Line PI Research Articles

Aspectos biológicos de Tuta absoluta (Lepidoptera: Gelechiidae) criada em folhas de diferentes genótipos de tomate

The resistance of tomato genotypes, Lycopersicon esculentum (Miller) (cv. Santa Clara, hybrids: Saladette Italian Ty Tyna, Santa Cruz Debora Ty, Salad Lumi and Saladette Italian Andrea Victory), Lycopersicon hirsutum f. glabratum (C,H, Mull.) (lines PI 134417 and PI 134418) and Lycopersicum pimpinellifolium (Just) (lines NAV 1062 and PI 126931) to Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) was evaluated under laboratory conditions. The line PI 134418 had the most negative effect on T. absoluta in comparison to the control (Santa Clara), lengthening the larval stage and reducing larval and global survival. The line PI 134417 also affected the development of T. absoluta lengthening the larval stage and reducing the larval survival. The other genotypes showed no negative effect on the biology of T. absoluta. We concluded that PI 126931 is susceptible and NAV 1062, Santa Clara, Tyna, Debora, Lumi and Andrea Victory are highly susceptible to T. absoluta, whereas PI 134418 and PI 134417 highlighted with high resistance and moderate resistance, respectively, to T. absoluta of antibiosis-type.

Screening Carrot Germplasm for Resistance to Xanthomonas hortorum pv. carotae

Xanthomonas hortorum pv. carotae (Xhc) causes bacterial blight of carrot (Daucus carota L.), is endemic in the primary regions of carrot seed production, and is readily seed-transmitted. Genetic resistance to Xhc is not well documented in commercially available carrot cultivars, and there has been little public research on screening for resistance. Carrot PI lines (n = 66), public inbred lines (n = 2), and commercial cultivars (n = 17) were assessed for response to Xhc in a greenhouse in 2012 based on the incidence and severity of bacterial blight symptoms after inoculation as well as Xhc population [colony-forming units (CFU)/g dry foliage] detected by dilution plating onto XCS agar, a semiselective medium for Xhc. Severity of bacterial blight averaged 8.8% ± 0.4% (mean ± se) with a range of 0% to 50%, and size of the Xhc population detected on the foliage averaged 8.16 × 109 ± 1.07 × 109 CFU/g (range, 1.38 × 104 to 3.28 × 1011 CFU/g) for individual plants. Eight putative resistant PI lines and five highly susceptible PI lines selected from the 2012 screening were evaluated again in 2013 with an additional two PI lines, 12 cultivars, two inbred lines, and 12 carrot wild relatives. In the 2013 trial, severity of foliar blight 6 weeks post-inoculation ranged from 0% to 90% (11.8% ± 0.4%), and Xhc population ranged from 4.90 × 104 to 1.30 × 1011 CFU/g dry foliage (1.00 × 1010 ± 5.29 × 108 CFU/g) for individual plants. Spearman’s correlation coefficient between the Xhc population detected and severity of bacterial blight was highly significant in the 2012 and 2013 trials (r = 0.52 and 0.62, respectively, at P < 0.0001). PI lines 418967, 432905, and 432906 were the most resistant based on Xhc population detected and could be used to develop resistant cultivars. Of the 12 carrot wild relatives screened, only Ames 7674 and SS10 OR displayed a relatively low severity of bacterial blight and population of Xhc on the foliage.

