Progress 10/01/16 to 09/30/19
Outputs
Target Audience:We are working closely with two companies interested in processing squash, one of which is also interested in production of rootstock hybrids for melon production. We will try to assist interested growers in New England on grafting techniques and on trialing some of our interspecific hybrid rootstocks. Vegetable growers who may use interspecific hybrids either for grafting or for production of squash are the ultimate target of our research, and are being kept informed of our progress through presentations at grower meetings and workshops. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?Several undergraduate students have contributed to this project over the past three years., some as part-time research assistants and others doing special research investigations for credits. A graduate student project focusing on the use of interspecific hybrids as grafting rootstocks for melons was completed in summer of 2017. Another graduate student is investigating the use of grafting techniques and interspecific hybrid rootstocks to promote flowering in recalcitrant tropical accessions and tropical species of Cucurbita which are potential sources of pest resistance. How have the results been disseminated to communities of interest?Results have been communicated at several grower and professional meetings during the past three years, and were communicated at two grower workshops in January of 2017, at a regional meeting of a professional society in January of 2017, and at the national meeting for the American Society for Horticultural Science in September of 2017, and at an International Cucurbit Conference in 2018. A publication on growth and productivity of interspecific hybrids was published in September of 2017. Other publications are in the submission process. I am cooperating with two seed companies to evaluate and possibly introduce interspecific hybrids for use as rootstocks, and also to utilize some of the breeding lines developed in this project for introducing intraspecific hybrids. What do you plan to do during the next reporting period to accomplish the goals?
Nothing Reported
Impacts
What was accomplished under these goals?
Interspecific hybridization is an important breeding tool that has not received enough attention for variety development of squash and pumpkins in North America. The root system of interspecific hybrids between cultigens of Cucurbita maxima crossed to those of C. moschata is vigorous and resistant to several soil borne diseases. Moreover, interspecific hybrids are seedless, and allowing photosynthates normally allocated for seed production to be partitioned into mesocarp tissue, thereby increasing economic yield. Interspecific hybridization between these species can also be utilized for transferring useful traits between species. Increasing the diversity of C. moschata and C. maxima breeding lines for making compatible interspecific crosses. As a result of breeding populations established in 2012, four new bush breeding lines of C. maxima and seven new breeding populations of C. moschata were developed by 2016/17. The new C. maxima lines have orange, 5 to 7 kg fruit, moderately high carotenoid contents, and about 50% greater selfed-seed yields than NH65. In the new C. moschata lines, fruit size ranges between 3 to 8 kg, shape from oval to ovate to somewhat elongate, and most have high β-carotene content. In 2015, we developed a new breeding population from a bush breeding line, NH.MaxBPB, crossed to 'Pink Banana'. Three sister lines, NH.Max273-6-15, NH.Max273-6-19, and NH.Max273-5-11, were developed from this population, characterized by 5 to 10 kg fruit, flesh DW of 11 to 12%, moderately low carotenoid content, and high seed count per fruit. Several more C. moschata lines have recently been developed from an Australian accession with good powdery mildew resistance crossed to a breeding line, NH.Mo125-1-10. Fruit in these new lines are either tan or mottled green/tan at maturity, weight 2 to 4.5 kg, with 12 to 17% DW and high β-carotene content. Evaluate the cross-compatibility of C. maximabreeding lines for producing interspecific hybrids with C. moschata. Cross compatibility of the new C. maxima breeding lines was compared to NH65 during the summer of 2017, using NH65, NH.Max2342-4, NH.Max5101-3, and NH.Max5102-9 as female parents and C. NH.Mo116-33-7, NH.Mo125-1-10, NH.Mo127-9-6-12, and NH.Mo42-36-3-6 as male parents. The most compatible cross was NH65 x NH.Mo116-33-7 (NH1349), with average seed yields of 166 seed per fruit. One of 8 fruit had mostly unfilled seed, but the other 7 fruit averaged 166 filled seed and 82 either unfilled or partially filled seed per fruit. With self-pollinations, NH65 averaged 119 seed per fruit, and NH.Max2432-4 had the highest average of 313 seed per fruit. Interspecific crosses with the latter breeding line averaged only 84 filled seed per