Cucurbit Grafting

Due to limited availability of arable land and high market demand for off-season vegetables, cucurbits (plants in the family Cucurbitaceae) are continuously cultivated under unfavorable conditions in some countries. These conditions include environments that are too cold, wet, or dry, or are cool low-light winter greenhouses. Successive cropping can increase salinity, the incidence of cucurbit pests, and soilborne diseases like fusarium wilt caused by Fusarium spp. These conditions cause various physiological and pathological disorders leading to severe crop loss. Chemical pest control is expensive, not always effective, and can harm the environment. Grafting can overcome many of these problems. In fact, in many parts of the world, grafting is a routine technique in continuous cropping systems. It was first commonly used in Japan during the late 1920s by grafting watermelon [Citrullus lanatus (Thunb.) Matsum. and Nakai] onto pumpkin [Cucurbita moschata Duchesne ex. Poir] rootstocks. Soon after, watermelons were grafted onto bottle gourd [Lagenaria siceraria (Molina) Standl.] rootstocks. This practice helped control declining yield due to soilborne diseases. China produces more than half the world's watermelons and cucumbers (Cucumis sativus L.), and approximately 20% of these are grafted. Use of rootstocks can enhance plant vigor through vigorous attainment of soil nutrients, avoidance of soil pathogens and tolerance of low soil temperatures, salinity, and wet-soil conditions. The type of rootstock affects cucurbit plant growth, yield, and fruit quality. Cucurbit grafting is rare in the United States, but with continued loss of quality disease-free farmland along with the phase-out of methyl bromide, the U.S. cucurbit industry sees grafting as an attractive option. Some seed companies now offer watermelon transplants grafted onto squash or bottle gourd rootstocks, and some transplant facilities offer grafting services. There have been thorough analyses of cucurbit grafting in other countries, but the literature in English is limited. This review summarizes the state of the cucurbit grafting industry on a global level, translating work published in many languages.     

Use of Cucumis metuliferus as a Rootstock for Melon to Manage Meloidogyne incognita

Root-knot nematode-susceptible melons (Cantaloupe) were grown in pots with varying levels of Meloidogyne incognita and were compared to susceptible melons that were grafted onto Cucumis metuliferus or Cucurbita moschata rootstocks. In addition, the effect of using melons as transplants in nematode-infested soil was compared to direct seeding of melons in nematode-infested soil. There were no differences in shoot or root weight, or severity of root galling between transplanted and direct-seeded non-grafted susceptible melon in nematode-infested soil. Susceptible melon grafted on C. moschata rootstocks had lower root gall ratings and, at high nematode densities, higher shoot weights than non-grafted susceptible melons. However, final nematode levels were not lower on the grafted than on the non-grafted plants, and it was therefore concluded that grafting susceptible melon on to C. moschata rootstock made the plants tolerant, but not resistant, to the nematodes. Grafting susceptible melons on C. metuliferus rootstocks also reduced levels of root galling, prevented shoot weight losses, and resulted in significantly lower nematode levels at harvest. Thus, C. metuliferus may be used as a rootstock for melon to prevent both growth reduction and a strong nematode buildup in M. incognita-infested soil.     

Presence of Fusarium oxysporum f. sp. melonis Race 1 in Soils Cultivated with Melon in the State of Colima (Mexico)

During years 2001, 2002 and 2003 the gravity of the Fusarium wilt in 1000 hectares of melon culture was evaluated in Colima (Mexico). In spite of the soil disinfections with methyl bromide, the losses could reach 25% of the final production. The analysis of 4 soil samples from the fields with ill plants, in a selective medium for Fusarium, allowed to detect the presence of F. oxysporum. By means of the presented technique “soil phytopathometry”, 31 isolates of F. oxysporum f. sp. melonis were obtained from the soil samples. The isolates were inoculated on melon plants to evaluate their pathogenicity. The 31 isolates inoculated, produced the symptoms of chlorosis and wilting, in melon cultivars that allowed us to affirm that all isolates were race 1 of F. oxysporum f. sp. melonis. Being this the first news of the presence of F. oxysporum f. sp. melonis in the state of Colima (Mexico).     

