Marketable Fruit Weight Research Articles

Yield and Fruit Quality Traits of Two Plantain Cultivars Grown at Two Locations in Puerto Rico under Black Leaf Streak Disease Pressure

Plantain (Musa balbisiana AAB) is a tropical rhizomatous perennial plant in the genus Musa spp., closely related to banana (Musa acuminata AAA). It is an important cash crop and staple for inhabitants in many parts of the world, including various ethnic groups in the United States. Black leaf streak disease (BLSD) or black sigatoka, caused by Pseudocercospora fijiensis (formerly Mycosphaerella fijiensis), is responsible for significant losses of this crop due to the high susceptibility of the most economically important cultivars. BLSD does not immediately kill plantain plants, but it causes severe leaf necrosis, which results in reduced photosynthetic area, thereby adversely impacting bunch weight and fruit production. Without cultural and chemical control, yields can be reduced by 20% to 80%, depending on severity. This study evaluated a BLSD-resistant cultivar, FHIA-21, against Maricongo, a standard commercial cultivar with no BLSD tolerance, at two locations in Puerto Rico on Ultisol (Corozal site) and Oxisol (Isabela site) soils. Total number of fruit and bunch yield were significantly higher at Isabela, with BLSD severity being significantly lower at this location. Average fruit production of ‘FHIA-21’ was significantly higher than that of ‘Maricongo’ at both locations, with fruit yields of 122,522 and 99,948 fruit/ha at Isabela and Corozal, respectively. Overall, fruit of ‘FHIA-21’ were significantly longer and had greater diameters than those of ‘Maricongo’. At Isabela, the mean bunch fruit weight was significantly higher for ‘FHIA-21’, but both cultivars exceeded the minimum local marketable fruit weight criterion of 270 g. At both locations, the numbers of functional leaves present at flowering and at harvest were significantly higher for ‘FHIA-21’ than for ‘Maricongo’, indicating more availability of photosynthetic area for ‘FHIA-21’ during the fruit-filling period. There were no significant differences between cultivars regarding the concentration of starch and soluble sugars for green fruit. Regarding ripe fruit, ‘FHIA-21’ had a significantly higher concentration of soluble sugars and less starch. In this study, ‘FHIA-21’ had good resistance against BLSD and, if accepted by consumers, is a viable alternative to current commercial cultivars. We also conclude from this study that the expression of the Banana streak virus (BSV) in planting material of this cultivar remains an unknown threat in yield decline of ‘FHIA-21’.

Evaluation of Horticultural Practices for Sustainable Tomato Production in Eastern Uganda

Tomato cultivars (Heinz 1370, MT 56, and Nuru F1), fungicide application (±), staking (±), and mulching (±) were tested for their effect on yield, disease severity, and gross margin in tomato production in the Kamuli District of Uganda. Treatments were arranged in a randomized complete block design with a factorial and split-plot arrangement in field plots in two growing seasons during 2013. Total and marketable fruit number, marketable fruit weight, gross margin, and disease severity, assessed using the area under disease progress curve, were measured. Disease-resistant and open-pollinated ‘MT 56’ in combination with fungicide application and soil mulch provided the highest marketable fruit number and marketable fruit weight and had a positive gross margin in the first growing season. A combination of ‘MT 56’ and treatments without applying fungicide and soil mulch resulted in the only positive gross margin in season two. Application of fungicides reduced disease severity (early blight, Alternaria solani Sorauer) for all cultivars in season one and for ‘Heinz 1370’ and ‘Nuru F1’ in season two, but did not affect disease severity for ‘MT 56’ in the second season. Using soil mulch reduced the severity of early blight disease, but decreased the gross margin when purchased. Staking did not affect yield, disease severity of plants, and decreased the gross margin. Cultivar MT 56 had the highest gross margin and marketable fruit and least disease severity, and seeds should be made available to small-landholder tomato farmers in Uganda to enhance their sustainable livelihoods.