fruit. In 2018 severe bird damage to young seedlings prevented preliminary evaluation of cross-compatibility with the NH.Max273 lines. In the summer of 2019, we compared cross-compatibility of NH.Max273 lines to that of NH65 using NH116-33-7 as the primary male parent. Fruit set was over 90% with all crosses and self-pollinations, but nearly half of the plants were lost as a result of severe bacterial wilt and crown rot. The selfed fruit of NH65 and the NH.Max273 lines averaged, respectively, 229 and 578 seeds per fruit. Two fruit of NH65 x 116-33-7 contained only a few seeds, but six crosses averaged 177 filled seeds per fruit, and the average proportion of unfilled or partially filled seed was 23.3%. Crosses of NH.Max273 lines x NH116-33-7 produced an average of 158 filled seed per fruit, but with a wide range of seed (59 to 383) per fruit, and high proportion (49.2%) of unfilled seed. Evaluate disease resistance, productivity, and culinary characteristics. In 2017, we compared eight new interspecific hybrids, comprised of four new C. moschata lines as the male parents, and NH65 and NH.Max5-10-3-9 as female parents. All hybrids with NH.Max5-10-3-9 as a parent displayed a large proportion of misshapen fruit and were not suitable for evaluation. Fresh weight yields of the best hybrids, NH1310 (NH65 x Mo936-1), NH1329 (NH65 x Mo125-1-10), and NH1351 (NH65 x NH.Mo42-36-3-6), were respectively, 59. 3, 47.5, and 65.6 t/ha. The % DW of flesh was high, 11.2 to 11.5%, resulting in high dry biomass yields, from 5.32 for NH1329 to 6.79 t/ha for NH1351. Open-pollinated, Dickinson Field strains account for over 90% of canned pie stock, and we have not generated interest from processing companies in utilizing interspecific F1 hybrids. As such, our research in 2018 and 2019 focused more on achieving greater seed productivity in interspecific crosses, evaluating rootstocks for grafting to different melon varieties, and using interspecific hybridization to transfer useful traits between C. moschata and C. pepo. Interspecific hybrids as rootstocks for grafting melons and squash. NH1320 (NH65 x NH.Mo176-29-1) was used extensively in grafting studies in 2015, 2016 and 2017, and FW yields of grafted 'Halona' melon plants were 45 to 155% higher than that of non-grafted plants. In 2018 and 2019, NH1349 was used as a rootstock for grafting studies because of good compatibility with melons and better seed yields than that of NH1320. Fruit from grafted plants is often larger than desired, prompting more grafting studies which include varieties with smaller fruit size. In 2018 we compared grafted (GR) and non-grafted (NG) melon plants, using two experimental NH hybrids, two small-fruited cantaloupe varieties, 'Sugar Cube' and 'First Kiss', and a large-fruited, Crenshaw melon, 'Honey Sak'. Fresh weight melon yields of GR plants of 'Honey Sak', 'First Kiss', and 'Sugar Cube' were respectively, 49%, 59% and 132% higher than that of NG plants. The mean soluble solids contents (SSCs) for melons of GR plants of 'First Kiss' (11.7%) and 'Sugar Cube' (12.5%) were significantly lower than the SSC of 13.9% for both of those varieties. The SSC in melons of NG (12.2%) and GR (12.5%) 'Honey Sak' were similar. Fruit size in GR Sugar Cube (1.3 kg) was significantly larger than in NG plants (1.0 kg); whereas, fruit size in grafted 'First Kiss' (1.34 kg) was not significantly different from that of non-grafted plants (1.22 kg). In 2019, we evaluated the effects of grafting in three melon varieties, 'True Love', 'Sugar Cube' and 'Sugar Rush'. Average FW plot yields for grafted plants of 'Sugar Cube', 'Sugar Rush', and 'True Love' were, respectively, 61.1, 73.7, and 60.1 kg, as compared to 46.2, 33.0 and 46.2 kg for non-grafted plants. Mean soluble solids contents were significantly higher in NG plants of 'Sugar Cube' (15.0%) and 'Sugar Rush' (13.6%), than that of GR plants (12.8%); however, soluble solids contents in both NG and GR treatments was well above the USDA fancy grade of 11%. The mean SSC content for 'True Love' was 11% in both GR and NG plants. Mean fruit weights for grafted plants of True Love' (2.55 kg), 'Sugar Cube' (1.22 kg), and 'Sugar Rush' (1.6 kg), were all significantly greater, respectively, than the weights of 1.81, 0.97, and 1.36 kg for non-grafted plants. We have further extended our grafting studies to developing grafting techniques for inducing flowering in short day, tropical accessions of C. moschata species that are often sources of disease resistance, but difficult to propagate in temperate climates. We have successfully employed early flowering interspecific hybrid and acorn breeding lines as rootstocks for inducing earlier flowering in tropical C. moschata germplasm with a short photoperiod. This technique allowed us to transfer gene(s) for powdery mildew resistance from a tropical accession, OSArd, into more favorable temperate germplasm during winter/spring of 2019.
