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Selection against pink stem borer (Sesamia non-agrioides Lef) (PSB) attack was performed in the maize (Zea mays L.) synthetic EPS12. The direct response of the EPS12 population to three cycles of selection to reduce tunnel length damage by PSB while maintaining yield was evaluated. [S.sub.0] (cycles of selection) and [S.sub.1] (selfed cycles of selection) generations and testcrosses to three testers were evaluated under artificial infestation with two corn borers, PSB and European corn borer (Ostrinia nubilalis Hubner) (ECB). Genotypes and the genotype x environment interaction were significant for tunnel length and yield. Differences among cycles of selection were significant for tunnel length, and the linear decrease for this trait (-1.80 cm [cycle.sup.1]) achieved during selection accounted for most of these differences. Yield was not significantly reduced with selection. Inbreeding for yield significantly increased due to selection. EPS12 crossed to EP42 showed a significant increase in yield with selection, while crosses to other testers showed a nonsignificant reduction in yield. Although crosses to EP42 were not significantly different for tunnel length, the high heterosis between EPS12 and EP42 and the increased yield of EPS12 x EP42 during selection suggest that inbred lines developed from advanced cycles of EPS12 could be crossed to EP42 to generate promising hybrids. In general, resistance to PSB and ECB was improved, while yield was maintained, inbreeding was increased, and yield of the cross EP42 x EPS12 was improved.

Early planting can contribute to increased grain yield of maize (Zea mays L.), but it requires cold tolerance. A limited number of cold-tolerant maize genotypes have been reported. The objectives of this study were to test a new strategy to improve cold tolerance in maize searching for broad x narrow genetic combinations that may be useful as base populations for breeding programs, to compare genotype performance under cold-controlled and field conditions, and to establish the major genetic effects involved in crosses between cold-tolerant inbred lines and populations. Nine cold-tolerant populations were crossed to five inbred lines and evaluated in a cold chamber and in the field. Most inbred line x population crosses performed better than populations per se or hybrids used as checks, both in the cold chamber and in the field, suggesting that broad x narrow genetic combination could be a suitable start point for further breeding programs for cold tolerance. The crosses between the inbred line EP80 and northwestern Spanish populations are the most promising base germplasm. In particular, EP80 x Puenteareas showed the greatest yield and good performance at the first stages of development under cold conditions. In addition, EP80 and Puenteareas showed favorable general combining ability for most traits. Early vigor rating would be the most suitable trait to select maize genotypes with superior cold tolerance during emergence and postemergence stages, because it was the only trait for which differences among genotypes were observed in both the cold chamber and the field. Although evaluation under controlled conditions is essential to test cold tolerance, field evaluations are complementary because no association was found between traits evaluated in both conditions.

Various pests, such as those in the order Lepidoptera, frequently feed on young maize (Zea mays) plants and pose a significant threat to plant development and survival. To manage this problem, maize generates a wide variety of responses to attack by pests, from activation of wound-response pathways to the release of volatile compounds. Mp708, an inbred line resistant to feeding by the larvae of the fall armyworm (Spodoptera frugiperda J.E. Smith Lepidoptera: Noctuidae), has been developed through traditional breeding methods, but its underlying mechanisms of resistance are still not completely understood. Mp708 has been shown to have a moderately high constitutive expression of jasmonic acid (JA) before infestation by fall armyworm. However, Tx601, a genotype susceptible to feeding by fall armyworm, activates JA pathway only in response to feeding, suggesting that Mp708 is "primed" to respond swiftly to an attack. Current research indicates that fall armyworm show a lack of preference to feeding on Mp708, leading to the hypothesis that volatiles constitutively released by the plant may also play an important role in its resistance. Analysis of volatiles released by Mp708 and Tx601 in the presence and absence of fall armyworm larvae identified (E)-β-caryophyllene, a terpenoid associated with resistance, released constitutively in Mp708. Fall armyworm fed samples of both Mp7O8 and Tx601 showed high transcript number of tps23, the gene responsible for the synthesis of (E)-β-caryophyllene. In addition, fall armyworm larvae show a preference for Tx601 whorl tissue over Mp708 tissue, and the dosage of Tx601 whorl with (E)-β-caryophyilene repels the fall armyworm. [ABSTRACT FROM AUTHOR]

