Watermelon Plants Research Articles

EFFECT OF PLANT SPACING AND APICAL SHOOT PINCHING ON GROWTH AND PRODUCTIVITY OF WATERMELON PLANTS UNDER SANDY SOIL CONDITIONS

The present work was carried out in Private Vegetable Farm at El- Heez, Al-WahaatAl-Baharyia District, Giza Governorate, Egypt, during two successive summer seasons of 2016 and2017, to study the effect of plant spacing and apical shoot pinching (ASP) stage on growth andproductivity of watermelon plants under sandy soil conditions using drip irrigation system. Resultsshowed that, the interaction between plant spacing at 30 cm and ASP at the 6th node gave the tallestplants, whereas the interaction between plant spacing at 60 cm and ASP at the 6th node gave thehighest values for each of number of leaves and branches/plant at 45 days after planting. On the otherside, planting watermelon at 45 cm and ASP at the 6th node increased average number of fruits/ plant,average fruit weight, yield/plant and total yield/faddan.

Genetic diversity of Fusarium solani f.sp. cucurbitae the causal agent of crown and root rot of watermelon in Tunisia using ISSR markers

Fusarium solani f.sp. cucurbitae (F.s.c.) Snyder and Hansen is one of the most important fungi causing serious damages to the cucurbits production areas in Tunisia. The goal of this investigation was to study the genetic characterization of F. solani f.sp. cucurbitae Tunisian population. Ten isolates of F.s.c. (F.s.c.1 to F.s.c.10) collected from infected watermelon plants in numerous regions of Tunisia; were subjected to PCR identification using ITS1-ITS4 primers pair, and Inter-simple sequence repeat (ISSR) technique. Results obtained confirmed the presence of F. solani f.sp. cucurbitae race 1 in Tunisia. ISSR dendrogram of the ten F.s.c. isolates generated by bi- and trinucleotide primers; and conducted by the unweight pair grouping using mathematical averaging (UPGMA) method from Nei’s genetic distance, revealed the presence of similarities between the isolates that ranged from 31 to 84%. The isolates F.s.c.8 (collected from Gabes) and F.s.c.4 (collected from Sidi Bouzid), were genetically dissimilar presenting the lowest similarity coefficient. In contrast; isolates F.s.c.3 (collected from Sfax) and F.s.c.1 (collected from Beja) were similar. Cluster analysis based on UPGMA of the ISSR markers data assembled F.s.c. isolates into two major groups. These results are helpful to develop integrated management and future breeding programs for plant resistance.

Identification of watermelon chlorotic stunt virus from watermelon and zucchini in Saudi Arabia

Symptomatic and non-symptomatic leaf samples of cucumber, zucchini, melon and watermelon plants were collected from three locations (Al-Ahsa in the East, Jizan in the South and Tabuk in the North) in the Kingdom of Saudi Arabia during 2013–2014. The detection of begomovirus infection was commenced with serological assay, rolling circle amplification and PCR amplification with universal begomovirus primers. The zucchini and watermelon samples tested positive for the presence of begomovirus infection in 53 and 39.6%, and 54.5 and 41.5% samples using serological and PCR-based detection, respectively. Based upon the core coat protein sequence, the full-length genomes of DNA-A and DNA-B were amplified and subsequently sequenced. The sequence analysis revealed that the two clones of DNA-A shared 96.9% nucleotide (nt) sequence identity with each other while they shared 95.9–98.4% nt sequence identity with watermelon chlorotic stunt virus (WmCSV) isolates reported so far. Similarly, the two DNA-B clones showed 91.8% mutual nt sequence identity, while sharing 95.2–95.5% nt sequence identity with all other reported DNA-B sequences. The phylogenetic dendrogram grouped both DNA-A clones into separate sub-groups, suggesting that both isolates were introduced separately into Saudi Arabia. The identification of WmCSV from zucchini in Saudi Arabia and other hosts in the neighbouring countries suggests that this virus is becoming an emerging threat to cucurbits in this region.