Publications
- Type:
Journal Articles
Status:
Under Review
Year Published:
2019
Citation:
Ohletz, J. L. and J. B.Loy. 2020. Grafting Melons Increases Yield, Harvest period and Resistance to Sudden Wilt in New England.
- Type:
Journal Articles
Status:
Under Review
Year Published:
2019
Citation:
Uretsky, J. and J. B. Loy. 2019. High Productivity Demonstrated for Interspecific Bush Cucurbita maxima x Vine Cucurbita moschata Squash Hybrids.
- Type:
Conference Papers and Presentations
Status:
Other
Year Published:
2018
Citation:
Ogden, A. B. and J.B. Loy. 2018. Use of Grafting to Promote Flowering in Late and Short-day Flowering Cultigens of Squash. Poster session, Cucurbitaceae 2018, Novermber 11 to 16, Davis, CA.
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Progress 10/01/17 to 09/30/18
Outputs
Target Audience:We are working closely with two companies interested in processing squash, one of which is also interested in production of interspecific hybrid rootstocks hybrids for melon production. There is interest from growers in New England to utilize rootstocks for grafting melons, and we will try to assist these individuals, both on grafting techniques and on trialing some of our interspecific hybrid rootstocks. Vegetable growers who may use interspecific hybrids either for grafting or for production of squash are the ultimate target of our research, and are being kept informed of our progress through presentations at grower meetings and workshops. Companies interested in potental use of our interspecific hybrids or squash breeding lines can contact us through a cooperating seed company. Changes/Problems:Objective one: We were not able to obtain adequate data on interspecific seed yields during the summer of 2018 because of early plant loss of the pollinating parent, NH.116-33-7-3, to bird predation, and also because of excessively rainy weather that hampered cross-pollination. There will be less emphasis on evaluating the productivity of interspecific hybrids because of weak interest by the processing industry. The major focus will be on using interespecific hybrids as rootstocks for melon culture because of the highly favorable results in consistently increasing melon yields of varieties adapted to the Northeast. An added objective will be to further refine grafting techniques for inducing flowering in tropical species because this technique holds promise for better acquisition and use of tropical Cucurbita germplasm that is currently deficient in germplasm banks. What opportunities for training and professional development has the project provided?Three undergraduate students have contributed to this project over the past year, as either part-time research assistants, summer assistants, or as involved in special research investigations for credit. A graduate student project focusing on the use of interspecific hybrids as grafting rootstocks for melons was completed in summer of 2017. Another graduate student is investigating the use of grafting techniques and interspecific hybrid rootstocks to promote flowering in recalcitrant tropical accessions and tropical species of Cucurbita. Tropical species and accessions are potential sources of pest resistance which can be transferred to domestic species. How have the results been disseminated to communities of interest?Results were communicated through various educational and professional meetings as well as visits by seed companies to the Kingman Research Farm to view research plots and get updated on research progress. What do you plan to do during the next reporting period to accomplish the goals?For a melon-compatible interspecific hybrid rootstock to be commercialized by a seed company and available to growers, hybrid seed must be reasonably priced. In Europe and Asia, rootstocks are largely used in protected agricultural settings, characterized by high tunnel or greenhouse crops having a high commercial value. As such, relatively high seed costs can be justified. In North America, use of rootstocks for melon production in the near future will likely be for field production, and thus, seed costs have to be reasonable, even with anticipated yield increases with grafted plants. Thus, our interspecific hybrid research is strongly focused on obtaining high seed yields in interspecific crosses. Melon grafting work will continue to identify the best hybrid melons and rootstocks for obtaining high yields and good eating quality. Work on the use of interspecific hybrids as rootstocks for use in inducing flowering in tropical species is an added objective that dovetails with this project. Such application of grafting may aid plant genetic resource units in propagating seed of recalcitrant tropical species, and also assist plant breeders in temperature regions to more easily utilize tropical accessions. In 2019, we will test more tropical species for flowering response to grafting.