A maize synthetic population was improved for resistance to the Mediterranean corn borer (MCB, Sesamia nonagrioides) while maintaining yield. The objectives of this research were to investigate whether yield and yield stability of the maize synthetic population named EPS12 were affected by selection for MCB resistance; also to determine which genotypic and environmental covariates could explain the genotype (G), environment (E) and genotype × environment (GE) effects for yield under corn borer infestation. Plants from three cycles of selection and their testcrosses to three inbred testers (A639, B93 and EP42) were evaluated at two locations in 2 years, under MCB and European corn borer infestations. After selection EPS12 was a more stable genotype. Hybrids derived from crosses between B93 and inbreds obtained from the initial cycles of selection could be recommended for cultivation in northern Spain. The yield of crosses between cycles of selection and testers increased when there were fewer days with temperatures >25°C and higher mean maximum temperatures. Differences in yield among these genotypes were mostly explained by resistance to corn borer attack. In general, among EPS12-derived materials, genetic characteristics that contribute to increased grain yield were also responsible for increased abiotic stress tolerance. [ABSTRACT FROM AUTHOR]

Sesamia nonagrioides causes high yield losses in maize in northwestern Spain. Therefore, a recurrent selection programme to improve resistance against this pest has been carried out in a maize synthetic population. The main purposes of this investigation were to determine which are the main components of genetic variance for stem tunnelling and yield under infestation, to determine the variance remaining after selection, and, finally, to establish the genetic relationship between traits used as selection criteria and other ear resistance and agronomic traits. A North Carolina Design I mating system was used. Individual analyses by year were carried out and additive variance was identified as the only significant component of the genetic variance for stem tunnel length while a dominant variance was significant for yield. Those variances have decreased due to selection, but not significantly. Selection could continue for more cycles as there is enough variance. Additive genetic correlation coefficients between tunnel length and yield could not be determined. Thereafter, we propose three different methodologies of the selection to determine the relationship between resistance and yield under infestation. [ABSTRACT FROM AUTHOR]

Our knowledge of the genetics of resistance to the pink stem borer ( Sesamia nonagrioides) in maize ( Zea mays) is restricted to a few crosses among maize inbreds. The objectives of this study were to enlarge our understanding of the genetics of traits related to damage by pink stem borer and yield under infestation and to use generation means analyses to compare per se and testcross performance for detecting epistatic effects. All generations, either per se or crossed to testers, were evaluated in a 10 × 10 triple lattice design under artificial infestation with S. nonagrioides in 2005 and 2006. Most traits fit an additive–dominance model; but evidence for epistasis for resistance and yield under infestation was shown. Epistasis, in general, did not appear to play an important role in the inheritance of yield under pink stem borer infestation. However, the epistasis contribution to maize yield performance could be important in some outstanding crosses such as EP42 × A637. Testcross generation means revealed epistatic effects undetected by the generation means analysis, but neither method was able to eliminate dominance effects that could prevail over epistatic effects. [ABSTRACT FROM AUTHOR]

Popcorn adapted to Spanish conditions could be an interesting and profitable alternative to field corn. However, little is known about breeding popcorn germplasm for adaptation to Spain. Sesamia nonagrioides Lefèvbre is the main insect pest affecting popcorn quality and yield under Spanish growing conditions. The objectives of the study were the search for sources of resistance to & nonagrioides among popcorn germplasm and to study the genetics of the resistance to S. nonagrioides attack. Eight breeding populations along with a five-inbred line diallel and two popcorn commercial checks were evaluated under S. nonagrioides infestation in 2 yr. Significant differences were found among general combining ability (GCA) effects for days to silking, & nonagrioides tunnel length, general appearance of the ear, kernel moisture, and yield. Specific combining ability (SCA) effects were found to be significant for yield and ear damage. Therefore, heterotic patterns among popcorn materials should be taken into account to generate new popcorn hybrids that are not only more productive but also have higher kernel quality. Breeding popcorn populations BSP4APC0 and PSPW1C1 could be base germplasms in a breeding program for obtaining parental inbreds of healthy kernel popcorn hybrids. New inbred lines could be generated from the cross BP1 × BP2 that would have improved GCA and SCA effects for S. nonagrioides resistance when crossed to South American inbreds. [ABSTRACT FROM AUTHOR]

