An experiment was carried out to find out the influence of such agronomic practices on severity of the disease and to seek a proper cultural practice for management late blight of potato (Phytophthora infestans). The experimental results showed that the severity of late blight disease could be minimized by reducing the depth of irrigation (i.e. ¼ of irrigation channel). It was observed that the disease severity could be minimized by increasing the row-to-row and plant-to-plant spacing (60 × 25 cm). It was also observed that when less than recommended dose of nitrogenous fertilizer (200 Kg N/ha) along with slightly more than recommended dose of phosphorus and potassium fertilizer (200 Kg P2O5/ha and 250 Kg K2O/ha) was applied, severity and spread of the disease was found to be under check. Therefore, for better management of late blight of potato the proper agronomic practices should be integrated with the application of fungicides. This will not only reduce the number of sprays but also reduces the health hazards owing to application of fungicides.

Potato is one of the key annual upland cash crops cultivated in the Jaffna District of Sri Lanka. However, potato farmers are challenged by climate extremes, increasing pest/disease loads and excessive use of agro-chemicals all of which are expected to increase in the future. To address these critical issues, a package of climate changeadaptive and eco-friendly agronomic practices that included mulching to conserve soil moisture, integrated pest management for crop protection and site-specific fertilizer management for efficient crop-soil nutrient management (adaptation package) was formulated and tested on potato (<em>Solanum tuberosum</em> L.) crops in seven farmer fields in Jaffna. The experiment was conducted in the major rainy season (Maha) of 2013/2014 and 2014/2015 and consisted of two treatments as Adaptation package (T₁) and Existing practice (T₂), which is the current farmers’ practices characterized with heavy reliance on chemical control of pests and diseases and application of inorganic fertilizers subsequent to decisions of farmer. The results revealed significant (p&lt;0.05) benefits of the above climate changeadaptive, eco-friendly agronomic package in terms of growth, yield, economic profit and environmental health of potato cultivation. Benefits of the adaptation package were greater in the drier and warmer 2014/15 Maha season, thus demonstrating its climate resilience. Therefore, the tested adaptation package can be recommended for adoption by the farmers to improve the yield of potato while promoting lower water and agro-chemical use thereby having increased resilience to climate change and improved environmental sustainability especially in the dry regions where potato is cultivated.

Potato late blight, caused by Phytophthora infestans, is one of the main diseases in potato production, causing major losses in yield. Applying environmentally harmful fungicides is the prevailing and classical method for controlling late blight, thus contaminating food and water. There is therefore a need for innovative research approaches to produce food sustainably. Here, we used a systems approach to identify sustainable management strategies for disease control in potato production in the Netherlands. We focussed not only on ecological processes, the classical approach, but also on decision-making concerning disease management. For that, we performed a literature study, stakeholder interviews and modelling using fuzzy cognitive mapping. Interviews were carried out with farmers, representatives of breeding companies and experts. The fuzzy cognitive map allows to identify major concepts and their influence on late blight management. Three management scenarios were analysed using the fuzzy cognitive map. Results show that published research on the control of potato late blight focusses on agronomic practices, plant breeding for resistance to late blight and chemical-based disease suppression. Farmers are strongly influenced by corporate (such as traders, breeders and retail) and public institutes and policies, each pushing their own objectives and interests. The fuzzy cognitive map showed that social and ecological processes are tightly related. The scenario analysis showed that increasing stakeholder cooperation and a change in market demands towards resistant cultivars could improve sustainability of late blight management. In contrast, policies restricting the use of fungicides would result in increased disease severity if no alternative strategies were implemented. Adoption of such strategies would require social-institutional support and facilitation. We conclude that our systems approach improves the understanding of the system dynamics which is necessary for developing and deploying effective strategies for controlling P. infestans.