Improving melon and cucumber photosynthetic activity, mineral composition, and growth performance under salinity stress by grafting onto Cucurbita hybrid rootstocks

The aim of the current work was to determine whether grafting could improve salinity tolerance of melon and cucumber, and whether possible induction of tolerance to salt stress was associated with the protection of the photosynthetic apparatus. Two greenhouse experiments were carried out to determine gas exchange, mineral composition, growth and yield of melon (Cucumis melo L. cv. Cyrano) and cucumber (Cucumis sativus L. cv. Akito) plants, either ungrafted or grafted onto the Cucurbita hybrid rootstocks (Cucurbita maxima Duch. × Cucurbita moschata Duch.), ??P360??, and ??PS1313??, respectively. Plants were grown hydroponically and supplied with two nutrient solutions ?? a nonsalinized control and a salinized solution which contained 40 mmol L^?1 of NaCl. Salinity induced a smaller decrease in leaf area index (LAI), in grafted-compared to ungrafted plants. Similarly, the P _N and g _s reduction in NaCl treatment compared to control were significantly lower in grafted plants (34% and 34%, respectively, for melon and 14% and 15.5%, respectively, for cucumber) compared to ungrafted plants (42% and 40%, respectively, for melon and 30% and 21%, respectively, for cucumber). In all grafting combinations, negative correlations were recorded between Na⁺ and Cl^? in the leaf tissue and P _N. Grafting reduced concentrations of sodium, but not chloride, in leaves. Under saline conditions a smaller reduction in melon and cucumber shoot biomass dry mass and fruit yield were recorded, with positive correlations between shoot biomass, yield and P _N. These results suggest that the use of salt tolerant Cucurbita rootstock can improve melon and cucumber photosynthetic capacity under salt stress and consequently crop performance.     

Use of Grafting and Calcium Cyanamide as Alternatives to Methyl Bromide Soil Fumigation and their Effects on Growth, Yield, Quality and Fusarium Wilt Control in Melon

Grafting melon (Cucumis melo L.) seedlings on to the Fusarium oxysporum f. sp. melonis (Fom) commercial resistant squash rootstocks ‘Mamouth’ and ‘Nun 9075 RT’ and soil sterilization with calcium cyanamide (CaCN₂, Perlka) were tested in 2001 and 2002 as alternatives to methyl bromide (MB) soil fumigation. Ungrafted seedlings of the F₁ melon hybrid ‘Galia’ were cultivated: (i) in soil sterilized by MB and then artificially infested with Fom (this served as a control), (ii) in soil artificially infested with Fom and then sterilized by MB, (iii) in soil artificially infested with Fom and then sterilized with CaCN₂ (Perlka), grafted seedlings on the commercial rootstocks, (iv) ‘Mamouth’ and (v) ‘Nun 9075 RT’ were cultivated in soil sterilized with MB and then artificially infested with Fom. The grafted plants on ‘Mamouth’ and ‘Nun 9075 RT’ and plants in the Perlka treatment (2001) developed mild symptoms, as indicated by the significantly lower leaf symptom index (LSI; average values 1.06, 1.08 and 1.07) and disease index (DI; average values 1.60, 1.25 and 2.33), respectively, when compared with the controls (average values of LSI = 2.65 and DI = 5.06). Plants grafted on ‘Mamouth’ and ‘Nun 9075 RT’ and plants in the Perlka treatment (2001) were more vigorous than the controls as assessed on plant height, stem diameter and root biomass. When compared with the controls, this resulted in an increased (over years) early production (326.3, 265.8 and 489.1%) and late production (371.0, 357.0 and 404.2%). Fruit size was also larger in early production (29.2, 50.9 and 32.3) and late production (4.3, 15.2 and 26.0). The total soluble solids (^oBrix) increased (over years) in early production (27.4, 39.6 and 47.9) and late production (7.59, 10.07 and 5.6) when compared with the controls. Thus, grafting on resistant squash rootstocks ‘Mamouth’ and ‘Nun 9075 RT’ and soil sterilization with Perlka had positive effects on growth, production and fusarium wilt control in melon.     