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Background: LIM (Lineage-11 (LIN-11), Insulin-1 (ISL-1), and Mechanotransduction-3 (MEC-3)) genes belong to a family that hold ubiquitous properties contributing to organ, seed, and pollen development as well as developmental and cellular responses to biotic and abiotic stresses. Lettuce (Lactuca sativa) is a highly consumed vegetable crop susceptible heat stress. High temperatures limit lettuce's overall yield, quality and marketability. Lettuce LIM genes have not been identified and their role in response to high temperatures is not known. Aiming to identify potential new targets for thermoresilience, we searched for LIM genes in lettuce and compared them with orthologous of several dicotyledons and monocotyledons plant species., Results: We identified fourteen lettuce LIM genes distributed into eight different subgroups using a genome-wide analysis strategy. Three belonging to DAR (DA means "large" in Chinese) class I, two DAR class II, one in the WLIM1, two in the WLIM2, one in the PLIM1, two in the PLIM2 class, one ßLIM and two δLIMs. No DAR-like were identified in any of the species analyzed including lettuce. Interestingly, unlike other gene families in lettuce which underwent large genome tandem duplications, LIM genes did not increase in number compared to other plant species. The response to heat stress induced a dynamic transcriptional response on LsLIM genes. All heat stress regimes, including night stress, day stress and day and night stress were largely responsible for changes in LIM transcriptional expression., Conclusions: Our global analysis at the genome level provides a detailed identification of LIM genes in lettuce and other dicotyledonous and monocotyledonous plant species. Gene structure, physical and chemical properties as well as chromosomal location and Cis-regulatory element analysis together with our gene expression analysis under different temperature regimes identified LsWLIM1, LsWLIM2b, LsDAR3 and LsDAR5 as candidate genes that could be used by breeding programs aiming to produce lettuce varieties able to withstand high temperatures., (© 2024. The Author(s).)

Lettuce is a highly perishable horticultural crop with a relatively short shelf-life that limits its commercial value and contributes to food waste. Postharvest senescence varies with influences of both environmental and genetic factors. From a larger pool of romaine lettuce genotypes, we identified three genotypes with variable shelf lives and evaluated their leaf morphology characteristics and transcriptomic profiles at preharvest to predict postharvest quality. Breeding line 60184 had the shortest shelf-life (SSL), cultivar 'Manatee' had an intermediate shelf-life (ISL), and 'Okeechobee' had the longest shelf-life (LSL). We observed significantly larger leaf lamina thickness and higher stomatal index in the SSL genotypes relative to the LSL cultivar. To identify molecular indicators of shelf-life, we used a transcriptional approach between two of the contrasting genotypes, breeding line 60184 and cultivar 'Okeechobee' at preharvest. We identified 552 upregulated and 315 downregulated differentially expressed genes between the genotypes, from which 27% of them had an Arabidopsis thaliana ortholog previously characterized as senescence associated genes (SAGs). Notably, we identified several SAGs including several related to jasmonate ZIM-domain jasmonic acid signaling, chlorophyll a-b binding, and cell wall modification including pectate lyases and expansins. This study presented an innovative approach for identifying preharvest molecular factors linked to postharvest traits for prolonged shelf., (© 2024. This is a U.S. Government work and not under copyright protection in the US; foreign copyright protection may apply.)

Understanding pathogen evolution over time is vital for plant breeding and deployment of host resistance. In the context of a soilborne pathogen, the potential of host-directed evolution of a Verticillium dahliae race 1 isolate and genotypic variation of V. dahliae associated with two major hosts (lettuce and tomato) were determined. In total, 427 isolates were recovered over 6 years from a resistance screening nursery infested with a single V. dahliae race 1 isolate. In a separate study, an additional 206 isolates representing 163 and 43 isolates from commercial lettuce and tomato fields, respectively, were collected. Analyses of isolates recovered from the screening nursery over 6 years revealed no changes in the race and mating type composition but did uncover seven simple sequence repeat (SSR) variant genotypes. No significant genotypic variation in V. dahliae was observed between or within fields of either lettuce or tomato but pathogen populations were significantly differentiated between these two hosts. Replicated virulence assays of variant SSR genotypes on lettuce differential cultivars suggested no significant difference in virulence from the wild-type race 1 isolate introduced into the field. This suggests that deployed race 1 host resistance will be robust against the widespread race 1 populations in lettuce-growing regions at least for 6 years unless novel pathogen genotypes or races are introduced into the system.