Impacts
What was accomplished under these goals?
We have established high productivity and improved pest resistance in certain interspecific hybrids between bush strains ofC. maxima (winter squash)and vine strains ofC. moschata,(pumpkin or crooknecksquash) but the number of hybrid combinations tested to date is small. A major thrust of the interspecific hybrid project is development of new breeding lines ofC. moschatawith improved culinary traits and new bush breeding lines ofC. maximawith higher seed yields in interspecific combinations. New interspecific combinations utilizing improved breeding lines should result in enhanced culinary traits in hybrids and more uniform hybrid seed production. The most promising use of our interspecific hybrids is for rootstocks for melon grafting. In melon grafting experiments with two recently developed interspecific hybrid rootstocks, NH1320 and NH1349, melon yields have been more than doubled in some melon varieties. Increasing the diversity of C. moschata and C. maxima breeding lines for making compatible interspecific crosses. The bush C. maxima breeding line NH65 was previously shown to be cross-compatible with cultigens of C. moschata. However, selfed seed yield in NH65 is moderately low. Three new bush breeding lines of C. maxima, genetically related to NH65, have been developed with selfed seed yields about double that of NH65, but in 2017 these lines showed poor compatibility in crossses to C. moschata. In C. moschata, four new inbred lines, NH. 176-29-1, NH.127-9-6-2, NH.125-1-10-7, and NH.116-33-7-3, have been tested for cross-compatibility with NH65, and the highest seed yields were obtained in 2017 with NH.116-3-7-3. Another set of bush C. maxima lines has been derived from a cross of NH65 to the variety 'Banana'. Fruit from sister lines selected from this population exhibited high seed yields, between 400 and 550 seeds per fruit, but only one line, NH.Ban273, had the requisite white seed type.Seed yields from greenhouse crosses of NH65 to NH.Ban273 in spring of 2018 suggested good cross-compatibility. As such, several sister lines from NH.Ban273 were evaluated in 2018, resulting in several F6 selections with high seed yield. Important phenotypic and culinary traits of new processing breeding lines. Starch contributes desirable textural properties to cooked squash, and we have demonstrated a high negative correlation (r2 = -81) between % mesocarp DW and water loss during cooking and processing. Dickinson Field type cultigens used for pie processing generally average between 5 to 6% DW which translates to about 0.5% starch content. In contrast, the flesh of our best C. moschata lines of processing squash range between 7 to as high as 18 to 19% DW, and also have been selected for high for content of β-carotene content. The Roche Yolk Color Fan (YCF) used for rating flesh color has a numerical range from 1 to 15 (light yellow to dark orange), with YCF values of 14 and 15 corresponding to high β-carotene content. Interspecific hybrids, on the other hand, have relatively high contents of xanthophylls, yellow carotenoids, including nutritionally important lutein. For canning, high carotene content is preferred because such carotenoids are more stable to cooking. Thus, although the interspecific hybrids appear to lack ideal carotenoid profiles for canning purposes, several of the new inbred lines of C. moschata may find use in processing as 'op' varieties. Because of higher starch contents and improved cultinary properties in these cultigens as compared to the traditional Dickinson Field varieties, they could be used for processing into baby food puree and frozen pack as well as for pie stock. Evaluating the productivity of Interspecific Hybrids. The interspecific hybrids NH1310, NH1329, and NH1349 have semi-bush growth habits combined with extensive lateral branching from the first 8 to 10 nodes, resulting in rapid leaf canopy development for more efficient photosynthesis and weed control. Furthermore, we have noted that most hybrids using NH65 as the female parent tend to produce uniform fruit shape; whereas, hybrids utilizing some of the newer bush C. maxima lines produced a high proportion of misshapen fruit and some of the early sets fail to develop, thus lowering fruit yields. Therefore, in experiments conducted to date, only interspecific hybrids with NH65 as the female parent have produced high FW yields. We did not evaluate productivity of interspecific hybrids in 2018, but interspecific hybrids using bush breeding lines derived from NH.Ban273 will be evaluated in the future. Interspecific hybrids as rootstocks for grafting melons and squash. Several UNH interspecific hybrids with NH65 as the female parent have been evaluated as rootstocks for grafting melon. One hybrid, NH1320 (NH65 x NH.176-29-1), exhibited good seed germination, seedling uniformity, and graft compatibility with melon, and thus, was used extensively for grafting research with melon in 2015 and 2016. Because NH1349 gives higher seed yields than NH1320, it was selected as a rootstock parent for grafting experiments conducted in 2018. In previous grafting studies, early growth and flowering of non-grafted plants exceeded that of grafted plants, so that yield increases in grafted plants was partially offset by earlier maturity in non-grafted plants. In the 2018 study, we used a new post-grafting method (healing stage), whereby grafted plants were grown under Illumitex Eclipse LID lights, F6 type (49.5% blue, 49.