Evaluation and Reselection of Wheat Resistance to Russian Wheat Aphid Biotype 2

ABSTRACTRussian wheat aphid (RWA, Diuraphis noxia, Mordvilko) biotype 2 (RWA2) is virulent to most known RWA resistance genes and severely threatens wheat (Triticum aestivum L.) production in the hard winter wheat area of the U.S. western Great Plains. We determined RWA2 reactions of 386 cultivars from China, 227 advanced breeding lines and recently released cultivars from the United States, 505 landraces from countries where RWA is endemic, and 31 genetic stocks developed in the United States, Australia, Canada, and Russia. The majority of wheat accessions from China and the United States were highly susceptible to RWA2. Only nine landrace accessions produced a homogeneous resistant reaction. In addition, highly resistant plants were identified in 28 heterogeneous landraces. Thus, reselection was conducted to purify some potential resistance sources, and the single‐plant progenies of 220 selected plants were evaluated. Homogeneous resistant or highly resistant lines were identified from seven previously heterogeneous landraces. Reselection line PI 626759‐20‐32 offered a high level of resistance similar to lines carrying Dn7, the rye (Secale cereale L.)‐derived resistance gene associated with undesirable bread‐making quality. PI 626759‐20‐32 has the potential to supplement or replace Dn7 as a new RWA2 resistance source in wheat breeding.

Abstract 5112: Histone deacetylase and proteasome inhibitors synergistically induce apoptosis in colon cancer, multiple myeloma and CTCL cells through induction of the immediate early genes ATF3 and JUN

Abstract Background/Aim: Histone deacetylase inhibitors (HDACi) are approved for the treatment of cutaneous T-cell lymphoma. We have previously demonstrated that HDACi-mediated apoptosis is linked to the induction of a defined transcriptional response involving up-regulation of the immediate-early (IE) genes FOS, JUN, ATF3, EGR1 and EGR3, in cell lines derived from multiple tumour types. To identify other drugs which induce a similar transcriptional response we compared the HDACi-induced transcriptional response with that induced by >1000 bioactive molecules using the Broad Institute's Connectivity Map database. The proteasome inhibitor, MG-262, was identified as inducing the most comparable transcriptional response to HDACi. Notably, combination treatment with HDAC and proteasome inhibitors has been shown to synergistically induce apoptosis in vitro, and a phase III trial of this combination demonstrated activity in patients multiple myeloma. The aim of this study was to determine whether these effects are mediated through the additive induction of IE genes. Methods: The effect of the HDACi SAHA and the clinically approved proteasome inhibitor Bortezomib, alone, and in combination, on apoptosis induction was determined in colorectal, multiple myeloma and CTCL cell lines PI staining and FACS analysis. Quantitative RT-PCR was performed to determine gene expression changes upon drug treatment. MAPK pathway activation and histone hyper-acetylation was determined by western blot analysis. Results: Single agent treatment of multiple cancer cells with SAHA or Bortezomib induced expression of the IE genes FOS, JUN and ATF3. In both cases IE gene induction was sustained over 24h. Proteasome inhibitor-induced IE gene expression and apoptosis was selectively dependent on activation of the JNK and p38 stress response pathways, while HDACi-mediated effects were selectively dependent upon the Sp1 and Sp3 transcription factors, indicating these agents induce IE gene expression and apoptosis via independent mechanisms. Co-treatment with Bortezomib and SAHA resulted in synergistic induction of IE gene expression and apoptosis in cell lines derived from multiple tumour types. Importantly, apoptosis induction by the combination was partially inhibited by siRNA-mediated downregulation of two IE genes, ATF3 and JUN. Conclusions: This study provides insight into the mechanistic basis by which combination treatment with HDAC and proteasome inhibitors synergistically induces apoptosis in tumour cells. Citation Format: Janson WT Tse, Anderly C. Chueh, Ian Y. Luk, Fiona Chionh, Yvonne Yeung, Georgia A. Corner, Dominic CH Ng, Hoanh Tran, Amardeep S. Dhillon, John M. Mariadason. Histone deacetylase and proteasome inhibitors synergistically induce apoptosis in colon cancer, multiple myeloma and CTCL cells through induction of the immediate early genes ATF3 and JUN. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 5112. doi:10.1158/1538-7445.AM2014-5112

Antibiosis in Soybean Genotypes and the Resistance Levels to Spodoptera eridania (Cramer) (Lepidoptera: Noctuidae).

