* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Vine Crops - Great Lakes Fruit, Vegetable and Farm Market EXPO
Ecology of Banksia wikipedia , lookup
Plant stress measurement wikipedia , lookup
Plant defense against herbivory wikipedia , lookup
History of botany wikipedia , lookup
Plant secondary metabolism wikipedia , lookup
Plant nutrition wikipedia , lookup
Venus flytrap wikipedia , lookup
Evolutionary history of plants wikipedia , lookup
History of herbalism wikipedia , lookup
Plant morphology wikipedia , lookup
Plant use of endophytic fungi in defense wikipedia , lookup
Ornamental bulbous plant wikipedia , lookup
Plant evolutionary developmental biology wikipedia , lookup
Historia Plantarum (Theophrastus) wikipedia , lookup
Plant physiology wikipedia , lookup
Plant breeding wikipedia , lookup
Plant ecology wikipedia , lookup
Gartons Agricultural Plant Breeders wikipedia , lookup
Flowering plant wikipedia , lookup
Perovskia atriplicifolia wikipedia , lookup
Plant reproduction wikipedia , lookup
Great Lakes Fruit, Vegetable & Farm Market EXPO Michigan Greenhouse Growers EXPO December 6-8, 2011 DeVos Place Convention Center, Grand Rapids, MI Vine Crops Where: Grand Gallery (main level) Room A & B Recertification credits: 2 (1B, COMM CORE, PRIV CORE) CCA Credits: PM(0.5) CM(1.0) Moderator: Phil Tocco, Agriculture & Natural Resources Educator, Jackson Co. MSU Extension 2:00 pm Bacterial Diseases of Vine Crops 2:30 pm Degradable Mulches: Will They Work in Melon Production? 2:50 pm Vince Lawson, Muscatine Island Research Farm, Iowa State Univ. The How’s and Why’s of Grafting Melons 3:20 pm Sally Ann Miller, Plant Pathology Dept., The Ohio State Univ. Richard Hassell, Environmental Horticulture Dept., Clemson Univ. Effects of Watermelon Pollenizers on Yield Josh Freeman, Horticulture Dept., Virginia Tech Univ. Managing Bacterial Diseases of Vine Crops Dr. Sally A. Miller The Ohio State University, Ohio Agricultural Research and Development Center, Department of Plant Pathology, Wooster, OH, 330-263-3678 There are a number of serious bacterial diseases of vine crops, most of which are seedborne. Bacterial diseases are very difficult to manage in vine crops in the field, therefore practices that prevent the establishment of these diseases are critical. Of the most serious diseases, angular leaf spot, Xanthomonas leaf spot, and watermelon fruit blotch are seedborne, while bacterial wilt is vectored by cucumber beetles. Yellow vine decline is a sporadically occurring bacterial disease of vine crops that is transmitted to plants by squash bugs. Bacterial leaf spot. This disease is caused by a species of Xanthomonas, and has become a serious problem in some pumpkin-growing areas in the Midwest, but the disease can also cause significant damage on other vine crops. Lesions on the leaves range from small and irregular to large and angular. Centers become necrotic and lesions are surrounded by a chlorotic halo (Fig. 1A). Leaf marginal necrosis can also occur. Lesions on fruit are raised and scabby, and often on the top of the fruit (Fig. 1B). Flat, watersoaked areas on fruits may also be observed (Fig. 1C). Spotted A B C Figure 1. Bacterial leaf spot on pumpkin leaf (A); raised, scabby spots on fruit (B); watersoaked lesions on fruit (C). Bacterial fruit blotch. Bacterial fruit blotch is caused by a pathogenic bacterium (Acidovorax avenae subsp. citrulli). This is mainly an economic disease of watermelon, although other vine crops can be affected. Symptoms on leaves are often inconspicuous. On seedlings, watersoaked lesions on the underside of the cotyledons become necrotic. The typical symptom of fruit blotch is a dark olive green spot on the upper surface of the fruit. The spot starts small but rapidly increases in size to cover the most of the fruit surface within approx. 10 days. Secondary microbes then invade and result in fruit rotting. Angular leaf spot. Angular leaf spot is caused by Pseudomonas syringae pv. Lachrymans, a bacterial plant pathogen that is favored by cool, wet conditions. It is a very serious problem in cucumbers and other vine crops. Symptoms on leaves include angular necrotic lesions surrounded by a chlorotic halo and sunken spots on fruit. This spots begin a small watersoaked lesions that expand on the surface and also extend well into the fruit, eventually reaching the seeds. A B Figure 2. Angular leaf spot lesions on a pumpkin leaf (A) and infection of cucumber fruit (B). Bacterial wilt. This disease is often observed on sunny days after vines begin to run. Individual leaves begin to droop or flag (Fig. 3A), but the plant recovers at first (see OSU Fact Sheet HYG-3121-96; http://ohioline.osu.edu/hyg-fact/3000/3121.html). Eventually the vine wilts and the entire plant dies. Cucumber and cantaloupes are often affected, but squash, pumpkins and less often, watermelon, are also attacked. This