% red, and 0.5% green spectrum) for the 12 days following grafting, prior to acclimating the seedlings in natural lightonly two days before transplanting. This post-grating protocol produced stocky, dark green plants that showed rapid early growth in the field. At 19 days after transplanting, grafted plants of Honey Sak, and Sugar Cube had 59 and 87% greater leaf area, respectively, than non-grafted plants. Data on leaf area were not obtained for the variety 'First Kiss'. Fresh weight melon yields of grafted plants of 'Honey Sak', 'First Kiss', and 'Sugar Cube' were respectively, 49%, 59% and 132% higher than that of non-grafted plants. Melons with a soluble solids contents (SSC) of 11% or higher are considered fancy grade. The mean SSCs for melons from grafted plants of Honey Sak, First Kiss, and Sugar Cube were, respectively, 11.7%, 12.5% and 12.2%. Unexpectedly, both Sugar Cube and First Kiss had an average SSC of 13.9%, were significantly higher than that of grafted plants. Our grafting work has expanded into developing grafting techniques that can be used for obtaining earlier flowering in tropical cultigens that are difficult to grow in temperate regions because they are adapted to flower under shorter day lengths. Such tropical species are useful sources of genes for disease resistance. Flowering in these species appears to be regulated by a florigen-type compound that stimulates flowering, and also by inhibitors in leaves which prevents flowering even when the florigen signal is present. Andrew Ogden, a doctoral student in horticulture successfully promoted flowering and fruit set in a short-day tropical accession during the summer of 2018 by grafting scions of a tropical accession to an early flowering interspecific hybrid rootstock, NH1310. Induction of flowering involves three techniques: (1) grafting scions of the tropical accession to an early flowering rootstock, (2) allowing a lateral branch of the rootstock to develop and provide photosynthate for growth of the scion, and (3) removing the initial leaves from the scions to prevent production of substances whichinhibit flowering.
Publications
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Progress 10/01/16 to 09/30/17
Outputs
Target Audience:We are working closely with two companies interested in processing squash, one of which is also interested in producing a rootstock hybrid for melon production. A third company company is utilizing one of our bush C. maxima lines for producing and testing interspecific hybrids. We will also be sharing seed of some of our interspecific hybrids with at least two universities active in grafting studies. There is interest from growers in New England to utilize rootstocks for grafting melons, and we will try to assist these individuals, both on grafting techniques and on trialing some of our interspecific hybrid rootstocks. Vegetable growers who may use interspecific hybrids either for grafting or for production of squash are the ultimate target of our research, and are being kept informed of our progess through presentations at grower meetings and workshops. Changes/Problems:A spike in the crow population caused substantial plant damage in some fields, impairing collection of yield data. What opportunities for training and professional development has the project provided?Several undergraduate students have contributed to this project over the past three years, some as part-time research assistants and others doing special research investigations for credits. A graduate student project focusing on the use of interspecific hybrids as grafting rootstocks for melons was completed in summer of 2017. Another graduate student is investigating the use of grafting techniques and interspecific hybrid rootstocks to promote flowering in recalcitrant tropical accessions and tropical species of Cucurbita. Tropical species and accessions are potential sources of pest resistance which can be transferred to domestic species. How have the results been disseminated to communities of interest?Results have been communicated at several grower and professional meetings during the past three years, and were communicated at two grower workshops in January