Root Yield Loss Research Articles

Artificial Neural Network Model for Predicting Carrot Root Yield Loss in Relation to Mechanical Heading

Modelling and predicting agricultural production processes have high cognitive and practical values. Plant growth, the threat of pathogens and pests, and the structure of agricultural machinery treatments are mostly non-linear, measurable processes that can be described mathematically. In this paper, a multiple regression analysis was carried out in the first step to check the non-linearity of the data and yielded a coefficient of determination of R2 = 0.9741 and the coefficient of determination corrected for degrees of freedom was R2adj = 0.9739. An artificial neural network model, called CH-NET, is then presented to predict the yield loss of carrot roots by leaving root mass in the field during harvest at the mechanical heading stage. The proposed network model has an architecture consisting of an input layer, three hidden layers with 12 neurons each, and an output layer with one neuron. Twelve input criteria were defined for the analysis and testing of the network, eight of which related to carrot root parameters and four to the heading machine. The training, testing, and validation database of the CH-NET network consisted of the results of field trials and tests of the operation of the patented (P.242097) root heading machine. The proposed CH-NET neural network model achieved global error (GE) values of 0.0931 t·ha−1 for predicting carrot root yield losses for all twelve criteria adopted. However, when the number of criteria is reduced to eight, the error increased to 0.0991 t·ha−1. That is, the prediction was realised with an accuracy of 90.69%. The developed CH-NET model allows the prediction of economic losses associated with root mass left in the field or contamination of the raw material with undercut leaves. The simulations carried out showed that minimum root losses (0.263 t·ha−1) occur at an average root head projection height of 38 mm and a heading height of 20 mm from the ridge surface.

Green Synthesized of Thymus vulgaris Chitosan Nanoparticles Induce Relative WRKY-Genes Expression in Solanum lycopersicum against Fusarium solani, the Causal Agent of Root Rot Disease.

Fusarium solani is a plant pathogenic fungus that causes tomato root rot disease and yield losses in tomato production. The current study's main goal is testing the antibacterial efficacy of chitosan nanoparticles loaded with Thyme vulgaris essential oil (ThE-CsNPs) against F. solani in vitro and in vivo. GC-MS analysis was used to determine the chemical constituents of thyme EO. ThE-CsNPs were investigated using transmission electron microscopy before being physicochemically characterized using FT-IR. ThE-CsNPs were tested for antifungal activity against F. solani mycelial growth in vitro. A pot trial was conducted to determine the most effective dose of ThE-CsNPs on the morph/physiological characteristics of Solanum lycopersicum, as well as the severity of fusarium root rot. The relative gene expression of WRKY transcript factors and defense-associated genes were quantified in root tissues under all treatment conditions. In vitro results revealed that ThE-CsNPs (1%) had potent antifungal efficacy against F. solani radial mycelium growth. The expression of three WRKY transcription factors and three tomato defense-related genes was upregulated. Total phenolic, flavonoid content, and antioxidant enzyme activity were all increased. The outfindings of this study strongly suggested the use of ThE-CsNPs in controlling fusarium root rot on tomatoes; however, other experiments remain necessary before they are recommended.

Differential response to the South American rice water weevil (Coleoptera: Curculionidae) damage of rice cultivars with contrasting levels of resistance: implications for field management.