Broccoli, cabbage, squash and watermelon response to halosulfuron preplant over plastic mulch

AbstractNutsedge species are problematic in plastic-mulched vegetable production because of the weed’s rapid reproduction and ability to penetrate the mulch. Vegetable growers rely heavily on halosulfuron to manage nutsedge species; however, the herbicide cannot be applied over mulch before vegetable transplanting due to potential crop injury. This can be problematic when multiple crops are produced on a single mulch installation. Field experiments were conducted to determine the response of broccoli, cabbage, squash, and watermelon to halosulfuron applied on top of mulch prior to transplanting. Halosulfuron at 80 g ai ha−1 was applied 21, 14, 7, and 1 d before planting (DBP), and 160 g ai ha−1 was applied 21 DBP. In all experiments, extending the interval between halosulfuron application and planting reduced crop injury. For squash and watermelon, visual injury, plant diameters/vine runner lengths, marketable fruit weights, and postharvest plant biomass resulted in similar values when applying 80 g ha−1 21 DBP and with the nontreated weed-free control. Reducing this interval increased injury for both crops. Visual crop injury and yield reductions up to 40% occurred, with halosulfuron applied 14, 7, or 1 DBP in squash and 1 DBP in watermelon. Broccoli and cabbage showed greater sensitivity, with injury and plant diameter reductions greater than 15%, even with halosulfuron applied at 80 g ha−1 21 DBP. Experimental results confirm that halosulfuron binds to plastic mulch, remains active, and is slowly released from the mulch over a substantial period, during rainfall or overhead irrigation events. Extending the plant-back interval to at least 21 d before transplanting did overcome squash and watermelon injury concerns with halosulfuron at 80 g ha−1, but not broccoli and cabbage. Applying halosulfuron over mulch to control emerged nutsedge before planting squash and watermelon would be beneficial if adequate rainfall or irrigation and appropriate intervals between application and planting are implemented.

Spring-seeded cereal rye suppresses weeds in watermelon

AbstractWeeds can cause significant yield loss in watermelon production systems. Commercially acceptable weed control is difficult to achieve, even with heavy reliance on herbicides. A study was conducted to evaluate a spring-seeded cereal rye cover crop with different herbicide application timings for weed management between row middles in watermelon production systems. Common lambsquarters and pigweed species (namely, Palmer amaranth and smooth pigweed) densities and biomasses were often lower with cereal rye compared with no cereal rye, regardless of herbicide treatment. The presence of cereal rye did not negatively influence the number of marketable watermelon fruit, but average marketable fruit weight in cereal rye versus no cereal rye treatments varied by location. These results demonstrate that a spring-seeded cereal rye cover crop can help reduce weed density and weed biomass, and potentially enhance overall weed control. Cereal rye alone did not provide full-season weed control, so additional research is needed to determine the best methods to integrate spring cover cropping with other weed management tactics in watermelon for effective, full-season control.

Integrated Management of Downy Mildew on Slicing Cucumber With Fungicides and Host Resistance But Not Trellising.

The objective of this study was to evaluate fungicide applications, host resistance, and trellising, alone and in combination, as management practices for downy mildew on slicing cucumber. A split-split plot experimental design was used with three and four replications in spring and fall 2017, respectively. The whole-plot treatment was fungicide, four applications of chlorothalonil (Bravo Weather Stik 6SC) alternated with three applications of cyazofamid (Ranman 400SC), or water. Split plots were nontrellised or trellised with four strings supported by stakes. Split-split plots were cultivar Bristol, which is intermediately resistant to downy mildew, or cultivar Speedway, which is susceptible to downy mildew with similar parentage as Bristol. In both seasons, area under the disease progress curve (AUDPC) values were lower with fungicides than water for both cultivars. In the spring, AUDPC for Bristol was lower than for Speedway regardless of fungicide treatment. In the fall, Bristol had a lower AUDPC than Speedway with fungicides, but the AUDPC did not differ between the two cultivars with water. The mean AUDPC for trellised plants (376.2) was lower than for nontrellised plants (434.0; P = 0.007). Fungicide applications increased marketable and total fruit weights in both seasons (P ≤ 0.0002). Marketable weight with fungicides was almost double (93% greater) the marketable weight with water. Marketable weight was 55% greater for Bristol than for Speedway in spring, but yields did not differ between cultivars in fall (season-by-cultivar interaction, P ≤ 0.0003). Because trellising had no effect on marketable yields (P = 0.11), trellising is not recommended for managing downy mildew on slicing cucumber. Of the three management techniques examined, fungicides had the largest effects on disease and yields, followed by cultivar resistance.