Introduction: Selection a proper crop rotation based on environmental conservation rules is a key factor for increasing long term productivity. On the other hand, the major problem in reaching agricultural sustainability is lack of soil organic matter. Recently, a new viewpoint has emerged based on efficient use of inputs, environmental protection, ecological economy, food supply and security. Crop rotation cannot supply and restore plant needed nutrients, so gradually the productivity of rotation system tends to be decreased. Returning the plant residues to the soil helps to increase its organic matter and fertility in long-term period. Wireworms are multi host pests and we can see them in wheat and barley too. The logic way for their control is agronomic practices like as crop rotation. Wireworms’ population and damages are increased with using grasses and small seed gramineas in mild winters, variation in cropping pattern, reduced chemical control, and cover crops in winter. In return soil cultivation, crop rotation, planting date, fertilizing, irrigation and field health are the examples for the effective factors in reducing wireworms’ damage. Materials and Methods: In order to study the effect of crop rotations, residue management and yield damage because of wireworms’ population in soil, this experiment was conducted using four rotation systems for five years in Jolgeh- Rokh agricultural research station. Crop rotations were included, 1) Wheat monoculture for the whole period (WWWWW), 2) Wheat- wheat- wheat- canola- wheat (WWWCW), 3) Wheat- sugar beet- wheat- potato- wheat (WSWPW), 4) Wheat- maize- wheat- potato- wheat (WMWPW) as main plots and three levels of returning crop residues to soil (returning 0, 50 and 100% produced crop residues to soil) were allocated as sub plots. This experiment was designed as split plot based on RCBD design with three replications. After ending each rotation treatment, the field was sowed with potato cv. Agria in each plot in 2011. At the harvest time tuber yield and also percent and severity of infection was determined. All data was analyzed statistically and Duncan test was used for comparison of means. Results and Discussion: Analysis of variance results showed that, potato tuber yield was affected by the crop rotation, the rate of returning residues, and also interaction between rotation × returning residues statistically (P≤0.01).When 1000 tuber was considered, analysis of variance results showed, crop rotation had a very significant effect (P≤0.01) on number and percent of infected tubers to wireworm and its holes. The most infected tubers ie.42.34 and holed i.e. 61.4 and totally 4.24% of tubers were belonged to the rotation 2, where in the rapeseed crop was preceding plant. The least one was achieved in rotation 1, with the rates of 27, 37 and 2.8% where in potato crop was not planted previously. The most infection to wireworm was found in 100% residue returning to the soil with 3.8% and the least one in no residue returning to the soil, i.e. 3.4 %. Results showed with increasing residue returning to the soil, the damage of wireworms is increased too. Conclusion: Generally applying crop rotation using different crops and residue returning to the soil is resulted in higher potato tuber yield. This increasing rate for tuber yield was 116% and 57 % when the preceding crops were wheat and rapeseed respectively compared to the mean of rotations 3 and 4. For the aim of sustainable production of potato and reducing of wireworm damage it is necessary we focus on other crop rotation and the importance of C:N ratio and the rate of residue returning to the soil. So we need to conduct new experiments with these purposes.

Cyst-forming nematodes are a major group of plant pests of economic importance worldwide. There are well-documented cases of suppressive soils where plant-parasitic nematodes are maintained at very low population densities by one or more microorganisms that co-exist in the same environment. The role of agronomic practices in the establishment and support of soil suppressiveness offer new possibilities in the management of these pests. To test if this specific suppressiveness would evolve under a five-year monoculture of susceptible potato in soil infested with Globodera pallida Pa3 populations Chavornay and Delmsen, a microplot study was conducted. Final populations of total eggs remained similar for Delmsen but oscillated for Chavornay. Proportions of diseased eggs increased dramatically at the first year after harvest and oscillated until the fifth year, especially for Chavornay. This suggested a predator - prey relationship of the nematode and a suppressive factor. Yields of total marketable potato tubers increased in Chavornay but decreased in Delmsen. In a greenhouse experiment, females developing in these soils were examined for inherent microbial communities through PCR-DGGE and pyrosequencing. Candidate microorganisms that possibly affected the egg health status of G. pallida were identified. The dominance of the fungus Malassezia, especially M. restricta, known for its pathogenic abilities on human and animal skin, a tissue that shares structural proteins with the nematodes cuticle, warrants further investigation. To examine if susceptible crops were crucial for the successful establishment of suppressive transfer, population dynamics of Heterodera avenae and H. filipjevi were monitored in microplots amended with a nematode suppressive oat monoculture soil and cropped to susceptible cereal hosts during four years. Although no effect of the amendment was detected on H. avenae or H. filipjevi population densities, or in plant growth and yield parameters, percentage of diseased eggs increased