Incidence Of Stem Rot Disease Research Articles

Evaluation of Tebuconazole 6% FS against Collar Rot, Stem Rot and Root Rot Disease Complex in Groundnut

Groundnut regarded as “king of oil seed crops” is an economic important food legume and edible oilseed crop in India, which severely suffers from soil borne diseases of groundnut, collar rot (Aspergillus niger), stem rot (Sclerotium rolfsii) and root rot (Rhizoctonia solani) causing major havoc causes significant economic losses. The field experiments were conducted to find out the efficacy of Tebuconazole 6% FS as a seed treatment fungicide against collar rot, stem rot and root rot diseases complex in ground nut during Rabi 2014-15 and Rabi 2015-16. The treatment Tebuconazole 6% FS @ 4.0 ml/10 kg and Tebuconazole 6% FS @ 5.0 ml/10 kg of seeds were found be the best treatments for seed germination, root and shoot length in during both the seasons.During first season, Tebuconazole 6% FS @ 5.0 ml/10 kg of seeds and Tebuconazole 6% FS @ 4.0 ml/10 kg of seeds were recorded 1.77 and 2.14 per cent collar rot incidence, 3.07 and 4.23 per cent stem rot disease incidence and 4.93 and 5.05 per cent root rot disease incidence, respectively. Similarly during second season, Tebuconazole 6% FS @ 5.0 ml/10 kg of seeds and Tebuconazole 6% FS @ 4.0 ml/10 kg of seeds were recorded 1.89 and 2.06 per cent collar rot incidence, 4.05 and 5.13 per cent stem rot incidence and 5.74 and 5.94 per cent root rot incidence, respectively. The highest pod yield was obtained from seed treatment with Tebuconazole 6% FS @ 5.0 ml/10 kg of seeds i.e. 20.22 q/ha and 20.10 q/ha during first and second season, respectively and Tebuconazole 6% FS @ 4.0 ml/10 kg of seeds recorded 20.12 q/ha and 20.00 q/ha of pod yield during first and second season, respectively.

Correlation of the Effect of Native Bioagents on Soil Properties and Their Influence on Stem Rot Disease of Rice

Soil is a crucial component for plant growth, as it provides water, nutrients, and mechanical support. Various factors, such as crop cultivation, microflora, nutrient addition, and water availability, significantly affect soil properties. Maintaining soil health is important, and one approach is the introduction of native organisms with multifaceted activities. The study evaluates the effects of introducing these microbes (Trichoderma asperellum strain TAIK1, Bacillus cabrialesii strain BIK3, Pseudomonas putida strain PIK1, and Pseudomonas otitidis strain POPS1) and their consortium, a combination of four bioagents, on soil health, plant growth, and the incidence of stem rot disease caused by Sclerotium oryzae in rice. Upon treatment of soil with the consortium of the four native bioagents mentioned above through seed treatment or soil application, variations/increases in the chemical properties of the soil were observed, viz., pH (8.08 to 8.28), electrical conductivity (EC) (0.72 to 0.75 d S m−1), organic carbon (OC) (0.57 to 0.68 %), available soil nitrogen (SN) (155 to 315 kg/ha), soil phosphorus (SP) (7.87 to 24.91 kg/ha), soil potassium (SK) (121.29 to 249.42 kg/ha), and soil enzymes (urease (0.73 to 7.33 µg urea hydrolyzed g−1 soil h−1), acid and alkaline phosphatase (0.09 to 1.39 and 0.90 to 1.78 µg of p-nitrophenol released g−1 soil h−1), and dehydrogenase (0.14 to 16.44 mg triphenyl formazan (TPF) produced g−1 soil h−1)), compared to untreated soil. Treatment of seeds with the consortium of four native bioagents resulted in a significant increase in plant height (39.16%), the number of panicles (30.29%), and average grain yield (41.36%) over control plants. Under controlled conditions, the bioagent-treated plants showed a 69.37% reduction in stem rot disease. The findings of this study indicate a positive correlation between soil properties (pH, EC, OC, SN, SP, SK, and soil enzymes) and plant growth (shoot and root length, fresh and dry weight) as well as a highly negative association of soil properties with stem rot disease severity. The results suggest that using native bioagents as a management strategy can control stem rot disease and enhance crop productivity, while reducing reliance on chemical management. These findings provide valuable insights into the development of sustainable agricultural practices that maximize productivity by minimizing negative environmental impacts, which promotes soil health, plant growth, and disease management.