The effects of soil conditions, soil sterilisation and seed treatmen on the emergence of cabbage in controlled temperature cabinets and the field

Previous cropping history of the soil and the changes that occurred in soil moisture content and temperature were the major factors determining the emergence of cabbage seedlings from pathogen-free seeds. Seedling losses caused by soil-borne pathogens could be high but these losses were prevented by seed treatment with metalaxyl or soil sterilisation with methyl bromide prior to sowing. The beneficial effects of metalaxyl and methyl bromide treatments were confirmed in field experiments involving repeated sowings of cabbage seeds. In experiments with sterilised soil and cabbage seed infected with Alternaria brassicicola emergence at – 0·2 bars soil moisture potential was reduced by 7·8–23.5% at 5, 10, 20, and 25°C. In the field, losses due to A. brassicicola were greatest when the soil became capped after sowing. The results show that recently developed fungicides may facilitate emergence under conditions extremely favourable for seed- and soil-borne pathogens. For maximum benefit, selection of seed treatments should be based on knowledge of the range of pathogens likely to reduce emergence.     

Autotoxic potential of cucurbit crops

Soil sickness is often observed in cucurbit crops such as Citrullus lanatus, Cucumis melo and Cucumis sativus, but not in cucurbit crops such as Cucurbita moschata, Lagenaria leucantha and Luffa cylindrica. Results showed that root aqueous extracts of Citrullus lanatus, Cucumis melo and Cucumis sativus were autotoxic, but those of Cucurbita moschata, Momordica charantia and Luffa cylindrica were less autotoxic to the radicle elongation of respective species. Plant growth of Citrullus lanatus, Cucumis melo and Cucumis sativus were greatly inhibited by autotoxic substances released from powered root tissue at a rate of 1 g per seedling. Root exudates of Citrullus lanatus, Cucumis melo and Cucumis sativus were autotoxic to radicle elongation and seedling growth of respective species. However, root exudates of Citrullus lanatus did not inhibit radicle elongation of Cucurbita ficifolia, which is commonly used as rootstock for the grafting of Citrullus lanatus, Cucumis melo and Cucumis sativus to decrease soil-borne diseases in commercial production. It seems possible to overcome autotoxicity in cucurbit crops by grafting on Cucurbita ficifolia. This revised version was published online in June 2006 with corrections to the Cover Date.     

Mycorrhizal dependence of four crops in a P-sorbing soil

The effect of methyl bromide and P fertilization on the growth of four agricultural crops in a P-sorbing soil was studied. Harvestable yields and P tissue content were significantly lower for celery (Apium graveolens L.), onion (Allium cepa L.) and pepper (Capsicum annuum L.) following fumigation. P fertilization up to 330 kg P ha⁻¹ as superphosphate could not reverse this effect. The highest P fertilizer treatment had 25.4 μg g⁻¹ bicarbonate-extractable P and 0.26 μg g⁻¹ water extractable P. This P level produced acceptable commercial yields when vesicular arbuscular mycorrhizae (VAM) were present (non-fumigated) and indicate the importance of the VAM association for these crops. In contrast, melon (Cucumis melo L.) growth was slightly greater following soil fumigation at all P fertilization rates. These findings indicate that crop VAM dependence and efficacy of VAM biotypes must be considered as essential components for P fertilization recommendations on fumigated P-sorbing soils. Formerly Gilat, now University of Kent, Kent, UK     

熏蒸剂溴甲烷对农田土壤微生物的影响

土壤微生物是反应土壤健康状况最敏感的生物学指标,溴甲烷残留不仅消耗臭氧层,影响生态平衡,还会造成土壤质量恶化和微生物群落结构的变化。为明确溴甲烷对农田土壤微生物群落结构及生态过程的影响,以兰州市红古区连续两年种植草莓的土壤为研究对象,测定熏蒸剂溴甲烷处理后土壤微生物量碳、基础呼吸、诱导呼吸和微生物代谢熵等相关指标,并运用磷脂脂肪酸法(PLFA)测定不同类群微生物的变化。结果表明:经溴甲烷熏蒸处理至培养结束(第90天)时土壤微生物基础呼吸和诱导呼吸分别下降0.6%和16.2%,并且与对照皆差异显著(P 0.05);微生物量碳培养结束时与对照差异显著(P 0.05),且减少5.6%;总体上微生物基础呼吸、诱导呼吸和微生物量碳都呈现先下降后逐渐恢复的趋势;微生物代谢熵(q CO_2)第15天后都高于对照,但随培养时间延长,处理组和对照组的差值逐渐降低,到培养期结束仍未恢复,相差5.1%。溴甲烷对土壤细菌(B)、真菌(F)和革兰氏阴性菌(GN)、革兰氏阳性菌(GP)都存在抑制作用; B、F含量分别较对照下降0.64%—8.72%、0.03%—5.61%;到培养期结束时,GP的量下降0.26%,GN下降10.42%,GN对溴甲烷的敏感性强于GP,且GN的变化具有滞后性;溴甲烷处理降低了B/F和GN/GP,但对GN/GP影响比对B/F的更为显著,土壤微生物压力指数增加。综上,说明施用溴甲烷使农田土壤微生物受到了长期的、持续的外源压力胁迫,溴甲烷在对有害微生物杀死的同时,也对有益微生物造成极大的伤害,不利于土壤优良性状的保持,使土壤中微生物丰富度和多样性下降。因此,实际应用中应充分考虑溴甲烷对土壤微生物带来的负面影响。     