Effect of Tomato Rootstock on Hybrid and Heirloom Tomato Performance in a Midwest High Tunnel Production System

High tunnels allow vegetable growers to extend the growing season, increase crop production, and improve produce quality. Tomatoes (Solanum lycopersicum L.) are the most widely grown crops in high tunnels; however, tomato production in high tunnels can be challenging. Continuous cropping in high tunnels can increase soil-borne disease pressure and can lead to soil salinity or nutrient depletion issues. Based on preliminary research, we hypothesized that use of the rootstock ‘RST-04-106-T’ would increase yield and quality of heirloom and hybrid tomato scions compared with nongrafted plants. To test this hypothesis, our research objectives were to assess marketable yields, fruit quality and nutritional value, and plant growth of grafted and nongrafted hybrid and heirloom tomatoes in a high tunnel production system. Grafted and nongrafted ‘Cherokee Purple’ (heirloom) and ‘Mountain Fresh Plus’ (hybrid) tomatoes were grown in the same high tunnel for two seasons (7 May–20 Oct. 2015 and 29 April–7 Oct. 2016) at the Horticulture Research Station in Ames, IA. Grafted plants produced significantly more marketable fruit, although marketable and total fruit weight did not increase significantly. Individual fruit size was unaffected by grafting. Across cultivars, mean soluble solids content (SSC) in fruit was 0.3 °Brix lower in grafted plants as compared with the nongrafted control. Grafting did not affect lycopene content of fruit. Grafting increased stem diameter by an average of 0.8 mm, but overall plant biomass was unaffected. The effect of grafting on leaf chlorophyll concentration (SPAD readings) was mixed. In addition, grafting increased leaf chlorophyll concentration in ‘Cherokee Purple’ but decreased it in ‘Mountain Fresh Plus’ plants. Grafting is a valuable tool in tomato production, but the impact of ‘RST-04-106-T’ rootstock use appears to be specific to certain soil types with high incidence of bacterial wilt.

Response of healthy local tomato (Solanum lycopersicum L.) populations to grafting in organic farming

Demands for tomato local varieties are increasing worldwide, especially in organic farming mainly for their high sensory value and attractive appearance. This is the case of the “Moruno” tomato type, widely grown in the Mediterranean countries and greatly due to its highly appreciated organoleptic attributes but low yield or a short postharvest period. For this reason, the study aimed to assess if grafting of local “Moruno” populations (Mor-62, Mor-204) using commercial rootstocks (King-Kong F1, K; Multifort F1, M; Spirit F1, S) affects yield, fruit nutritional and functional composition, postharvest storage and consumer acceptance. Results showed differences between both populations, while rootstocks were only different for the glucose content and the flavour quality. Grafting improved the marketable yield (~43%), fruit number (~22%) and mean fruit weight (~12%), but had no incidence on the blossom-end rot disorder. This technique increased the carotenoid (lycopene, β-carotene and total carotene) content but decreased the organic acids (malic and citric) and sugar (fructose and glucose) rates, while ascorbic acid was not affected. The fruit postharvest storage was not practically modified. However, the overall flavour preference and visual appearance varied depending on the scion.

Growing Watermelon in High-Altitude Trans-Himalayan Ladakh

The feasibility of growing watermelon, a warm season crop, was studied under a low-input cultivation system in open field condition in the high-altitude (elevation 3344 m) trans-Himalayan Ladakh region. The mean marketable yield of five cultivars in different treatments varied from 13.0 ± 2.7 to 30.4 ± 5.3 and 11.8 ± 2.9 to 27.4 ± 4.0 t ha−1 in 2014 and 2015, respectively. Treatment of black polyethylene mulch (BPM) increased marketable yield by 23.3% to 59.2% depending on year and cultivar. The best-performing cultivar (Bejo-2000) under BPM yielded 28.9 t ha−1 marketable fruit, which suggested that watermelon can successfully be grown in open field condition in the trans-Himalaya. Harvest began on 18 August 2014 and 26 August 2015. Average marketable fruit weight ranged from 2.9 to 5.3 kg, and TSS ranged from 9.3 to 11.3°Brix depending on cultivar. Temperature 10 cm beneath the BPM was 2.8 ± 0.3 °C higher than in nonmulched soil. BPM reduced 73% weed and saved 77% time in manual weeding.

Correlation & path analysis in local germplasm and characters association of ivy gourd (Coccinia grandis L.)