disease is caused by Erwinia tracheiphila and is moved from plant to plant by striped (Fig. 3B) and 12-spotted cucumber beetles. In the spring, the beetles emerge from the ground and feed on young plants, introducing bacteria into the leaves or stems and spreading the pathogen from plant to plant. The bacteria reproduce in the water-conducting vessels, producing gums that interfere with water transport. A diagnostic test for bacterial wilt is the observation of sticky ooze between cut pieces of stem after touching them together then gently pulling them apart (Fig. 3C). A B C Figure 3. Young pumpkin plant with early bacterial wilt symptoms (A); striped cucumber beetle (B); bacterial ooze test (C) to confirm diagnosis of bacterial wilt. Bacterial Disease Management Steps Bacterial diseases generally can’t be controlled once they are established in a field and weather conditions are favorable. Therefore prevention is critical, from seed purchase through field production. 1) Purchase seed that has been tested and shown to be negative for seedborne bacterial pathogens. This is not a guarantee that plant pathogenic bacteria are absent since low populations may be undetectable. However, using tested seed is the first line of defense against bacterial diseases. Some seed companies advertise partial resistance in some varieties to angular leaf spot. 2) If seed has not been tested, consider seed treatment with hot water. This is somewhat risky since in large-seeded vegetables germination may be reduced. The following method is suggested by researchers in Australia (R. G. O’Brien and Christine Horlock, Agency for Food and Fibre Sciences, Horticulture): If seed has not been rated disease free, an effective seed treatment has been developed. Both internal and external contamination can be eliminated by soaking seed for 25 minutes in a water bath maintained at 55 °C. After treatment, place seed in running tap water to bring the temperature down quickly, then dry seed without delay. Seed should be sown within 2 days. Note that this treatment may lower the germination of some seed lots. Test a sample before committing large quantities of expensive seed. 3) Do not over-water seedlings in the greenhouse; try to keep the tops as dry as possible. Minimize touching and handling the plants. Scout seedlings for small, water-soaked spots; if water-soaked spots are observed, send a sample to a reputable lab for diagnosis. If bacterial disease is confirmed, throw away all flats containing symptomatic seedlings. Apply copper-based fungicides to seedlings in the greenhouse. 4) For field production, select growing sites with good drainage and airflow, full sunlight and low humidity. 5) Avoid overhead irrigation to prevent leaf wetness. 6) Insure adequate, but not excessive fertility. 7) Protect plants from cucumber beetle feeding at least until the 4th true leaf stage to reduce the risk of bacterial wilt. Floating row covers can provide a barrier between plants and the beetles that carry the bacteria. The covers also protect plants from squash bugs that may transmit the yellow vine decline pathogen. Foliar applied insecticides may also be used – for pumpkins insecticides should be applied after seedling emergence if the threshold of 0.5 beetles per plant at the cotyledon stage or 1 beetle per plant at the 1st or 2nd leaf stage is exceeded. Pre-plant insecticide application (seed treatment or in-furrow) is also effective. 8) If early in a disease epidemic, removal of infected plants may help to slow the spread of disease. When doing this, make sure not to spread the disease by hand or infested equipment. Diseased plants must be burned (depending on local ordinances) or buried. Cull piles only serve to spread diseases. 9) Spray plants with copper-based fungicides to slow progress of the disease. 10) Destroy foliage and vines as soon as possible after harvest to help manage yellow vine decline. Evaluating Degradable Mulches for Muskmelon Production Vince Lawson, Muscatine Island Research Farm, Iowa State University 111 North St., Fruitland, Iowa 52749 [email protected] Introduction Plastic mulches can provide vegetable growers with earlier crop maturity, better yields and quality, improved disease, insect and weed control, and more efficient fertilizer and water use. However, a downside to using plastic mulches is the rather high cost of removal and disposal at the end of the season. One solution to this problem has been the development of degradable mulches that can be left in the field after harvest to break apart and disappear. Unfortunately, mulch performance hasn’t always met expectations. Currently, there are different ways and means of making degradable films creating questions for growers concerning which one is best for their operation. The objective of this study was to evaluate three different types of degradable mulches