Research Projects

<body topmargin=0 leftmargin=0 marginheight=0 marginwidth=0> <table cellpadding=0 cellspacing=0 border=0><tr> <td valign="top" colspan=3 height=82 BGCOLOR="#000066" TEXT="#F7F7FF"> <div> <FONT SIZE="5" COLOR="#FFFFFF" FACE="Arial" ><B>Linda Wessel-Beaver  -- University of Puerto Rico at Mayaguez        </B></FONT><B>     |     </B><A HREF="index.htm" TARGET="_top" TITLE="Linda WesselBeaver University of Puert"><U><B>home</B></U></A></div> <div> <A HREF="id2.htm" TARGET="_top" TITLE="Publications"><U>Publications</U></A>   |   <B>Research Projects</B>   |   <A HREF="id4.htm" TARGET="_top" TITLE="Teaching and Education"><U>Teaching and Education</U></A>   |   <A HREF="id16.htm" TARGET="_top" TITLE="Tropical Pumpkin (Squash) Breeding"><U>Tropical Pumpkin (Squash) Breeding</U></A>   |   <A HREF="id6.htm" TARGET="_top" TITLE="Links"><U>Links</U></A></div> <div> </div> </td> </tr><tr> <td valign="top" width=200 BGCOLOR="#BBBBBB" TEXT="#080000"> <div> <IMG SRC="18cc2220.jpg" border=0 width="194" height="34" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></div> <bR> <div> <A HREF="id3_m.htm#tstar_94" TARGET="TRLX_Middle" TITLE="Research Projects"><U>Insect Resistance in Tropical Pumpkin</U></A></div> <div> <A HREF="id3_m.htm#tstar_117" TARGET="TRLX_Middle" TITLE="Research Projects"><U>Virus Resistance in Tropical Pumpkin</U></A></div> <div> <A HREF="id3_m.htm#hatch_421" TARGET="TRLX_Middle" TITLE="Research Projects"><U>Breeding Tropical Specialty Crops</U></A></div> <div> <A HREF="id3_m.htm#tstar_123" TARGET="TRLX_Middle" TITLE="Research Projects"><U>New and Emerging Viruses affecting</U></A></div> <div> <A HREF="id3_m.htm#tstar_123" TARGET="TRLX_Middle" TITLE="Research Projects"><U>Cucurbits</U></A></div> <div> <A HREF="id3_m.htm#tstar_123" TARGET="TRLX_Middle" TITLE="Research Projects"><U>in Puerto Rico</U></A></div> <bR> </td> <td valign="top" height=398 BGCOLOR="#FFFFFF" TEXT="#080000"> <div> <I>Research Projects</I></div> <div> Research team (left to right): graduate student Robert McPhail-Medina, technician Obed Román-Hernández, graduate student Angela Linares Ramírez. At Isabela, Puerto Rico, Substation</div> <bR> <bR> <div> <B><IMG SRC="1932d830.jpg" border=0 width="557" height="387" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></B></div> <bR> <div> <B> <A NAME="tstar_94"><IMG BORDER="0" SRC="1x1.gif" HEIGHT="1" ALIGN="bottom" WIDTH="1" HSPACE="0" VSPACE="0" ></A></B><B>TSTAR 94 (Sep-2004 to Sep-2007)</B></div> <bR> <div> <B>Screening Tropical Pumpkin and Related Species for Melonworm Resistance</B></div> <bR> <div> Dr. Linda Wessel Beaver (PI)</div> <bR> <div> <B>Objectives:</B></div> <bR> <div> 1. Screen tropical pumpkin (<I>Cucurbita moschata)</I> and related germplasm for resistance to melonworm.</div> <div> 2. Initiate incorporation of newly identified melonworm resistance into horticulturally improved tropical pumpkin breeding material.</div> <bR> <div> <I>      Diaphania hyalinata</I> L. is the primary pest of tropical pumpkin in Puerto Rico and causes economic damage to cucurbit crops throughout the Caribbean region (Medina Gaud et al., 1989; Guillaume and Boissot, 2001; personal observations of author). A similar species, the pickleworm <I>D. nititalis</I> L. tends to be more important in more northern regions of the placecountry-regionAmericas. <I>Diaphania</I> spp. are among the most important pests of cucurbits in Florida (Capinera, 2000; Elsey, 1985: Webb, 1994). Melonworm causes more damage to <I>Cucurbita</I> species in placeStateFlorida than does the pickleworm (Webb, 1994). Other members of the cucurbit family, such as cucumber, melon and watermelon, are also hosts, but the insect favors <I>Cucurbita</I> species such as tropical pumpkin, summer squash and zucchini. Melonworm damage is caused by the larval stages of the insect, and is usually confined to the foliage. Left uncontrolled, the damage is often severe, leaving only the leaf veins intact, resulting in a lace-like appearance. If the available foliage is exhausted, the larvae will eat, or even burrow into, the fruit, leaving scars on the rind or promoting internal fruit rots. </div> <bR> <div>       In 1999, 90% of squash/pumpkin growers in Florida responding to a survey reported use of chemical insecticides on 100% of their crop (Mossler and Nesheim, 2002). No survey data