Response of female melon fly, Bactrocera cucurbitae, to host-associated visual and olfactory stimuli

In a series of studies conducted in Hawaii under seminatural conditions, we quantified the response of sexually mature, host‐seeking female melon flies, Bactrocera cucurbitae (Coquillett) (Diptera: Tephritidae), to different types of visual and chemical host‐associated stimuli with the main aim of developing a monitoring device for females. Experiments were conducted using Tangletrap‐coated fruit mimics of either spherical (8 cm diameter) or cylindrical (4.3 cm diameter; 15 cm length) shapes coated with different artificial color pigments both at the ground level and at the tree‐canopy level so as to take into account the foraging behavior of adult melon flies. Females were particularly attracted to objects of spherical shape colored either yellow, white, or orange; these three pigments offered the highest reflectance values. Cucumber (Cucumis sativus L.) (Cucurbitaceae) odor was more attractive to females than odors of three other cultivated host fruit [zucchini, Cucurbita pepo L. var. medullosa Alef. (Cucurbitaceae); papaya, Carica papaya L. (Caricaceae); or tomato Solanum lycopersicum L. (Solanaceae)] or of ivy gourd [Coccinia grandis (L.) Voigt (Cucurbitaceae)], one of the major wild hosts of melon fly in Hawaii. A combination of both visual and olfactory stimuli was needed to elicit high levels of response compared to each stimulus offered alone. We discuss our results in relation to the potential implementation of improved female monitoring and/or attract‐and‐kill strategies for melon flies in Hawaii.     

Comparison of the ribosomal RNA genes in four closely relatedCucurbitaceae

Cucurbitaceae are characterized by a high copy number for nuclear ribosomal RNA genes. We have investigated the genomic ribosomal DNA (rDNA) of four closely related species of this family with respect to structure, length heterogeneity, and evolution. InCucumis melo (melon) there are two main length variants of rDNA repeats with 10.7 and 10.55kb.Cucumis sativus (cucumber) shows at least three repeat types with 11.5, 10.5, and 10.2kb.Cucurbita pepo (zucchini) has two different repeat types with 10.0 and 9.3kb. There are also two different repeat types inCucurbita maxima (pumpkin) of about 11.2 and 10.5kb. Restriction enzyme mapping of the genomic rDNA of these four plants and of cloned repeats ofC. sativus shows further heterogeneities which are due to methylation or point mutations. By comparison of the restriction enzyme maps it was possible to trace some evolutionary events in the family ofCucurbitaceae. Some aspects of regulation and function of the middle repetitive rRNA genes (here between 2000 and 10000 copies) are discussed.     

Soil Suppressiveness to Fusarium Wilt of Melon, Induced by Repeated Croppings of Resistant Varieties of Melons

A field soil, artificially infested with pathogenic isolates of Fusarium oxysporum f. sp. melonis was continuously used for screening resistant varieties of melon to Fusarium wilt. After 9–10 years of continuous cropping with resistant varieties, the soil had developed induced suppressiveness. Seven to 9 experimental replantings of the induced suppressive soil with the susceptible cultivar of melon, ‘Ein-Dor', nullified its suppressiveness. This was expressed by 90 % disease incidence. Only 2 replantings were required to obtain the same disease incidence in an adjacent field of a conducive soil. Nonpathogenic isolates of F. oxysporum, isolated from the rhizospheres of melon seedlings, induced various degrees of soil suppressiveness when added to soil at various ratios to the pathogenic isolate.     