for ease of use, speed of breakdown and how they influence transplanted muskmelon performance. Materials and Methods The degradable mulches included in this evaluation were a 0.6 mil clear and a 0.6 mil black biodegradable mulch (trade name BioTelo) from Dubois Agrinovation, Quebec, Canada; a 0.9 mil clear and a 0.9 mil black photodegradable mulch from Poly Expert Inc., Quebec, Canada; and a 0.4 mil clear and a 0.5 mil black oxo-biodegradable mulch from Eco-One, Ontario, Canada. All mulches were 4 ft wide. Mulch treatments were laid in the field on April 25 using a Rain Flo raised bed mulch layer. Trial design was a randomized complete block with three replications. A plot consisted of a single row of mulch 50 ft long. Muskmelon plants, cultivar Aphrodite, were transplanted on May 18 using a Holland pot transplanter capable of planting through mulch. Weed control was achieved by applying Prefar herbicide to beds before laying mulch and applying Strategy and Sandea herbicides between the beds after laying the mulch. Normal cultural practices were followed for irrigation, fertilization and pest control. Mulch strength (puncture resistance) was measured once a month with a Chatillon digital force gauge. Mature muskmelon fruit were harvested during July 21 through August 8 to determine effect of mulch on early and total yield. Results and Discussion The biodegradable (0.6 mil) and the oxo-biodegradable (0.5 mil) mulches were noticeably thinner than the photodegradable (0.9 mil) mulches. Because of their thinness, and possibly because of their composition, they were quite fragile and difficult to install in the field, or transplant on, without tearing or puncturing. In fact, we couldn’t use the transplanter’s press wheels without splitting the biodegradable or oxo-biodegradable films. The thicker and stronger photodegradable mulches were similar to conventional mulches and used without difficulty. All the black mulches provided good weed control but weeds grew thickly under the clear mulches even though herbicide was used, possibly because of field location and weather conditions. When the sun did shine weeds under the clear photodegradable mulch became burnt and stunted due to high temperatures under the mulch. But the clear biodegradable and to a lesser extent the clear oxo-biodegradable didn’t trap the heat under the mulch due to tears and holes allowing the weeds to grow unchecked. Early and total yield of the clear biodegradable mulch treatment, and the total yield of the clear oxo-biodegradable mulch treatment, was reduced because of weed competition (Table 1). Special instructions that come with the biodegradable and oxo-biodegradable mulches recommend they be laid immediately before planting to get maximum benefit from the mulch before breakup. Regrettably, as it worked out, the mulch treatments were laid on April 25, but due to weather conditions and time restraints, we weren’t able to transplant till May 18, about three weeks later. Evidently, this was too long of a time period as they started breaking up shortly after muskmelon transplanting causing weed problems. Muskmelon yield data are presented in Table 1. All of the black mulches and the clear photodegradable mulch produced good total yield. Normally, because of soil warming, clear mulches enhance early season crop growth and early yield but that wasn’t the case this season. Conditions after transplanting were cool, cloudy and rainy resulting in slow vine growth on both clear and black mulches. Then toward late June the weather became hot and sunny resulting in vigorous growth. Under these conditions the clear mulches didn’t produce early season yields that were any better than the black mulches. A problem was noted on fruit picked from the black biodegradable mulch plots. By harvest time the black biodegradable mulch was breaking down and becoming brittle and soft enough that fragments would stick to the bottoms of the heavy muskmelon fruit where they sat on the mulch. With some effort the fragments could be brushed off by hand but in large pickings hand brushing wouldn’t be feasible. A digital force meter was used to determine puncture resistance of the mulches and monitor how fast they lost their elasticity in the field after installation (Table 2). The clear biodegradable and oxo-biodegradable mulches gave the weakest readings after field installation and lost strength fairly rapidly. The readings also found that the buried edges of the black and clear photodegradable mulches still had good elasticity and strength in September at the end of the season. Summary The photodegradable mulches, because of their strength, were the easiest to use, produced good yields, but in the fall after disking, left the largest pieces of plastic in the field. The oxo-biodegradable mulches were thin and fragile making them difficult to work with. However, the