Inheritance and QTL mapping of leaf rust resistance in the European winter wheat cultivar ‘Beaver’

Genetic studies were conducted on an European winter wheat cultivar, Beaver, to determine the mode of inheritance of leaf rust resistance at seedling and adult plant growth stages using a recombinant doubled haploid population, Beaver/Soissons. Greenhouse studies indicated the involvement of genes Lr13 and Lr26 in governing leaf rust resistance at seedling growth stages, whereas, adult plant resistance (APR) in the field with pathotypes carrying virulence individually for Lr13 and Lr26 showed trigenic inheritance for the population. Marker regression analysis of adult plant field data indicated the involvement of six significant QTLs (chromosomes 1B, 3B, 3D, 4B, 4D and 5A) in year 2005, four QTLs (1B, 3B, 4B and 5A) in 2006, and six QTLs (1A, 1B, 3B, 4A, 4B and 5A) in 2007 for reducing leaf rust severity. QTLs on chromosomes 1B, 4B and 5A were considered the most important because of their detection across years, whereas QTLs on chromosomes 1A, 3B, 3D and 4A were either inconsistent or non-significant and unexplained. Based on an association of closely linked markers with phenotypic data, putative single gene stocks were identified for each consistent QTL and crossing was initiated to develop populations segregating for each to permit fine mapping of the identified regions.     

Electrophoretic variation among and within strains of ‘kharkof’ wheat maintained at 11 locations

Summary The hard red winter wheat (Triticum aestivum L.) cultivar Kharkof was introduced to the United States at the turn of the century and has been included as the long-term check for the Southern and Northern Regional Performance Nurseries since 1930. Seed of Kharkof is typically maintained at each site at which the nurseries are grown. We obtained samples of Kharkof from 10 sites and the USDA Small Grains Collection in Beltsville, MD. Up to 54 individual kernels per strain were ground and evaluated for gliadin electrophoretic patterns. Strains from Beltsville, MD and Aberdeen, ID were completely uniform for gliadin patterns; they differed from each other and from all other strains. Seven strains were highly polymorphic, with 7 to 14 gliadin patterns occurring in each. However, there were large differences in pattern frequencies among strains, with the Ft. Collins, CO and Columbia, MO strains at one extreme, the Manhattan, KS and Lincoln, NE strains at the other, and the St. Paul, MN; York, NE; and Clovis, NM strains intermediate. Strains from Dallas and Chillicothe, TX were completely uniform for a pattern that also occurred in all of the polymorphic strains. The two Texas strains also had esterase and -amylase isoelectric focusing patterns different from the others, and the Beltsville strain had a different -amylase pattern. We concluded that the strains from Beltsville and Aberdeen were not Kharkof, that the Texas strains were derived from a single-plant selection out of Kharkof, and that the remaining strans have diverged through natural selection possibly operating in conjunction with genetic drift, outcrossing, and seed mixtures.     

Embryo lethality in wheat × rye hybrids—mode of inheritance and the identification of a complementary gene in wheat

Crosses between hexaploid wheat and rye can only succeed when pre- and post-zygotic barriers have been overcome. A rye gene determining embryo lethality (Eml-R1), which is involved in post-zygotic isolation, has been mapped to chromosome 6R. In the present paper the mode of inheritance of Eml-R1 was studied by employing a wheat/rye chromosome 6R addition line. We show that Eml-R1 exists in at least two alternative forms, with the mutant allele Eml-R1b being dominant with respect to wild-type Eml-R1a. Furthermore, we have exploited nulli-tetrasomic lines of wheat to detect a complementary wheat gene present on chromosome 6A. This gene has been designated Eml-A1.     