up to 65.5% under the third cropping season, and yield was almost not constrained compared to the non-infested control plots. This suggested that the monoculture of susceptible crops was sufficient to induce and support the establishment of suppressive factors. In a climate chamber experiment, the suppressive potential of the oat monoculture and two soils from intensive cereal cropping systems (one from conventional, one from organic farming) was tested against H. avenae female populations. Results of this experiment indicated a suppressive potential of the monoculture and intensive cereal cropping soils. Furthermore, a high similarity in suppressive potential and microbial communities between organic and conventional farming soils suggested a stronger effect of the cropping rather than the farming system. It was tested if tolerant sugar beet cultivars permit soil suppressiveness to establish by allowing some reproduction of the primary parasite, necessary for the increase of antagonists. Population dynamics and egg health status of Heterodera schachtii Schach0 and Schach1 were monitored under a four-year sugar beet monoculture of susceptible, resistant and tolerant genotypes. Pasteuria nishizawae and Dactylella oviparasitica were included in this study, as representative model organisms for an obligate bacterial parasite and a facultative antagonist, respectively. The ability of D. oviparasitica and P. nishizawae to suppress the populations of H. schachtii was inconsistent, compared to the corresponding controls. However, irrespective of the treatment and the cultivar, eggs became soon diseased, so by the third cropping cycle, diseased eggs represented over 90% of the total eggs. As expected, in each cropping season the tolerant genotype yielded the highest in both pathotypes. The presence of nematode-controlling factors in this monoculture of susceptible, resistant and tolerant sugar beet cultivars, that may be responsible for the dramatic increase of diseased eggs, was suggested. Findings of these studies proportionate baseline data that complement the evidence of the potential of agronomic practices to induce and support the establishment of soil suppressiveness. In this study, monoculture or intensive cropping of susceptible host crops, and cultivation of resistant and tolerant host genotypes, supported the development of soil suppressive factors against different cyst-nematodes mostly in increased proportions of diseased eggs.

Planting depth and intra row spacing are among the important agronomic practices in potato seed production. However, farmers in Ethiopia often use haphazard planting depth and intra row spacing, which contributes to the low yield. Thus, the study was conducted to assess the effect of planting depth and intra row spacing on growth, seed tuber yield and quality of potato under Holetta condition, during 2015 off growing season. Four levels planting depth (12cm, 15cm, 18cm and 21cm) and intra row spacing (15cm, 20cm, 25cm and 30cm) were combined in 4x4 factorial arrangements and laid out in randomized complete block design with three replications. Data were collected on growth, seed tuber yield and physical quality parameters and analyzed using SAS Version 9.0 statistical software. Results revealed that both the main and interaction effect of planting depth and intra row spacing significantly (P< 0.05) influenced most parameters studied except for main stem number, specific gravity and dry matter content. Deeper planting (21cm) delayed emergence, flowering and physiological maturity by about 6.16, 8.76 and 8.08 days, respectively, and plant height decreased by 3.67cm compared to planting depth of 12cm. Similarly, heaviest average tuber weight and high number of large sized tubers were gained from depth of 21cm while depth of 18cm resulted in higher a verge tuber yield. Plants grown at intra row space of 30cm took significantly longest days to flower and physiological maturity and the shortest in plant height than those grown intra row spacing of 15cm. The average tuber yield per hill, average tuber weight, large sized tuber number and yield produced at intra row spacing of 30cm is significantly (P<0.05) higher than those obtained from intra row spacing of 15cn by 33.37,23.16,47.64 and 36.67 %, respectively. The interaction of 18cm x30cm depth and intra row spacing resulted in highest average number of tubers while combination of closer intra row (15cm) with deeper (21cm) and shallow depth (12cm) resulted in the lowest one. The highest number and yield of total and marketable tuber number and yield were harvested at the interaction of 18cm x 15cm depth. Whereas, the lowest marketable number and yield of tubers was obtained from the shallow depth (12cm) combined with wider intra row spacing (30cm). Similarly, potato planted at 18cm x15cm depth and intra row spacing resulted in maximum number and yield of under, small and medium sized tubers. In conclusion, most studied yield and quality parameters of the tested variety had superior response to interaction effect of 18cm x 15cm, 15cmx15cm and 18x20cm depth and intra row spacing. Therefore, planting depth of 15cm and 18cm combined with intra row of 15and 20cm can be used as preliminary information for further investigation of high marketable and better quality seed tuber yield. However, the present study was done only for one season at one location; it would be advisable to repeat the experiment for more number of years and locations to come up with comprehensive recommendations

