia maxima). One of the most widely used applications of growth regulators in onions is to retard shoot growth after harvest. Application of maleic hydrazide has been shown to inhibit onion shoot growth in storage (Abdel-Rahman and Isenberg, 1974). Their work also showed that applications of abscisic acid could induce early senescence and prolong storage life. There have not been many citations of growth stimulants having effects on onions with a single citation in a trade journal (Holland, 1996). The objective of these experiments were to determine if any of several growth stimulants would have a positive effect on onion growth. These results have been previously published (Boyhan et al., 2001, 2007). MATERIALS & METHODS All experiments were arranged as randomized complete block designs with four replications. All spray treatments were applied with a backpack sprayer to runoff. All transplant dips had plants held in the treatment solution for a period of two minutes. Table 1 has a complete list of experimental treatments. RESULTS & DISCUSSION In general none of the products tested had any affect on onion growth or size (Tables 2-6, Figure 1). There was a treatment effect on variety Pegasus with humic acids and micronutrients, or cytokinins resulting in greater percent marketable bulbs after 4.5 months of controlled atmosphere storage compared to the untreated check (Table 4). The 2-hydroxypropanoic acid, however, did not differ from the untreated check (Table 4). Results of our studies do not support a benefit from the application of growth stimulants to short-day onions. Generally, growers expect to have 80% or more of their crop in the jumbo class so exogenous applications of growth stimulants, even if they worked, would be only marginally useful. Clearly, lack of positive results or variable results are of very little Value to growers. Consistent results from year to year over a wide range of environments and conditions are necessary to justify the added costs to growers. LITERATURE CITED Abdel-Rahman, M. and F.M.R. Isenberg. 1974. The role of exogenous plant regulators in the dormancy of onion bulbs. J. Agr. Sci. 82:113-116. Boatright, S.R. and J.C. McKissick. 2007. 2006 Georgia Farm Gate Vegetable Report. Coop. Ext. Serv. Area Rpt. AR-07-02 Boyhan, G., R. Hill, and D. Thigpen. 2007. Evaluation of Kelpak growth regulator effects on onion growth and yield. Ga. Onion Res.-Ext. Rpt. Coop. Res.-Ext. Publ. No. 3-2007:66-69. Boyhan, G.E., W.M. Randle, A.C. Purvis, P.M. Lewis, R.L. Torrance, D.E. Curry, and D.O. Linton. 2001. Evaluation of growth stimulants on short-day onions. HortTechnology 11:3842. Holland, S. 1996. Using plant growth regulators on onions. Onion World 12:34-35. Table 1. Treatment list, formulations, trade names, rates, application methods and timing for each experiment. Treatment Formulation Trade name Rate (fl oz/gal) Application method Application date Experiment 1, Tattnall County, Ga., 1997 1 2-hydroxypropanoic acid Propel 1.2 Foliar spray 18 Mar. 1997 2 Water Foliar spray 18 Mar. 1997 Experiment 2, Toombs County, Ga., 1997 1 2-hydroxypropanoic acid Propel 1.2 Foliar spray 18 Mar. 1997 2 Water Foliar spray 18 Mar. 1997 Experiment 3, Bamboo Farm, Savannah, Ga., 1998 1 Nothing 2 Water and surfactant Foliar spray 27 Feb. 1998 3 2-hydroxypropanoic acid Propel 1.2 Transplant dip 27 Feb. 1998 4 2-hydroxypropanoic acid Propel 1.2 Foliar spray 27 Feb. 1998 5 10% humic acid & 5% adjuvants with 4% humic acid, unspecified seaweed extracts and micronutrients Super Shot-40 and Super PGA VII Plus 1.6 0.4 Transplant dip and foliar spray 27 Feb. 1998 and as a spray every 10 days 6 10% humic acid & 5% adjuvants Super Shot-40 1.6 Transplant dip and foliar spray 27 Feb. 1998 and as a spray every 10 days 7 4% humic acid, unspecified seaweed extracts and micronutrients Super PGA VII Plus 0.4 Transplant dip and foliar spray 27 Feb. 1998 and as a spray every 10 days Experiment 4, Bamboo Farm, Savannah, Ga., 1999 Factorial Design (5 x 2) 1 Water & surfactant 2 2-hydroxypropanoic acid Propel 1.2 Foliar spray 21 Dec. 1998 3 10% humic acid and 5% adjuvants with 4% humic acid, unspecified seaweed extracts and micronutrients Super Shot-40 and Super PGA VII Plus 0.5 1.6 Transplant dip and foliar spray Dip: 21 Dec. 1998 (0.6 fl oz/gal with Super PGA VII Plus only) Spray: 