The southern armyworm (SAW) Spodoptera eridania (Cramer) is one of the most common armyworm species defoliating soybeans. Preliminary screening trials have indicated that some soybean genotypes exhibit resistance to SAW. Therefore, in this study, we evaluated the development of SAW larvae fed on ten soybean genotypes in order to identify genotypes with antibiosis-type resistance. Neonate SAW larvae were daily fed with young leaves collected from plants at the vegetative growth stages V4-V5. Larval development and survival were recorded. Genotypes PI 227687 and PI 227682 delayed larval, pupal, and larva-adult development and yielded larvae with the lowest weight and survival and pupae with the lowest weight. Genotypes IAC 100 and DM 339 also negatively affected larval and pupal development and larval survival but at a lower level. Based on our results, the soybean lines PI 227687 and PI 227682 could be used as sources of genes for soybean breeding programs aiming to develop high yield, SAW-resistant cultivars. Moreover, further trials must be carried out under field conditions to validate if the commercial cultivars IAC 100 and DM 339, which expressed moderate levels of antibiosis-type resistance in the laboratory, are effective in suppressing SAW larvae populations.

Phytophthora Root Rot Resistance in Soybean E00003

ABSTRACTPhytophthora root rot (PRR) is a devastating disease in soybean [Glycine max (L.) Merr.] production. Michigan elite soybean E00003 is resistant to Phytophthora sojae and has been used as a resistance source in breeding. Genetic control of PRR resistance in this source is unknown. To facilitate marker‐assisted selection (MAS), the PRR resistance loci in E00003 and their map locations need to be determined. In this study, a genetic mapping approach was used to identify major PRR‐resistant loci in E00003. The mapping population consists of 240 F4–derived lines developed by crossing E00003 with the P. sojae susceptible line PI 567543C. In 2009 and 2010, the mapping population was evaluated in the greenhouse for PRR resistance against P. sojae races 1, 4, and 7, using modified rice (Oryza sativa L.) grain inoculation method. The population was genotyped with seven simple sequence repeat (SSR) and three single nucleotide polymorphism (SNP) markers derived from bulk segregant analysis. The heritability of resistance in the population ranged from 83 to 94%. A major locus, contributing 50 to 76% of the phenotypic variation, was mapped within a 3 cM interval in the Rps1 region. The interval was further saturated with more BARCSOY SSRs and SNPs with TaqMan assays. Two SSRs and three SNPs within the Rps1k gene were highly associated with PRR resistance in the mapping population. The major resistance gene in E00003 is either allelic or tightly linked to Rps1k. The molecular markers located in the Rps1k gene can be used to improve MAS for PRR resistance.

A comparison of disease severity measurements using image analysis and visual estimates using a category scale for genetic analysis of resistance to bacterial spot in tomato

Bacterial spot caused by several Xanthomonas spp. is an economically important disease of tomato (Solanum lycopersicum L.). Host resistance to the disease is partially dominant or incomplete, which requires accurate assessment of disease severity for genetic studies of resistance. In the present study, three independent experiments were conducted to investigate the feasibility of using image analysis to estimate foliar disease severity of bacterial spot in tomato. The resistant line PI 114490 and the susceptible line OH 88119 were used in the first experiment, five tomato lines (PI 114490, PI 128216, Hawaii 7981, Hawaii 7998, and Fla. 7600) with a range of resistance and OH 88119 were used in the second experiment, and 439 F2 individuals from a cross between OH 88119 and PI 114490 were used in the third experiment. Tomato plants were spray-inoculated with bacterial spot race T3. Five diseased leaves from each plant were randomly collected and scanned to obtain digital images 21 days after inoculation. The disease severity (% leaf area) was measured using image analysis. The susceptible line OH 88119 showed the most severe disease. The resistant line PI 114490 showed the least severe disease, and was not significantly different to PI 128216 or Hawaii 7981. These results indicated that image analysis could be used to distinguish tomato lines with different resistance to bacterial spot. Marker-trait association analysis identified four quantitative trait loci conferring resistance to race T3 in PI 114490 using data obtained from image analysis, the Horsfall-Barratt (HB) category scale data, and HB midpoint converted values. However, the disease severity was slightly underestimated using the HB category scale and the phenotypic variation explained by each marker was overestimated using the HB category data compared to using the image analysis-measured disease severity data. Therefore, image analysis could provide a consistent, accurate and reliable method compared to the HB scale to estimate disease severity for genetic studies of foliar bacterial spot in tomato.