Oryzophagus oryzae (Costa Lima) (Coleoptera: Curculionidae) is a major pest of flooded rice paddies throughout South America, and species with very similar life histories are present in many rice-producing regions of the world (collectively rice water weevils, RWWs). The damage caused by RWW larvae on rice cultivars with contrasting levels of resistance ('BRS Pampa CL'= 'Pamp': susceptible, 'BRS Atalanta'='Atal': resistant-antibiosis) was evaluated in two consecutive years in the field under seven infestation levels: 0, 2, 4, 6, 8, 10 and 20 adult couples per cage with plants. Higher densities of adults increased the number of leaf-feeding scars and larvae on roots, respectively, at the rate ≤2.14 and 2.75 in Pamp and 2.23 and 2.48 in Atal, with the total number of larvae generated being lower in Atal. Grain yield was negatively impacted with increasing larval density on the roots, mainly by decreasing root volume and the number of grains per panicle. Root injury intensity and yield loss showed a nonlinear relationship. It was found that significant yield losses occurred with 8.37 larvae per plant in Pamp and 9.80 larvae per plant in Atal CONCLUSION: The results provided the first evidence of a tolerance limit for RWW larval damage that, even though similar between cultivars of contrasting resistance, corresponds to twice the current conventional level for larval control in Brazil. We also discuss here the potential of applying tolerance limits to manage the RWW adult population in rice fields. © 2022 Society of Chemical Industry.

Risk factors associated with cassava brown streak disease dissemination through seed pathways in Eastern D.R. Congo.

Vegetatively propagated crops are particularly prone to disease dissemination through their seed systems. Strict phytosanitary measures are important to limit the impact of diseases as illustrated by the potato seed system in Europe. Cassava brown streak disease (CBSD) is a devastating disease caused by two viral species collectively named cassava brown streak viruses (CBSVs). CBSD can cause substantial root yield losses of up to 100% in the worst affected areas and is easily transmitted through stem cuttings. In Eastern and Central Africa, the epidemiology of CBSVs in the local socio-economical context of production remains poorly known while a better understanding would be an asset to properly manage the disease. This lack of information explains partially the limited efficiency of current regulatory schemes in increasing the availability of quality seed to smallholders and mitigating the spread of pests and diseases. This study surveyed the epidemiology of CBSVs in Uvira territory, Eastern D.R. Congo, and its drivers using a multivariate approach combining farmer’s interview, field observation, sampling and molecular detection of CBSVs. Investigation on the epidemiology of CBSD revealed that three clusters in the study area could be identified using five most significant factors: (i) symptoms incidence, (ii) number of whiteflies, (iii) types of foliar symptoms, (iv) cutting’s pathways and (v) plant age. Among the three clusters identified, one proved to be potentially interesting for seed multiplication activities since the disease pressure was the lowest. Through risk assessment, we also identified several key socio-economic determinants on disease epidemy: (i) factors related to farmer’s knowledge and awareness (knowledge of cassava pests and diseases, knowledge of management practices, support from extension services and management strategies applied), (ii) factors related to the geographical location of farmer’s fields (proximity to borders, proximity to town, distance to acquire cuttings), as well as (iii) the pathways used to acquire cuttings.

African cassava whitefly and viral disease management through timed application of imidacloprid

Cassava whitefly are a group of cryptic species within the Bemisia tabaci sensu lato complex that causes significant damage to cassava in Africa. B. tabaci Sub-Saharan Africa 1 (SSA1) is the major species in the study region which transmits plant-virus diseases to cassava and causes direct feeding damage. Benefits from management of cassava viral diseases through deployment of resistant varieties are being undermined by their susceptibility to B. tabaci SSA1 and the problem is exacerbated by high populations of B. tabaci in cassava fields. To develop a clean seed system that is disease-free, the judicious use of insecticides is required to manage this pest and vector. This study evaluated the effect of timing of insecticide application on controlling B. tabaci SSA1 population abundance and damage to cassava. Field trials were carried out between 2017 and 2018 in Kamuli and Wakiso districts of Uganda using the widely available insecticide Imidacloprid. Three cassava cultivars (NAROCASS1, SAUTI, KBH/2002/026) were planted in a randomized complete block trial design replicated three times. The insecticide was applied in split-plots designated as: (i) no protection (NP), no insecticide applied (control), (ii) early protection (EP), insecticide applied 2 times between 0 and 4 months after planting, (iii) long protection (LP), insecticide applied 3 times between 0 and 8 months after planting, and (iv) total protection (TP), insecticide applied 4 times between 0 and 12 months after planting. Except for control plots, stem cuttings were first dipped into a diluted solution of Imidacloprid prior to planting. Bi-monthly data were collected on the B. tabaci population, feeding damage, cassava mosaic disease and cassava brown streak disease. Stem cuttings and root yields were determined at harvest. The marginal rate of return for each treatment was calculated to determine cost effectiveness. Insecticide application effectively reduced B. tabaci populations, feeding damage and disease spread. Cassava yield differed significantly with insecticide treatment and amongst cultivars. Root and stem yield losses of >60% was recorded in unprotected control plots. The marginal rate of return of the early protection (0–4 MAP) program was 163%. We discuss these findings and the implication for judicious use of insecticides as part of a cassava clean seed system.