is available for Puerto Rico, but the situation is probably similar. Use of insect-resistant crops is economically and environmentally advantageous. Economic benefits are derived from the yields saved from loss to insect pests and the money saved by not applying insecticides that would have been applied to susceptible varieties. Ecological and environmental benefits are derived in part because of reduced use of insecticides. The increase in species diversity that results from the reduced use of insecticides promotes a less polluted, more sustainable agroecosystem. </div> <bR> <bR> <div> <B> <A NAME="tstar_117"><IMG BORDER="0" SRC="1x1.gif" HEIGHT="1" ALIGN="bottom" WIDTH="1" HSPACE="0" VSPACE="0" ></A></B><B>T</B><B>STAR 117 (Sep-2007 to Sep-2009)</B></div> <bR> <div> <B>Cross Protection and Genetic Approaches to Control of Viruses in Tropical Pumpkin</B></div> <bR> <div> Dr. José Carlos Rodríguez (PD)</div> <div> Department of Crop Protection</div> <bR> <div> Dr. Linda Wessel Beaver (Co-PD)</div> <div> Department of Agronomy and Soils</div> <bR> <div> <B>Objectives: </B></div> <bR> <div> (1) Characterize strains of zucchini yellow mosaic virus (ZYMV), papaya ringspot virus (PRSV) and other viruses infecting tropical pumpkin in Puerto Rico.</div> <div> (2) Evaluate the effectiveness of inoculation with mild strains of ZYMV and PRSV as a method of cross-protection against severe strains. </div> <div> (3) Incorporate genes for resistance to ZYMV and PRSV into traditional and semi-bush varieties of tropical pumpkin.</div> <bR> <div> Puerto Rico, production of tropical pumpkin has been constrained by various pests and diseases, by the use of inappropriate production practices and by the planting of unimproved varieties. Past research at the Puerto Rico Experiment Station of the UPR has addressed some of these problems. In particular, new varieties have been developed with improved insect resistance, better fruit quality and a semi-bush growth habit. However, an area that has not been address is that of viral diseases.  </div> <bR> <div> Cucurbit crops in general are affected by a large number of viral diseases. Lecoq et al. (1998) describes 36 “major” viruses infecting cultivated members of the <I>Cucurbitaceae</I>. Nearly all of them have a wide range of cucurbit and non-cucurbit hosts. A survey of incidence of cucurbit viruses in Puerto Rico and Florida was conducted from 2000 to 2003 (Paz-Carrasco and Wessel-Beaver, 2002; unpublished data from L. Wessel-Beaver and S.E. Webb). This survey was initiated because cucurbit researchers were observing an increasing problem with mosaic virus diseases in both Puerto Rico and Florida.  Determining which viruses occur is an important first step towards control of the problem, be it via management techniques or genetic resistance. Over 70% of the samples collected in Puerto Rico tested positive for one of two viruses: Papaya Ring Spot Virus (PRSV) and Zucchini Yellow Mosaic Virus (ZYMV). Among the cucurbits surveyed (cucumbers, watermelons and melons, summer squash (<I>C. pepo</I>) and tropical pumpkin), tropical pumpkin had by far the highest incidence of virus. PRSV and ZYMV were also important viral diseases on cucurbits in Florida, although the overall incidence was lower than in Puerto Rico. Mossler and Nesheim (2003) estimate that 30 percent of the squash acreage in Florida is affected by virus diseases, with PRSV being the most important. The year-round growing season in Puerto Rico likely contributes to the higher occurrence of viral diseases in Puerto Rico compared to Florida. </div> <bR> <div> Because of their importance in both Puerto Rico and Florida (and other areas of the Caribbean), our research focuses on PRSV and ZYMV. Both of these diseases reduce the yield and quality of all cucurbits including tropical pumpkin (Lecoq et al., 1998). No specific data is available for tropical pumpkin (<I>C. moschata</I><FONT SIZE="3" COLOR="#000000" FACE="Arial" >), </FONT>but yields losses in <I>C. pepo</I><FONT SIZE="3" COLOR="#000000" FACE="Arial" > </FONT>can be up to 100% if 50% of the plants are infected with ZYMV by the first harvest (Yarden et al. 2000). Early infection in tropical pumpkin in placePuerto Rico may render the plant unable to produce fruit, or produce unmarketable fruits (L. Wessel-Beaver, unpublished data). Later infections