of 2017, at a regional meeting of a professional society in January of 2017, and at the national meeting for the American Society for Horticultural Science in September of 2017. A publications on growth and development of interspecific hybrids was published in September. I am cooperating with two seed companies to evaluate and possibly introduce interspecific hybrids in the future. What do you plan to do during the next reporting period to accomplish the goals?For a melon-compatible interspecific hybrid rootstock to be commercialized by a seed company and available to growers, hybrid seed must be reasonably priced. In Europe and Asia, rootstocks are largely used in protected agricultural settings, characterized by high tunnel or greenhouse crops having a high commercial value. As such, relatively high seed costs are can be justified. In North America, use of rootstocks for melon production in the near future will likely be for field production, and thus, seed costs have to be reasonable, even with anticipated yield increases with grafted plants. Thus, our interspecific hybrid research is strongly focused on obtaining high seed yields in interspecific crosses. As part of our approach to improve interspecific compatibility, we have developed interspecific breeding lines, and in particular, lines that mimic C. moschata in descriptive characteristics, but which genetically, are derived partially from C. maxima. The rationale for developing these lines is that they may be much more fertile in crosses to C. maxima than standard C. moschata cultigens, but may still offer the same advantages and degree of compatibility as rootstocks for melons. If this research comes to fruition, it would markedly lower the costs of hybrid seed production.
Impacts
What was accomplished under these goals?
Winter squash is an important crop throughout the Northeast, but continued viability of this crop depends upon the continued improvement of varieties in terms of productivity, eating quality, and disease resistance.Breeding efforts have focused on developing interspecific hybrids; these hybrids are more productive than traditional varieties, and also have better resistance to common diseases and insects plaguing squash.Because interspecific hybrids are resistant to most soil-borne diseases affecting cucurbit crops, an important use of these hybrids worldwide is to serve as rootstocks for grafting to melons, a high-value crop in the Northeast. Increasing the diversity of Cucurbita moschata and C. maxima breeding lines for making compatible interspecific crosses. We demonstrated previously that certain cross combinations of C. maxima x C. moschata can be exceedingly productive, in part, because interspecific hybrids are sterile and do not have to allocate assimilate for seed production. The bush C. maxima breeding line NH65 was previously shown to be more cross-compatible with cultigens of C. moschata than other C. maxima cultigens. However, seed yield in NH65 is moderately low with self-fertilization, suggesting the need to develop additional compatible bush processing lines of C. maxima with improved seed yield. A C. maxima breeding population was produced by crossing NH65 to another bush strain, NH245-10 which performed relatively well in crosses to C. moschata. As a result of selection in several segregating generations over the past five years, four new bush breeding lines of C. maxima have been developed. In 2017, mean seed yields per fruit of two new bush C. maxima lines, NH.Max2342 (311 seed) and NH.Max5101-3, (232 seed) were at least double that of NH65 (117 seed). Flesh quality was relatively poor in most of the C. moschata lines being used for interspecific crosses and appeared to contribute to moderately poor quality in interspecific hybrids. To improve C. moschata germplasm, a breeding population was made in 2010, involving the variety Large Cheese, a NH breeding line (NH421) with powdery mildew resistance (PMR) and high carotenoid content, and a Dickinson Field processing strain from Rupp Seeds (SC936). After several generations of selection, five new processing strains were developed. These new breeding lines have high carotenoid contents, and the major carotenoid is β-carotene, a relatively stable carotenoid for steam processing. These lines were shown in 2016 and 2017 to have a range of flesh dry weights (DW) from about 7 to 13%, roughly corresponding to starch contents between 1 and 4%. Starch contributes desirable textural properties to cooked squash, and in fall of 2016, we demonstrated a high negative correlation (r2 = -81) between % mesocarp DW and water loss during cooking and processing. Evaluate the cross-compatibility of C. maxima breeding lines for producing interspecific hybrids with C. moschata. To compare cross-compatibility of the new C. maxima breeding lines with