black oxo-biodegradable mulch did provide good weed control and produced a good muskmelon yield. After disking at the end of the season the oxo-biodegradable mulches left long strips in the field but they were smaller and more brittle than the photodegradable remnants and aren’t expected to interfere with next season’s field work. The biodegradable mulches were also fragile and needed careful handling. Due to a delay between mulch laying and transplanting the clear biodegradable mulch broke up too quickly resulting in severe weed competition and low muskmelon yield. Note that muskmelon production is an experimental usage as Dubois Agrinovation recommends the clear biodegradable (BioTelo) mulch be used for early corn production. The black biodegradable mulch worked reasonably well for muskmelon production except for the small fragments that would stick to the bottom of the fruit at harvest. To their credit, the biodegradable mulches were, by far, the best looking at the end of the season in terms of breakdown and disappearance. After disking in September all that remained were small brittle pieces. Table 1. Aphrodite muskmelon early and total yield by mulch treatments. Early Number Fruit wt Number Mulch treatment fruit/acre Cwt/acre lb fruit/acre Clear photodegradable 1864 106.6 5.8 5900 Clear oxo-biodegradable 1760 101.2 5.6 5072 Clear biodegradable 104 4.8 4.7 2277 Total Cwt/acre 351.8 286.1 119.0 Fruit wt lb 6.0 5.7 5.2 Black photodegradable Black oxo-biodegradable Black biodegradable 1967 2070 1035 109.8 126.8 66.9 5.7 6.0 6.3 5796 6417 5279 335.4 399.0 342.1 5.8 6.3 6.6 Trial Mean LSD 0.05 1467 861 86.0 52.4 5.7 0.9 5123 1427 305.6 76.1 5.9 n.s. Table 2. Mulch strength readings in lbf (pound-force) required to puncture. All readings taken from top of mulch bed except for September 10 readings in parenthesis which were taken on buried edges. Mulch treatment May 10 June 10 July 10 August 10 Sept. 10 Clear photodegradable 1.35 1.12 1.19 0.97 0.87 (1.33) Clear oxo-biodegradable 0.39 0.29 0.23 0.15 0.14 (0.24) Clear biodegradable 0.45 0.23 0.14 0.03 0.05 (0.17) Black photodegradable Black oxo-biodegradable Black biodegradable 0.95 0.61 0.49 0.91 0.57 0.39 0.81 0.56 0.33 0.57 0.39 0.11 0.48 (0.87) 0.33 (0.40) 0.09 (0.36) The How’s and Why’s of Grafting Melons Richard L. Hassell Clemson University, CREC, 2700 Savannah Highway, Charleston, SC 29414 Introduction Vegetable Grafting is most common in European and Asian countries where crop rotation is no longer an option and available land is under intense use (Lee, 1994). Grafting is an alternative approach to reduce crop damage due to soil borne pathogens and increase plant abiotic stress tolerance which increases crop production (Cohen et al., 2007). We discuss and outline four grafting methods that are available for vegetable production in cucurbits; approach graft, hole insertion graft, one cotyledon graft and the side graft. History of graft methods The initial grafting method used for cucumber was cleft grafting (Ishibashi, 1959), but after the introduction of approach grafting, this technique became widespread in Japan because of its higher success rate and the uniform growth of grafted seedlings. In Italy the most common have been the approach and cleft methods (Bianco, 1990; Morra, 1997; Buzi, 2002) but currently the one cotyledon method and the hole insertion methods are used (Amadio, 2004). A high proportion (in Spain more than 90%) of watermelon plants are grafted using the one cotyledon method (Miguel and Maroto, 2000). In France both the side insertion and the approach grafting have been used in cucumber (Brajeul et al., 1998). Top Insertion Grafting is the most popular method used in China, since it is suitable for Lagenaria and inter-specific squash as rootstocks and requires few materials, has a high efficiency, 1,500+ plants/day/worker, and simpler management requirements. Manual grafting There are two methods of grafting, manual and machine. In manual grafting, the grafting and post-grafting operations require three to four people, each assigned to a specific step in the process (Lee and Oda, 2003). Cucurbits are usually grafted once the first true leaf appears but before it reaches full development both in the rootstock and scion seedlings. In order to reach this stage for both the scion and the rootstock, planting dates will vary depending on the rootstock chosen. Uniformity in both germination and growth of the rootstock and scion are critical to the grafting survival. Different grafting approaches have been adapted depending on scion and rootstock purpose, grafting technique, farmers’ experience, and post grafting management condition. Approach (tongue graft), hole insertion and one cotyledon grafts (Slant graft) are the current preferred methods. Modifications to these methods have been done by growers adapting to there particular