English

Watermelon plants can be naturally infected by several viruses in single or mixed infections, of which the diagnosis is difficult and require specific techniques. This study aims to detect and to verify the presence of Cucumber mosaic virus (CMV), Papaya ringspot virus type W (PRSV-W), Watermelon mosaic virus (WMV), Zucchini lethal chlorosis virus (ZLCV), Zucchini yellow mosaic virus (ZYMV), and the main cucurbit viruses in Brazil using multiplex reverse transcriptase polymerase chain reaction (RT-PCR) assay. Oligonucleotides were designed towards the conserved regions of the virus genomes. In the duplex-PCR, it was possible to detect all the virus combinations, except ZLCV with ZYMV. The amplified product sizes were 644 bp (CMV), 535 bp (WMV-2), 398 bp (PRSV-W), 244 bp (ZLCV), and 214 bp (ZYMV). To test the efficacy of the methodology, we analyzed plants with virus symptoms from four municipalities in the state of Tocantins, located at Brazilian Cerrado. Mixed infections were detected in 80% of samples in all the municipalities. The multiplex RT-PCR assay can be used to detect and differentiate watermelon viruses that affect crops in the state of Tocantins.   Key words: Cucumovirus, multiplex RT-PCR, Orthotospovirus, potyvirus, watermelon.

Gas exchanges and production of watermelon plant under salinity management and nitrogen fertilization

ABSTRACT In the Brazilian semi-arid region, the occurrence of water with high salt concentrations is common, making it a limiting factor for the agricultural production. The water-use salinity management strategies are an alternative capable of minimizing the deleterious effects of the stress on plants. This study aimed to evaluate the gas exchanges and production of ‘Sugar Baby’ watermelon plants under strategies of irrigation with saline water and nitrogen fertilization. The experiment was conducted in a randomized block design, arranged in a 6 x 2 factorial scheme, with five replicates, corresponding to six irrigation strategies with saline water applied at different phenological stages of the crop (control - irrigation with low-salinity water throughout the entire crop cycle, and salt stress at the vegetative stage, vegetative/flowering stage, flowering, fruiting and fruit maturation) and two nitrogen rates (50 % and 100 %, equivalent to 50 mg and 100 mg of N kg-1 of soil). Two levels of water salinity were studied: one with a low and the other with a high level of electrical conductivity (0.8 dS m-1 and 3.2 dS m-1, respectively). The salinity of 3.2 dS m-1 in the vegetative/flowering and fruit maturation phases decreases the stomatal opening, transpiration and CO2 assimilation rate. The level with 50 % of N provides a higher assimilation rate of CO2 and fresh fruit mass. The watermelon plant expresses a greater sensitivity to saline stress in the vegetative and flowering phases, a situation that results in a decreased fruit size.

Insights Into a Watermelon Virome Contribute to Monitoring Distribution of Whitefly-Borne Viruses

The composition of a plant virome may represent spatiotemporal patterns of plant virus abundance. Using next generation sequencing, we investigated the viromes of watermelon fruits grown in two adjacent open fields located in Eastern Israel: Kalia and Mitzpe-Shalem. The two viromes were comprised of distinct virus species and genera. Studying spatial and temporal effects on virus occurrence, we detected the crinivirus Cucurbit yellow stunting disorder virus in Kalia and not in Mitzpe-Shalem, irrespective of collection time. A spatial effect was also observed regarding the occurrence of the begomovirus Watermelon chlorotic stunt virus, which was not detected in watermelons from Kalia, but rather in watermelon fruit in Northern Israel in 2018. A temporal effect was observed on the appearance of the ipomovirus Cucumber vein yellowing virus, which was detected in watermelons from Kalia in 2017 and was absent in the 2016 virome analysis. Importantly, regardless of temporal and spatial effects, the crinivirus Cucurbit chlorotic yellows virus, which was new to Israeli landscape, was detected in all the tested watermelon plants. These changes in viral abundance were associated with an early whitefly (Bemisia tabaci) occurrence, which might be the cause for the severe disease spread in watermelons.