Dissection of the Genetic Basis of Resistance to Stem Rot in Cultivated Peanuts (Arachis hypogaea L.) through Genome-Wide Association Study.

Peanut (Arachis hypogaea) is an important oilseed and cash crop worldwide, contributing an important source of edible oil and protein for human nutrition. However, the incidence of stem rot disease caused by Athelia rolfsii poses a major challenge to peanut cultivation, resulting in significant yield losses. In this study, a panel of 202 peanut accessions was evaluated for their resistance to stem rot by inoculating plants in the field with A. rolfsii-infested oat grains in three environments. The mean disease index value of each environment for accessions in subsp. fasitigiate and subsp. hypogaea showed no significant difference. Accessions from southern China displayed the lowest disease index value compared to those from other ecological regions. We used whole-genome resequencing to analyze the genotypes of the accessions and to identify significant SNPs associated with stem rot resistance through genome-wide association study (GWAS). A total of 121 significant SNPs associated with stem rot resistance in peanut were identified, with phenotypic variation explained (PVE) ranging from 12.23% to 15.51%. A total of 27 candidate genes within 100 kb upstream and downstream of 23 significant SNPs were annotated, which have functions related to recognition, signal transduction, and defense response. These significant SNPs and candidate genes provide valuable information for further validation and molecular breeding to improve stem rot resistance in peanut.

Deciphering the mechanism of Trichoderma spp. consortia possessing volatile organic compounds and antifungal metabolites in the suppression of Sclerotium rolfsii in groundnut

Groundnut, one of the oilseed crops is severely infected with necrotropic pathogen Sclerotium rolfsii, incurring huge economic loss to farmers. In the present study, the microbial volatiles (mVOCs) produced by six different Trichoderma spp. was tested for its in vitro efficacy against S. rolfsii IS (BDI)-8 infecting groundnut. Among the six isolates, Trichoderma longibrachiatum T (SP)-20 exhibited the maximum percentage inhibition (84.44%) followed by T (AR)-10 (75.44%) and TNAU TA (75.33%) in dual culture assay against S. rolfsii. Besides, volatiles of T. longibrachiatum T (SP)-20 and T. asperellum T (AR)-10 effectively reduced the mycelial growth of S. rolfsii by 61.11 and 54.44% respectively in paired plate assay. Co culturing of Trichoderma spp. with S. rolfsii produced specific antimicrobial mVOCs viz., Isolongifolan-7-ol and Trans-sesquisabinene hydrate, which could induce plant growth promotion and inhibited the growth of S. rolfsii. Application of consortia of Trichoderma longibrachiatum T (SP)-20 + Trichoderma asperellum T (AR)-10 as seed treatment at 4 g/kg and soil application at 50 g/pot before sowing and at 30 DAS (Days After Sowing), along with mahua oil cake as soil application at 100 g/pot recorded least stem rot disease incidence of 11.34% in pot culture. Besides, upregulation of a novel antifungal metabolite 6-pentyl-2H-pyran-2-one (6-PP) was also noticed in groundnut through GC-MS analysis. Thus, it is concluded that microbial volatiles and metabolites from Trichoderma spp. play an important role in resistance to S. rolfsii in groundnut.