Genetic diversity of wheat–rye 1BL.1RS translocation lines derived from different wheat and rye sources

Many studies have been conducted to determine the relative effects of the 1BL.1RS translocation on various traits in wheat. The effects of different wheat (Triticum aestivum L.) genetic backgrounds and rye (Secale cereale L.) sources have been addressed as major factors for inconsistent agronomic performance and end-use-quality traits of 1BL.1RS translocation wheats. However, all these studies were accomplished by using 1BL.1RS translocations with impure wheat genetic bases and narrow rye origins. The objective of this study was to test the genetic effects of centric fusion translocations by using primary 1BL.1RS lines derived from various pure wheat lines and rye sources. Twenty-one primary 1BL.1RS translocation lines were created from crosses between two pure wheat lines and three Chinese local rye varieties. These translocation lines and their wheat parents were then evaluated in southwestern China. The results provide direct evidence of the diverse effects of the different wheat parents and rye sources, taking part in 1BL.1RS translocations, on resistance to diseases, agronomic performance, and end-use quality traits. The highest amount of genetic diversity was observed in 1BL.1RS translocations derived from the same wheat lines and diverse rye varieties. The results suggest that the genetic diversity of 1BL.1RS translocation lines may originate from the different wheat genetic backgrounds, from different rye sources, from their interaction, and from the translocation itself. Creation of diverse 1BL.1RS translocations offers ample possibilities to introduce more variation into wheat for improved performance.     

Construction of ‘compound’ rust resistance genes in maize

Summary The Rp1 locus of maize is a complex rust resistance locus where multiple resistance genes are clustered. Rare recombination events between Rp1 genes or alleles can produce two or more detectable genes linked in coupling phase. Such compound genes can then be manipulated as a single gene in breeding programs. Several compound Rp1 genes, each carrying two or three tightly linked resistance genes, were constructed to test their utility in controlling common rust. While none of the lines carrying single Rp1 genes were resistant to all of the characterized North American P. sorghi biotypes, most of the two component and all of the three component Rp1 complexes were resistant. The potential for utilization of compound resistance genes in other crop species is discussed.     

Effect of antioxidants in controlling enzymatic browning of minimally processed persimmon ‘Rojo Brillante’

‘Rojo Brillante’ is an important variety of persimmon that after removal of the astringency with high levels of CO₂, maintains firmness and sweetness, making possible its commercialization as a fresh-cut commodity. However, the commercial success of the product is limited mainly by enzymatic browning. This work presents the effect of a wide range of antioxidants on enzymatic browning of ‘Rojo Brillante’ persimmon combining in vitro (extracts and precipitates) and in vivo (cut tissue) studies. Preliminary screening of the antioxidants, determined by absorbance and color measurements of persimmon extracts and pellets, showed that 4-hexylresorcinol (Hexyl), citric acid (CA) and calcium chloride (CaCl₂) were effective at controlling browning at 10 mM; whereas, ascorbic acid (AA) required a higher concentration (25 mM). Peracetic acid, cyclodextrin, cysteine, and hexametaphosphate were not effective at controlling browning, even at a concentration of 50 mM. In in vivo studies, AA (1.12%) and CA (0.21%) were the most effective treatments to control enzymatic browning of fresh-cut material, reaching the limit of marketability in 5–7 days, whereas, Hexyl and CaCl₂ did not reach 1 day of storage. The results showed that optimum concentrations in cut tissue did not always correlate with the in vitro studies, indicating that antioxidants have an effect not only in browning reactions, but also in metabolic activity and cell wall changes during wound-induced reactions. The results provide relevant information for further development of minimally processed ‘Rojo Brillante’ persimmon during storage at 5 °C.     

Monosomic analysis of fertility restoration in common wheat ‘Prof. Marchal’

Summary In common wheat (Triticum aestivum L.) a monosomic set of Chinese Spring and male-sterile Janus (with cytoplasm of T. timopheevi Zhuk.) were used to determine the chromosomal location of Rf-genes in Professeur Marchal. As revealed by test cross data, a major gene cofeerring fertility restoration was present in Prof. Marchal on chromosome 1B. A significant deviation towards sterility was observed in some fest cross progenies. Chromosome 1B of Chinese Spring appeared to carry a dominant restoring gene, which caused partial restoration of fertility.     

Genetics of stem rust resistance in the durum wheat accession ‘Reichenbachii’

Summary Inheritance of seedling reactions to cultures of races TLM and MBCT of Puccinia graminis f.sp. tritici was studied in crosses of the resistant durum Reichenbachii with susceptible Marruecos 9623 and DZ04-118. The Chi-square test for goodness of fit was used to analyze segregating populations. Two independent recessive genes appeared to control resistance of Reichenbachii to both TLM and MBCT. Depending upon the cross, the two genes interacted cumulatively to condition immunity or higher levels of resistance than either parent conditioned singly. There was no evidence of maternal influence on the inheritance of resistance. Resistance genes in Reichenbachii were recessive; therefore, breeders should consider the use of relatively large F₂ populations to effectively transfer these genes to cultivars with good agronomic characteristics.     