Management of Meloidogyne incognita on Cucumber with a New Nonfumigant Nematicide Fluopimomide.

Cucumber (Cucumis sativus L.) is an economically important vegetable crop in China. Southern root-knot nematode (Meloidogyne incognita) is a significant obstacle in cucumber production, causing severe root damage and yield losses. Moreover, resistance development to fosthiazate, and poor mobility of abamectin, have led to failure to control this nematode. It is of great interest to growers and the vegetable industry to explore novel nonfumigant nematicides that can provide adequate control in an environmentally friendly manner. Fluopimomide (FM), a new chemical having a similar structure to fluopyram, was shown to exhibit toxic effects on fungi and nematodes. The efficacy of FM to reduce infection of M. incognita in cucumber was evaluated under greenhouse and field conditions. In the greenhouse, FM at all test rates resulted in a 22.5 to 39.6% and 31.3 to 55.0% reduction in the population density of M. incognita in the soil at 30 and 60 days after treatment (DAT), respectively, compared with the nontreated control. FM at 500 and 750 g ha-1 reduced (P < 0.05) root galling, meanwhile increasing plant height compared with the nontreated control at 30 and 60 DAT. In the field trials, FM at 500 and 750 g ha-1 decreased the population density of M. incognita and root galling 57.2 to 69.9% compared with the untreated control, while enhancing cucumber yield in two consecutive years. Furthermore, FM at 500 g ha-1 combined with fosthiazate was the most effective treatment showing a synergistic effect on reducing population densities of M. incognita, which was significantly greater than either FM or fosthiazate by themselves. In summary, FM has considerable potential for managing M. incognita on cucumber.

Insights into the Host Specificity of a New Oomycete Root Pathogen, Pythium brassicum P1: Whole Genome Sequencing and Comparative Analysis Reveals Contracted Regulation of Metabolism, Protein Families, and Distinct Pathogenicity Repertoire.

Pythium brassicum P1 Stanghellini, Mohammadi, Förster, and Adaskaveg is an oomycete root pathogen that has recently been characterized. It only attacks plant species belonging to Brassicaceae family, causing root necrosis, stunting, and yield loss. Since P. brassicum P1 is limited in its host range, this prompted us to sequence its whole genome and compare it to those of broad host range Pythium spp. such as P. aphanidermatum and P. ultimum var. ultimum. A genomic DNA library was constructed with a total of 374 million reads. The sequencing data were assembled using SOAPdenovo2, yielding a total genome size of 50.3 Mb contained in 5434 scaffolds, N50 of 30.2 Kb, 61.2% G+C content, and 13,232 putative protein-coding genes. Pythium brassicum P1 had 175 species-specific gene families, which is slightly below the normal average. Like P. ultimum, P. brassicum P1 genome did not encode any classical RxLR effectors or cutinases, suggesting a significant difference in virulence mechanisms compared to other oomycetes. Pythium brassicum P1 had a much smaller proportions of the YxSL sequence motif in both secreted and non-secreted proteins, relative to other Pythium species. Similarly, P. brassicum P1 had the fewest Crinkler (CRN) effectors of all the Pythium species. There were 633 proteins predicted to be secreted in the P. brassicum P1 genome, which is, again, slightly below average among Pythium genomes. Pythium brassicum P1 had only one cadherin gene with calcium ion-binding LDRE and DxND motifs, compared to Pythium ultimum having four copies. Pythium brassicum P1 had a reduced number of proteins falling under carbohydrate binding module and hydrolytic enzymes. Pythium brassicum P1 had a reduced complement of cellulase and pectinase genes in contrast to P. ultimum and was deficient in xylan degrading enzymes. The contraction in ABC transporter families in P. brassicum P1 is suggested to be the result of a lack of diversity in nutrient uptake and therefore host range.