Incidence of stem rot disease of groundnut in relation to weather parameters in major groundnut growing areas of Telangana

Groundnut (Arachis hypogaea L.) is an important oilseed crop and the economic production of groundnut is constrained by soil-borne diseases. Stem rot, caused by the necrotrophic fungus Sclerotium rolfsii, was the most common soil-borne disease in groundnut. A roving survey was conducted in major groundnut growing areas of Telangana during kharif 2019 and rabi 2019-20 to collect a preliminary data of the incidence level and pattern of prevalence of the stem rot disease. The district of Warangal has the highest incidence of stem rot. The lowest incidence of stem rot was found in Telangana's Wanaparthy and Nagarkurnool districts. Disease incidence was correlated with weather parameters, during Kharif-2019, temperature, relative humidity and rainfall showed positive correlation, whereas evaporation showed negative correlation, during Rabi-2019-20, temperature, relative humidity and evaporation showed positive correlation and rainfall showed negative correlation. This study provided an elementary idea about the per cent disease incidence as well as paved the path for developing ecosystem specific management strategy to reduce impact of soil borne diseases of groundnut in different districts of Telangana.

Combined Application of Trichoderma longibrachiatum T(SP)-20 and Trichoderma asperellum T(AR)-10 in the Management of Stem Rot of Groundnut

Background: Sclerotium rolfsii is a soil borne notorious pathogen widely affecting pulses, vegetables, oil seeds, flowers and ornamentals recording high yield loss. In groundnut it causes stem rot. The current study is focused towards management of S. rolfsii using combined application of Trichoderma spp. under field condition. Methods: Twenty-five isolates of Trichoderma spp. were screened initially against the stem rot pathogen through dual culture method. The effective Trichoderma spp. again assessed by agar well diffusion method and their secondary metabolites were identified using GC-MS. Result: From the 25 isolates, T. longibrachiatum and T. asperellum were inhibitory to the growth of S. rolfsii. The isolate T(SP)-20 of T. longibrachiatum showed 84.44% inhibition of mycelial growth of pathogen followed by T(AR)-10 of T. asperellum (75.55%). The major compounds present in GC-MS analysis of T. longibrachiatum and T. asperellum are 2-Tricosenoic acid (3.29%), Hexadecane (3.12%) and Phenol (27.18%), 2, 6, 10-Trimethyltridecane (3.44%) respectively. At field level combined application of effective T. longibrachiatum and T. asperellum excelled well in reducing stem rot disease incidence (82.67%) when compared to individual species.

THE EFFECT OF ANTAGONIST PLANTS IN SUPPLYING THE PROGRESS OF THE EVENT OF GANODERMA SP ROOT DISEASE

Activity Testing the Effect of Antagonist Plants in Suppressing the Development of Incidence of Root Rot Disease Ganoderma sp. aims to determine the effect of antagonist plants in suppressing the development of stem rot disease incidence of Ganoderma sp. in oil palm nurseries. The study used a randomized block design with 7 treatments, namely Ganoderma+ginger isolate, Ganoderma+turmeric isolate, Ganoderma+lemongrass isolate, Ganoderma+temulawak isolate, Ganoderma+garut isolate, Ganoderma isolate and control. Each treatment with 5 replications with 2 sample plants. The parameters observed were the development of disease incidence through symptoms, height and number of leaf midribs of oil palm seedlings. The data were analyzed using the SPSS program. The effect of the treatment was analyzed by using fingerprints. If there is a treatment that has a significant effect, further tests are carried out with Duncan's Multiple Distance Test (DMRT) with a level of : 0.05. Based on the test results, it was found that the incidence of Ganoderma stem rot disease was the fastest, highest and most developed in each observation, namely in the treatment using ginger and lemongrass antagonists. While the lowest incidence of disease was found in the treatment of arrowroot, turmeric and temulawak. These antagonist plants have exudate containing antibiotics that can inhibit the growth of the Ganoderma fungus. The development of oil palm seedling plant height is strongly influenced by the physical properties of the soil and the presence of Ganoderma pathogens. While the Ganoderma pathogen did not affect the development of the number of leaf midribs, but only caused changes in leaf color such as necrosis.