Degreening behavior in ‘Fallglo’ and ‘Lee × Orlando’ is correlated with differential expression of ethylene signaling and biosynthesis genes

Two citrus types (‘Fallglo’ and ‘Lee × Orlando’) exhibiting differential fruit degreening response when treated with ethylene were selected. Fruit were harvested at commercial maturity but at different developmental periods (Harvest I, II and III). Rate of color change was greater in ‘Fallglo’ than in ‘Lee × Orlando’ when fruit were treated with 5 μL L⁻¹ of ethylene for 24 h. After 24 h of transfer of fruit to ethylene-free storage, rate of change decreased in ‘Fallgo’ and exhibited varied response in ‘Lee × Orlando’ depending on harvest date. ‘Fallglo’ fruit from Harvests I and II were completely degreened at the end of storage for 7 d; however ‘Lee × Orlando’ were not and were green in color. No difference in seedling triple response was observed between ‘Fallglo’ and ‘Lee × Orlando’ and sequences of the four ethylene receptors were identical between them. Expression of genes involved in ethylene biosynthesis and signaling pathways were studied in flavedo to test if differences in these pathways were correlated with differential ethylene sensitivity of the citrus types. Basal levels of ACS2 and ACO expressions declined as maturity progressed, and ethylene-induced expression of ACS1 and ACO were influenced by fruit maturity. At Harvests I and II, ethylene-induced increase in ACS1 and ACO expressions and ACC levels were greater in ‘Fallglo’ than in ‘Lee × Orlando’. Ethylene treatment influenced MACC content only during Harvest I in ‘Lee × Orlando’. MACC levels were generally higher in ‘Lee × Orlando’ than in ‘Fallglo’. Expressions of ETR1 and ETR2 were ethylene responsive in ‘Fallglo’ and only ETR1 expression was ethylene responsive in ‘Lee × Orlando’. Ethylene had more impact on ETR1 expression in ‘Fallglo’ than in ‘Lee × Orlando’. Ethylene had a negative effect on ETR3 expression which was more pronounced in ‘Lee × Orlando’ than in ‘Fallglo’. Expressions of ERS1, CTR1, EIN2, EIL1 and EIL2 were not affected by ethylene in both citrus types. Expression of chlorophyllase gene and rate of total chlorophyll degradation were higher in ‘Fallglo’ than in ‘Lee × Orlando’ during ethylene treatment. Differential degreening behavior of ‘Fallglo’ and ‘Lee × Orlando’ correlated with peel maturity, and factor(s) downstream of ethylene signaling but upstream of ethylene biosynthesis play a role in the differential sensitivity.     

Yield and yield components of wheat and maize in wheat–maize intercropping in the Netherlands

Intercropping is widely used by smallholder farmers in developing countries, and attracting attention in the context of ecological intensification of agriculture in developed countries. There is little experience with intercropping of food crops in Western Europe. Yields in intercrops depend on planting patterns of the mixed species in interaction with local growing conditions. Here we present data of two years field experimentation on yield and yield components of a wheat–maize intercrop system in different planting configurations in the Netherlands. Treatments included sole crops of wheat (SW) and maize (SM), a replacement intercrop consisting of strips of six wheat rows alternating with two maize rows (6:2WM), as well as subtractive or additive designs, based on skip-row (6:0WM, 0:2WM) and add-row (8:2WM, 6:3WM) configurations. The land equivalent ratio (LER) of intercrops varied from 1.18 to 1.30 in 2013 and from 0.97 to 1.08 in 2014. Wheat grown in the border rows of wheat strips had higher ear number per meter row, greater kernel number per ear, and greater yield per meter row than wheat in inner rows and sole wheat, indicating reduced competition. Wheat in the border rows in the intercrops had, however, reduced thousand kernel weight and harvest index, indicating that competition in border rows intensified over time. Intercropping negatively affected maize biomass and thousand kernel weight, especially in add-row treatments. This study indicates that there is a potential yield benefit for the wheat–maize intercropping system under Western European growing conditions. However, the LER was affected by yearly variation in weather conditions and significantly greater than one in only one of the two years of the study.     