Deciphering differences in the chemical and microbial characteristics of healthy and Fusarium wilt-infected watermelon rhizosphere soils.

Plant health is determined by the comprehensive effect of soil physicochemical and biological properties. In this study, we compared the chemical properties and microbiomes of the rhizosphere soils of healthy, Fusarium oxysporum-infected, and dead watermelon plants and attempted to assess their potential roles in plant health and Fusarium wilt expression. The rhizosphere soils were collected from watermelon plants grown in a greenhouse under the same field management practices, and various soil microbial and chemical characteristics were analyzed. The rhizosphere soil of healthy plants had the lowest abundance of F. oxysporum and pH and the highest contents of ammonium (NH4+) and nitrate (NO3-). The relative content of hemicellulose was decreased in the rhizosphere soil of F. oxysporum-infected plants. The differences in soil microbial compositions among the watermelons at the three health statuses were obvious, and their microbiomes changed gradually along with plant health status. The microbiome in the rhizosphere soil of healthy plants had the highest relative abundances of potential antagonists and the lowest relative abundances of potential pathogens. The specific microbial composition together with some chemical properties of the rhizosphere soil of healthy plants might be responsible for inhibiting Fusarium wilt expression.

Interference of Palmer amaranth (Amaranthus palmeri) Density in Grafted and Nongrafted Watermelon

AbstractWatermelon [Citrullus lanatus(Thunb.) Matsum & Nakai] grafting is commonly used for management of diseases caused by soilborne pathogens; however, little research exists describing the effect of grafting on the weed-competitive ability of watermelon. Field experiments determined the response in yield, fruit number, and fruit quality of grafted and nongrafted watermelon exposed to increasing densities of Palmer amaranth (Amaranthus palmeriS. Watson). Grafting treatments included ‘Exclamation’ triploid (seedless) watermelon grafted on two interspecific hybrid squash rootstocks ‘Carnivor’ and ‘Kazako’, with nongrafted Exclamation as the control. Weed treatments includedA. palmeriat densities of 1, 2, 3, and 4A. palmeriplants per watermelon planting hole (0.76-m row) and a weed-free control. IncreasingA. palmeridensities caused significant reductions (P <0.05) in marketable watermelon yield and marketable fruit number. Watermelon yield reduction was described by a rectangular hyperbola model, and 4A. palmeriplants planting hole−1reduced marketable yield 41%, 38%, and 65% for Exclamation, Carnivor, and Kazako, respectively. Neither grafting treatment norA. palmeridensity had a biologically meaningful effect on soluble solids content or on the incidence of hollow heart in watermelon fruit.Amaranthus palmeriseed and biomass production was similar across weed population densities, but seed number per femaleA. palmeridecreased according to a two-parameter exponential decay equation. Thus, increasing weed population densities resulted in increased intraspecific competition amongA. palmeriplants. While grafting may offer benefits for disease resistance, no benefits regarding weed-competitive ability were observed, and a consistent yield penalty was associated with grafting, even in weed-free treatments.

IDENTIFICATION OF MICROBES ANTAGONISTIC AGAINST Fusarium oxysporum ISOLATED FROM RHIZOSPHERE ZONE OF WATERMELON

This research was aimed to isolate and identify microbes which antagonistic against Fusarium oxysporum, the causative agent of vascular wilt in watermelon plants. The antagonistic microbes were isolated from soil samples collected from rhizosphere of watermelon farm located at west Sanur village, South Denpasar, Bali. Isolation of fungi and bacteria were conducted on potato dextrose agar medium (PDA) and nutrient agar medium (NA), respectively. Fungal isolates were then observed under light microscope for its morphological characteristics before identification using a reference book. Bacterial isolates were characterized using various tests, such as gram stain reaction, existence of endospores, catalase reaction, and ability to ferment various sugars. Their characteristics were then compared with those described in a reference book. Two fungal species (Trichoderma harzianum and Trichoderma viride) and two bacterial antagonists (Pseudomonas sp. and Bacillus sp.) were found to have potential to be developed as biocontrol agents to inhibit the growth of F. oxysporum.