22 Mar. 1999, 1 Apr. 1999, 12 Apr. 1999 4 0.004% cytokinin Soil Triggrr 0.16 Soil drench 21 Dec. 1998, 22 Mar. 1999 5 0.012% cytokinin Foliar Triggrr 0.2 Foliar spray 21 Dec. 1998, 22 Mar. 1999 Cultivars 1 Pegasus 2 Wannamaker cultivar mix Experiment 5, Vidalia Onion & Vegetable Res. Center, Lyons, Ga., 2007 1 Untreated check 2 Ecklonia maxima seaweed extract Kelpak 32 Foliar spray 24 Jan., 7 & 20 Feb. 2007 3 Ecklonia maxima seaweed extract Kelpak 64 Foliar spray 24 Jan., 7 & 20 Feb. 2007 4 Ecklonia maxima seaweed extract Kelpak 128 Foliar spray 24 Jan., 7 & 20 Feb. 2007 1.0 fl oz/gal = 7.8 mL•L Table 2. Effect of 2-hydroxypropanoic acid on yield and bulb size of short-day onions at two locations, 1997. Bulb diam Percent jumbos Yield Location/treatment (inches) (≥3 inches) (No. 50-lb bags/acre)
Ja ,chang Fung Martel - One of the best experts on this subject based on the ideXlab platform.
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Effects of extreme events on the productivity of dairy Farms
2020Co-Authors: Ja ,chang Fung MartelAbstract:The Intergovernmental Panel on Climate Change (IPCC) has estimated that by 2050, Australia will be one of the most negatively impacted regions by climate change. More frequent and severe extreme events such as heatwaves, droughts or floods present significant challenges to the productivity and profitability of climate-dependant agricultural sectors, with economic losses of up to 19%. Australian dairy regions are expected to experience greater frequency, duration and severity of extreme climatic events in the next 20 years. Thus, the primary objective of this research was to analyse the impacts of extreme heat events and other extreme climatic events on the plant and animal productivity of pasture-based dairy Farms in Australia. In the first part of this thesis, we reviewed the impact of climate change on pasture-based dairy systems with a focus on extreme climatic events. The review provides insight into current methods for assessing and quantifying the risk of heat stress impacts on pastures and animals. We found the temperature humidity index (THI) to be one of the most appropriate indicators of heat stress in dairy cattle. Adapting milking routines, calving times and introducing heat tolerant animals are some proposed strategies to reduce the incidence of animal heat stress while alternative pasture species, better adapted to heat waves and prolonged periods of water deficit, are proposed for improved pasture production in future climates. We next investiGated regional milk production losses in 99 commercial dairy Farms during a real, pervasive period of excessive heat in Australia. Using an auto-regressive time-series approach, we demonstrated that present heat events have significant detrimental effects on the milk production of dairy Farms. Cumulative regional milk production during a spring heat event in November 2009 were reduced by 3.4% in milk yield, 3.9% in energy-corrected milk and by 4.1% in terms of milk solids. AggreGated losses for the nine-day heat event were estimated at 13,000 kg milk solids, with a Farm Gate Value of AUD$65,000. This study found significant spatial variability in production losses at the regional level, providing insight into the impact of extreme heat events on the dairy industry. Such economic losses demonstrated the impact of heat stress on dairy cows as well as the need for the dairy industry to proactively implement adaptations, particularly in spring and summer, when the risk of heat events is higher. Given the importance of heat stress in dairy systems, we conducted a systematic literature review and meta-analysis to quantify the effects of heat stress on dairy cows through a relationship between dry matter intake (DMI) and THI. The review accounted for differences between countries, breeds, stage in lactation and parity. There was a significant negative correlation (r =-0.82) between THI and DMI, wherein DMI was reduced by 0.45 kg/d for every unit increase in THI. This result facilitates standardisation of heat stress and feed intake comparison across studies, including differences between countries, breeds, stage in lactation and parity. Primiparous and multiparous cows did not show significant differences in the reduction of DMI at increasing THIs. While differences in