Efficient Enumeration of All Ladder Lotteries with <i>k</i> Bars

A ladder lottery, known as the “Amidakuji” in Japan, is a common way to choose an assignment randomly. Formally, a ladder lottery of a permutation π = (p1, p2, . . . , pn) is a network with n vertical lines (lines for short) and many horizontal lines (bars for short) as follows (see Fig. 1). The i-th line from the left is called line i. The top ends of the n lines correspond to π. The bottom ends of the n lines correspond to the identical permutation (1, 2, . . . , n). Each bar connects two consecutive lines. Each number pi in π starts at the top end of line i, and goes down along the line, then whenever pi comes to an end of a bar, pi goes horizontally along the bar to the other end, then goes down again. Finally pi reaches the bottom end of line pi. We can regard a bar as a modification of the “current” permutation. In a ladder lottery a sequence of such modifications always results in the identical permutation (1, 2, . . . , n). The ladder lotteries are strongly related to primitive sorting networks, which are deeply investigated by Knuth [2]. A comparator in a primitive sorting network replaces pi and pj by min (pi, pj) and max (pi, pj), while a bar in a ladder lottery always exchanges them. Given a permutation π = (p1, p2, . . . , pn) the minimum number of bars to construct ladder lotteries of π is equal to the number of “reverse pairs” in π, which are pairs (pi, pj) in π with pi > pj and i < j. A ladder lottery of π with the minimum number of bars is optimal. The ladder lottery in Fig. 2 has eight bars, and its corresponding permutation (2,6,4,1,5,3) has eight reverse pairs: (2,1), (6,4), (6,1), (6,5), (6,3), (4,1), (4,3) and (5,3), so the ladder lottery is optimal. In [5] we gave an algorithm to enumerate all optimal ladder lotteries of a given permutation π. The algorithm generates all optimal ladder lotteries of π in O(1) time for each. The idea of our algorithm in [5] is as follows. We first define a tree structure Tπ, called the family tree, among optimal ladder lotteries, in which each vertex of Tπ corresponds to each optimal ladder lottery and each edge of Tπ corresponds to a relation between two optimal ladder lotteries. Then we design an efficient algorithm to generate all child vertices

Identification of sources of resistance to damping-off and early root/hypocotyl damage from Rhizoctonia solani in common bean (Phaseolus vulgaris L.)

Rhizoctonia solani causes economically important root and hypocotyl diseases in common bean throughout the world. Root health is a vital factor in plant development and root diseases would negatively influence water and nutrient uptake as well as cause direct stand reduction and root rot damage to the crop. An efficient common bean screening method to evaluate damping-off and early root/hypocotyl damage from R. solani was developed and used to identify dry bean lines with levels of resistance to this disease. Two sets of 163 and 111 lines previously evaluated for drought tolerance in Nebraska and Puerto Rico were evaluated for damping-off resistance and early root/hypocotyl damage under greenhouse conditions. Disease severity on plants was identified based on above-ground symptoms, seedling survival and root lesions using a rating scale of 1 (resistant) to 9 (susceptible). In the first set of lines representing commonly grown dry bean cultivars, germplasm and sources of damping-off resistance, the Rhizoctonia mean rating ranged from 1.7 to 3.9; Phaseolus vulgaris lines PI 310668 and PI 533249 had the highest damping-off resistance. In the second set of the best lines from a drought tolerance shuttle breeding program the Rhizoctonia mean rating was between 2.6 and 5.7. The availability of drought tolerant dry bean lines allowed the testing of the hypothesis that there was a correlation between selecting for drought tolerance and R. solani damping-off resistance. No correlation between mean disease rating and drought tolerance was found, but adapted dry bean lines such as NE14-08-176 released as SB-DT1, and NE14-08-225 were identified with moderate damping-off resistance and drought tolerance. Lines with both traits and other attributes will facilitate development of resistant bean cultivars to manage damping-off caused by R. solani.