Occurrence of Melon Necrotic Spot Virus in Crete (Greece)

Since 1982 melon plants cv. Galia grown in plastic houses showed severe leaf and stem necrosis. A virus isolated from affected plants infected only Cucurbitaceae. Systemic infections were only developed in melon and Luffa acutangula, while a severe hypocotyl necrosis was observed in watermelon. Purified virus sedimented in sucrose gradients as a single component and reacted only with antisera to melon necrotic spot virus (MNSV). Seed transmission (22.5%) of the virus was observed m melon plants grown from seed of naturally infected melons, but the virus could not be detected in triturated seeds. The virus could be isolated from leachate of contaminated soil and melon plants became infected when grown in contaminated soil or when watered with suspensions of virus. These properties suggest that the virus is an isolate of MNSV.     

Comparative mapping of ZYMV resistances in cucumber (Cucumis sativus L.) and melon (Cucumis melo L.)

Zucchini yellow mosaic virus (ZYMV) routinely causes significant losses in cucumber (Cucumis sativus L.) and melon (Cucumis melo L.). ZYMV resistances from the cucumber population TMG1 and the melon plant introduction (PI) 414723 show different modes of inheritance and their genetic relationships are unknown. We used molecular markers tightly linked to ZYMV resistances from cucumber and melon for comparative mapping. A 5-kb genomic region (YCZ-5) cosegregating with the zym locus of cucumber was cloned and sequenced to reveal single nucleotide polymorphisms and indels distinguishing alleles from ZYMV-resistant (TMG1) and susceptible (Straight 8) cucumbers. A low-copy region of the YCZ-5 clone was hybridized to bacterial artificial chromosome (BAC) clones of melon and a 180-kb contig assembled. One end of this melon contig was mapped in cucumber and cosegregated with ZYMV resistance, demonstrating that physically linked regions in melon show genetic linkage in cucumber. However the YCZ-5 region segregated independently of ZYMV resistance loci in two melon families. These results establish that these sources of ZYMV resistances from cucumber TMG1 and melon PI414723 are likely non-syntenic.     

The occurrence of sclerotium rot on Momordica charantia caused by Sclerotium rolfsii in Korea

Sclerotium rolfsii is one of the most destructive pathogens and thought to affect a broad range of plant hosts. In July 2014, an occurrence of sclerotium rot was observed on bitter melon (Momordica charantia L.) in Jinju, South Korea. The rot symptoms were most developed on stems and fruit near the soil line, and infected bitter melon plants withered and eventually died. White mycelial mats with numerous sclerotia were produced on diseased stems and fruit near the soil surface. Based on the morphological characteristics, pathogenicity tests, and DNA sequencing and phylogenetic analysis of the internal transcribed spacer (ITS) ribosomal RNA (rRNA) gene region, the causal fungus was identified as S. rolfsii Saccardo. This is the first report of sclerotium rot caused by S. rolfsii on bitter melon in Korea. The recent occurrence of sclerotium rot on bitter melon poses a potential threat to its production in Korea.     

Towards better use of Indonesian peatlands with paludiculture and low-drainage food crops

The current drainage-based peatland management systems in Indonesia result in high fire risks, soil subsidence and CO₂ emissions. This study aims to assess different alternatives of peatland crops in order to help prevent further degradation of peatlands in Indonesia. We focus on tropical peatland crops that provide food and that are of particular interest to smallholders. We compare various peatland food crops that are commonly grown with no drainage (paludiculture) or drainage below 50 cm in our study area, Central Kalimantan, Indonesia in terms of sustainability, profitability, scalability of the market and acceptability to farmers. Our results show that sago (Metroxylon sagu), banana (Musa paradisiaca) and pineapple (Ananas comosus) followed by water spinach/kangkong (Ipomoea aquatica), kelakai/edible fern (Stenochlaena palustris), illipe nut/tengkawang (Shorea spp.), dragon fruit (Hylocereus undatus), mangosteen (Garcinia mangostana) and sweet melon/melon (Cucumis melo) are the best options based on the aggregated scores for these criteria (but precaution should be taken when planting crops that require low drainage). Sago palm and illipe nut have the highest scores for both sustainability and scalability of market, whereas banana, pineapple and sweet melon have the highest scores in term of the scalability of market and acceptability to farmers. We also address key opportunities and bottlenecks for the development of paludiculture food crops and present recommendations for the implementation of paludiculture in Indonesian peatlands.

