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Biodiversity, genetics, biotechnology and breeding

Session 2


Developments in breeding of bulbous crops from a genetics and genomics perspective

Paul Arens (, Giorgio Tumino, Danny Esselink, Jan van Kan, Richard Immink

Wageningen University and Research, Plant Breeding, Wageningen, Netherlands

Wageningen University Phytopathology, Netherlands
Wageningen University Molecular Biology, Netherlands

Breeding of bulbous crops is challenging because of the crop specific characteristics in most important geophytes like tulip and lily that need more time and effort to deal with. In this overview we will go into some of the new developments and research in the Netherlands in attempting to overcome or deal with such problems in generation time, reproduction, genome size and phenotyping for disease resistance. The focus will be on genetic and genomics aspects of these bulb specific characteristics rather than recent developments into bulb production.

Keywords: bait-seq, effector screening, genome assembly, RNA-seq


Distant hybridization of Hemerocallis with Eremurus and Lycoris

Yi Lv (, Yike Gao, Yuxuan Zhou, Ying Wang, Yuxuan Cui, Jing Zhou Beijing Forestry University, Beijing, China

Hemerocallis spp. is a perennial plant with high ornamental and economic value. However, long-term hybridization between closely related species has made it difficult ot ob tain innovative Hemerocallis germplasm. Distant hybridization can greatly enrich genetic diversity. Consequently, a four-year hybridization study was carried out with Hemerocallis, Eremurus, and Lycoris. Artificial pollination was conducted to overcome the pre-zygotic reproductive barrier; embryo rescue was carried out to overcome the post-zygotic barrier. The interfamily hybrid was identified, cytological and phenotypic observations were performed. Analysis of cross- compatibility revealed that reproductive isolation strongly hinders distant hybridization. For the hybridization between Hemerocallis and Eremurus, a total of 752 Hemerocallis flowers were pollinated, the fruit set rate is 0–5.26%, and only obtained 1 hybrid embryo. And 378 Eremurus flowers were pollinated, no fruit was acquired. For the hybridization between Hemerocallis and Lycoris, a total of 1597 Hemerocallis flowers were pollinated. The fruit set rate was 0.41% and 1 hybrid embryo was obtained. And 1446 Lycoris flowers were pollinated, the fruit set rate is 0–61.82%, 121 hybrid embryos were obtained. The pre-zygotic isolation between Hemerocallis and Eremurus was more severe than Hemerocallis and Lycoris. After 7 months of embryo rescue, an interfamily hybrid seedling was obtained. The hybrid was identified by inter-simple sequence repeat (ISSR). The growth rate of interfamily hybrid seedlings was at least five weeks slower than that of Lycoris interspecific hybrid seedlings. The hybrid owned the same chromosome number as the paternal plants (2n = 22) and showed maternal overall phenotypic characteristics. Distant hybridization between Hemerocallis and Lycoris exhibits severe reproductive isolation, but the hybrid seedlings can still be obtained. This research lays the foundation for the future development of Hemerocallis breeding and distant hybridization.

Keywords: daylily, embryo rescue, foxtail lily, interfamily hybridization, intergeneric hybridization, lycoris, reproductive isolation


Intergeneric hybridization and endosperm culture of Lycoris

Yike Gao (, Yuxuan Zhou, Yi Lv

Beijing Forestry University, Beijing, China

Lycoris (Amaryllidaceae) is an important bulb flower, which has great potential in both landscaping and cut flower applications. It is difficult to obtain innovative Lycoris germplasm by conventional crossbreeding. To enrich the ornamental characteristics of Lycoris plants, intergeneric hybridization between Lycoris and Hippeastrum was conducted. Further, endosperm culture was adopted in this study for improving the ploidy level of Lycoris. During this experiment, 298 Lycoris and 276 Hippeastrum were pollinated. The results showed that the fruit setting rates of Lycoris × Hippeastrum and Hippeastrum × Lycoris were both high, 65.8% and 64.9% respectively. But Lycoris × Hippeastrum obtained much more ovules than Hippeastrum × Lycoris, with 347 and 19 ovules respectively. The endosperm culture was unsuccessful in the two intergeneric hybrid combinations, but two seedlings were obtained in the interspecific hybrid Lycoris aurea × Lycoris tsinlingensis four months after pollination. During this presentation,asthebackgroundandreferenceofthisstudy,thesuccessfulcases of intergeneric hybridization and endosperm culture of monocotyledon plants will be reviewed, as well as the research progress of methods to overcome the barriers of intergeneric hybridization of monocotyledon plants. Also, the types of barriers to intergeneric hybridization of Lycoris as a parent and the suitable conditions for endosperm culture of Lycoris will be discussed.

Keywords: distant hybridization, embryo rescue, hippeastrum, ploidy breeding, postzygotic disorder


Breeding Impatiens for resistance to the fungal disease impatiens downy mildew (Plasmopara obducens)

Mark P. Bridgen (, Victor Zayas, James Keach

Cornell University, Ithaca, NY, USA 2University of Hawaii, Hawaii, USA

Impatiens walleriana, commonly known as impatiens, is one of the most popular annual bedding plants and an important source of income for many greenhouse growers and landscapers in the United States and Europe. However, the advent of Impatiens Downy Mildew (IDM),Plasmopara obducens, changed the plant’s status and economic value. IDM is a pathogen that has become virulent against this species of Impatiens; it leaves plants defoliated and commercially unviable. IDM is a disease that is very difficult to manage. Fungal oospores allow reinfection to occur and it is theorized that the oospores can remain in soil for up to 10 years. Commercial fungicides are ineffective at eradicating the disease and only temporarily prolong the health of the plant. Consumers who are not able to use these fungicides still see the impact of the disease in their gardens. By 2011, the pathogen had spread worldwide and become a significant problem in the landscape. This disease results in wilting, leaf and flower drop and ultimately death of this important bedding plant. In the past 10 years, sales of Impatiens walleriana have plunged because of this devastating disease. There was a critical need for breeding research with Impatiens to develop resistance to IDM; we began a breeding program at Cornell University to accomplish this. In 2015, we successfully confirmed that IDM-resistance is genetically inherited with impatiens. A traditional breeding program was begun to hybridize Impatiens walleriana plants with resistant Impatiens species. We demonstrated that the popular Impatiens walleriana is compatible for cross-fertilization with other impatiens species that are resistant to IDM and that the ornamental qualities of the common impatiens can be combined with the disease resistance of the wild relatives to produce improved plants. By 2016, two hybrid plants were developed that were resistant to the disease. These two plants were used for further breeding with the ultimate goal of developing seed-propagated lines of Impatiens that are resistant to IDM. Hybrid plants that are produced from our breeding program are grown in the field and challenged with natural IDM inoculations to identify resistant plants. Impatiens plants are selected that have little or no infection, no defoliation, and are able to complete their life cycle throughout the growing season. Our breeding uses inbred lines to generate hybrid plants that are resistant to IDM. Good ornamental traits, in addition to IDM resistance, are our breeding objectives. The new plant products that will be generated from this research will have great potential for the ornamental horticulture industry.

Keywords: disease resistance, Impatiens, plant breeding



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