Expression of late maturity α-amylase in wheat containing gibberellic acid insensitivity genes

Summary Two wheat cultivars, Spica and Lerma 52, which consistently produce high levels of -amylase during the later stages of grain development (late maturity -amylase), were crossed with a set of four near-isogenic lines carrying the tall (rht) allele or one of the dwarfing genes Rht1, Rht2 or Rht3 (GA-insensitive alleles). The F₁ and F₂ populations were developed and analysed for grain -amylase and plant height. The Rht3 gene exhibited the strongest influence on plant height and strongly inhibited new -amylase synthesis during the later part of grain ripening. By comparison, Rht1 and Rht2 had a less pronounced effect but still significantly reduced the expression of late maturity -amylase. These observations suggest that gibberellic acid is involved either directly or indirectly in this phenomenon. The implications of the effect of dwarfing genes on expression of late maturity -amylase are discussed in relation to cultivar improvement and to the identification and control of high -amylase germplasm.     

Partial self-compatibility in ‘Tombul’ and ‘Montebello’ hazelnuts

Summary Self-pollination of hazelnut (Corylus avellana L.) cultivars in 1988 and 1990 revealed the existence of partial self-compatibility in Tombul and Montebello. Percent cluster set in these cultivars averaged 44 and 20%, respectively, but was less than 10% in 8 other cultivars investigated. Percent cluster set from pollination with Segorbe averaged 62 and 41% in 1988 and 1990, respectively. Self-pollination produced 40% fewer nuts per cluster and twice as many blanks as cross-pollination. All cultivars and selections have an active sporophytic incompatibility system.Evaluation of self-compatibility in seedlings from the cross Montebello × Compton revealed that the partial self-compatibility of the maternal parent was transmitted to some of the progeny. Self-pollination resulted in greater than 10% cluster set in two selections, OSU 41.134 and OSU 43.025, in both years, but only in 1988 in OSU 42.089 and Willamette. Three other selections had very low set in both years. Results of incompatible crosses with standard testers were generally in agreement with those of self-pollination, except that the S₂ tester induced greater set on 3 genotypes in 1988 and the S1 tester on 2 genotypes in 1990 than self-pollination. The partial self-compatibility of Montebello, OSU 41.134, and OSU 43.025 appears to be due to a failure of their stigmas to prohibit pollen tube growth in incompatible crosses. There is no evidence of a pollen-part mutation in Montebello, nor is there evidence that partial self-compatibility is due to the interaction of S-alleles, as Barcelona, which has the same alleles as these three genotypes, failed to set nuts in all incompatible crosses.     

Integrated ethylene and temperature conditioning for induction of ripening capacity in ‘Anjou’ and ‘Comice’ pears

‘Anjou’ and ‘Comice’ pears from three harvest dates were conditioned to develop ripening capacity by exposure to 100 μL L⁻¹ ethylene at 20 °C for 0, 24, 48, or 72 h, followed by varying durations of temperature conditioning at −0.5 or 10 °C. Ripening capacity was tested by measuring fruit firmness after 7 d at 20 °C after completion of conditioning treatments. Fruit firmness was also measured after conditioning but before ripening, and was designated “shipping firmness”, indicative of the potential for the fruit to withstand transport conditions without physical injury. Ripening capacity in both cultivars developed more rapidly with later harvest date, increasing duration of ethylene conditioning, and increasing duration of temperature conditioning. Ripening capacity developed much more rapidly at 10 °C than at −0.5 °C. Useful durations of temperature conditioning at 10 °C were limited by fruit softening below acceptable values of shipping firmness. However, sequential combinations of ethylene and temperature conditioning at both −0.5 and 10 °C were identified wherein post-conditioning shipping firmness was acceptable.     