Resistance to soybean aphid among wild soybean lines under controlled conditions

The soybean aphid, Aphis glycines Matsumura, is frequently a serious pest of soybean in the U.S. and Canada, and an occasional pest of soybean throughout its native range in Asia. Large infestations of this aphid cause economic loss to soybean by reductions in seed yield and oil concentration. Host-plant resistance is a potential alternative to insecticides for managing soybean aphid, and various sources may be evaluated, including adapted cultivars, landraces, and wild ancestors of the crop. To date, few studies have evaluated wild soybean for resistance to soybean aphid. In this study, initial screening assays indicated 20 wild soybean lines with resistance to soybean aphid, and three of the 20 lines had notable resistance in subsequent choice and no-choice assays. Significantly fewer soybean aphids settled on lines PI 468397 A and PI 479749 than on susceptible lines in choice assays, and aphid populations were low and moderately low on these two respective lines in no-choice assays. Populations of soybean aphid on a third line, PI 549046, were equal to or less than those on a resistant check over 3 wks in a no-choice assay. Based on results of the respective choice and no-choice assays, resistance to soybean aphid was manifested as both antixenosis and antibiosis in PI 468397 A and PI 479749, and as antibiosis in PI 549046. This is apparently the first report of resistance to soybean aphid in these three lines, and they provide soybean breeders and pest management practitioners new sources for developing aphid-resistant soybean lines.

Differential gene expression in response to Papaya ringspot virus infection in Cucumis metuliferus using cDNA-amplified fragment length polymorphism analysis.

A better understanding of virus resistance mechanisms can offer more effective strategies to control virus diseases. Papaya ringspot virus (PRSV), Potyviridae, causes severe economical losses in papaya and cucurbit production worldwide. However, no resistance gene against PRSV has been identified to date. This study aimed to identify candidate PRSV resistance genes using cDNA-AFLP analysis and offered an open architecture and transcriptomic method to study those transcripts differentially expressed after virus inoculation. The whole genome expression profile of Cucumis metuliferus inoculated with PRSV was generated using cDNA-amplified fragment length polymorphism (cDNA-AFLP) method. Transcript derived fragments (TDFs) identified from the resistant line PI 292190 may represent genes involved in the mechanism of PRSV resistance. C. metuliferus susceptible Acc. 2459 and resistant PI 292190 lines were inoculated with PRSV and subsequently total RNA was isolated for cDNA-AFLP analysis. More than 400 TDFs were expressed specifically in resistant line PI 292190. A total of 116 TDFs were cloned and their expression patterns and putative functions in the PRSV-resistance mechanism were further characterized. Subsequently, 28 out of 116 candidates which showed two-fold higher expression levels in resistant PI 292190 than those in susceptible Acc. 2459 after virus inoculation were selected from the reverse northern blot and bioinformatic analysis. Furthermore, the time point expression profiles of these candidates by northern blot analysis suggested that they might play roles in resistance against PRSV and could potentially provide valuable information for controlling PRSV disease in the future.

Feeding non-preference by Spodoptera frugiperda and Spodoptera eridania on tomato genotypes

Larvae of the genus Spodoptera spp. are highly polyphagous and can cause economical losses in several agricultural crops. Given their growing importance in the tomato crop, especially for industry, this work aimed to evaluate the feeding non-preference by larvae of Spodoptera frugiperda (J. E. Smith, 1797) and Spodoptera eridania (Cramer, 1782) on tomato genotypes and classify them by the levels of resistance. The commercial cultivar Santa Clara was set as the susceptible standard and line PI 134417 as the resistant standard to evaluate the lines PI 134418, PI 126931, LA 462 and LA 716. Feeding non-preference tests were performed under non-choice and free-choice conditions to evaluate the genotype attractiveness to larvae at predetermined times after their release, as well as the leaf area consumed. Overall, the genotypes LA 716 and PI 126931 were the least attractive to S. frugiperda, whereas Santa Clara was the most attractive and consumed. For S. eridania, the genotypes PI 126931, LA 462, LA 716 and PI 134418 were the least preferred for feeding, and Santa Clara and PI 134417 were the most attractive and consumed. The genotypes LA 716 and PI 126931 are moderately resistant to S. frugiperda and S. eridania; PI 134418 and LA 462 are moderately resistant to S. eridania; PI 134417 is susceptible to S. frugiperda and S. eridania; and Santa Clara is highly susceptible to both S. frugiperda and S. eridania.