Improving the grafted-plant rate in triploid watermelons by optimizing the water moisture in substrates and the usage of scion

Abstract The cost of growing triploid watermelon seedlings has increased due to their low-efficiency grafting. The first priority in growing seedless watermelon seedlings is increasing the grafted-plant and seed-utilization rates. This study aimed to improve the grafted-plant rate by screening the most suitable substrate formulation, optimizing water moisture in the substrate, and evaluating the effect of different scions to improve seed-utilization rate. Five combinations of substrate (S1 to S5) and seven relative humidity levels (45%, 50%, 55%, 60%, 65%, 70%, and 75%) were used. Three types of scions (yellow bud, Ts-1; two cotyledons did not unfold, Ts-2; and first true leaf appeared, Ts-3) were tested. Results showed that the combination of S1 exhibited the best seed-utilization rate which was 71.6%. Moreover, the most suitable water moisture in the substrate ranged from 50% to 55%. The usage of the scion from Ts-3 significantly increased the grafting survival, grafted plant and seed-utilization rates by 13.7%, 10.1% and 22%, respectively, compared with the conventional method. Our study suggested that the best time to use the scion and the rootstock was during the seedling stage when the first true leaf unfolded. The proposed method decreased the production cost of seedlings and significantly improved the efficiency of grafting procedures. The results of this work are applicable to the technique of growing seedlings and can thus guide growers of high-quality grafted plants of triploid watermelon.

Critical Period for Weed Control in Grafted and Nongrafted Watermelon Grown in Plasticulture

AbstractField experiments determined the critical period for weed control (CPWC) in grafted and nongrafted watermelon [Citrullus lanatus(Thumb.) Matsum. & Nakai] grown in plasticulture. Transplant types included ‘Exclamation’ seedless watermelon as the nongrafted control as well as Exclamation grafted onto two interspecific hybrid squash (ISH) rootstocks, ‘Carnivor’ and ‘Kazako’. To simulate weed emergence throughout the season, establishment treatments (EST) consisted of two seedlings each of common purslane (Portulaca oleraceaL.), large crabgrass [Digitaria sanguinalis(L.) Scop.], and yellow nutsedge (Cyperus esculentusL.) transplanted in a 15 by 15 cm square centered on watermelon plants at 0, 2, 3, 4, and 6 wk after watermelon transplanting (WATr) and remained until the final watermelon harvest at 11 WATr. To simulate weed control at different times in the season, removal treatments (REM) consisted of two seedlings of the same weed species transplanted in a 15 by 15 cm square centered on watermelon plants on the same day of watermelon transplanting and allowed to remain until 2, 3, 4, 6, and 11 WATr, at which time they were removed. Season-long weedy and weed-free controls were included for both EST and REM studies in both years. For all transplant types, aboveground biomass of weeds decreased as weed establishment was delayed and increased as weed removal was delayed. The predicted CPWC for nongrafted Exclamation and Carnivor required only a single weed removal between 2.3 and 2.5 WATr and 1.9 and 2.6 WATr, respectively, while predicted CPWC for Kazako rootstock occurred from 0.3 to 2.6 WATr. Our study results suggest that weed control for this mixed population of weeds would be similar between nongrafted Exclamation and Exclamation grafted onto Carnivor. But the observed CPWC of Exclamation grafted onto Kazako suggests that CPWC may vary with specific rootstock–scion combinations.

Genome-wide analysis of the WRKY family genes and their responses to cold stress in watermelon