The experiment was carried out with 30 genotypes in completely randomized block design with 3 replications to study the association among fruit weight and its components and their direct and indirect influence on total marketable fruit weight of ivy gourd at Department of Horticulture, Rajasthan College of Agriculture, Maharana Pratap University of Agriculture and Technology, Udaipur during kharif season 2017–18 in completely randomized design with three replications. Correlations study revealed that phenotypic correlation coefficient was slightly higher than corresponding value of genotypic correlation for majority of the characters. Fruit weight has highest significant positive correlation with total chlorophyll and significant negative correlation with fruit volume. The correlation between phosphorus and fruit diameter was negative significant. Path analysis study revealed that average leaf length has showed highest positive direct effect on fruit weight followed by total chlorophyll content in leaves, petiole length, ascorbic acid content whereas, moisture, inter nodal length, fruit length, leaf width showed negative direct effect on the fruit weight.

Managing Fusarium Wilt of Watermelon with Delayed Transplanting and Cultivar Resistance.

Fusarium wilt of watermelon caused by Fusarium oxysporum f. sp. niveum is a serious, widespread disease of watermelon throughout the southern United States. To investigate whether soil temperature affects disease development, three cultivars of triploid watermelon were transplanted March 17 to 21, April 7 to 11, and April 26 to May 2 in 2015 and 2016 at Charleston, SC, and Tifton, GA into fields naturally infested with F. oxysporum f. sp. niveum. Incidence of Fusarium wilt was lower with late-season than with early and midseason transplanting in all four experiments (P ≤ 0.01). Cultivar Citation had more wilted plants than the cultivars Fascination and Melody in three of four experiments (P ≤ 0.05). In South Carolina, planting date did not affect weight and number of marketable fruit ≥4.5 kg apiece. In Georgia in 2016, weight and number of marketable fruit were greater with late transplanting than with early and midseason transplanting. In both states, yield and value for Fascination and Melody were higher than for Citation. Soil temperature averaged over the 4-week period after transplanting was negatively correlated with disease incidence for all four experiments (r = -0.737, P = 0.006). Transplanting after mid-April and choosing a cultivar with resistance to F. oxysporum f. sp. niveum race 1, like Fascination, or tolerance, like Melody, can help manage Fusarium wilt of watermelon and increase marketable yields in the southern United States.

Performance of Grafted Seedless Watermelon Plants with and without Root Excision under Inoculation with Fusarium oxysporum f. sp. niveum Race 2

Fusarium wilt of watermelon can be effectively managed by grafting with resistant rootstocks. Excision and regeneration of grafted seedling roots is a common practice among cucurbit-grafting nurseries that has not been thoroughly examined. The objectives of this study were to compare the performance of grafted and nongrafted watermelon plants under both greenhouse and field conditions when inoculated with Fusarium oxysporum f. sp. niveum (FON) race 2, and assess the effect of root excision on growth of grafted plants with Cucurbita moschata and Cucurbita maxima × C. moschata rootstocks. Two greenhouse experiments (Fall 2015 and Spring 2016) and one field trial (Spring 2016) of seedless watermelon ‘Melody’ were conducted in this study. In both greenhouse experiments, inoculated, nongrafted watermelon plants showed a significantly higher percentage of recovered Fusarium spp. colonies (70% to 75%) compared with grafted treatments (0% to 7.5%). Some plant growth measurements, including the longest vine length and aboveground fresh and dry weight, indicated less vigorous growth for nongrafted plants compared with the grafted treatments. Significantly higher percent recovery of Fusarium spp. below the graft union was observed in the grafted plants with root excision and regeneration treatment (3.7%) in contrast to the intact root treatment (0.5%), suggesting that the root excision method may possibly create entry points for FON infections. Overall, the root excision treatment showed little influence on aboveground growth and root characteristics of grafted plants. Yield of grafted watermelon with FON inoculation in the fumigated field trial was significantly higher than that of noninoculated, nongrafted ‘Melody’ (NGM) control as reflected by the increase of fruit number and size. Averaged over all the grafted treatments, the increase in marketable fruit number and weight reached 108.3% and 240.9%, respectively, and the total fruit number and weight increase was at 80.0% and 237.2%, respectively. However, grafted plants also exhibited greater levels of root-knot nematode infestation as indicated by the significantly higher root galling ratings. Results from this study demonstrated that grafting with squash rootstocks can effectively limit FON colonization in seedless watermelon plants, although more research in rootstock selection and testing is needed to optimize the use of grafted plants for improving plant growth and fruit yield.