Genetics of Reniform Nematode Resistance in Gossypium arboreum Germplasm Line PI 529728

Reniform nematode (Rotylenchulus reniformis) is a serious pathogen of cotton in the United States and management has been difficult due to the lack of resistant upland cotton (Gossypium hirsutum) varieties. The diploid G. arboreum germplasm line PI 529728 was identified as a potential new source of R. reniformis resistance. Line PI 529728 was crossed with the highly susceptible G. arboreum germplasm line PI 529729 to develop F1, BC1F1, and F2 populations that were screened for nematode resistance under controlled environmental conditions to determine the genetics of resistance. The 10 F1, 69 BC1F1, and 332 F2 plants were inoculated with 1,000 vermiform nematodes and the number of swollen females on the root systems was determined 28 days after inoculation. The F1 plants supported more nematodes than the susceptible control genotype PI 529251 (G. hirsutum accession Deltapine 16) indicating resistance was a recessive trait. For the BC1F1 and F2 populations, plants supporting the same or a reduced level of infection that developed on the resistant control genotype PI 163068 (G. barbadense accession Texas 110) were rated as resistant. Based on this classification of resistance and susceptibility, it was predicted that a single recessive gene was conferring resistance; although, the BC1F1 population had more susceptible plants than expected. Additionally, highly resistant plants were observed in the BC1F1 and F2 populations. This information will aid in the introgression of R. reniformis resistance from PI 529728 into upland cotton for the development of resistant varieties.

Stability Analysis of Incidence of Tomato Spotted Wilt in Virginia-Type Peanut Cultivars and Breeding Lines

ABSTRACT Tomato spotted wilt (TSW) caused by Tomato spotted wilt tospovirus (TSWV) has become a serious constraint to peanut (Arachis hypogaea L.) production in the Virginia-Carolina production area. Regression stability analysis was applied to TSW incidence data collected in 64 trials conducted over 17 years to determine if an array of 31 virginia-type cultivars and breeding lines exhibited variation in their reactions to increasing levels of general TSW intensity compared with the standard field-resistant cultivar Georgia Green and hirsuta-type line PI 576636. Eight cultivars (NC 7, NC 9, NC 10C, NC-V 11, NC 12C, Perry, Phillips, and Brantley) had mean effects greater than zero (P&amp;lt;0.01) while Bailey, four Bailey siblings, and N96076L, Bailey's resistant parent, all had mean effects less than zero (P&amp;lt;0.01). The deviations of the slope of regression on environmental index (β̂k) for four of the eight susceptible cultivars were greater than zero, indicating greater than average reaction to increased levels of TSW. The β̂k for Bailey indicated that its response to increasing levels of TSW was flat. PI 576636 was confirmed as a highly field-resistant line. The slopes of Georgia Green, the standard TSWV-resistant runner-type cultivar, the Bailey siblings and N96076L did not differ from the average of all lines. The correlation between mean effect and β̂k was r = 0.693, indicating that approximately half the variation in β̂k could be explained by mean effects. However, the regression analysis provided information useful in describing the TSW reactions of the lines and cultivars.