     

Factors affecting the phytoaccumulation of weathered, soil-borne organic contaminants: analyses at the ex Planta and in Planta sides of the plant root

Persistent Organic Pollutants (POPs) in the soil–plant system were tracked from their origin in the bulk soil, into the rhizosphere soil pore water, to the xylem sap, and up to the aerial plant tissue. Specifically, the profiles of both chiral and achiral components of technical chlordane along this continuum were examined in detail for members of the Cucurbitaceae family: Cucurbita pepo L. subsp. pepo (“Black Beauty” true zucchini), Cucurbita pepo L. intersubspecific cross (“Zephyr” summer squash), and Cucumis sativus (“Marketmore” cucumber). The experiments were based on the use of mini-rhizotrons for collection and analysis of rhizosphere soil pore water for organic pollutants, as well as for low molecular weight organic acids (LMWOAs). In addition, the xylem sap and aerial plant tissue for intact, homografted, and heterografted C. pepo “Black Beauty” and C. sativus “Marketmore” plants were compared. The data indicate that profiles of the chlordane components in the pore water show no alteration in chiral patterns from those in the bulk soil and may be interpreted by physicochemical partitioning coefficients. Low molecular weight organic acids (LMWOAs) in the rhizosphere were observed to have a minor impact on bioavailability of the pollutants. However, once the pollutants cross the root membrane, major distinctive uptake and enantioselective patterns are apparent in the xylem sap, which are maintained in the aerial tissue. These in planta patterns are based on plant genotype. Specifically, grafting experiments with compatible heterografts of C. pepo and C. sativus establish that the chiral patterns are fully dependent on the plant root. The genotypic dependence of the data suggests possible mechanisms for phytoaccumulation.     

Relationship Between Crop Losses and Initial Population Densities of Meloidogyne arenaria in Winter-Grown Oriental Melon in Korea

To determine the economic threshold level, oriental melon (Cucumis melo L. cv. Geumssaragi-euncheon) grafted on Shintozoa (Cucurbita maxima × Cu. moschata) was planted in plots (2 × 3 m) under a plastic film in February with a range of initial population densities (Pi) of Meloidogyne arenaria. The relationships of early, late, and total yield to Pi measured in September and January were adequately described by both linear regression and the Seinhorst damage model. Initial nematode densities in September in excess of 14 second-stage juveniles (J2)/100 cm³ soil caused losses in total yields that exceeded the economic threshold and indicate the need for fosthiazate nematicide treatment at current costs. Differences in yield-loss relationships to Pi between early- and late-season harvests enhance the resolution of the management decision and suggest approaches for optimizing returns. Determination of population levels for advisory purposes can be based on assay samples taken several months before planting, which allows time for implementation of management procedures. We introduce (i) an amendment of the economic threshold definition to reflect efficacy of the nematode management procedure under consideration, and (ii) the concept of profit limit as the nematode population at which net returns from the system will become negative.     

Evaluation of Streptomyces spp. for biocontrol of gummy stem blight (Didymella bryoniae) and growth promotion of Cucumis melo L.

Gummy stem blight of Cucumis melo L. (melon) caused by Didymella bryoniae is a serious disease in the major production area of northwest China. Two Streptomyces isolates (Streptomyces pactum A12 and S. globisporus subsp. globisporus C28) previously isolated from the Qinghai-Tibet Plateau were investigated regarding their biocontrol of gummy stem blight and growth promotion of melon under controlled conditions. Streptomyces A12 and C28 indicated obvious antagonistic activity against D. bryoniae in vitro. Both A12 and C28 significantly decreased disease severity and AUDPC (area under the disease progress curve) of melon gummy stem blight in vivo (P < 0.05). Ten-fold dilution of C28 culture filtrate was more effective in controlling the disease compared with other treatments, the disease reduction effects were 41.0–64.2%. The mean fresh weights were increased by 40.4% for plants, 44.2% for roots, and 40.3% for aerial parts, when A12 was applied in both nursery soil and transplanted soil. Streptomyces C28 also increased the mean fresh weights of melon plants by 18.4–49.0% compared with the control in pot trial. Streptomyces A12 and C28 showed substantial colonization abilities in the rhizosphere and on the rhizoplane of melon plants. Results demonstrated that Streptomyces A12 and C28 were of positive effect on the biocontrol of gummy stem blight and growth promotion of Cucumis melo L.