The effect of the ‘Golden Promise’ dwarfing gene on partial resistance to leaf rust and powdery mildew in spring barley

Summary F₂-plant progenies, derived from seven crosses between susceptible erectoides breeding lines and conventional, nutans breeding lines with partial resistance to leaf rust incited by Puccinia hordei Otth., derived from Vada x Cebada Capa, were examined in a field and a glasshouse experiment. In the field experiment, the nutans plant progenies generally were more resistant to leaf rust and powdery mildew than the erectoides progenies. In the glasshouse experiment, the components of partial resistance to leaf rust of six erectoides and six nutans progenies derived from one cross were studied. The nutans progenies generally had lower infection frequencies than erectoides progenies with a similar infection level in the field experiment. The variation for leaf rust and powdery mildew infection in the field was similar for the nutans and erectoides progenies. This suggests that erectoides lines with a fairly high level of partial resistance to leaf rust and powdery mildew can be selected from these populations.     

Induction of ripening capacity in ‘Packham's Triumph’ and ‘Gebhard Red D’Anjou’ Pears by temperature and ethylene conditioning

Methods were tested for rapid induction of ripening capacity in ‘Packham's Triumph’ and ‘Gebhard Red D’Anjou’ pears in order to facilitate early marketing. Fruit of each cultivar were harvested at the onset of maturity and conditioned to develop ripening capacity by exposure to 100 μL L⁻¹ ethylene at 20 °C for 0, 24, 48, or 72 h, followed by varying durations of temperature conditioning at −0.5 or 10 °C. Ripening capacity was tested by measuring fruit firmness after 7 d at 20 °C after completion of conditioning treatments. Fruit firmness was also measured after conditioning but before ripening, and was designated “shipping firmness,” indicative of the potential for the fruit to withstand transport conditions without physical injury. With temperature conditioning at −0.5 °C only, ‘Packham's Triumph’ pears needed 45 d to develop ripening capacity, while ‘Gebhard Red D’Anjou’ pears were not capable of fully ripening after 60 d, the longest duration tested. Using ethylene only, 72 h exposure was necessary to develop full ripening capacity in both cultivars, and adequate shipping firmness was maintained. Using temperature conditioning at 10 °C, ripening capacity in ‘Packham's Triumph’ and ‘Gebhard Red D’Anjou’ developed within 10 and 20 d, respectively, but shipping firmness in ‘Gebhard Red D’Anjou’ was compromised at 20 d. In both cultivars, 24 or 48 h in ethylene followed by 5 d at 10 °C induced ripening capacity while maintaining adequate shipping firmness.     

Upregulation of polyphenol-related genes prevents ‘skin burning’ of well-colored ‘Cameo’ apples stored under stressful controlled atmosphere conditions

‘Skin burning’ of ‘Cameo’ apples resulting in poorly colored fruit can occur in storage under high CO₂ condition. To elucidate possible reasons for this physiological disorder, we assessed the differential expression of polyphenol-related genes. Poorly colored and well-colored mature ‘Cameo’ apples were stored under either high (3%) or low (0.7%) CO₂ levels, both in combination with 1% O₂, and monitored for seven months for ‘skin burning’. Samples were obtained by the end of storage period, and qPCR analyses were conducted using gene specific primers. We found expression levels of chalcone synthase (MdCHS), chalcone isomerase (MdCHI), anthocyanidin synthase (MdANS), flavonol synthase (MdFLS), dihydroflavonolreductase (MdDFR), and leucoanthocyanidinreductase (MdLAR1) genes to be substantially higher in well-colored compared to poorly colored apples. The delay in establishing the stressful controlled atmosphere (CA) storage condition (3% CO₂ level) led to significantly higher expression levels of MdLAR1, MdCHI, anthocyanidinreductase (MdANR) and flavanone 3-hydroxylase (MdF3H), which may explain the lower incidence of ‘skin burning’ by delayed CA fruit. On the other hand, after seven months in storage, the expression levels of phenylalanine ammonia-lyase (MdPAL), MdCHS, MdCHI, MdDFR, MdFLS, and MdF3H, were significantly higher in poorly colored injured apples, which reflect a feedback mechanism to synthesize more polyphenols to counteract the stressful storage condition.     

Utilization of alien genes to enhance Fusarium head blight resistance in wheat – A review

Fusarium head blight (FHB) is a destructive disease of wheat worldwide. Sources of resistance to FHB are limited in wheat. Search for novel sources of effective resistance to this disease has been an urgent need in wheat breeding. Fusarium head blight resistance has been identified in relatives of wheat. Alien chromatin carrying FHB resistance genes has been incorporated into wheat through chromosome addition, substitution, and translocation. Relatives of wheat demonstrate a great potential to enhance resistance of wheat to FHB.     