Off-season Production of Tomato (Lycopersicon esculentum L.) Under Different Shading and Mulching Materials

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PRODUCTIVITY AND QUALITY OF AQUAPONICALLY GROWN TOMATO (Solanum lycopersicum L.) SUPPLEMENTED WITH DIFFERENT NUTRIENT SOLUTIONS

Tomato (Solanum lycopersicum L.) is an important vegetable in the country which is consumed both raw and as processed product. This study aimed to evaluate the growth, yield, postharvest qualities and profitability of aquaponically grown tomato supplemented with different nutrient solutions. The study was laid out in Randomized Complete Block Design with 8 treatments replicated 3 times. Tomato fruits were first harvested 60 days after transplanting with 100 percent survival rate. Early flowering of tomato plant was observed when applied with VSU liquid nutrient formulation (VSU-LNF) with node number ranging from 13.33-14.00 bearing the first flower. Growth parameters such as plant height, number of lateral shoot, root length and fruit size are stimulated by the application of VSU liquid nutrient formulation and in combination with ferments. This also resulted to high number and weight of marketable fruit in tomato plant. Carotenoid and chlorophyll contents of the fruits were higher in aquaponically grown tomato supplemented with fermented kuhol (Pomacea canaliculata L.). Free radical scavenging activity was found highest in the fruit of tomato grown in aquaponic system supplemented with combined VSU liquid nutrient formulation with fermented malunggay (Moringa olifera). However, vitamin Cand sugar content of tomato fruits were found highest when supplemented with combine VSU liquid nutrient formulation and fermented kuhol. No significant differences were obtained on firmness, percent weight loss, respiration rate at 2 and 4 weeks after storage, titratable acidity, fruit nitrogen, pH of fruit, oxidation reduction potential, electrical conductivity and total dissolved solids. On the other hand, higher moisture content of the tomato fruits were observed with the application of VSU liquid nutrient formulation and in combination with ferments. Therefore, high yield was produced with the application of VSU liquid nutrient formulation which resulted to higher net return. Aquaponically grown tomato supplemented with VSU-LNF produced lesser yield but with considerable net return.

Characterization of Blueberry shock virus, an Emerging Ilarvirus in Cranberry.

Blueberry shock virus (BlShV), an Ilarvirus sp. reported only on blueberry, was associated with scarring, disfigurement, and premature reddening of cranberry fruit. BlShV was detected by triple-antibody sandwich enzyme-linked immunosorbent assay and reverse-transcription polymerase chain reaction, and isometric virions of 25 to 28 nm were observed in cranberry sap. The virus was systemic, although unevenly distributed in plants. The coat protein of BlShV from cranberry shared 90% identity compared with BlShV accessions from blueberry on GenBank. Phylogenetic analysis of isolates of BlShV from cranberry collected from Wisconsin and Massachusetts did not indicate grouping by state. BlShV was detected in cranberry pollen, and seed transmission of up to 91% was observed. Artificial inoculation of cranberry flowers by pollination did not cause virus transmission. In some Nicotiana spp., rub inoculation of leaves with homogenized BlShV-positive cranberry flowers resulted in systemic infection. Cranberry plants recovered from symptoms the year after berry scarring occurred but continued to test positive for BlShV. The virus caused significant reduction in the average number of marketable fruit and average berry weight in symptomatic cranberry plants but recovered plants yielded comparably with healthy plants. Although recovery may limit the immediate economic consequences of BlShV, long-term implications of single- or mixed-virus infection in cranberry is unknown.

Growth and yield of tomato (Solanum lycopersicum) as influenced by different soil organic amendments and types of cultivation

Tomato is one of the most profitable crops in the Philippines and is extensively cultivated throughout the world. However, its production faces different pest and disease problems, particularly bacterial wilt which greatly reduces yield. Two separate studies were conducted simultaneously in a single factor experiment arranged in randomized complete block design (RCBD) with three (3) replications. The studies were conducted to evaluate the effects of the different soil organic amendments on the growth and yield of tomato in the open field (Study I) and under protective structure (Study II) with the following treatments: control, cabbage waste, carbonized rice hull, chicken dung, hagonoy, wedelia, and wild sunflower. Protective structure grown plants had better protection against detrimental heavy rain and strong light intensity, thus had better performance in terms of lower bacterial wilt infection and weed incidence, higher percentage survival, enhanced flowering, and a higher yield than those grown in the open field. On the other hand, only the weight of marketable fruits and total yield were enhanced by the application of the different soil organic amendments. All amendments had similar effects but were superior than the control. Protected cultivation gave a higher net return than the open field. In particular, sunflower amended plants under structure were the most profitable, by almost 8 times compared to the open field.

