Generation and characterisation of colchicine-induced polyploid Lavandula × intermedia

Double podding in cultivated chickpeas (Cicer arietinum L.) can increase yield and yield stability. In the present study, we performed reciprocal crosses of ‘kabuli’ (double podded) and ‘desi’ (single podded) chickpeas to determine (i) the expressivity and penetrance of double podding, (ii) the correlations of yield and yield components, and (iii) the heritability of double podding, flower color, and stem pigmentation in F₂ plants. Reciprocal crosses were performed with two genotypes, AC 2969 (kabuli) and ICC 4969 (desi), to generate F₁ and F₂ plants. The results indicated hybrid vigor (heterosis) for yield in F₁ plants and better performance of F₂ plants. Yield and yield components of some lines in F₂ were superior to the best parent, indicative of transgressive segregation. In particular, the presence of double podding (‘s’ allele) significantly increased yield in some of the transgressive segregants. Expressivity and penetrance of the ‘s’ allele depends on the background of the female parent. Some of the double podding progeny had greater seed yields than those of the single podding progeny and greater seed yields than the best parents. Double podding, stem pigmentation, and pink flowers each appears to be governed by a single recessive gene. Stem pigmentation and pink flowers appear to be linked traits that depend on the genetic background of the crossed chickpeas. Taken together, our studies of reciprocal crosses of kabuli and desi chickpeas clearly showed that yield could be improved by selection for transgressive phenotypes that have double podding.     

Epistasis in an Andean × Mesoamerican cross of common bean

The objective of this investigation was to check if epistasis is present in Andean × Mesoamerican beans crosses using triple test cross (TTC) method. The parents of the segregating population were Carioca–MG (Mesoamerican) and BRS Radiante (Andean). In July 2005, F₂ progenies (backcrossed with the parents and F₁ generation) were evaluated at two locations for three characters: number of pods plant⁻¹, number of grains plant⁻¹ and grain weight plant⁻¹. The presence of epistasis was detected for all yield components. In the partitioning of epistasis in additive x additive (i) and dominant x dominant (j) and dominant × additive (l) it was observed that, for the traits number of pods/plant and number of grains/plant, only epistasis of the type (j) + (l) were significant. For the trait grain mass/plant, all types of epistasis were significant.     

QTL × genetic background interaction: predicting inbred progeny value

Failures of the additive infinitesimal model continue to provide incentive to study other modes of gene action, in particular, epistasis. Epistasis can be modeled as a QTL by genetic background interaction. Association mapping models lend themselves to fitting such an interaction because they often include both main marker and genetic background factors. In this study, I review a model that fits the QTL by background interaction as an added random effect in the now standard mixed model framework of association analyses. The model is applied to four-generation pedigrees where the objective is to predict the genotypic values of fourth-generation individuals that have not been phenotyped. In particular, I look at how well epistatic effects are estimated under two levels of inbreeding. Interaction detection power was 8% and 65% for pedigrees of 240 randomly mated individuals when the interaction generated 6% and 20% of the phenotypic variance, respectively. Power increased to 21% and 94% for these conditions when evaluated individuals were inbred by selfing four times. The interaction variance was estimated in an unbiased way under both levels of inbreeding, but its mean squared error was reduced by 40% to 70% when estimated in inbred relative to randomly mated individuals. The performance of the epistatic model was also enhanced relative to the additive model by inbreeding. These results are promising for the application of the model to typically self-pollinating crops such as wheat and soybean. The U.S. Government's right to retain a non-exclusive, royalty-free license in and to any copyright is acknowledged.     