The WRKY transcription factors play important roles in various physiological processes, especially in regulating plant resistance to environmental stresses. Watermelon (Citrullus lanatus) plants suffer from various stressful climate conditions during their growth, especially cold stress. However, little information about the exact role of WRKYs in watermelon responses to cold was available. In this study, a total of 57 candidate ClWRKY genes from watermelon genome were identified and they were distributed unevenly on 11 chromosomes. After excluding five ClWRKY genes with incomplete WRKY domains, phylogenetic analysis showed that the remaining 52 ClWRKY genes could be divided into three groups with 11 members in Group 1, 34 in Group 2, and seven in Group 3. The ClWRKY genes in group 2 could be further classified into five subgroups with three members in 2a, five in 2b, 13 in 2c, six in 2d, and seven in 2e, respectively. The expression profiles of ClWRKY genes in response to cold stress could be classified into four types: four ClWRKY genes had little or no change in transcript levels, seven ClWRKY genes had irregular expression patters, 17 ClWRKY genes were upregulated, and 25 ClWRKY genes were downregulated. The different regulation patterns of ClWRKY genes in response to low-temperature treatment revealed that the WRKY gene family was crucial for cold stress tolerance and there were multiple regulatory pathways involved in cold resistance.

Economic injury levels and sequential sampling plans for control decision-making systems of Bemisia tabaci biotype B adults in watermelon crops.

Decision-making systems are essential parts of integrated pest management programs. The whitefly Bemisia tabaci (Hemiptera: Aleyrodidae) is a major pest of many crops, including watermelon (Citrullus lanatus), the second most consumed fruit worldwide. However, there are still no studies on decision-making systems for B. tabaci on this crop. Thus, we aim to determine a decision-making system to control B. tabaci biotype B on watermelon crops. The highest densities of B. tabaci biotype B reduced the yield of watermelon crops by up to 56%. Watermelon plants were more susceptible to the pest at the vegetative stage than at the reproductive stage. The economic injury levels of B. tabaci biotype B when watermelon prices were low, average, and high were respectively, 0.52, 0.21 and 0.13 adults leaf-1 at the vegetative stage, and 1.69, 0.69 and 0.44 adults leaf-1 at the reproductive stage. The sequential plans reached the same decisions as the conventional plan, and reduced the time and cost of sampling by up to 92.68%. The decision-making systems determined in this study enable an expedited and proper decision to be made for controlling B. tabaci, biotype B and can be used in different price situations for watermelon and in crops at different phenological stages. © 2018 Society of Chemical Industry.

Keanekaragaman Serangga pada Tanaman Semangka (Citrullus lanatus (Thunb.) Mansf.)

The aims of this reseach was to determine the diversity, abundance of insects on watermelon based on ecological function .The method used in this research was survey with a random sampling techniques on watermelon plants. Insect observations conducted in three phases, ie before flowering, during flowering and during fruiting. The results showed the insects were obtained consisting of five orders, ie Orthoptera, Coleoptera, Hemiptera, Hymenoptera and Diptera. The role of each order is fitofag / herbivores are dominated by the family of the order Orthoptera and Coleoptera. Most families from the order Orthoptera, Coleoptera, Hymenoptera and Diptera act as predators. Insects that act as pollinators dominated by the family of the order Hymenoptera and Diptera. The Order Hemiptera act as pests. Insect abundance in watermelon crop was highest in fruiting phases ie 1103 individuals (50.61%). While the abundance in the phase prior to flowering and during flowering phase successively obtained the total of 132 individuals (10.62%) and 727 individuals (38.77%) respectivelly. Shannon-Wiener Diversity index (H'), Evenness index (E) of insects in the phase before flowering H '= 1.642, E = 0.3691, in the current phase of flowering H' = 2.231, E = 0, 5474, and the fruiting phase H '= 2.613, E = 0.7575. Based on the ecosystem function the highest diversity was insect pest (H' = 1,56, E 0,6799), following by insect pollinators (H' = 1,44, E 0,8489), and the lowest was predator (H' = 1,235, E 0,8598), (In watermelon farming, insect community was dominated by pest, escpesially during fruiting phase.