Comparison of Common Vetch Plant Growth, Arsenic and Nutrients Uptakes in the Clean and Arsenic-Contaminated Soils

ABSTRACT Common vetch plant (Vicia sativa L.) growth under various arsenic (As) loads was investigated in the clean (1st year cultivation) and As-contaminated soils (2nd year cultivation). The total dry weight (DW) of common vetch gradually increased by the application of low concentration of As-contaminated irrigation waters (IWs) while the decrease of total DW to lower than the control plant at high As loads was observed. Compared with the control plant, the aboveground biomass yield loss was 7.6% and 61.6% in the 1st and 2nd cultivation years, respectively. The root dry (RDW) loss was about 36% in the 2nd cultivation year while the 1st year crop root yield loss was 56.5%. In the 1st cultivation year crops, the root As amount was about 1.8–1.9 fold higher than in the shoots while it reached to about 4–11 fold in the 2nd year crops. Although, common vetch might be defined as a highly tolerant plant to As in the clean soil, results demonstrated that the As tolerance of plant could decline when the usage of As-contaminated IWs for a prolonged time. Application of As-contaminated waters for a long time caused the changes of macro (N, P, Ca, Mg, and K) and microelements (Fe, Mn, Cu, Zn) transportation from the root to aboveground biomass.

FIELD EVALUATION OF BIOLOGICAL CONTROL AGENTS AND CALCIUM-BASED FERTILIZERSTO CONTROL PLASMODIOPHORA BRASSICAE IN BROCCOLI (BRASSICA OLERACEA VAR.ITALICA)

ABSTRACT Broccoli plants are frequently attacked by the biotrophic pathogen Plasmodiophora brassicae, which leads to continuous significant economic losses during its cultivation. Finding environmentally friendly methods to control this aggressive pathogen is a priority. Here, broccoli plants were sown in a field that has been previously reported with a high incidence of the pathogen showing dramatic root damage and yield loss. Field evaluations were performed to evaluate lump weight, root weight, and lump diameter after soil application with Trichoderma spp., Bacillus sp., humic acids, commercial plant defense elicitor, calcium carbonate (CaCO3), and calcium nitrate (Ca(NO3)2). Treatments were applied individually and in combination during two continuous and independent production seasons (rainy and dry seasons) in the year 2018.In summary, the application of CaCO3 increased the lump weight by 25% respective to its control, but only during thedry season. Moreover, the best treatment giving a consistent increase in lump weight (20% to 50% compared to its non-treated control depending on the season) was the combination of all treatments (biological and calcium-based fertilizers) when tested during both seasons. Taking all together, it was found some alternatives that increased the production of broccoli in fields infested with Plasmodiophora brassicae. These alternatives will be validated in the future in different soil types and agricultural environments.

Single nucleotide polymorphism‐based haplotypes associated with Meloidogyne javanica resistance in Brazilian soybean germplasm