Performance of upland coloured cotton germplasm lines in line × tester crosses

Anthracnose is a serious disease affecting dry bean production especially in the cool highland areas worldwide. The objective of this research was to study the inheritance of anthracnose resistance in market-class dry beans. A complete diallel set of crosses was generated from nine diverse parents comprising six resistant and three susceptible to anthracnose. The F₁ and F₂ crosses and parents were artificially inoculated with Colletotriclum lindenumthianum Race-767 in a growth room. There was significant variation for anthracnose resistance among genotypes. General combining ability (GCA) and specific combining ability effects were significant for resistance, indicating importance of both additive and non-additive effects, respectively. Preponderance of GCA effects (66%) suggested that additive effects were more important than non-additive effects (24%), which were also reflected by high heritability estimates (70%), and suggested that simple selection or backcrossing would be useful for improving the resistance in market class varieties. The study was not conclusive on whether epistatic gene action played a major role, but if available it might have biased the dominance gene effects. Reciprocal effects (10%) were not significant (P > 0.05), suggesting that cytoplasmic genes did not play a major role in modifying anthracnose resistance. Parental lines G2333, AB136, NAT002, and NAT003 showed highly negative GCA effects qualifying them as suitable parents for transferring resistance genes to their progenies. A few major genes, 1–3, displaying partial dominance conditioned anthracnose resistance, suggesting a possibility of using marker-assisted selection to improve anthracnose resistance in market-class dry beans.     

Mapping QTLs associated with Fusarium-damaged kernels in the Nanda 2419 × Wangshuibai population

Fusarium head blight (FHB), or scab, is a devastating wheat disease worldwide, reducing both grain yield and quality. The percentage of Fusarium-damaged kernels (FDK) directly reflects the damage level caused by scab on wheat grains and its variation represents the so-called type IV scab resistance in germplasm. To identify genes governing type IV resistance and investigate its relationship with other scab resistance types, we mapped QTLs associated with percent FDK using data from three different field evaluations of the recombination inbred line (RIL) population derived from the susceptible cultivar Nanda 2419 × the scab-resistant cultivar Wangshuibai. Five QTLs related to percent FDK were identified in at least two different trials, for which Wangshuibai contributed four of the resistance alleles. Most of the FDK-related QTLs, including the three with larger effects, QFdk.nau-2B, QFdk.nau-3B and QFdk.nau-4B, mapped to intervals associated with either type IV resistance or type II resistance. Moreover, most of the major type I and type II resistance QTLs detected previously were associated with type IV resistance, suggesting that resistance to initial infection and disease spread play major roles in conditioning less FDK. Therefore, breeders have options to choose inoculation methods based on their expertise and resources without risking significant loss of information when using percent FDK as the disease index. The most useful scab resistance QTLs for breeding would be those with stable influences on FDK and/or deoxynivalenol (DON) accumulation besides the initial infection and disease spread. Chunjun Li and Huilan Zhu contributed equally to this work.     

Parental effects on the performance of cultivated × wild species hybrids in potato

Valuable genetic diversity in diploid wild Solanum species can be accessed through crosses to haploids (2n = 2×) of the tetraploid cultivated potato, Solanum tuberosum. Haploid-wild species hybrids segregate for the ability to tuberize in the field. In addition, they vary in male fertility, vine size, stolon length, and tuber size. In this study, three haploids were crossed with nine diploid wild Solanum species and 27 hybrid families were evaluated in the field for two years. The proportion of male fertile hybrid clones varied depending on the wild species parent. A large effect of the female parent was detected for vine size, stolon length, tuber size, percent tuberization, and percent plants selected for agronomic quality. An exceptional haploid (US-W4) was identified for the production of agronomically desirable haploid-wild species hybrids. In hybrids derived from US-W4, differences among wild species parents were observed for agronomic quality. Superior hybrids were produced by S. berthaultii and S. microdontum. Reciprocal crosses were evaluated for a subset of families. When the wild species was used as the female parent, male fertility was restored, but tuberization and tuber size were reduced. Careful selection of both haploid and wild species parents can result in a large proportion of fertile, agronomically desirable hybrid offspring.     

Phenotypic diversity and relationships of fruit quality traits in inter-specific almond × peach backcrosses breeding progenies