EFFECT OF THE COMBINED APPLICATION OF MANURE COMPOST AND Trichoderma sp. ON PRODUCTION PARAMETERS AND STEM ROT DISEASE INCIDENCE OF SHALLOT

Manure compost is a type of organic fertilizer derived from animal feces. Even though compost has a slow-release nature, it can be a good alternative to chemical fertilizers. The addition of Trichoderma sp. as a decomposer microorganism can accelerate nutrient availability. The objective of this study was to determine the effect of the combined application of different types of manure compost and doses of Trichoderma sp. on the growth performance, yield as well as stem rot disease incidence of shallot (Allium cepa L. var. aggregatum). The study was carried out using a split-plot design (P 0.05) with the types of manure compost as the main plot with five levels (no compost, cattle manure, chicken manure, goat manure, and petrogenic compost), and different doses of Trichoderma as subplots with three levels (no Trichoderma, 200 kg ha-1, and 400 kg ha-1). In general, the combined application of manure compost and Trichoderma significantly increased growth performance and yield of shallot compared to no compost (B0) and Trichoderma (T0). However, no differences were observed between manure compost and the addition of Trichoderma. Growth performance of shallots grown in soil amended with cattle manure compost was better compared to the other treatments. The use of 5 t ha-1 cattle manure compost combined with 400 kg ha-1 Trichoderma increased yield by 10.02 t ha-1 and reduced stem rot diseases incidence by 0.67%.

Pengaruh dekomposisi Trichoderma virens pada berbagai jenis kompos kotoran ternak untuk menekan penyakit busuk pangkal batang bawang merah

Palu Valley shallot production is still very low namely 5.31 tonnes/ha when compared to national production which reaches 9.7 tonnes/ha, this is due to the attack of the base stem rot disease caused by Fusarium oxsyporum f.sp. cepae. This study aims to determine the effect of various types of organic fertilizer decomposed by Trichoderma virens on the incidence of stem rot disease and shallot yields. The research was conducted at the Laboratory of Pests and Plant Diseases, Faculty of Agriculture, Tadulako University, and shallot planting in Oloboju Village, Sigi Biromaru District, Sigi Regency, Central Sulawesi Province and lasted from March 2018 to August 2018. This research used a Randomized Block Design (RBD) with five treatments consisting of, without organic fertilizer (B0), cow manure 10 tons/ha + Trichoderma virens 100g/L (B1), chicken manure 10 tons/ha + T. virens 100g/L (B2), goat manure 10 tons/ha + T. virens 100g/L (B3), and petrogenic 5 tons/ha+ T. virens 100g/L (B4). The results showed that the use of 10 tons/ha cow manure decomposed by T. virens (B1) can reduce the intensity of stem rot disease on the Palu Valley shallot which is 5.61% to be 1.88% (3rd week) and 2.89% to be 0.98% (7th week), and increase shallot yield from 4.09 tons/ha to be 7.48 tons/ ha.

Selenium (Se) reduces Sclerotinia stem rot disease incidence of oilseed rape by increasing plant Se concentration and shifting soil microbial community and functional profiles

Sclerotinia stem rot (SSR), a soil-borne plant disease, cause the yield loss of oilseed rape. Selenium (Se), a beneficial element of plant, improves plant resistance to pathogens, and regulates microbial communities in soil. Soil microbial communities has been identified to play an important role in plant health. We studied whether the changes in soil microbiome under influence of Se associated with oilseed rape health. SSR disease incidence of oilseed rape and soil biochemical properties were investigated in Enshi district, “The World Capital of Selenium”, and soil bacterial and fungal communities were analyzed by 16S rRNA and ITS sequencing, respectively. Results showed that Se had a strong effect on SSR incidence, and disease incidence inversely related with plant Se concentration. Besides, soil Se enhanced the microbiome diversities and the relative abundance of PGPR (plant growth promoting rhizobacteria), such as Bryobacter, Nitrospirae, Rhizobiales, Xanthobacteraceae, Nitrosomonadaceae and Basidiomycota. Furthermore, Soil Se decreased the relative abundance of pathogenic fungi, such as Olpidium, Armillaria, Coniosporium, Microbotryomycetes and Chytridiomycetes. Additionally, Se increased nitrogen metabolism, carbohydrate metabolism and cell processes related functional profiles in soil. The enrichment of Se in plants and improvement of soil microbial community were related to increased plant resistance to pathogen infection. These findings suggested that Se has potential to be developed as an ecological fungicide for biological control of SSR.