Epistatic effects on grain yield of soybean [Glycine max (L.) Merrill

Studies addressing the estimation of genetic parameters in soybean have not emphasized the epistatic effects. The purpose of this study was to estimate the significance of these effects on soybean grain yield, based on the Modified Triple Test Cross design. Thirty-two inbred lines derived from a cross between two contrasting lines were used, which were crossed with two testers (L1 and L2). The experiments were carried out at two locations, in 10 x 10 triple lattice designs with 9 replications, containing 32 lines (Pi ), 64 crosses (32 Pi x L1 and 32 Pi x L2 ) and controls. The variation between ( ͞L1i + ͞L2i - ͞Pi ) revealed the presence of epistasis, as well as an interaction of epistasis x environment. Since the predominant component of epistasis in autogamous species is additive x additive (i type), we suggest postponing the selection for grain yield to later generations of inbreeding in order to exploit the beneficial effects of additive x additive epistasis.

Não preferência para oviposição e alimentação por Tuta absoluta (Meyrick) em genótipos de tomateiro

Este trabalho buscou selecionar genótipos de tomateiro resistentes a Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae), dos tipos não preferência para oviposição e alimentação, em testes com e sem chance de escolha. As espécies utilizadas foram Solanum lycopersicum L. (cv. Santa Clara, os híbridos: Saladete Italiano Ty Tyna, Santa Cruz Débora Ty, Salada Lumi, Saladete Italiano Andrea Victory e Santa Cruz Ty Carina Ty), S. habrochaites S. Knapp &amp; D.M Spooner (linhagens PI 134417 e PI 134418) e S. pimpinellifolium L. (linhagens NAV 1062 e PI 126931). Nos testes de não preferência para oviposição, foram contados o número de ovos por planta às 24, 48 e 72 horas, após a liberação dos adultos. Para os testes de não preferência para alimentação, foram avaliados a atratividade das larvas pelos genótipos em cada repetição a 1, 3, 5, 10, 30, 60, 120, 360, 720 e 1440 minutos, após a liberação das larvas e massa consumida pelas larvas. Constatou-se que os genótipos de tomateiro avaliados não apresentam resistência dos tipos não preferência para oviposição. Já o genótipo PI 134417 apresenta resistência do tipo não preferência para alimentação.

Enzyme activity in wheat breeding lines derived from matings of low polyphenol oxidase parents

Polyphenol oxidase (PPO) in grain plays a major role in time-dependent discoloration of wheat (Triticum aestivum L.) products, especially fresh noodles. Breeding wheat cultivars with low or nil PPO activity can reduce undesirable product darkening. The low PPO line PI 117635 was crossed to two low PPO wheats, IDO580 and ‘IDO377s’, to determine whether matings between wheats with low levels of grain PPO would result in complementation, such that lines with still lower or nil PPO would be generated. Progeny in a population derived from PI 117635/IDO580 displayed no variation in PPO activity. In the F3:4 populations derived from PI 117635/IDO377s, and the reciprocal IDO377s/PI 117635, normal distributions of low to high PPO activity were observed. Field-grown populations (F3:5; F3:6) derived from IDO377s crosses were analyzed for PPO activity and used to determine whether lines with nil PPO activity were generated. Of 239 lines, 154 were verified to have PPO activity that was not significantly different from the low PPO durum (Triticum turgidum var durum) cultivar ‘Ben’. PCR analysis showed that the populations were fixed for a putative low PPO allele at Ppo-A1. Using markers for Ppo-D1, it was found that the average PPO activity of lines with 490 bp PCR fragments from PPO29 was significantly lower than that of lines with 560 bp fragments from STS01. These results disagreed with that predicted from previous reports for markers for Ppo-D1 alleles. Thus, breeders should exercise caution when making selections using markers for alleles at Ppo-D1, as known markers might predict erroneous phenotypes and genotypes in some wheat backgrounds.