Background: Strong acid inhibition increases cure rates with triple therapy and 14-day are more effective than 7-day treatments. The combination of amoxicillin plus metronidazole at full doses has been shown to overcome metronidazole resistance and to achieve good eradication rates even in patients harboring resistant strains. No previous studies have been reported in Latin-America with this optimized triple-therapy scheme., Aims: The aim of the present study was to assess the eradication rate and tolerance of a new first-line treatment regimen associating strong acid inhibition, amoxicillin and metronidazole., Methods: Patients from the Clínica de Gastroenterología of the Hospital de Clínicas (Montevideo, Uruguay) were included. Hp status was mainly assessed by at least one of the following: histologyor urea breath test (UBT). A 14-day treatment was prescribed comprising esomeprazole 40mg twice a day plus amoxicillin 1g and metronidazole 500mg, both three times a day. H. pylori cure was assessed by UBT., Results: Forty-one patients were enrolled. Mean age was 53.3±13 years and 17.1% of patients were male. Main indications for treatment were: functional dyspepsia (27.5%), gastritis (45%), gastric or duodenal erosions (20%), gastric ulcer (5%) and intestinal metaplasia (2.5%). H. pylori eradication was achieved in 33 of the 37 patients who returned for follow-up. Eradication rates were 80.5% (95% CI: 68.4-92.6) by intention-to-treat (ITT) analysis and 89.2% (95% CI; 79.2-99.2) per protocol (PP). No major side effects were reported; 26 patients (65.8%) complained of mild side effects (nausea, diarrhea and headache)., Conclusions: Cure rates of this triple therapy including esomeprazole, amoxicillin and metronidazole were 81% per ITT and the treatment was well tolerated. These optimal results with a simple clarithromycin-free triple therapy are better than described for standard triple therapy but there is still room for improvement to reach the desired target of 90% per ITT., (Copyright © 2017 Elsevier España, S.L.U., AEEH y AEG. All rights reserved.)

Verticillium longisporum is an economically important vascular pathogen of Brassicaceae crops in different parts of the world. V. longisporum is a diploid hybrid that consists of three different lineages, each of which originated from a separate hybridization event between two different sets of parental species. We used 20 isolates representing the three V. longisporum lineages and the relative V. dahliae, and performed pathogenicity tests on 11 different hosts, including artichoke, cabbage, cauliflower, cotton, eggplant, horseradish, lettuce, linseed, oilseed rape (canola), tomato, and watermelon. V. longisporum was overall more virulent on the Brassicaceae crops than V. dahliae, which was more virulent than V. longisporum across the non-Brassicaceae crops. There were differences in virulence between the three V. longisporum lineages. V. longisporum lineage A1/D1 was the most virulent lineage on oilseed rape, and V. longisporum lineage A1/D2 was the most virulent lineage on cabbage and horseradish. We also found that on the non-Brassicaceae hosts eggplant, tomato, lettuce, and watermelon, V. longisporum was more or equally virulent than V. dahliae. This suggests that V. longisporum may have a wider potential host range than currently appreciated.

Verticillium dahliae is a soilborne, economically significant fungal plant pathogen that persists in the soil for up to 14 years as melanized microsclerotia (ms). Similarly, V. longisporum is a very significant production constraint on members of the family Brassicaceae. Management of Verticillium wilt has relied on methods that reduce ms below crop-specific thresholds at which little or no disease develops. Methyl bromide, a broad-spectrum biocide, has been used as a preplant soil fumigant for over 50 years to reduce V. dahliae ms. However, reductions in the number of ms in the vertical and horizontal soil profiles and the rate at which soil recolonization occurs has not been studied. The dynamics of ms in soil before and after methyl bromide+chloropicrin fumigation were followed over 3 years in six 8-by-8-m sites in two fields. In separate fields, the dynamics of ms in the 60-cm-deep vertical soil profile pre- and postfumigation with methyl bromide+chloropicrin followed by various cropping patterns were studied over 4 years. Finally, ms densities were assessed in six 8-by-8-m sites in a separate field prior to and following a natural 6-week flood. Methyl bromide+chloripicrin significantly reduced but did not eliminate V. dahliae ms in either the vertical or horizontal soil profiles. In field studies, increases in ms were highly dependent upon the crop rotation pattern followed postfumigation. In the vertical soil profile, densities of ms were highest in the top 5 to 20 cm of soil but were consistently detected at 60-cm depths. Six weeks of natural flooding significantly reduced (on average, approximately 65% in the total viable counts of ms) but did not eliminate viable ms of V. longisporum.