Streptomyces sp. RP1A-12 mediated control of peanut stem rot caused by Sclerotium rolfsii

Sclerotium rolfsii Sacc. is a destructive soilborne fungal pathogen with a wide host range that includes peanuts. Biological control offers an interesting alternative to fungicides for sustainable management of soilborne diseases. The current investigation is aimed at evaluating one potential biocontrol agent Streptomyces sp. RP1A-12 for growth promotion and the management of peanut stem rot disease caused by S. rolfsii under field conditions. Preliminary studies conducted under in vitro and the greenhouse conditions showed promising results against the stem rot pathogen. Further in vitro and pot experiments conducted to assess Streptomyces sp. RP1A-12 for its growth promoting abilities using whole organisms have shown an increase in seed germination, root and shoot length. Other parameters like nodule number and plant biomass were also significantly increased over control treatments indicating that the test bioagent possesses growth promoting abilities along with disease suppression capabilities. Subsequently field studies were carried out for two consecutive rainy seasons. The bioagent was applied as whole organism and partially purified crude metabolites. Results indicate the bioagent reduced stem rot disease incidence by 64–67% and 22–49% respectively in two field trials conducted with notable increase in yield. Partially purified Streptomyces sp. RP1A-12 metabolites exhibited an even greater effect in reducing the incidence and severity of stem rot compared to the pathogen inoculated control.

Isolation, characterization and comparative analysis of plant-associated bacteria for suppression of soil-borne diseases of field-grown groundnut in Vietnam

Groundnut (Arachis hypogaea L.) is an important oil seed crop worldwide and used extensively for feed and food. In Vietnam, groundnut cultivation is hampered by several soil-borne fungal pathogens, in particular Sclerotium rolfsii. To develop sustainable measures to control stem rot disease caused by S. rolfsii, plant-associated bacteria were isolated from the stem base and roots of groundnut plants grown in farmer fields in central Vietnam and tested for activity against S. rolfsii. Among a total of 3,360 randomly selected bacterial isolates, only thirteen (0.4%) inhibited hyphal growth of S. rolfsii. BOX-PCR and 16S-rDNA sequence analyses revealed that these bacterial isolates were genetically diverse and belonged to three bacterial Phyla, i.e. the γ-Proteobacteria (Pseudomonas), Firmicutes (Bacillus) and Bacteroidetes (Chryseobacterium). Nethouse and field experiments conducted in central Vietnam showed that treatment of groundnut seeds or field soil with strains of each of these three bacterial genera significantly reduced the incidence of stem rot disease, led to significant yield increases of up to 21% and did not have adverse effects on nodulation. The level of disease protection provided by the bacterial strains was similar to that achieved by the fungicide tebuconazole. Comparative analysis of the biocontrol efficacy of the indigenous Pseudomonas strain R4D2 with that of two exogenous, antagonistic Pseudomonas strains from the Netherlands showed that in field trials the indigenous strain R4D2 better colonized the roots of groundnut, reduced stem rot (S. rolfsii), black collar rot (Aspergillus niger), and bacterial wilt (Ralstonia solanacearum), and more consistently enhanced groundnut yield.

Ozonation Efficacy in the Treatment of Soil-Borne Phytophthora sojae in Cultivating Soybeans

Ozonation was studied for inactivating Phytophthora sojae, a predominant soybean pathogen that causes root and stem rot, and pre-and post-emergence soybean damping-off. Typically, fungicides are used to treat soils to control the damage from P. sojae to soybean production. An environmentally friendly method of ozonation was studied for inactivating P. sojae, a model Phytophthora pathogen that affects a wide range of high-value crops. Assays of artificially inoculated soil samples with P. sojae were treated with different doses of gaseous ozone. This study showed that a dosage of 0.47 g.kg-1 O3 in the soil totally prevented root and stem-rot disease incidence by P. sojae. The findings of this research clearly indicate that ozonation is an efficient alternative to chemical fungicides in the inhibition of Phytophthora diseases in the soil, hence a balancing feedback loop reinforcing the soil system as natural capital.