operation. The approach technique, which have high survivor rate in general, and are chosen by non-experienced farmers who are looking into grafting for the first time, have plenty of space, and adequate labor. One cotyledon and hole insertion grafts require specialized tools and a healing chamber for a high survivor rate and require time to learn. In addition the graft junction needs to be above ground during transplanting to avoid the direct contact between scion and soil since the grafted plants are susceptible to soil born disease if the adventitious root reaches the ground. Automatic (machine driven) grafting The first semiautomatic grafting system for cucumber was commercialized in 1993 and multiple others have been developed since then, a simple grafting machine can produce 600 grafts per hour with 2 operators as compared to manual grafting making about 1,000 grafts per person per day (Suzuki et al., 1998; Masanao and Hisaya, 1996; Lee and Oda, 2003). In Spain the automated methods represents less than the 5% of the total but may be as high as 10% in Japan and China. Machine grafting is done using a simple machine or a grafting robot which is expensive. This also requires highly uniform seedlings to increase the grafting efficiency. New machines are currently being developed in Japan and Korea that are much more forgiving and require less labor to operate. The technique used by these machines is the one cotyledon graft. It is well adapted for machine operation and has a high rate of success. However, they cut the hypocotyls off the rootstock at ground level as part of the grafting procedure. The hypocotyl is cut near the root to induce root growth. The increased production of primary roots enhances the plant’s tolerance to cold and heat and ensures vigorous growth. However, this added procedure needs an exclusive grafting facility and it is more dependent on the condition of the soil. At present, 40 percent of watermelon grafting in Japan is done by this method (Suzuki et al., 1998; Masanao and Hisaya, 1996; Lee and Oda, 2003). Material and Graft Methods Quality seed and proper plant growth procedures of both rootstocks and scion material are critical for grafting to be successful. High quality seed with a uniform germination is a must at a first step. If primed seed is available take advantage of it. Rootstock seed is generally sown five to seven days prior to scion in cell trays or germination beds. Scion is sown in trays or germination beds following the germination requirements of the seeds. The cotyledon of rootstocks should be fully expanded when the scion emerges, keeping the scion at low relative humidity before grafting can minimize microorganism problems. Watermelon scion are harvested (1 or 2 days) after they emerge, are rinsed with clean water, treated with fungicides or disinfectant, e.g. Physan 20 or peroxyacetic acid/ hydrogen peroxide, to minimize the microorganism damage to the grafting. There are many requirements for cucurbit rootstock. The compatibility between rootstock and scion should be high and stable. The rootstock should have good tolerance to abiotic stress, resistance to soil born diseases, and not negatively affect fruit quality. In general, grafting compatibility is related to taxonomic affinity. Luffa and melon have higher compatibility with nettle melon compared to Chinese pumpkin and waxgourd (Wei et al., 2006). Grafting incompatibility can occur at early stage as vascular connection can not form properly after grafting. Grafting incompatibility can be delayed until fruiting stage, when massive nutrition and water are needed. Grafted plants declined early and successful harvesting is impossible. Incompatibility is less of a problem for those crops, e.g., cucumber and summer squash, which are harvested with immature fruits. There is positive correlation between the vigor of grafted watermelon and the similarity of protective isozymes, e.g., peroxidase and superoxide dismutase, between grafted and regular seedlings (Zhang et al., 2006). The age of rootstock and scion also plays an important role in compatibility. Optimal seedling age varies for species and different grafting methods. If seedlings are too young, they are too tender to handle during grafting process and to old may cause un-wanted meristematic re-growth tissue. Once the grafting has taken place, the proper healing chamber in needed to insure complete union has taken place. Some nurseries producing grafted plants have chambers to maintain temperature above 20 ºC in the tongue method and around 25 ºC. Air humidity (RH) is maintained between 85% to 100% (Miguel, 1997). Most nurseries acclimate in small plastic tunnels inside the greenhouses where it is possible to maintain a high RH (above 85%). Shading is often required during summer months. 