Yield losses of asymptomatic strawberry plants infected with Strawberry mild yellow edge virus

After successive vegetative propagation cycles, strawberry (Fragaria × ananassa Duch.) plants often accumulate multiple virus species that result in viral symptoms and losses in yield and quality. However, strawberry plants infected by a single virus species usually remain asymptomatic with unknown effects on fruit production and quality. In this context, the effect of Strawberry mild yellow edge virus (SMYEV) on fruit production was studied in strawberry plants, cultivar Camarosa, over two years. Asymptomatic SMYEV-infected plants showed a significant reduction in total and marketable fruit number and weight compared with healthy plants. These reductions ranged between 28% and 63%, depending on the parameter measured and the production cycle. Fluctuations in SMYEV concentration in the plants was detected throughout the crop cycle, suggesting that samples for virus diagnosis should be taken when the plant has the highest virus concentration; in this study, this occurred at the end of the crop cycle. These results show that analyzing symptomless strawberry plants should be part of a virus disease management plant and an important component to control the quantitative and qualitative impacts of SMYEV on strawberry yield.

Microclimate and agronomical effects of internal impermeable screens in an unheated Mediterranean greenhouse

In unheated greenhouses in mild-winter areas, low-cost, fixed, water-impermeable plastic screens are frequently installed in winter cycles of the vegetable crops more sensitive to fungal diseases. They are used to prevent rain and condensation falling on the crop and to improve the greenhouse air temperature. Two experiments were carried out to quantify how fixed and movable impermeable screens affect microclimate and crop behaviour in an unheated greenhouse in a mild-winter area. The fixed screen improved the night-time temperature and humidity of the air below the screen, and reduced the water condensation on its inner plastic surface or the proliferation of fungal diseases, but did not completely prevent it. Compared to the greenhouse without screen, the movable screen, usually unfolded at night, increased the night-time temperature of the air and the crop, reduced the night-time relative humidity of the air below the screen, prevented the water condensation on the screen or the crop, accelerated melon crop development, and significantly increased early marketable yield of melon fruits and their quality, but it did not substantially affect the substrate temperature, or the total marketable yield of melon fruits. In the comparison of the greenhouse with fixed versus movable screen, no substantial differences were found for a winter cucumber cycle in night-time temperature and relative humidity of the air below the screens, in shoot biomass or in fresh weight of total and marketable cucumber fruits. This can be mainly attributed to the small differences between both treatments in the shortwave radiation reaching the crop.

Functional identity has a stronger effect than diversity on mycorrhizal symbiosis and productivity of field grown organic tomato

Abstract Beneficial soil biota, and in particular, arbuscular mycorrhizal fungi (AMF) are increasingly being recognized as key elements of organic and low-input agriculture where agrobiodiversity is central to enhanced crop production. However, the role of AMF in diversified organic systems, especially in field crops, is still poorly understood. A 3-year field experiment was carried out in Central Italy to investigate whether organic cropping systems that promote species and genetic diversity are more prone to mycorrhizal symbiosis increasing tomato growth, production and yield quality. Three tomato cultivars with varying genetic diversity were grown following four cover treatments: Indian mustard ( Brassica juncea L. Czern.), hairy vetch ( Vicia villosa Roth), a commercial mixture of seven cover crop species (Mix 7) and no-till fallow. Plants were either inoculated or not in nursery, with the two AMF isolates Funneliformis mosseae (IMA1) and Rhizoglomus intraradices (IMA6) used alone or mixed in a 1:1 volume ratio. On average, Mix 7 produced higher shoot dry matter (5.0 t ha −1 ) than V. villosa (3.5 t ha −1 ) or B. juncea (2.5 t ha −1 ). Pre-transplant inoculation increased tomato root colonization at flowering and harvest compared to the non inoculated plants (31.8 vs 23.6%) and cv. Rio Grande was on average the best colonized. The mean fresh weight of marketable fruits was 18.4, 28.0 and 28.6 t ha −1 for cvs. Rio Grande, Roma and Perfect Peel, respectively. Cover crops inconsistently affected tomato marketable fruit production in year 1, while in years 2 and 3, Vicia villosa and Mix 7 showed the best effect respectively. In year 3, among the pre-inoculated plants those treated with isolate IMA6 showed a higher production of marketable fruit number m −2 (56.7) than those inoculated either with IMA1 (51.5) or the mixed inocula (52.1). Most fruit quality parameters were affected by tomato genotype. This study shows that while increased agrobiodiversity is important to increase agroecosystem resilience, AMF, crop and cover crop functional identity may be more important than diversity per se to promote mycorrhizal symbiosis and productivity of field grown organic tomato.