AbstractThe root‐knot nematode (RKN) species Meloidogyne javanica (MJ) causes substantial root damage and yield loss in susceptible soybean [Glycine max (L.) Merr.] cultivars. In this study, a genome wide association study (GWAS) was undertaken to identify genomic regions controlling RKN resistance in a soybean association‐mapping panel, using single nucleotide polymorphism (SNP) markers and haplotype information. This study was carried out with a sample (n = 124) from the Coodetec soybean gene bank, including some commercial Brazilian varieties. For the phenotypic evaluations MJ inoculum was obtained from roots of cultivar CD 206, a highly susceptible soybean used to maintain MJ for studies at Coodetec. The cultivars CD 208 and BRS CONQUISTA were used as resistant checks while CD 206, R7, and Nidera NA 5909 RG were used as susceptible checks and all 124 lines were genotyped with 6,000 SNP markers. MJ resistance determinants in the soybean panel were linked to SNPs with significant effects, with nine SNPs distributed along chromosomes 7, 13, and 20. The observed average MJ resistance in the group of soybean entries with haplotype GCT, ACC, ACT, and GCC in the markers Gm20_44446670_G_A, Gm13_29739984_C_A and Gm07_8166605_T_C, respectively, represents moderately resistant genotypes. Gm13_29739984_C_A and Gm07_8166605_T_C discriminated resistant and susceptible cultivars better than the marker Gm20_44446670_G_A. These results are particularly promising for soybean‐breeding programs, by not only identifying new resistance‐associated haplotypes, but also suggesting new genetic mechanisms in RKN‐resistance sources.

Storage root yield response to leaf harvest of improved and local cassava varieties in DR Congo

ABSTRACT Although cassava is usually grown for its starchy roots, cassava leaves are an important vegetable and protein source in sub-Saharan countries. Eleven cassava mosaic disease (CMD) tolerant and two susceptible varieties were planted in six trials; leaves were harvested at 4, 8 and 11 months after planting (MAP) and storage roots were harvested at 12 MAP. Edible leaf and storage root dry matter yields were strongly affected by variety and interacted with location. Edible leaf yields ranged from 209 to 435 kg ha−1 DM among varieties. Storage root yields ranged from 2540 to 9250 kg ha−1 DM among locations and from 2470 to 7550 kg ha−1 among varieties. Leaf harvest caused 15.8% storage root yield loss. Susceptible varieties produced lowest edible leaf (209 kg ha−1) and storage root (2530 kg ha−1) yields in all locations. Improved varieties suffered storage root yield reductions of 5–25.8%, equivalent to 400–1550 kg ha−1. Edible leaf yield and storage root yield were not correlated. Variety TME419 produced the highest average storage root yields in 3 of 6 locations. The three best leaf producing varieties were not among the best storage root producers, indicating an incompatibility of the two production objectives.

Identification of additional /novel QTL associated with resistance to cassava green mite in a biparental mapping population.

Cassava green mite [CGM, Mononychellus tanajoa (Bondar)] is the most destructive dry-season pest in most cassava production areas. The pest is responsible for cassava fresh root yield losses of over 80%. Deployment of CGM resistant cultivars is the most cost-effective and sustainable approach of alleviating such production losses. The purposes of this study were to validate the stability of CGM resistance genes found in previously published results, to identify new genes for CGM resistance in bi-parental mapping population and estimate the heritability of the trait. A total of 109 F1 progeny derived from a cross between CGM resistant parent, TMEB778 and a very susceptible parent, TMEB419 were evaluated under CGM hotspot areas in Nigeria for two cropping seasons. A total of 42,204 SNP markers with MAF ≥ 0.05 were used for single-marker analysis. The most significant QTL (S12_7962234) was identified on the left arm on chromosome 12 which explained high phenotypic variance and harboured significant single nucleotide polymorphism (SNP) markers conferring resistance to CGM and leaf pubescence (LP). Colocalization of the most significant SNP associated with resistance to CGM and LP on chromosome 12 is possibly an indication of a beneficial pleiotropic effect or are physically linked. These significant SNPs markers were intersected with the gene annotations and 33 unique genes were identified within SNPs at 4 – 8MB on chromosome 12. Among these genes, nine novel candidate genes namely; Manes.12077600, Manes.12G086200, Manes.12G061200, Manes.12G083100, Manes.12G082000, Manes.12G094100, Manes.12G075600, Manes.12G091400 and Manes.12G069300 highly expressed direct link to cassava green mite resistance. Pyramiding the new QTL/genes identified on chromosome 12 in this study with previously discovered loci, such on chromosome 8, will facilitate breeding varieties that are highly resistant CGM.