Retaining crop residue is an important agronomic practice in sustainable agriculture, particularly to maintain soil organic carbon (SOC). To evaluate the effect of the retention of different types of crop residues on SOC and labile fractions, a long-term rice-based crop rotation experiment was established with five different winter cropping practices: (1) rice-fallow (RF), (2) rice–wheat (RW), (3) rice–potato with rice straw mulch (RP), (4) rice–green manure (Chinese milk vetch; RG), and (5) rice–oilseed rape (RO). The results showed that the annual rice yields in the RP, RO, RG, and RW treatments were not significantly different from each other, but 13.3%, 10.2%, 10.3%, and 8.4% higher, respectively, than in the RF treatment. Furthermore, the soil properties in the RP system improved significantly compared with those at the initiation of the study, with increases of 14.7% in total N, 17.5% in total P, 77.2% in available K, and 13.9% in SOC content. Considering the slight rice yield increase and superiority in the annual net income, the RP treatment seems to be a promising rotation system to meet the sustainability requirements for the agro-ecosystem. The responses of the labile SOC fractions (i.e., microbial biomass C (MBC), dissolved organic C (DOC), hot-water extractable C (HWC), permanganate-oxidizable C (KMnO4-C), and particulate organic C in the 0–20cm layer) to the crop rotation systems with the retention of different crop residues over the period of 11 years were specific to the types of the rotation system and closely related to the soil fertility properties. The RP treatment had comparatively higher content of DOC, HWC, MBC, and KMnO4-C than the other treatments in both 0–10cm and 10–20cm depths. The RW treatment had higher KMnO4-C content but lower MBC and POC content than the other treatments. The RO treatment had lower MBC content compared to the other treatments, while the opposite results were found in the RG treatment. Furthermore, the DOC content was improved by the winter crop growth. The changes in labile SOC might be attributable to the types of residues retained.

Citrus is economically important fruit crop grown throughout Ethiopia at small and commercial scales. However, citrus production and productivity in many parts of Ethiopia is seriously threatened by leaf and fruit spot disease. This disease has been reported to cause high yield and quality losses on citrus. Nevertheless, limited information have been available on the etiology of the causal pathogen and epidemiology of the disease. Therefore, surveys and laboratory works were conducted to assess the distribution, incidence and severity of leaf and fruit spot disease of citrus, and to characterize the causal pathogen under laboratory conditions using cultural, morphological, pathogenicity and molecular features. Surveys were conducted on forty-nine citrus orchards in twenty-eight districts in the major citrus growing areas of Ethiopia. Disease prevalence, incidence and severity on citrus leaves and intact fruits were determined using random sampling techniques. During the surveys, the status of citrus production and management practices were also assessed using questionnaire and field observations. Infected citrus leaves and fruits samples collected from various orchards were surface sterilized and isolated on water agar and potato dextrose agar media. Pure cultures were prepared using single spore or hyphal tip for each fungal isolate. The daily colony growth was measured and the growth rate at daily basis was calculated, while colony color and density were assessed by visual observation. Each fungal isolate culture was also evaluated for conidial and mycelial morphology by the help of stereomicroscope. Pathogenicity test for each isolate was conducted using citrus detached leaves following the standard procedure. The identity and phylogenetic relationships of the fungal isolates were analyzed using three sets of universal primers that span internal transcribed spacers, portion of long subunit region of the nuclear ribosomal DNA and partial actin gene sequences. The distribution and frequency of microsatellite loci in C. gloeosporioides genome were analyzed by generating pair-end reads from C. gloeosporioides isolate using the high-throughput Illumina sequencing platform, and reads were de novo assembled into a draft genome. Simple sequence repeat markers were developed from the draft assembled whole genome sequences of C. gloeosporioides. Fifty simple sequence repeat markers across the genome were screened using thirteen geographically representative C. gloeosporioides isolates. The polymorphic simple sequence repeat markers were used to analyze the genetic diversity and population structure of C. gloeosporioides isolates from different geographical regions of Ethiopia. The survey results showed that leaf and fruit spot disease of citrus has widely distributed in the wet humid areas of the south, southwest, central and northwest parts of Ethiopia. However, the disease was not recorded in the low moisture areas of the southeast, the central rift valley and the eastern parts of the country. The disease prevalence in the districts surveyed ranged from zero to 100%. The damage of leaf and fruit spot disease varied with citrus species and locations. The overall mean incidences and severities of the disease were highest on sweet oranges followed by mandarins. Lemons and limes were the least affected citrus species. Disease incidences and severities were higher in Jimma town, Abeshege, Aleta Wendo, Kebena, Mana, Gomma, Ginbo and Debre Werk districts. Disease incidences in the different orchards ranged from zero to 81.7% on leaves and from zero to 100% on fruits. Disease severity also varied from zero to 75% on leaves and from zero to 100% on fruits. The questionnaire assessment and field observations indicated that various citrus species (sweet orange being the major species) and