reduce general plant vigor and lower yields. Many growers in Puerto Rico harvest tropical pumpkin over a period of many weeks or months, often applying additional applications of nitrogen fertilizer in order to extend the harvest. Viral infections on older plants can severely limit the ability of these plants to continue to produce fruit. </div> <bR> <div> PRSV and ZYMV are members of the potyvirus genus and are transmitted by aphids in a nonpersistent manner. This means that the insect needs to feed on an infected host for only a few seconds to pick up the virus, and needs an equally short time feeding on a new host to pass on the virus. Aphids reproduce at a very high rate, and in a tropical environment like Puerto Rico, aphids are nearly always present. PRSV and ZYMV are known to be present in a number of weeds and in other crops on the island such as papaya (L. Wessel-Beaver, unpublished data; M. Ferwerda-Licha, personal communication). This combination of nearly limitless host sources and insect vectors, along with the nonpersistent type of virus transmission, means that chemical or other types of insect control will have little effect on reducing the incidence of these diseases. </div> <bR> <div> Other options for PRSV and ZYMV control include cross-protection and genetic resistance. McKinney (1929) was the first to show that plants already infected with a virus can be protected against infection by a related strain of the same virus. In a manner analogous to a vaccination, cross-protection is achieved by artificially inoculating a crop with a mild strain of a virus, typically at the seedling stage before infection by a severe strain can occur. In practice, the technique is most adaptable to a situation where relatively small acreages of a crop are involved, where seedlings could be inoculated before transplanting to the field, and where other control measures might not be possible. This situation would apply to tropical pumpkin in Puerto Rico as well as in Florida. One of the real success stories of cross protection is with cucurbits, particularly against ZYMV.  Cross protection of cucurbit crops has enjoyed commercial success in Israel (Yarden et al., 2000) and Taiwan (Fuchs et al., 1998). The low efficiency of chemical control of vectors and the overlap of the crops observed in Puerto Rico are additional aspects suggesting that studies should be conducted to established cross-protection as an effective disease control practice. The molecular, biological and serological characterization of the virus strains will allow us to understand the variability of the local strains as well the putative relatedness with others strains reported from other pumpkin growing regions.  The nucleotide sequence determination will permit the molecular differentiation of strains (wild and severe) allowing further searching for new protective strains as well as studying the molecular mechanisms regulating the cross protection dynamic.</div> <bR> <div> Options for genetic control of virus include both genetically engineered and classical approaches. In 1994, virus-resistant summer squash (<I>C. pepo</I>) became the first genetically engineered crop to be approved for food use in the U.S. (Agbios, 2005). Its use is also approved in Canada, but not in other parts of the world. Resistance is produced via the insertion of coat protein sequences into the plant genome (Quemada and Groff, 1993). The current technology provides resistance to ZYMV, but not to PRSV (Agbios, 2005). The level of resistance in cultivars carrying these sequences is strong. Still, there are a number of limitations to the use of genetically engineered resistance. First, the resistance is not available in tropical pumpkin (<I>C. moschata</I>). Inserting the coat protein sequences into tropical pumpkin is surely possible, but the cost and issues of intellectual property rights make it difficult to justify this approach for a crop that is not as widely grown as summer squash. Perhaps even more important is the issue of acceptance of genetically modified (GM) crops. This is an even more controversial issue for vegetable crops like cucurbits compared to field crops like corn or soybeans. For these reasons we believe that a genetic engineering approach to breeding for PRSV and ZYMV resistance in tropical pumpkin in Puerto Rico is