Nineteen agrochemical traits of 20 almond inter-specific backcrosses progenies were evaluated and compared for three consequence years to find out their phenotypic diversity and determine the relationships of fruit quality traits in almond × peach backcrosses breeding progenies. The variation was observed for traits of phenology parameters (blooming time, ripening time), Physical parameters (fruit weight, width, height, shape, thickness, skin pubescences, colour and flower type), chemical parameters (total sugar content, soluble solids content and acidity) and sensory parameters (attractiveness, taste, and flavor) and yield. Many fruit characteristics that are important to breeders are present in this collection. A high variability was found in the evaluated almond progenies and significant differences were found among them in all studied quality attributes. Year-by-year variations were observed for majority of traits. A significant correlation was found among the fruit height, fruit width, skin pubescences and yield. Fruit height showed a significant positive correlation with fruit weight and fruit thickness and some other traits and a negative correlation with the titratable acidity, skin pubescences and fruit flavour. A high negative correlation was found between the fruit weight and titratable acidity (?0.8). Low coefficients were got between the flower colour and skin pubescences. In addition, principal component analysis it possible to established similar groups of genotypes depending on their quality characteristics and to study relationships among pomological traits in almond progenies evaluated.     

Intergeneric hybrid between Chrysanthemum × morifolium and Artemisia japonica achieved via embryo rescue shows salt tolerance

Using embryo rescue, we generated an intergeneric hybrid between Chrysanthemum × morifolium ‘Maoyan’ and Artemisia japonica Thunb. Cytological tests confirmed that regenerated plantlets were all genuine hybrids possessing 45 chromosomes, with 27 chromosomes inherited from C. × morifolium (2n = 6x = 54) and the other 18 derived from A. japonica (2n = 4x = 36). Hybrid plant flowered normally. The shape and color of the hybrid flowers and leaves resembled those of chrysanthemum, while leaf width, leaf length, plant height, and inflorescence diameter were intermediate between those of the parents. Hybrid plant had higher levels of chlorophyll and free proline, and lower concentrations of malondialdehyde and Na⁺, than the maternal parent (C. × morifolium), and these levels were correlated with the hybrid’s enhanced salt tolerance. These results clearly demonstrate that intergeneric hybridization is an effective method of cultivar improvement in chrysanthemum.     

Inheritance of anthocyanin content in the ripe berries of a tetraploid × diploid grape cross population

Variation patterns and inheritance of anthocyanin content in the ripe berries of a tetraploid × diploid table grape cross population were investigated in two successive years. The population segregated for three different ploid levels: dipolids, triploids, and tetraploids. A total of 28 different anthocyanins were detected and quantified in the progeny population. Transgressive segregation for the total anthocyanin content was observed in all the three ploid progeny populations. The total anthocyanin content increased as the ploid level increased. The broad sense heritabilities (H²) of the total anthocyanin content were all relatively high, ranging from 0.53 to 0.98, 0.57 to 0.97 and 0.43 to 0.94 in the diploid, triploid and tetraploid population, respectively. Our results suggested that the total anthocyanin content followed an additive inheritance model in this polyploid segregation population. We also observed that the relative contribution of individual anthocyanins to the total anthocyanin content varied significantly among different ploid populations, suggesting that genetic background has important impact on the accumulation of the individual anthocyanin compounds. These results will help develop better breeding strategies in a polyploid table grape breeding program for improving the content of anthocyanins, an important class of polyphenolics possessing antioxidant activities and many other health-related benefits.     

Quantitative trait loci of acid detergent fiber and grain chemical composition in hulled × hull-less barley population

Cultivated barley is the major livestock feed grain in the Northern Plains and Northwestern United States due to the fact that its short growing season and limited rainfall limit the planting and production of corn. Starch and fiber content play a significant role in feedlot performance of animals raised on barley feed. To study the underlying genetic locations and mechanisms for these traits, a recombinant inbred line population was derived from a cross between the hulled barley cultivar Valier and a hull-less Swiss landrace line, PI370970. Valier has a high acid detergent fiber content (ADF) and low starch and protein while PI370970 contains low ADF and high starch and protein content. To detect associated QTLs, data were collected and analyzed from irrigated and rain-fed environments. A total of 30 main effect QTLs and four epistatic QTLs were identified which conditioned ADF, starch and protein content under rain-fed, irrigated and combined analyses. These QTLs were located on chromosomes 2H, 3H, 5H, 6H and 7H. Major ADF and starch QTL were identified on chromosome 7H near the nud locus (the locus controlling hulled vs. hull-less caryopsis). High heritability estimates for both ADF and starch content suggest that early selection for these traits during breeding would be productive. Low ADF-QTL were independently verified in a second population in a different genetic background.     