varieties with two to seventy years of age were produced by smallholder and commercial farmers. The assessment also showed that diseases and insect pests, poor agronomic and irrigation practices, and shortage of adapted high yielding varieties were the major citrus production constraints in the country. In the present surveys, it has been observed that commercial citrus orchards practice field sanitation, pruning, irrigation, and fertilizer and pesticide applications. However, most of the orchards of the smallholders were not well managed. The colony characters such as color, density and daily growth rate varied among fungal isolates. The colonies varied from white to dark gray in color. The majority of the isolates produced circular, wooly or cottony colonies with pale brown or grayish white color. The fungal isolates produced colonies with compact, medium or sparse density. The average daily colony growth rate ranged from 0.04 to 2.3 cm. Some isolates were very slow-growing, whereas most cultures had characteristic fast-growing compact aerial mycelia. Majority of the fungal isolates did sporulate, but the type of conidiathey produced were not similar. These isolates produces hyaline, ovoid to oblong, slightly curved or dumbbell shaped conidia. Pathogenicity tests on detached leaf assays also revealed the association of most of the fungal isolates with foliar disease symptoms of the test citrus cultivars. Based on the multilocus analyses, more than 85% of the fungal isolates were belonged to Colletotrichum species complex (81% were C. gloeosporioides). The phylogenetic analysis of the isolates based on multilocus sequences delineated them as C. gloeosporioides sensu lato (broad sense) and C. boninense spp. complexes. Each single locus sequence analysis also identified 163 isolates as C. gloeosporioides or its teleomorph Glomerella cingulata. These findings provide information on the causal pathogen of leaf and fruit spot disease of citrus in Ethiopia and suggest the need for in-depth studies to determine the role of C. gloeosporioides species complex in leaf and fruit spot disease epidemiology. The results also demonstrated that multilocus sequences are reliable methods for phylogenetic analysis of species within the genus Colletotrichum. These findings provide baseline information for further population genetic studies of the pathogen. The information will also be useful in developing effective disease management practices against C. gloeosporioides. A genomewide microsatellite database of 5030 microsatellite motifs were identified in C. gloeosporioides genome. Of these, 94.6% were perfect motifs. Trinucleotide repeats were the most frequent; whereas penta- and hexanucleotide motifs were the least abundant. The number of motifs decreased as the number of the repeats increased. A/T repeats were more abundant than G/C repeats in the C. gloeosporioides genome. In penta- and hexanucleotide repeats, GC-rich motifs were predominant. Twenty-one simple sequence repeat markers showed polymorphism and demonstrated allele diversity among the thirteen test isolates of C. gloeosporioides. This small-scale population study could serve as a proof-of-concept showing that the genome sequencing approach was successfully applied for microsatellite discovery and development of simple sequence repeat markers. Twenty-three polymorphic simple sequence repeat markers produced a total of 118 alleles among the 163 C. gloeosporioides isolates. The polymorphic information content values ranged from slightly to highly informative. The gene diversity among the loci ranged from 0.106 to 0.664. Analysis of molecular variance showed that 85% of the total variation was due to the differences of isolates within a population. The genetic differentiation in the total populations was low as evidenced by high level of gene flow estimate (Nm=4.8) between populations. Populations of Ethiopian C. gloeosporioides from citrus were generally characterized by a low level of genetic diversity. Unweighted Neighbor-joining and population structure analyses grouped the isolates into three major clusters regardless of their geographic origins. The microsatellite markers developed and used in this study were useful to comprehend the genetic diversity and population structure of C. gloeosporioides isolates from main citrus growing regions of Ethiopia. Despite regional differences, the observed genetic diversity in all four populations was lower than expected suggesting inter-regional exchanges of planting materials and/or fruits, and dispersal of inoculum among the regions. Information generated in this study were useful in understanding the pathogen biology and provided basis for other studies on disease development, host-pathogen interaction, and developing disease management strategies for the control of leaf and fruit spot disease of citrus in Ethiopia. The SSR markers developed in this study could be used to characterize C. gloeosporioides isolates that infect other fruit crops. In conclusion, the disease should be managed at any cost. Frequent disease monitoring and precautions are essential. Care should be taken during transporting the planting materials and fruits from affected areas to locations where the disease is not recorded. Citrus growers should apply soil fertility management practices in their orchards, and practice general hygiene and sanitary measures. Application of relatively safe fungicides could reduce the disease damage. It is also necessary to investigate the reactions of the available citrus cultivars to the pathogen and select disease tolerant/resistant scions. In the long term, integrated disease management approaches including biocontrol need to be in place in the country