not warranted at present. We are using classical approaches to breeding for virus resistance, using genes already available within <I>C. moschata</I> germplasm in our plant breeding program at UPR. </div> <bR> <bR> <div> <B> <A NAME="hatch_421"><IMG BORDER="0" SRC="1x1.gif" HEIGHT="1" ALIGN="bottom" WIDTH="1" HSPACE="0" VSPACE="0" ></A></B><B>HATCH 421 (Sep-2007 to Aug-2009)</B></div> <bR> <div> <B>Development, Release and Distribution of Vegetable Cultivars for Puerto Rico</B></div> <bR> <div> Dr. Linda Wessel Beaver, PD</div> <div> Department of Agronomy and Soils</div> <bR> <div> Prof. Sonia Martínez, Co-PD</div> <div> Department of Horticulture</div> <bR> <div> Dr. José Carlos Rodríguez, Co-PD</div> <div> Department of Crop Protection</div> <bR> <div> Prof. Evelyn Rosa, Co-PD</div> <div> Department of Crop Protection</div> <bR> <div> Prof. Guillermo Fornaris, Co-PD</div> <div> Department of Horticulture</div> <bR> <div> <B>Objectives:</B></div> <bR> <div> 1. Carry out selection and purification in germplasm of traditional types of vegetables and produce segregating populations for use in future breeding efforts</div> <div> 2. Continue the on-going tropical pumpkin breeding program.</div> <div> 3. Test advanced genetic materials in farmers' fields in collaboration with the Cooperative Extension Service </div> <div> 4. Release and distribute seed of best performing open-pollinated vegetable cultivars</div> <div> 5. Prepare educational materials to assure wide distribution of released vegetable cultivars</div> <bR> <div>       The vegetable industry in Puerto Rico is of considerable importance on the placeIsland, with a farm gate value of over $50 M per year (Anonymous, 2006). Consumption of vegetables, a major part of the USDA's food pyramid, contributes to the health and well-being of Puerto Ricans. The types of vegetable crops grown in Puerto Rico range from well-known species such as tomatoes and onions, to lesser-known specialty crops such as tropical pumpkin (<I>calabaza</I>) and sweet cherry pepper (<I>ají dulce</I>). Commercial sources of seed are available for some of these crops, but these cultivars often do not have the attributes preferred by local growers and consumers. Nearly all commercial vegetable cultivars are F1 hybrids that are sold in seed lots too large for the small Puerto Rican grower and whose seed is quite costly. Additionally, seed from these cultivars will not breed true in the following generation, obliging the grower to purchase new seed for the next growing season. Many small seed companies in the U.S. now sell small-scale quantities of open-pollinated (OP) vegetable seed for those growers interested in organic production, in the lower cost of OP seed, or simply interested in saving their own seed for planting the following generation. Because OP seed is easier to produce, it is generally far less costly than F1 seed. However, the cultivars available are seldom adapted to the tropics. Finally, there are other Puerto Rican vegetable crops for which a commercial source of seed simply does not exist. The development and distribution of improved local OP vegetable cultivars would be an important contribution to the Puerto Rico vegetable industry as well as supply consumers with the types of produce needed for traditional Puerto Rican cuisine. </div> <bR> <div>       Tropical pumpkin or <I>calabaza </I>(<I>Cucurbita moschata</I>) has been the focus of breeding efforts in the Puerto Rico Agricultural Experiment Station for a number of years. Germplasm of several other vegetable crops, including sweet chili pepper or <I>aji dulce </I>(<I>Capsicum chinense</I>), “Rosita” eggplant (<I>Solanum melongena</I>), and the <I>blanco del país </I>cooking pepper (<I>Capsicum annuum</I>) has been collected and characterized, but no cultivars have been recently released. Other local vegetable crops have received almost no attention in terms of cultivar development and distribution. For tropical pumpkin the process of development and distribution is ongoing and merits continued effort. For some of the other crops (sweet chili pepper in particular) elite germplasm is available, but the final steps of on-farm trials, release, and distribution of cultivars have not been carried out. In nearly all local vegetable crops the proper protocols for carrying out the maintenance and multiplication of open-pollinated vegetable cultivars under Island conditions (with its year-around growing season, high humidity, strong disease and pest pressures) have not been well-delineated. This project proposes to bridge the gap between germplasm collection, characterization and conservation research activities and the actual use of these genetic resources by stakeholders, including farmers and consumers.