Intergeneric hybrids between Chrysanthemum morifolium ‘Nannongxiaoli’ and Artemisia vulgaris ‘Variegata’ show enhanced resistance against both aphids and Alternaria leaf spot

Intergeneric hybridization is an effective way of improving crop resistance against biotic and tolerance to abiotic stresses. Here, we describe an intergeneric hybrid between Chrysanthemum morifolium ‘Nannongxiaoli’ and Artemisia vulgaris ‘Variegata’ using ovule rescue. Chromosome counting confirmed that out of the 124 regenerated plantlets, 19 were genuine hybrids, carrying the expected hybrid number of somatic chromosomes (45, representing 27 from ‘Nannongxiaoli’ and 18 from ‘Variegata’). The 19 genuine hybrids were vigorous, flowered normally and possessed the cut flower characteristics of ‘Nannongxiaoli’. The hybrids were more resistant against both aphid infestation and Alternaria leaf spot inoculation than the ‘Nannongxiaoli’ parent, but less than the ‘Variegata’ parent.     

QTLs for Fusarium head blight response in a wheat DH population of Wangshuibai/Alondra‘s’

Summary A doubled haploid (DH) wheat population derived from the cross Wangshuibai/Alondra‘s’ was developed through chromosome doubling of haploids generated by anther culture of hybrids. Fusarium head blight (FHB) was evaluated for three years from 2001 to 2003 in Jianyang, Fujian Province, China, where epidemics of FHB have been consistently severe. After 307 pairs of simple sequence repeat (SSR) primers were screened, 110 pairs were polymorphic between Wangshuibai and Alondra`s’, and used to construct a genetic linkage map for detection of quantitative trait loci (QTLs). A stable QTL for low FHB severity was detected on chromosomes 3B over all three years, and QTLs on chromosomes 5B, 2D, and 7A were detected over two years. Additional QTLs on chromosomes 3A, 3D, 4B, 5A, 5D, 6B and 7B showed marginal significance in only one year. Six QTLs were detected when phenotypic data from three years were combined. In addition, significant additive-by-additive epistasis was detected for a QTL on 6A although its additive effect was not significant. Additive effects (A) and additive-by-additive epistasis (AA) explained a major portion of the phenotypic variation (76.5%) for FHB response. Xgwm533-3B and Xgwm335-5B were the closest markers to QTLs, and have potential to be used as selectable markers for marker-assisted selection (MAS) in wheat breeding programs.     

Dynamics of ascorbic acid in ‘Braeburn’ and ‘Gala’ apples during on-tree development and storage in atmospheres conducive to internal browning development

The underlying causes as well as chemical and biochemical alleviation for CO₂-induced browning in apple fruit are poorly understood. Ascorbic acid (AsA) dynamics in ‘Braeburn,’ a susceptible cultivar, and ‘Gala’, a resistant cultivar, were evaluated during on-tree development and storage at 0.5 °C in air or controlled atmospheres (CA) containing 1 kPa O₂ and 1, 3 or 5 kPa CO₂. ‘Braeburn’ fruit treated with diphenylamine (DPA) was also stored for 1 month to determine effects on browning incidence and AsA concentration. ‘Braeburn’ apples had significantly higher (p ≤ 0.05) AsA levels than ‘Gala’ during on-tree development, and storage. No correlation between AsA and maturity/ripening indices for ‘Braeburn’ or ‘Gala’ was apparent. Histochemical localization of fruit AsA showed a staining intensity consistent with the quantity analytically determined, and showed that AsA is diffusely distributed throughout the cortex in both cultivars during on-tree development. During storage, AsA was localized to the periphery of brown tissue in ‘Braeburn’ and to the coreline and cortex proximal to the peel in ‘Braeburn’ and ‘Gala’ tissues. DPA decreased browning development during storage, however, no correlation between DPA treatment and AsA quantity in healthy or brown cortex tissue was observed. The results indicate AsA quantity alone is not an indicator of CO₂ sensitivity in these two cultivars.