Impact of shade-net intensities on root yield and quality of Asparagus racemosus: A viable option as an intercrop

The impact of shade net intensity on plant growth and on the yield components root yield, time of root harvest and shatavarin IV content in roots of shatavari were observed. The plants were grown under different green shade net intensity (SNI) (0, 25, 50, 75 and 90%) and harvested at three different times (06, 12 and 18 months of transplanting). The maximum number of stems/plants, stem weight, root length, root diameter, fresh root weight and dry root weight were observed under 0% SNI followed by 25% SNI. Shatavarin IV content in roots was higher all plants raised under all SNIs as compare to 0% SNI (open field conditions) however, it was maximum (8.53 μg g−1) in plants under 25% SNI. Total chlorophyll and carotenoids content were increased with increase in SNIs. Maximum root yield gain was observed at twelve months after transplanting (TP) as compared to six and eighteen months of harvesting. This study indicates that shatavari could be cultivated as an intercrop (25% SNI) for fetching higher shatavarin IV content without causing significant root yield loss.

Economic Evaluation of Rainwater Harvesting and Conservation (RWHC) Technologies for Sweet Potato Cultivation in Sierra Leone

A field trial was conducted to evaluate the economic performance of rainwater harvesting and conservation (RWHC) technologies for sweet potato cultivation in Sierra Leone during five intensive cropping seasons (2014 second – 2016 second cropping season) at the on-station research site of the Njala Agricultural Research Centre. The experiment was laid out in a randomized complete block design in three replications following a factorial combination of two levels of mulch (no mulch and mulch) and three levels of RWH structures (open ridge, tied ridge and arch ridge). Six RWHC technologies evaluated: open ridge without mulch (OR-M), open ridge with mulch (OR+M), tied ridge without mulch (TR-M) and tied ridge with mulch (TR+M), arch ridge without mulch (AR-M) and arch ridge with mulch (AR+M). Profitability (gross margin, net income and breakeven), investment (NPV, IRR and BCR) and sensitivity analyses (25% root yield loss and 10% fall in the market price of sweet potato roots) were used to evaluate the economic performance of the RWHC techniques. The TR+M (SLL 2,091,280) had the highest net income followed by the AR-M (SLL 693,640) and AR+M (SLL 2,218,160) RWHC technologies. The traditional OR-M was not profitable (SLL -2,487,760) for sweet potato cultivation. Based on the cost of production, the OR-M, OR+M, and TR-M RWHC technologies require a root yield increase of 50.5%, 3.0% and 35.4% to breakeven. The AR+M had the highest and positive net seasonal cash flow returns throughout the five cropping seasons. The breakeven point on the net season seasonal cash flow returns for the TR+M, AR-M and OR+M RWHC technologies was in the 2015 main cropping season. At discount rates of 10%, 15%, 20% and 25% the highest NPV was obtained from the AR+M followed by the TR+M and AR-M RWHC technologies. The highest IRR was obtained from the AR+M (111%) followed by TR+M (84%) and AR-M (61%). The AR+M, TR+M and AR-M RWHC technologies had benefit-cost ratios greater than 1. Under uncertain conditions of 25% root yield loss and 10% fall in the market price of sweet potato roots, the AR+M and TR+M are the most profitable RWHC technologies that could be invested in. These technologies should, therefore, be promoted for adoption through on-farm trials in order to enhance intensive sweet potato cultivation on upland gravelly soils in Sierra Leone.

Field Evaluation of a Binary Sex Pheromone for Sweetpotato Vine Borer (Lepidoptera: Crambidae) in Hawaii.