Grafting Watermelon and Using Plastic Mulch to Control Verticillium Wilt Caused by Verticillium dahliae in Washington

Verticillium wilt, caused by the soilborne fungus Verticillium dahliae, is a significant disease affecting watermelon (Citrullus lanatus) production in Washington State. This field study at three locations in Washington in 2015 compared verticillium wilt susceptibility, fruit yield and quality of nongrafted watermelon, and grafted plants grown with black plastic and clear plastic mulch. Overall for grafting treatments, area under disease progress curve (AUDPC) values were higher for nongrafted ‘TriX Palomar’ (765) than for ‘TriX Palomar’ grafted onto ‘Super Shintosa’ (132), ‘Tetsukabuto’ (178), or ‘Just’ (187). Overall for mulch, the AUDPC value was higher for plants grown with black plastic mulch (385) than for plants grown with clear plastic mulch (237). Overall for location, the AUDPC value was lowest at Eltopia (84), intermediate at Othello (182), and highest at Mount Vernon (680). At season end, more Verticillium microsclerotia were present in stems of nongrafted ‘TriX Palomar’ than in grafted treatment stems at Eltopia and Mount Vernon, but not at Othello. Differences in microsclerotia presence occurred only in the top or scion portion of the stem, but not in the graft union, rootstock, or crown portions of the stem. There was no difference due to mulch in regard to Verticillium microsclerotia detected in stem assays. After harvest, V. dahliae soil density under black plastic mulch increased 6-fold at Eltopia, 4.7-fold at Othello, and 1.9-fold at Mount Vernon. In contrast, V. dahiae soil density under clear plastic mulch was nearly identical to the level at planting at each location (<1, 2.6, and 27 cfu/g at Eltopia, Othello, and Mount Vernon, respectively). There was a significant interaction between grafting and location for fruit yield such that there was no difference at Eltopia and Othello, but at Mount Vernon, yield of nongrafted ‘TriX Palomar’ was lower (7.4 kg/plant) than for grafted plants (average 13.0 kg/plant). The number and weight of marketable fruit per plant were higher at Othello (4.0 and 27.65 kg/plant, respectively) than at Eltopia (2.0 and 12.23 kg/plant, respectively) and Mount Vernon (2.2 and 11.63 kg/plant, respectively). Fruit firmness was greater overall for all three grafted treatments (average 2.67 N) than for nongrafted ‘TriX Palomar’ (2.20 N), but there was no difference in total soluble solids (TSS) or lycopene content of fruit due to grafting. Yield, fruit firmness, and TSS did not differ due to mulch type; however, lycopene content was greater for plants grown with black plastic mulch than with clear plastic mulch at Eltopia. There was no difference in TSS due to location, but fruit firmness was lower at Eltopia and Othello (2.20 and 2.44 N, respectively) than at Mount Vernon (3.00 N), whereas lycopene content was less at Mount Vernon (27.85 μg·g−1) than at Eltopia or Othello (38.58 and 36.54 μg·g−1). The results of this study indicate that although verticillium wilt symptoms were visible in watermelon plants when V. dahliae level was <3 cfu/g of soil, watermelon yield was not reduced. However, when V. dahliae soil density was >50 cfu/g of soil, yield was greater for grafted plants and for plants grown with clear plastic mulch.

EFFECT OF NITROGEN FERTILIZATION ON YIELD AND QUALITY OF WATERMELON, CV. TOP GUN

ABSTRACT Nitrogen (N) is the second most important nutrient required by watermelons that can limit their growth and affect fruit quality when deficient. We evaluated the soil (N-nitrate) and foliar N contents and soluble-solid content of the watermelon 'Top Gun' in Brazil at six rates of N fertilization (0, 50, 100, 150, 200 and 250 kg ha-1). N-nitrate and foliar N levels increased linearly with rate. Number of total and marketable fruit, weight of total and marketable fruit and total and marketable yields varied quadratically with rate. N rates of 187 and 184 kg ha-1 produced the highest total and marketable yields, respectively. The rate of N fertilization did not significantly affect total-solid content.