Biology and biocontrol of Sclerotinia sclerotiorum (Lib.) de Bary in oilseed Brassicas

Sclerotinia sclerotiorum (Lib.) de Bary is a necrotrophic plant pathogen infecting over 500 host species including oilseed Brassicas. The fungus forms sclerotia which are the asexual resting structures that can survive in the soil for several years and infect host plants by producing ascospores or mycelium. Therefore, disease management is difficult due to the long term survivability of sclerotia. Biological control with antagonistic fungi, including Coniothyrium minitans and Trichoderma spp, has been reported, however, efficacy of these mycoparasites is not consistent in the field. In contrast, a number of bacterial species, such as Pseudomonas and Bacillus display potential antagonism against S. sclerotiorum. More recently, the sclerotia-inhabiting strain Bacillus cereus SC-1, demonstrated potential in reducing stem rot disease incidence of canola both in controlled and natural field conditions via antibiosis. Therefore, biocontrol agents based on bacteria could pave the way for sustainable management of S. sclerotiorum in oilseed cropping systems.

A possibility of chitinolytic bacteria utilization to control basal stems disease caused by Ganoderma boninense in oil palm seedling

The utilization of chitinolytic bacterial isolates Enterobacter sp. KR05, Enterobactercloacae LK08, Bacillus sp. BK13, Enterobacter sp. BK15, and Bacillus sp. BK17 to control basal stem rot disease caused by Ganoderma boninense in oil palm seedling was studied. Antagonistic assay of chitinolytic bacterial isolates to G. boninense was conducted in minimum salt medium agar with 2% colloidal chitin as sole carbon source. To examine ability of the isolates in reducing basal stem rot disease incidence, the 3 to 4 months old of oil palm seedlings were treated by pouring oil palm seedling growing media with chitinolytic bacterial isolates a day prior infestation of G. boninense spores. The result showed that all chitinolytic isolates inhibited the growth of G. boninense in vitro. Hyphal abnormalities that is, dwarf, tiny, curled, twisted and bulby hyphae were observed after antagonistic assay. All chitinolytic isolates were able to reduce the disease incidence on the oil palm seedling to some extent. The isolates might infest into the oil palm seedling root as endophytes. Key words: Antagonistic assay, chitinolytic bacteria, Ganoderma boninense, hyphal abnormality, oil palm.

Effects of seeding rate and plant density on sclerotinia stem rot incidence in canola

Sclerotinia stem rot (Sclerotinia sclerotiorum Lib. deBary) affects canola wherever it is grown. Seeding rates, which are believed to affect the microclimate beneath the canopy, were evaluated for their impact on sclerotinia stem rot incidence. A study with five seeding rates (2.2 kg/ha, 3.3 kg/ha, 6.7 kg/ha, 13.3 kg/ha and 20.0 kg/ha) and four canola cultivars chosen for their variation in canopy structure and lodging resistance was conducted in Carman, Manitoba, Canada, in 2001 to 2003. A significant relationship between sclerotinia stem rot disease incidence (DI) and seeding rate was found. With an increase in seeding rate, the DI was significantly increased in the mean of the canola cultivars, and individually, only in the lodging-prone cultivar AC Excel. Lodging significantly increased for all cultivars when seeding rates exceeded the standard 6.7 kg/ha. Multiple regression analysis revealed that both plant density and lodging explain the majority of the variation in DI. Both plant density and lodging resistance varied in having a larger influence on DI depending on the year and cultivar analysed. Our results indicate that increasing seeding rate does modify the microenvironment and increases the potential for lodging, which may be responsible for plant-to-plant spread of this disease.