The sweetpotato vine borer, Omphisa anastomosalis (Guenée), is a primarily Asian pest of sweetpotato, Ipomoea batatas L. Damage by O. anastomosalis infestation can cause root yield losses of 30%–50%. A binary sex pheromone for O. anastomosalis, consisting of Type I [(10E,14E)-10,14-hexadecadienal (E10,E14-16:Ald)] and Type II [(3Z,6Z,9Z)-3,6,9-tricosatriene (Z3,Z6,Z9-23:H)] components, was identified in Vietnam from extracts of female pheromone glands. A structurally similar Type II compound [(3Z,6Z,9Z)-3,6,9-docosatriene (Z3,Z6,Z9-22:H)], not recovered from female pheromone glands, was also found to synergize the attractiveness of the Type I component. Additional field work has been needed to determine whether these synergistic enhancements of attractiveness also occur in other parts of the geographical distribution of this moth species. Herein, results of studies are reported which document that both Z3,Z6,Z9-23:H and Z3,Z6,Z9-22:H also synergistically enhance male response to E10,E14-16:Ald in Hawaii sweetpotato field populations. Trap catch tends to be enhanced with increase of dose and lower Type I:Type II ratios. Among the compound doses and ratios tested, trap catch increased with the addition of the Type II component by over 13 times relative to traps baited with the Type I component alone, which significantly enhanced sweetpotato vine borer detection. Using a 2.0 mg: 4.0 mg Type I: Type II loading, there was continued catch over 12 wk, during which time the Type I component weathered at a faster rate than the Type II component. This binary sex pheromone seems to have promise for both monitoring and suppression of field populations of O. anastomosalis throughout its geographical range.

Effect of Cassava Mosaic Disease (CMD) on Yield and Profitability of Cassava and Gari Production Enterprises in Sierra Leone

Cassava Mosaic Disease (CMD) seriously affects cassava (Samura et al., 2013; Fargette et al., 1988). There is limited information on tuberous root yield loss and the profitability of growing improved and local varieties infected with the cassava mosaic virus for tuber and gari production in Sierra Leone. The objectives of the study were to determine yield loss associated with cassava mosaic disease and conduct cost benefit analysis (budgets and break-even analysis) on cassava production using two improved varieties (SLICASS 4 and 6) compared against the local susceptible variety Cocoa, for gari production and Cocoa as a poundable enterprises for the boil and eat market. Activity 1 involved the establishment of a yield loss trial using the paired plot technique. Activity 2 assessed productivity of cassava and gari production. Data collected were analysed using the analytical frame work that incorporates the concept of gross margin analysis as describe by Brown (1979). This included cost benefit analysis (CBA), the net social benefit (NSB) or the excess of total benefit over total cost represents the net present value (NPV) and The Internal Rate of Returns (IRR).The yield loss associated with the local variety Cocoa under this system was 4.27 t/ha which is equivalent to 38.92% yield loss resulting from the cassava mosaic disease infection. SLICASS 4 and SLICASS 6 recorded positive returns to production of tubers and gari. The local variety Cocoa enterprises for gari under the same condition recorded a negative returns even in the 6 year. However Cocoa for the boil and eat market had the highest profit level. The implication of this study is that breeding effort should be geared towards high yielding mosaic resistant varieties that are poundable more profitable and suits the cultural and domestic demand of the producers, processors and consumers.