Several maize, Zea mays L., inbred lines developed from an Antiguan maize population have been shown to exhibit resistance to numerous aboveground lepidopteran pests. This study shows that these genotypes are able to significantly reduce the survival of two root feeding pests, western corn rootworm, Diabrotica virgifera virgifera LeConte, and southern corn rootworm, Diabrotica undecimpunctata howardi Barber. The results also demonstrated that feeding by the aboveground herbivore fall armyworm, Spodoptera frugiperda (J. E. Smith), before infestation by western corn rootworm reduced survivorship of western corn rootworm in the root tissues of some, but not all, genotypes. Likewise, the presence of western corn rootworm in the soil seemed to increase resistance to fall armyworm in the whorl in several genotypes. However, genotypes derived from the Antiguan germplasm with genetic resistance to lepidopterans were still more resistant to the fall armyworm and both rootworm species than the susceptible genotypes even after defense induction. These results suggest that there may be intraplant communication that alters plant responses to aboveground and belowground herbivores.

The Mediterranean corn borer or pink stem borer (MCB, Sesamia nonagrioides Lefebvre) causes important yield losses as a consequence of stalk tunneling and direct kernel damage. B73 and Mo17 are the source of the most commercial valuable maize inbred lines in temperate zones, while the intermated B73 x Mo17 (IBM) population is an invaluable source for QTL identification. However, no or few experiments have been carried out to detect QTL for corn borer resistance in the B73 x Mo17 population. The objective of this work was to locate QTL for resistance to stem tunneling and kernel damage by MCB in the IBM population. We detected a QTL for kernel damage at bin 8.05, although the effect was small and two QTL for stalk tunneling at bins 1.06 and 9.04 in which the additive effects were 4 cm, approximately. The two QTL detected for MCB resistance were close to other QTL consistently found for European corn borer (ECB, Ostrinia nubilalis Hübner) resistance, indicating mechanisms of resistance common to both pests or gene clusters controlling resistance to different plagues. The precise mapping achieved with the IBM population will facilitate the QTL pyramiding and the positional cloning of the detected QTL.

Recurrent selection has been reported as successful for improving maize resistance against corn borers. This study was conducted to determine if phenolics concentration in maize changes during recurrent selection to improve stalk resistance to the Mediterranean corn borer. Three cycles of selection [EPS12(S)C0, ESP12(S)C2, and EPS12(S)C3] from the maize synthetic population EPS12 and test crosses to inbred lines A639, B93, and EP42 were field grown and artificially infested with Mediterranean corn borer larvae, and the pith tissues were sampled for biochemical analyses. Two major simple phenolic acids [p-coumaric (p-CA) and trans-ferulic (E-FA) acids] were identified in free and cell-wall fractions, whereas four isomers of diferulic acid (DFA) (8-5'l, 5-5', 8-o-4', and 8-5' benzofuran form) were present in the cell-wall bound fraction. The selection cycles EPS12(S)C0 and EPS12(S)C3 showed less damage and higher cell wall phenolics concentrations than the cycle EPS12(S)C2. In addition, higher concentrations of total DFAs were associated with shorter tunnel length and lower numbers of larvae per stem. The current study shows new and concrete evidence that the cell-wall bound phenolics could have a determinative role in the resistance to the Mediterranean corn borer, although future development of recurrent and divergent selection cycles will clarify this point.

The leaf sheaths of selected inbred lines of maize (Zea mays L.) with variable levels of stem resistance to the Mediterranean corn borer Sesamia nonagrioides (Lefèvbre) were evaluated for antibiotic effect on insect development. Phytochemical analyses of leaf sheaths were conducted for cell wall phenylpropanoid content to gain a better understanding of maize-resistance mechanisms. Laboratory bioassays established that sheath tissues from different genotypes significantly affected the growth of neonate larvae. Three hydroxycinnamates, p-coumaric, trans-ferulic, and cis-ferulic acids, and three isomers of diferulic acid, 8-5', 8-O-4', and 8-5' b (benzofuran form), were identified. Significant negative correlations were found between larvae weight and diferulic acid content for six genotypes. These results are in agreement with previous studies concerning the role of cell wall structural components in stem borer resistance.