NH65, cross-pollinations were performed during the summer of 2017 between NH65, NH.Max2342, NH.Max5101-3, and NH.Max5102-9, and three C. moschata lines that had performed well in preliminary crosses made in 2016. All cross combinations exhibited a high percentage of fruit set, however, fruit numbers were not sufficiently large in several combinations to draw conclusions. The most compatible cross was NH65 x NH.Mo116-33-7 (NH1349) which averaged 166 well-filled seed per fruit, higher seed counts than that obtained in NH65 selfed (see above). Partially filled seed was negligible in NH65, averaged only 11 in NH1349. Although self-fertilized seed yields were high for two of the new C. maxima lines (see above), they did not perform well in hybrid combinations. Even those that averaged reasonably high yields of well-filled seed, such as for NH.Max5101-3 x NH.Mo127-9-6 (122 seed) and NH.Max2342 x NH.Mo125-1-10 (88 seed), the proportion of partially filled seed was between 30 to 35%, unacceptably high. Evaluate productivity and culinary characteristics in experimental interspecific hybrids. Because NH1310 consistently out-yields open-pollinated processing strains of C. moschata, we now employ this interspecific hybrid as the control cultigen when evaluating yield of processing squash or pumpkin. In 2017, we compared eight different interspecific hybrids for fruit yield and flesh attributes. All hybrids exhibited vigorous growth and set a heavy fruit load. Adjacent squash and pumpkin lines provided an ample pollen source for the sterile hybrids. Five of the eight hybrids displayed a high proportion of misshapen fruit, and were judged not suitable for processing. Mean FW yield of NH1310 was 73.7 mt/ha, slightly higher than FW yields obtained previously. FW yields of NH1329 and NH1351 were, respectively, 59.2 and 67.2 mt/ha, both high values for processing squash in New England. Soluble solid contents (SSC) were unusually high in 2017, with all three hybrids displaying SSCs slightly above 11%, contributing to DW biomass yields of 8.4, 7.7 and 6.6 mt/ha, respectively, for hybrids NH1310, NH1351, and NH1329. The fruit DW biomass yields of NH1310 and NH1351 are 22 to 32% higher than the highest DW biomass yields we have recorded in several years of testing processing squash. The high DW values also contribute to desirable flesh texture and squash palatability. Flesh color and carotenoid contents, as judged from the Roche Yolk Color Fan, were respectively, 12.3, 13.0 and 12.7, for hybrids NH1310, NH1329, and NH1351. These values are acceptable for processing squash, but the yellow pigment hue indicatesa relatively high proportion of xanthophylls (hydroxy carotenoids) such as lutein and a lessor content of β-carotene. Interspecific hybrids as rootstocks for grafting melons. We have shown that melon grafted to squash rootstocks can considerably increase yields and extend the growing season. Several UNH interspecific hybrids have been evaluated as rootstocks for grafting melon, and hybrids with NH65 as a parent have shown good compatibility. NH1320 (NH65 x NH.Mo176-29-1) exhibits good seed germination, seedling uniformity, and graft compatibility with melon, and thus, has been used extensively in grafting studies. Based on cross-compatibility studies during summer of 2016, several interspecific hybrids were selected for compatibility as rootstocks in spring of 2017. Graft compatibility was based on thepercentage of successful graft unions and growth of grafted seedlings to the 10-leaf stage in 10 cm pots. NH1349, NH65 x NH.Mo116-33, appeared especially compatible for grafting and was field-tested using the UNH-bred variety, True Love. Yield data was compromised by extensive crow damage to fruit, but plant growth was vigorous, fruit yield appeared high, and SSC was high. However, fruit size was variable and some fruits were larger than desired for New England markets. From the seed production side, cross-compatibility of this same hybrid was high in 2017 (see above), warranting future additional field grafting studies.
Publications
- Type:
Journal Articles
Status:
Published
Year Published:
2017
Citation:
Uretsky, J. and J.B. Loy. 2017. Evaluation of morphological traits associated with productivity in F1 interspecific (Cucurbita
maxima Duch. x C. moschata Duch.) hybrid processing squash. HortScience 52:1156-1163.
- Type:
Theses/Dissertations
Status:
Published
Year Published:
2017
Citation:
Martin, J. L. (2017). Grafting melons increases yield, harvest period and resistance to sudden wilt (Order No. 10623695). Available from Dissertations & Theses @ University of New Hampshire; ProQuest Dissertations & Theses A&I. (1983465858). Retrieved from http://libproxy.unh.edu/login?url=https://search-proquest-com.libproxy.unh.edu/docview/1983465858?accountid=14612
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