Characterization of the recessive resistance gene cyv1 of Pisum sativum against Clover yellow vein virus

Two recessive resistance genes against Clover yellow vein virus (ClYVV), cyv1 and cyv2, have been previously reported. We recently screened resistant peas from a separate set of pea lines and classified them into two groups according to their distinct modes of resistance. We later revealed that one group carries cyv2, encoding eukaryotic translation initiation factor 4E (eIF4E), in linkage group (LG) VI. We explored the possibility that the resistance gene, tentatively designated non-cyv2, that confers resistance to the other group, was actually cyv1. We found that PI 236493, which carries cyv1, had restricted cell-to-cell movement of ClYVV similar to that in non-cyv2 peas including PI 429853. PI 429853 was crossed with susceptible line PI 250438. Mapping of F2 progeny revealed that non-cyv2 was 4 cM from the simple sequence repeat marker AB40, whose loci are close to cyv1, mo, and sbm-2 mapped in LG II, which mediates resistance to other potyviruses. Moreover, PI 429853 crossed with PI 236493 produced F1 progeny resistant to ClYVV, raising the possibility that non-cyv2 is allelic to cyv1. Because mo was previously mapped with eIF(iso)4E in LG II, we examined the possibility that non-cyv2, cyv1, and mo encoded eIF(iso)4E. However, there was no difference in the nucleotide sequence of the eIF(iso)4E-coding region between susceptible and resistant pea lines. The eIF(iso)4E gene was equivalently expressed in both PI 429853 and PI 250438 before and after ClYVV infection. Our results suggest that these resistance genes are unlikely to encode eIF(iso)4E on LG II.

Inheritance and mapping of stem rust resistance of wheat line PI 410966

Stem rust caused by Puccinia graminis f. sp tritici of wheat (Triticum aestivum L.) is one of the most destructive cereal diseases globally. Concern about the disease has increased since 1999 with the discovery in Uganda of a new virulent race of Pgt, designated as race TTKSK (also known as Ug99). The objectives of this experiment were to characterize the resistance and to determine the chromosomal location of the stem rust resistance in the spring wheat line PI 410966. A mapping population was developed from a cross between PI 410966 and a susceptible wheat line OK3040. An inoculation test with isolate 04KEN156/04 of race TTKSK was conducted at the USDA-ARS Cereal Disease Laboratory in the F6:7 generation, and the F6:7 phenotypic data were used to genetically map the resistance gene to the centromeric region on chromosome 2BS. The single locus explained the observed F6:7 resistant and susceptible scores. The location of the gene and molecular marker banding profiles of the diagnostic markers suggest that...

Transcriptome analysis of resistant soybean roots infected by Meloidogyne javanica.

Soybean is an important crop for Brazilian agribusiness. However, many factors can limit its production, especially root-knot nematode infection. Studies on the mechanisms employed by the resistant soybean genotypes to prevent infection by these nematodes are of great interest for breeders. For these reasons, the aim of this work is to characterize the transcriptome of soybean line PI 595099-Meloidogyne javanica interaction through expression analysis. Two cDNA libraries were obtained using a pool of RNA from PI 595099 uninfected and M. javanica (J2) infected roots, collected at 6, 12, 24, 48, 96, 144 and 192 h after inoculation. Around 800 ESTs (Expressed Sequence Tags) were sequenced and clustered into 195 clusters. In silico subtraction analysis identified eleven differentially expressed genes encoding putative proteins sharing amino acid sequence similarities by using BlastX: metallothionein, SLAH4 (SLAC1 Homologue 4), SLAH1 (SLAC1 Homologue 1), zinc-finger proteins, AN1-type proteins, auxin-repressed proteins, thioredoxin and nuclear transport factor 2 (NTF-2). Other genes were also found exclusively in nematode stressed soybean roots, such as NAC domain-containing proteins, MADS-box proteins, SOC1 (suppressor of overexpression of constans 1) proteins, thioredoxin-like protein 4-Coumarate-CoA ligase and the transcription factor (TF) MYBZ2. Among the genes identified in non-stressed roots only were Ser/Thr protein kinases, wound-induced basic protein, ethylene-responsive family protein, metallothionein-like protein cysteine proteinase inhibitor (cystatin) and Putative Kunitz trypsin protease inhibitor. An understanding of the roles of these differentially expressed genes will provide insights into the resistance mechanisms and candidate genes involved in soybean-M. javanica interaction and contribute to more effective control of this pathogen.