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Joshua K. Craver, Chad T. Miller, Kimberly A. Williams and Nora M. Bello

variety ( Yencho et al., 2012 ). Intumescences on sweetpotato have not been extensively studied, and very few published research articles discuss the development of this disorder on the crop. One paper, “Intumeszenze fogliari di ‘Ipomoea batatas,’” was

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D. Michael Jackson, Howard F. Harrison, Robert L. Jarret and Phillip A. Wadl

of the agromorphological variability and yield components among sweetpotato [ Ipomoea batatas (L.) Lam] landraces Afr. J. Plant Sci. 5 123 132 < https://pdfs.semanticscholar.org/77d5/b143951758bed0df6e57073c050726787725.pdf > Aguoru, C.U. Uhia, P

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Nicholas A. George, Kenneth V. Pecota and G. Craig Yencho

selected sweetpotato ( Ipomoea batatas (L) Lam.) varieties and breeding clones, p. 281–286. Scientist and farmer: Partners in research for the 21st century. Program Report, 1999–2000. Program Report 1999–2000. International Potato Center, Lima, Peru Martin

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Ming Liu, Aijun Zhang, Xiaoguang Chen, Rong Jin, Hongmin Li and Zhonghou Tang

). Sweetpotato [ Ipomoea batatas (L.) Lam.] is an important human food, animal feed, and industrial raw material, which is grown in more than 100 countries and mainly produced in China ( FAO, 2011 ; Jin, 2012 ). Sweetpotato is a typical “K-favoring” crop ( Tang

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R.L. Jarret, N. Gawel and A. Whittemore

Twenty-four accessions of Ipomoea, representing 13 species of section Batatas and the outgroup species I. gracilis and I. pes-caprae were analyzed for restriction fragment length polymorphisms. Polymorphisms were detected by probing Southern blots of restriction enzyme-digested genomic DNA with 20 low or moderate copy number sequences isolated from an I. batatas cv. Georgia Red genomic library. Data were analyzed cladistically and phenetically. Ipomoea trifida, I. tabascana, and collection K233 are, of the materials examined, the most closely related to sweetpotato (I. batatas). Ipomoea littoralis, the only Old World species in the section, is a sister species to I. tiliacea. Ipomoea littoralis, I. umbraticola, I. peruviana, I. cynanchifolia, and I. gracilis are shown to be diploid (2n = 2x = 30). In contrast, I. tabascana is tetraploid (2n = 4x = 60). The intrasectional relationships of section Batatas species and the role of tetraploid related species in the evolution of the cultivated I. batatas are discussed.

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Meng Wei, Aijun Zhang, Hongmin Li, Zhonghou Tang and Xiaoguang Chen

and S deficiency during wheat grain filling J. Expt. Bot. 59 3675 3689 Islam, M.S. Yoshimoto, M. Yahara, S. Okuno, S. Ishiguro, K. Yamakawa, O. 2002 Identification and characterization of foliar polyphenolic composition in sweetpotato ( Ipomoea batatas

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Janice R. Bohac, Alfred Jones and Daniel F. Austin

Previous work in this laboratory identified high levels of unreduced (2n) pollen in the tetraploid (4×) Ipomoea spp. Acc. 81.2. This work provided indirect evidence that 2n pollen was involved in the evolution of the 6x ploidy level of the cultivated sweetpotato (I. batatas). To further study the role of 2n pollen in sweetpotato evolution, we examined plants of Acc. 81.2. plants of five sweetpotato cultivars, and 100 randomly selected heterozygous sweetpotato seedlings. The 4× Acc. 81.2 was determined to be I. batatas. High levels of large 2n pollen were confirmed in Acc. 81.2, and low levels of 2n pollen were observed in `Sulfur' and in 16% of the sweetpotato seedlings. Presence of monad, dyad, and triad sporads confirmed that the large 2n pollen grains were the result of nonreduction in the sporad stage. These new findings are direct evidence that 2n pollen was involved in the evolution of the 6× ploidy level of sweetpotato. This is the first report of a 4× accession classified as I. batatas; it is also the first report of 2n pollen in 6× I. batatas The widespread presence of 2n pollen in sweetpotato suggests that the trait can be used to advantage in breeding programs to introgress genes from wild 4× Ipomoea spp. into cultivated 6× sweetpotato without adverse effects on genetic stability or fertility.

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R.L. Jarret, N. Bowen, S. Kresovich and Z. Liu

Simple sequence repeats (SSRs) were isolated from a size-fractionated genomic DNA library of sweetpotato [Ipomoea batatas (L.) Lam.]. Screening of the library with five oligonucleotide probes, including; (GT)11, (AT)11, (CT)11, (GC)11, and (TAA)8, detected the occurrence of 142 positive colonies among ≈12,000 recombinants. Automated DNA sequencing revealed the presence of simple, compound, perfect, and imperfect SSRs. Five homologous PCR primer pairs were synthesized commercially and used to screen 30 sweetpotato clones for the occurrence of SSR polymorphisms. All primer pairs produced an amplification product of the expected size and detected polymorphisms among the genotypes examined. The potential for the use of SSRs as genetic markers for sweetpotato germplasm characterization is discussed.

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Arthur Villordon, Don La Bonte and Robert Jarret

The presence of copia-like retrotransposon sequences in sweetpotato [Ipomoea batatas (L.) Lam.] was investigated. PCR-based amplification using primers to highly conserved copia-like reverse transcriptase sequences produced several products corresponding to the expected target size (≈300 bp) that were subsequently isolated and cloned. A random sample of the clones were sequenced and all six reading frames were translated into their corresponding amino acid sequences. Sequence analysis revealed the presence of 22 copia-like reverse transcriptase sequences corresponding to various subfamilies. The presence of several sequence families in the genome is indicative of past or recent transposition activity. Southern blot analysis suggested that these copia-like sequences were present in several hundred copies in the sweetpotato genome. Data also showed retrotransposon insertion polymorphisms between a limited sample of virus-tested and virus-infected sweetpotato clones, indicating putative activity and mobility. This investigation documented the presence of copia-like retrotransposon sequences in the sweetpotato genome. This is an important step in clarifying the possible association between mobile genetic elements and the unusually high incidence of somatic mutations that may result in clonal decline in sweetpotato and other asexually propagated crops. Data presented provides information on the possible use of retrotransposons as genetic markers for sweetpotato crop improvement.

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Sweet potato (Ipomoea batatas L. Lam) ranks second in world wide root and tuber production. Loss of genetic resources in the primary centers of origin have been occurring for a number of years. Utilization of the genetic diversity of wild types and related species cart expand breeding potential and efficiency. Two species, Ipomoea trifida and Ipomoea triloba, have been identified as possible progenitor species or sweet potato. Plant improvement at the cellular level using protoplasts is a novel alternative to conventional breeding practices. Protoplast plating efficiency appears to be genotype dependent. Roots have been regenerated from Ipomoea trifida protoplasm calli on Murashige and Skoog's medium containing zeatin or kinetin.