Growth and yield of hydroponic watermelon with straw compost substrate and gibereline (GA3) application

Watermelon plant in Indonesia are generally grown on paddy fields at an altitude of 0-500 m above sea level (asl) as intercrops between paddy planting seasons. The difficulties of watermelon cultivation are to achieve uniform and steady fruits quality (sweetness and weight). Implementation of hydroponics watermelon technology is an effort to increase production and productivity without disrupting rice production as a food crop. The objectives of this study were to examine the effects of straw compost substrate and gibereline application to watermelon growth and yield . The research was conducted in Cilamaya Kulon of Karawang district (35 m asl) in October 2015 until January 2016. The research method used was experimental research using factorial randomized block design of 2 factors. The first factor was the ratio of planting medium consisted of 3 levels of treatment ie the ratio of straw compost with sand (1: 3, 1: 1 and 3: 1) and the second factor was the concentration of gibberellin (GA3) consisting of 4 levels of gibberellin concentration (0 ppm; 50 ppm; 150; ppm and 250 ppm). The results showed that gibberelline and straw compost ratio with sand did not occur interaction but influenced independently giving the composition of planting medium (1: 1) to plant height, fruit weight and fruit sweetness. Gibberelline concentration 50 ppm independently affects the number of leaf. The optimum growth and yield of water melon were obtain if straw compost application equal to 50%(v/v).

Descripción y comparación entre morfotipos de Fusarium brachygibbosum, F. falciforme y F. oxysporum patogénicos en sandía cultivada en Sonora, México

Recientemente se ha identificado a Fusarium brachygibbosum, F. falciforme y F. oxysporum como causantes de marchitez y muerte en plantas de sandía en Sonora, México. Debido a la escasa información morfológica acerca de F. brachygibbosum y con el fin de establecer las características macroscópicas y microscópicas distintivas entre las especies, en el presente trabajo se realizó la descripción de cuatro morfotipos F. brachygibbosum y su comparación con tres de F. falciforme y dos de F. oxysporum. La categorización de los morfotipos se realizó, con base en la forma de crecimiento, tonalidades del micelio y el color desarrollado en agar-dextrosa-papa, a partir de 32 aislados de Fusarium patogénicos en sandía. Los cuatro morfotipos de F. brachygibbosum presentaron clamidosporas sencillas o dobles, de pared gruesa, intercalares y terminales. Monofiálides cortas y escasas polifiálides. Macroconidios con células apicales en ligera forma de gancho y células basales con forma típica o ligera forma de pie. El mayor grosor de paredes fue distintivo en las clamidosporas de F. brachygibbosum. La morfología de los macroconidios fue diferente en las tres especies. Una característica distintiva en los morfotipos de F. falciforme fueron las monofiálides largas y delgadas; mientras que en los de F. oxysporum fue la ausencia de septos en los microconidios. El tamaño de los macroconidios y microconidios fue significativamente diferente entre los morfotipos, pero no entre las especies.

Genome duplication improves the resistance of watermelon root to salt stress

Salinity is a major abiotic stress factor that affects crop productivity. Roots play an important role in salt stress in plants. Watermelon is a salt-sensitive crop; however, tetraploid watermelon seedlings are more tolerant to salt stress than their homogenotype diploid ancestors. To obtain insights into the reasons underlying the differences in salt tolerance with respect to the ploidy of plants, self-grafted and cross-grafted diploid and tetraploid watermelon seedlings were exposed to 300 mM NaCl for 8 days. After the treatment, the tetraploid rootstock-grafted watermelon plants showed higher salt stress tolerance than the diploid plants. There were no significant differences in the physiological effects between the rootstocks with the same ploidy. The tetraploid rootstock-grafted watermelon plants exhibited higher net photosynthetic rate, leaf stomatal conductance and transpiration rate than the diploid rootstock-grafted watermelon plants throughout the salt treatment process. The activities of antioxidant enzymes and contents of osmoregulatory compounds in the roots were higher in the tetraploid rootstock-grafted watermelon plants than in the diploid plants during the entire salt response process. Higher Na+/K+ ratio was found in all parts of diploid rootstock-grafted watermelon, especially in the roots, K+ and Na+ were preferentially accumulated in the aerial parts (leaves and stem) than in the roots, which might be driven by the Na+/H+ antiporter, as evidenced by the higher transcript levels for SOS, PMA1, HKT1 and NHX1 in the roots. Taken together, our results suggest that genome duplication improves the resistance of watermelon root to salt stress.