the DMITHI relationship between lactating and non-lactating cows were not significant, effects of THI on DMI were significantly different across lactation stages. We also investiGated the efficacy of cooling strategies and showed that cooling adaptations became important above THI 68, indicating that this THI could be viewed as a threshold at which cooling should be provided. Passive cooling (e.g. shading) was more effective than active strategies (e.g. fans and sprinklers) at alleviating the reduction in DMI. The meta-analysis and development of the THI-DMI relationship allows users to predict effects of heat stress across environments and animal genotypes and will be useful both from disciplinary (e.g. animal nutrition) and systems modelling perspectives. Having examined historical impacts of extreme climatic events on dairy Farms, we next evaluated the relative influence of pasture and animal heat stress on the productivity of whole dairy Farming systems and under two future climate scenarios, accounting for variation in extreme climatic events. Future climate projections were developed using monthly regional climate scaling factors based on Representative Concentration Pathway 8.5 for 2050 from 40 global circulation models. Climate projections accounted for increased frequencies of extreme events with more heatwaves, longer droughts and more extreme rainfall events than historical climates. A whole Farm systems model was used to quantify the relative effects of heat stress on pasture growth rates, animal DMI and milk production in three major dairy locations in Australia. Although contemporary systems models are well equipped to account for pasture responses to temperature, often they do not account for heat stress effects on livestock. Hence, we used the THI-DMI relationship developed in the previous chapter to account for the relative importance of animal heat stress and contrasted this to the effects of heat stress on plants that were implicit to the model outputs. We found that effects of animal heat stress on DMI and lactation were greater than the effects on the same variables caused by plant heat stress. Across sites and climate scenarios, the relative impact of animal heat stress ranged between 10-30% versus 2-15% in plants, suggesting that past modelling of the impacts of heat stress on pasture-based dairy systems may have underestimated the extent to which heat stress influenced DMI and lactation. Under future climates, effects of heat stress on pasture and animal DMI were more pronounced than under historical climates, as future climates were both hotter and drier. Relative to historical climates, lactation was reduced by 11-35% by 2050 across sites when both plant and animal heat stress were considered. This thesis provides insight into the effect of future climates on dairy systems as extreme events increase in frequency, severity and duration. Extreme heat events will challenge the productivity of temperate perennial ryegrass grazing systems by compromising pasture quality and quantity, creating a seasonal feed-supply gap on pasture-based dairy Farms. As heat events become more frequent in many regions, pasture-based dairy Farmers will be forced to adapt to remain profitable and maintain good animal welfare standards. Beneficial adaptations may include the nutritional management of dairy cows to account for the energetic and nutritional costs associated with heat stress while maintaining low metabolic heat production, planting trees for outdoor shading, and incorporating heat- and drought tolerant pasture species. Future systems modelling work should account for the impacts of heat stress on dairy cows, as this aspect can be even larger than impacts of heat stress on pastures. In addition, future experimental and modelling work of pasture-based dairy should consider the implementation of ‘animal-focused’ heat mitigation adaptations. While shading and sprinklers are beneficial in countries such as the US, where animals are confined, such strategies are not always practical in Australian pasture-based systems. Successful adaptation of future grazing systems can only be truly achieved through systematic analyses of future challenges and opportunities arising from changing climates, highlighting the need for studies such as those conducted here