6-8 days after grafting, plants are acclimated to the natural conditions of the greenhouse buy slowing dropping the humidity. The best conditions for grafting to take: temperature 22 – 28 OC, RH close to 100%, very low light intensity for the first 5 – 7 days (Miguel, 1997). Humidifiers can be purchased, however, remember that to much free water can lead to disease pressure and loss of graft union. A fog or mist is the preferred method. Listed below are the standard procedures used in each of the grafting types currently used today. These procedures for each method are provided by D. Liere (Syngenta Seeds Inc., 2007) 1. Approach graft. (Tongue Graft) -Scion seeds should be sown 7 days before rootstock seeds are sown. 242-cell tray is used for both. -After rootstock has fully developed cotyledons and scion has cotyledon and first true leaf, plants are pulled out from the tray and laid on a table (Note: 1 day before doing the grafting, trays should be watered heavily). -Do an angle cut into the hypocotyl of rootstock approximately half way with a razor blade, and make an oppositely angled cut on the hypocotyl of scion. These cuts need to be made so that the scion will be on top the rootstock when completed. -Two cut hypocotyls are placed together, then sealed with aluminium foil to help healing and preventing the graft from drying out. -The two plants are transplanted into a 72-cell tray, and tray is watered heavily until soil is completely wet. Trays should then be moved into a greenhouse (Note: After trays have been placed in the greenhouse water only as needed). -The top of the rootstock is cut off 5 days after grafting, and the bottom of scion is cut off 7 days after the top of the rootstock is removed. -After the bottom of the scion is cut off, must wait 2 days for the plants to be ready to transplant. -Grafted plants are maintained in the greenhouse until the plants are ready for transplanting. Do not need a humidity chamber. (Recommendation: Plants should not be older than 33 days before transplanting). 2. Hole insertion graft. -Scion seeds should be sown 7 days before rootstock seeds. - Rootstock seeds are sown in a 72-cell tray. Scion seeds are sown in 242-cell tray. Trays for rootstock should be watered very well and trays for triploid scion should be watered to the best moisture for germination. Trays are maintained at 80 °F for germination. - When both cotyledons and first true leaf start to develop, the rootstock plant is ready to graft (about 10 days after sowing). Remove growing point with a sharp probe, and then open a slit on upper portion of the rootstock hypocotyl. - Scion is angled cut on hypocotyl, and then inserted into the slit on the rootstock. - Two cut surfaces are matched together and held with a grafting clip. -Grafted plants should be maintained at 77 °F and 100 % humidity in a growth room. Keep the plants in the dark for 3 days (after the third day, keep plants in the growth chamber for one more day with the lights on) before moving them into the greenhouse. -After moving from growth chamber, grafted plants are maintained at 70-85 °F in the greenhouse until scion is connected well with the rootstock (Recommendation: Plants should not be older than 33 days before transplanting). 3. One cotyledon graft. (Slant Graft) -Scion seeds should be sown 7 days before rootstock seeds. -Rootstock seeds are sown in 72-cell tray. Scion seeds are sown in 242-cell tray. Trays for rootstock should be watered very well and trays for triploid scion should be watered to the best moisture for germination. Trays are maintained at 80 °F for germination. -When both cotyledons and first true leaf start to develop, the rootstock plant is ready to graft (about 10 days after sowing). -One cotyledon with the growing point is cut with a razor blade following the angle of the leaf petiole. The hypocotyl of the scion is cut in opposite angle. -Two cut surfaces are matched and held together with a grafting clip. -Grafted plants should be maintained at 77 °F and 100 % humidity in a growth chamber, and keep the plants in the dark for 3 days (after the third day, keep plants in the growth chamber for one more day with the lights on) before moving them into a greenhouse. -After moving from growth chamber, grafted plants are maintained at 70-85 °F in the greenhouse until scion is connected well with the rootstock (Recommendation: Plants should not be older than 33 days before transplanting). 