Stem rot disease incidence on faba beans in an artificially infested field

Stem rot, a destructive fungal disease caused by Sclerotinia trifoliorum Eriksson, is a serious problem for many important crops including faba beans (Vicia faba L.). Field experiments were carried out for five consecutive years in northern Greece to study the period of infection of S. Trifoliorum and the disease incidence in faba beans grown in a field that was artificially infested by placing various numbers of fungal sclerotia into the soil during the sowing period. Disease severity was very low (< 4%) in all growing seasons, whereas a high percentage of infection (13.3 to 95.0%) was observed under controlled environment. Apothecial production in the field occurred from November to early January. Symptoms of fungal infection on faba bean plants were observed from early February to early April, with the most infection occurring during March. Faba bean plants were infected by mycelium, after myceliogenic germination of sclerotia, at the base of the stem close to the soil surface. Visible, water-soaked lesions appeared before flower initiation. Disease severity was not significantly correlated with monthly rainfall (r = 0.11) nor with mean monthly temperature (r = 0.15) over five growing seasons. The growth stage of plants and the absence of an energy source during ascospore release, as well as the mode of sclerotial germination (myceliogenic), may have been the critical factors responsible for the low disease severity in the field.

Row Orientation and Seeding Rate on Yield, Grade, and Stem Rot Incidence of Peanut with Subsurface Drip Irrigation1

Abstract A 2-yr study was conducted on a Tifton loamy sand (fine-loamy, kaolinitic, thermic Plinthic Kandiudults) soil near Sasser, GA during the 2001 and 2002 growing seasons to determine the effects of three plant row orientations (single, twin, and multi-row) and two plant populations on the pod yield, market grade, and stem rot disease incidence of peanut when irrigated with subsurface drip irrigation (SDI). Seeds were planted at the recommended rate [20 seeds/m; 1.0R (recommended rate)] and half the recommended rate (10 seeds/m; 0.5R). Plots were irrigated daily to replace estimated daily evapotranspiration (ETa). Twin row orientation had the highest pod yield with 5407 kg/ha compared with the other row orientations, which averaged 4897 kg/ha. Market grade (total sound mature kernels, TSMK) for the twin and diamond row orientation was 1% point higher (74.7%) compared with the single row orientation. Pod yield was 8.5% greater for the 1.0R seeding rate compared with the 0.5R seeding rate. Stem rot incidence was highest in the single row orientation and lowest in the diamond row orientation. Within the three row orientations, kernel size distribution characteristics showed jumbo kernels had mixed percentages, with medium and ones showing no differences. The 1.0R plant population did have 4.4 % more jumbo kernels than the 0.5R plant population. This study indicates that twin row orientation and planted at the recommended rate (1.0R) had the best pod yield and market grade compared with single row orientation when irrigated with SDI.

Comparison of Drip and Sprinkler Irrigation Systems for Applying Metam Sodium and Managing Stem Rot on Potato.

Drip and sprinkler systems were compared for effectiveness as preplant metam sodium chemigation systems and conduciveness to late-season development of stem rot disease on potato. Sclerotia of Sclerotium rolfsii were used in a bioassay to test efficacy of metam sodium treatments. Drip application of metam sodium (532 liters/ha, 32.8% a.i.) through lines at 7 cm of depth in preformed beds (depths from bed top unless stated otherwise) killed all test sclerotia at 15-, 30-, or 46-cm depths. Drip application of the metam sodium through drip lines at 41 or 46 cm of depth resulted in 0 to 17 or 68 to 80% survival, respectively, of test sclerotia at 15 cm of depth; but all the sclerotia at 30 or 46 cm of depth were killed. Compared with the drip applications, sprinkler chemigation with metam sodium generally treated beds less effectively (8 to 100% of sclerotia survived at 15 cm, 62 to 100% at 30 or 46 cm). On flat ground, drip and sprinkler chemigation (metam sodium, 560 liters/ha) performed equally (4, 37, and 77% survival at 15-, 45-, and 75-cm depths, respectively). After potato planting and artificial soil infestation with S. rolfsii (5 to 6 weeks before harvest), subsurface drip-irrigated plots (line depth of 41 or 46 cm) had lower incidence of stem rot disease at harvest (13 to 23% on tubers) than that in sprinkler plots (56 to 62%). The low incidence of disease was associated with relatively dry surface soil. Subsurface drip chemigation with metam sodium in preformed plant beds does not consistently eradicate S. rolfsii sclerotia near the upper bed surface but, in an arid climate, it is less conducive than sprinkler irrigation to development of stem rot disease of potato.