Quantitative trait loci for dry matter digestibility and particle size traits in two-rowed × six-rowed barley population

More than half of the barley grown in the USA is used for livestock feed, with the remaining stocks diverted for human food and malting purposes. The use of barley grain as a major source of cattle feed has been criticized because of its rapid digestion in the rumen, which can result in digestive disorders in cattle. In sacco dry matter digestibility (ISDMD) and particle size (PS) after dry rolling have been found to play a role in the feedlot performance of barley as a feed grain. Reducing the rate of ISDMD is predicted to result in significantly improved animal health and average daily gain. A recombinant inbred line population derived from a cross between a high ISDMD, two-rowed barley cultivar (Valier) and a six-rowed Swiss landrace line (PI370970) exhibiting far slower ISDMD has been developed for studying the underlying genetic locations and mechanisms of these traits. To detect associated quantitative trait loci (QTLs), we collected and analyzed data from irrigated and rain-fed environments. A significant negative correlation was observed between ISDMD and PS. High heritability estimates for ISDMD and PS suggest that early selection for these traits during breeding would be achievable. Four QTLs were identified on chromosomes 2H, 6H, and 7H, explaining 73–85% of ISDMD phenotypic variation, while three QTLs on 2H and 7H were associated with variation in PS and explained 58–77% of its variation. A major QTL on chromosome 2H tightly linked to the morphology-modifying gene vrs1 was found to dramatically control 35–62% of the phenotypic variation of ISDMD and 26–53% of that of PS. The impact of the vrs1 locus on ISDMD was validated in two populations representing different genetic backgrounds. Our results suggest that it may also be advantageous to simultaneously overlap these QTLs around the vrs1 locus.     

Genetic variation,genotype × environment interaction,and selection for tipburn resistance in lettuce in multi-environments

Tipburn is a calcium related and environmentally induced physiological disorder causing economic damage in all lettuce (Lactuca sativa L.) production regions. The objectives of this research were to determine (1) the genetic variation for tipburn incidence, (2) the genotype (G) × environment (E) interaction (GE) for tipburn incidence, and (3) the efficiency of field selection for tipburn resistance. Tipburn incidence was recorded over 2 years in Salinas, CA, and Yuma, AZ, for 55 romaine, crisphead, green leaf, and red leaf type cultivars, and over 3 years in Quebec for 15 romaine cultivars. Analysis revealed that G, E, and GE affected tipburn incidence, including crossover interactions that were not repeatable over years. This indicates that cultivar/breeding line evaluations should be based on mean performance and stability over multiple environments. Among lettuce types, only crisphead had significant genetic variability for tipburn resistance, reflecting the greater breeding effort applied to this type compared romaine, green and red leaf types. Analysis of a dataset with five romaine cultivars in eight environments in California, Arizona, and Quebec for 2 years revealed that Yuma in 2006 and Saint-Blaise in 2005 were highly correlated (r = 0.923, P < 0.05), and were the most discriminating and most representative environments for tipburn evaluation. Single plant selection for tipburn resistance in three F₂ romaine populations was ineffective. Further, the degree of head closure was significantly associated with tipburn incidence. Identification and selection of morphological characters associated with resistance in conjunction with direct selection against tipburn may be an effective method for genetic improvement of tipburn resistance.     

Mapping quantitative trait loci controlling pre-harvest sprouting resistance in a red × white seeded spring wheat cross

Hard white wheat (Triticum aestivum L.) is a value-added product because of its processing advantages over red wheat; however, white wheat tends to be more susceptible to pre-harvest sprouting (PHS). To identify quantitative trait loci (QTLs) associated with PHS tolerance, we developed a doubled haploid (DH) mapping population from the cross AC Domain (red seeded) × White-RL4137 (white seeded). A genetic map was constructed using microsatellite markers located on chromosome groups 3, 4, 5 and 6. A population of 174 DH lines was characterized for important aspects of PHS including sprouting index, germination index, Hagberg falling number and seed coat colour. A total of 11 QTLs were identified on group 3 chromosomes and on chromosome 5D. Seven QTLs associated with the PHS traits were found to be co-incident with seed coat colour on chromosomes 3A, 3B and 3D. The 5D PHS QTL was notable because it is independent of seed coat colour.