4. Side graft. -Scion seeds should be sown 7 days before rootstock seeds. - Rootstock seeds are sown in 72-cell tray. Scion seeds are sowed in 242-cell tray. Trays for rootstock should be watered very well and trays for triploid scion should be watered to the best moisture for germination. Trays are maintained at 80 F for germination. -When both cotyledons and first true leaf start to develop, the rootstock plant is ready to graft (about 10 days after sowing). A slit is cut on the hypocotyl of rootstock with a razor blade. An angle cut is done on the hypocotyl of the scion, and then inserted into the slit in the hypocotyl of the rootstock. -Two cut surfaces are matched together and held with a grafting clip. - Grafted plants should be maintained at 77 °F and 100 % humidity in a growth chamber, and keep the plants in the dark for 3 days (after the third day, keep plants in the growth chamber for one more day with the lights on) before moving them into a greenhouse. -The top of the rootstock is cut off 5 days after grafted plants are moved from high humidity growth chamber. Plants are maintained in the greenhouse until scion is connected well to the rootstock (Recommendation: Plants should not be older than 33 days before transplanting). Effect of Special Pollenizers on Watermelon Yield Josh Freeman, Department of Horticulture, Virginia Tech Eastern Shore Agricultural Research and Extension Center 33446 Research Drive, Painter, Virginia 23420 [email protected] Over the last decade the popularity of seedless watermelon has increased greatly and now occupies most of the U.S. market. When growers transfer acreage to seedless watermelon production, they must take into account that triploid (seedless) watermelon plants do not produce enough viable pollen to pollinate themselves. Diploid (seeded) cultivars can provide the pollen for the triploid cultivar. To achieve optimal yields, 20% to 33% of the plants in the field should be diploid. Traditionally, dedicated rows have been set aside for seeded cultivars within the field of seedless watermelons. A wide range of pollenizer cultivars have now been designed to be planted in-row between triploid plants. By eliminating dedicated row space in the field for pollenizers, the number of triploid plants and watermelons harvested per acre should increase. These pollenizer cultivars are relatively new and the concept itself is new. Nearly all pollenizer cultivars available have thin vines that have a high degree of lateral branching and reduced foliage. The most important characteristics of these cultivars are: 1. proliferation of male flowers and pollen, 2. non-competitive growth habit, 3. and distinct fruit size or rind pattern. It is important that the cultivars have high numbers of male flowers throughout the season in order to provide adequate pollen for fruit set in the triploid crop. One of the greatest drawbacks to using special pollenizer varieties is the cost of the seed, which is generally 3 times that of hybrid diploid watermelon seed. There is also no return gained directly from special pollenizer varieties because they do not produce marketable fruit. There has been interest among growers to reduce input costs by using standard seeded varieties inrow, much like special pollenizer varieties would be used. Previous research has indicated that there are significant differences in flower production between special pollenizer varieties and standard diploid varieties. There are also experimental results that have shown a decreased seedless watermelon yield when a standard diploid cultivar was used as a special pollenizer. However, other experimental data indicates that seedless watermelon yield is not reduced in this situation. Some research has also indicated that standard diploid varieties used as in-row pollenizers may reduce seedless watermelon yield through competition while special pollenizer varieties do not. Another factor that could contribute greatly to the productivity of the seedless watermelon production system is foot traffic during harvest operations. If a standard diploid variety is used in-row and is intended to be harvested, this may increase foot traffic and subsequent vine damage. Many times, harvest crews will not harvest seeded and seedless fruit at the same time, so this would lead to an extra trip through the field for the harvest crew. This would also be the case if a row is dedicated to a standard pollenizer that is intended to be harvested. Growers must decide whether the added input costs of special pollenizers are a good investment for their operation or if they have a significant market for seeded watermelons. Also they must decide if the added traffic in a field of seedless watermelons are worth the seeded fruit they will gain. Unfortunately there is no research to quantify the effect of foot traffic on seedless watermelon yield. The results may also vary from year to year if standard varieties are used in-row based on variations in growing conditions. Resources Freeman, J.H., G.A. Miller, and S.M. Olson. Performance of Selected Diploid Watermelon Pollenizers. University of Florida IFAS Extension Publication #HS1081. http://edis.ifas.ufl.edu/hs332 Freeman, J.H. and S.M. Olson. Using In-Row Pollenizers for Seedless Watermelon Production. University of Florida IFAS Extension Publication #HS1079. http://edis.ifas.ufl.edu/hs333