Susceptibility of Okra Accessions to Root Knot Nematode

ABSTRACTThe root knot nematode, Meloidogyne incognita (Kofoid and White) Chitwood, is an important pest of okra [Abelmoschus esculentus (L) Moench], causing root galling and yield losses in commercial and local consumption cultivars. Use of expensive, toxic nematicides needs to be replaced with genetic improvement of plants for resistance to nematodes. A study was conducted to determine pathogenicity of root knot nematode on okra accessions and their degree of resistance to the nematode. Okra accessions obtained form the National Centre for Genetic Resources and Biotechnology, Ibadan, Oyo State, Nigeria, were exposed to 0 or 5000 eggs of M. incognita per plant. Two seeds from each accession were sown in pots containing a sterilized sandy loam soil and thinned to one plant per pot before inoculation with nematodes. Data were collected on plant height, shoot weight, fruit weight, numbers of galls, and nematode population in roots and soil. Reductions in plant height due to M. incognita infection ranged from 13.69% to 75.64%, shoot weight from 13.69% and 67.24%, and fruit weight from 12.96% to 53.29%. Accessions NG/TO/JUN/09/007, NHGB/10/048, NG/AA/SEP/09/040, NHGB/09/057, and NG/SA/DEC/07/0528 were tolerant to M. incognita. Accessions CEN/009, NG/AA/SEP/09/038, NG/SA/DEC/07/498, and NHGB/09/055 were susceptible to M. incognita infection. Resistance to root knot nematode may be able to be achieved through breeding.

Citrus phytophthora diseases: Management challenges and successes

Phytophthora spp. are present in nearly all citrus groves in Florida and Brazil and phytophthora-induced diseases, especially foot and root rot, have the potential to cause economically important crop losses. Disease-related losses due to root rot are difficult to estimate because fibrous root damage and yield loss are not always directly proportional. Challenges from phytophthora diseases have been addressed in both countries by enacting phytosanitary requirements for production of pathogen-free nursery trees in enclosed structures, propagated from indexed and certified pathogen-free sources, in conjunction with several other cultural management practices. In Florida groves, a statewide soil sampling program provides growers with soil propagule counts to estimate the damage that Phytophthora spp. are causing to fibrous roots. The results can be used along with rootstock tolerance, soils, topography, irrigation, and drainage to make a decision for the need to treat with fungicides in addition to modification of cultural managements. Huanglongbing (HLB), caused by the psyllidtransmitted bacterium Candidatus Liberibacter asiaticus (Las), was detected in Brazil and Florida in the mid-2000s. Given the increasing incidence of HLB and deterioration of root density due to Las damage, research experiences and current phytophthora data trends suggest the need for more comprehensive management of root health by reducing the impact of abiotic and biotic stresses, including the interaction with Phytophthora spp.

Optimal fertilizer application for Panax notoginseng and effect of soil water on root rot disease and saponin contents

BackgroundBlind and excessive application of fertilizers was found during the cultivation of Panax notoginseng in fields, as well as increase in root rot disease incidence. MethodsBoth “3414” application and orthogonal test designs were performed at Shilin county, Yunnan province, China, for NPK (nitrogen, phosphorus, and potassium) and mineral fertilizers, respectively. The data were used to construct the one-, two-, and three-factor quadratic regression models. The effect of fertilizer deficiency on root yield loss was also analyzed to confirm the result predicted by these models. A pot culture experiment was performed to observe the incidence rate of root rot disease and to obtain the best range in which the highest yield of root and saponins could be realized. ResultsThe best application strategy for NPK fertilizer was 0 kg/667 m2, 17.01 kg/667 m2, and 56.87 kg/667 m2, respectively, which can produce the highest root yield of 1,861.90 g (dried root of 100 plants). For mineral fertilizers, calcium and magnesium fertilizers had a significant and positive effect on root yield and the content of four active saponins, respectively. The severity of root rot disease increased with the increase in soil moisture. The best range of soil moisture varied from 0.56 FC (field capacity of water) to 0.59 FC, when the highest yield of root and saponins could be realized as well as the lower incidence rate of root disease. ConclusionThese results indicate that the amount of nitrogen fertilizer used in these fields is excessive and that of potassium fertilizer is deficient. Higher soil moisture is an important factor that increases the severity of the root rot disease.

Forecasting of root damage, plant lodging and yield loss caused by western corn root worm larval feeding based on larval population density

Vorhersage von Wurzelschaden, Lagerschaden und Ertragsverlusten durch Larvenfras des Westlichen Maiswurzelbohrers auf der Grundlage der Larvenpopulationsdichte