Antagonistic potential of certain soilborne fungal bioagents against Monosporascus root rot and vine decline of watermelon and promotion of its growth

Monosporascus cannonballus responsible for cucurbits Monosporascus root rot and vine decline, isworldwide spread notably in Tunisia. The most appropriate strategies to suppress disease development are thoseable to reduce the ascospores population using eco-friendly approach treatments. Seven soilborne fungal isolateswere tested in vitro (by dual confrontation technique) and in vivo in the greenhouse as potential bioagents againstthree virulent M. cannonballus isolates. In vivo experiments were divided into two assays, preventive and curativetreatments. Trichoderma viride and T. harzianum exhibited high inhibitory activities against M. cannonballusmycelial growth with values more than 90%, followed by Aspergillus niger (87.89%) and Paecilomyces victoriae(80.44%). Furthermore, these two Trichoderma spp. when applied preventively and curatively in in vivo trials,reduced significantly disease incidence (8.33% and 16.67-20.83%), root disease index (0.79-0.8 and 1.25-1.17),and reduced also ascospores index (1.5-1.54 asc/g of peat) and (2.54-2.42 asc/g of peat), respectively, incomparison with control treatments. Moreover, T. viride and T. harzianum enhanced the growth development ofwatermelon plants treated preventively and curatively in the greenhouse. They significantly improved differenthorticultural measurements with mean values of plant height (76.75-79.83 cm, and 81.83-80.92 cm), root volume(2.39-2.22 cm3, and 1.84-1.88 cm3), above grounds fresh weight (16.07-16.57 g, and 12.84-14.93 g) and dry wt.(2.49-2.6 g, and 2.66-2.70 g), underground fresh wt. (0.725-0.654 g, and 0.717-0.690 g) and dry wt. (0.147-0.214g, and 0.156-0.152 g). Based on current results, it appears that Trichoderma spp. could be employed in soiltreatments to promote watermelon plant growth and development.

Amonium and Nitrate Of Soil In Relation To Water Table Fluctuation At The Tidal Rice Fields

The reclaimed lowlands of Indonesia with the respective of 256 hectares of secondary block consist of 16 hectares of tertiary blocks, were used for rice plant production. Paddy was planted during the rainy season of November to February. It was followed by water melon plant in March to May. Then corn was growed in the dry season of June to September finally. Fluctuations of water table in the farm is very crucial in determining the cropping calender. Water management with free drainage approach is influenced by tidal water movement into the tertiary canals bordering the farmers fields. A constant water retention -10 cm below the canal bank has increased the water table in the farm from -10 cm to +20 cm. Water retention (controlled drainage) mode was applied by the farmers especially during the rice growing period. The release of water in the canal to a depth of -50 cm below the canal bank had lowered the water table level to -20 cm. During almost 200 days of experimental work, soil and water samples were taken by 11 times. The content of NO 3 - , NH 4 + and pH of the soil sample and be analyzed in relation to the water table fluctuation. Groundwater level does not show the effect on nitrate release on the urea application stocked. however, on the high ground water level it appears to be more in control of ammonium release compared to the ground water level of -20 cm.

English

Identification of resistant germplasms is crucial for crop breeding. The aim of this study was to determine the reaction of accessions of watermelon plants to Meloidogine enterolobii using two experiments. In the first experiment, 20 accessions were evaluated, and in the second, the four most promising accessions were selected in the first experiment and two controls. Both experiments were implemented under a completely randomized design with ten replications. Each parcel consisted of a plastic pot containing autoclaved soil inoculated with 2,200 eggs of M. enterolobii. Among the variables studied, the egg number and reproduction factor showed a high positive correlation. The subsamples indicated a wide variation among and within each accession (p < 0.01). At the end, variation in the response among and within the accessions was observed regarding the reproduction factor. Of the accessions evaluated, accessions 9 and 10 exhibited potential for the implementation of breeding programs. Key words: Citrullus lanatus, resistance, vegetable genetic capabilities