</div> <bR> <div> <B> <A NAME="tstar_123"><IMG BORDER="0" SRC="1x1.gif" HEIGHT="1" ALIGN="bottom" WIDTH="1" HSPACE="0" VSPACE="0" ></A></B><B>TSTAR 12</B><B>3</B><B> (Sep-2008 to Sep 2010)</B></div> <bR> <div> <B>Characterization and control of new and emerging viruses affecting cucurbits in </B></div> <div> <B>Puerto Rico</B> </div> <bR> <div> Dr. José Carlos Rodríguez, PD</div> <div> Department of Crop Protection</div> <bR> <div> Dr. Linda Wessel Beaver, Co-PD</div> <div> Department of Agronomy and Soils</div> <bR> <div> Dr. Consuelo Estéves, Co-PD</div> <div> Department of Crop Protection</div> <bR> <div>     Virus and severe virus vector outbreaks are a frequent and major cause of low yields and phytosanitary limitations to growing cucurbits in placePuerto Rico.  Vein clearing symptoms in pumpkins and severe decline in watermelon plants have been observed associated with a new virus in placePuerto Rico. Many watermelon growers have experienced complete crop losses. The new emerging virus has been successfully transmitted by whiteflies, an invasive vector species first documented in placePuerto Rico in the late 1980's. In a survey conducted to assess the types and prevalence of viruses infecting cucurbits, eighty-seven cucurbit plants (mainly pumpkin and watermelon) showing virus-like symptoms were collected from ten municipalities and 100% were positive for at least one of the tested viruses. Serologic tests showed more than 90% of the samples to be positive for potyvirus, including <I>Papaya ringspot virus</I> (PRSV), <I>Zucchini yellow mosaic virus</I> (ZYMV) and at least one uncharacterized virus serologically and molecularly related to this family.  RT-PCR conducted with potyvirus degenerate primers amplified a coat protein gene fragment of expected size from samples with this new virus. The amplicons have been sequenced to identify more specifically the potyviruses. Our current research program is using information from characterization of potyviruses to aid in the development of cultivars resistant to PRSV and ZYMV and for selection of mild strains for cross protection. </div> <bR> <div> We will be using a multidisciplinary approach to combine greenhouse and field evaluation of watermelon and pumpkin genotypes for resistance to viral infection, to conduct mechanical and vector transmission assays and to do bio-molecular characterization of the new emerging potyvirus(es).</div> <bR> <div> The objectives of this grant are to: </div> <bR> <div> <IMG BORDER="0" SRC="Symb075c00b700f000000000.gif" HEIGHT="16" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">Characterize new virus(es) associated with cucurbits in placePuerto Rico.</div> <div> <IMG BORDER="0" SRC="Symb075c00b700f000000000.gif" HEIGHT="16" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">Study the effectiveness of virus resistance being incorporated into pumpkin cultivars AND screen watermelon varieties to identify potential sources for resistance to this new virus in placePuerto Rico.</div> <div> <IMG BORDER="0" SRC="Symb075c00b700f000000000.gif" HEIGHT="16" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">Develop new cultural practices to mitigate the losses associated with the early transmission of whitefly-vectored cucurbit viruses. </div> <bR> <bR> <bR> <bR> <bR> <bR> <bR> <bR> </td> <td valign="top" width=200 BGCOLOR="#BBBBBB" TEXT="#080000"> <div> <U><IMG SRC="195b88d0.jpg" border=0 width="184" height="141" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></U></div> <div> Sweet chile pepper or ají dulce (<I>Capsicum chinense</I>) is an important ingredient in the preparation of Puerto Rican cuisine. Local farmers have difficulty finding seed of this important specialty crop. A team of University of Puerto Rico researchers lead by Dr. Linda Wessel-Beaver are attempting to purify selected landraces and release open-pollinated cultivars. </div> <bR> <bR> </td> </tr></table></body>