Backcross Progeny Research Articles

Development and characterization of mutant winter wheat (Triticum aestivum L.) accessions resistant to the herbicide quizalofop.

New herbicide resistance traits in wheat were produced through the use of induced mutagenesis. While herbicide-resistant crops have become common in many agricultural systems, wheat has seen few introductions of herbicide resistance traits. A population of Hatcher winter wheat treated with ethyl methanesulfonate was screened with quizalofop to identify herbicide-resistant plants. Initial testing identified plants that survived multiple quizalofop applications. A series of experiments were designed to characterize this trait. In greenhouse studies the mutants exhibited high levels of quizalofop resistance compared to non-mutant wheat. Sequencing ACC1 revealed a novel missense mutation causing an alanine to valine change at position 2004 (Alopecurus myosuroides reference sequence). Plants carrying single mutations in wheat's three genomes (A, B, D) were identified. Acetyl co-enzyme A carboxylase in resistant plants was 4- to 10-fold more tolerant to quizalofop. Populations of segregating backcross progenies were developed by crossing each of the three individual mutants with wild-type wheat. Experiments conducted with these populations confirmed largely normal segregation, with each mutant allele conferring an additive level of resistance. Further tests showed that the A genome mutation conferred the greatest resistance and the B genome mutation conferred the least resistance to quizalofop. The non-transgenic herbicide resistance trait identified will enhance weed control strategies in wheat.

Further characterization of diabetes mellitus and body weight loss in males of the congenic mouse strain DDD.Cg-A(y.).

The Ay allele at the agouti locus causes obesity and promotes linear growth in mice. However, body weight gain stops between 16 and 17 weeks after birth, and then, body weight decreases gradually in DDD.Cg-Ay male mice. Body weight loss is a consequence of diabetes mellitus, which is genetically controlled mainly by a quantitative trait locus (QTL) on chromosome 4. This study aimed to further characterize diabetes mellitus and body weight loss in DDD.Cg-Ay males. The number of β-cells was markedly reduced, and plasma insulin levels were very low in the DDD.Cg-Ay males. Using a backcross progeny of DDD × (B6 × DDD.Cg-Ay) F1-Ay, we identified one significant QTL for plasma insulin levels on distal chromosome 4, which was coincidental with QTL for hyperglycemia and lower body weight. The DDD allele was associated with decreased plasma insulin levels. When the DDD.Cg-Ay males were housed under three different housing conditions [group housing (4 or 5 DDD.Cg-Ay and DDD males), individual housing (single DDD.Cg-Ay male) and single male housing with females (single DDD.Cg-Ay male with DDD.Cg-Ay or DDD females)], diabetes mellitus and body weight loss were most severely expressed in individually housed mice. Thus, the severity of diabetes and body weight loss in the DDD.Cg-Ay males was strongly influenced by the housing conditions. These results demonstrate that both genetic and nongenetic environmental factors are involved in the development of diabetes mellitus and body weight loss in the DDD.Cg-Ay males.

Inheritance of Resistance to Deltamethrin in Aedes aegypti (Diptera: Culicidae) From Cuba.

The development of pyrethroid resistance in Aedes aegypti (L) (Diptera: Culicidae) is a serious concern because major A. aegypti control programs are predominantly based on pyrethroid use during epidemic disease outbreaks. Research about the genetic basis for pyrethroid resistance and how it is transmitted among mosquito populations is needed. The objective of this study was to determine how deltamethrin resistance is inherited in the Cuban A. aegypti-resistant reference strain. Here, a field population of A. aegypti from Santiago de Cuba (SAN-F14), subjected to 14 generations of selection for high deltamethrin resistance level (91.25×), was used to prepare reciprocal F1 and backcross progeny with the insecticide-susceptible Rockefeller strain. Bioassays with larvae were performed according to World Health Organization guidelines. The activities of metabolic enzymes were assayed through synergist and biochemical tests. The null hypothesis of the parallelism test between the two probit regression lines of the reciprocal F1 (susceptible females × resistant males and vice versa) was not rejected at the 5% significance level (P = 0.42), indicating autosomal inheritance. The LC50 response of both F1 progenies to deltamethrin was elevated but less than the highly resistant SAN-F14 strain. DLC values for the F1 progenies were 0.91 and 0.87, respectively, suggesting that deltamethrin resistance in the SAN-F14 strain is inherited as an autosomal incompletely dominant trait, involving at least two factors, which implies a faster development of deltamethrin resistance in larvae and lost product effectiveness. Metabolic enzymes including esterases and cytochrome P-450 monooxygenases but not glutathione-S-transferases were involved in deltamethrin resistance in larvae.

Candidate Genes Expressed in Tolerant Common Wheat With Resistant to English Grain Aphid.

The English grain aphid, Sitobion avenae (F.) (Hemiptera: Aphididae), is a common worldwide pest of wheat (Triticum aestivum L.). The use of improved resistant cultivars by the farmers is the most effective and environmentally friendly method to control this aphid in the field. The winter wheat genotypes 98-10-35 and Amigo are resistant to S. avenae. To identify genes responsible for resistance to S. avenae in these genotypes, differential-display reverse transcription-polymerase chain reaction was used to identify the corresponding differentially expressed sequences in current study. Two backcross progenies were obtained by crossing the two resistant genotypes with the susceptible genotype 1376. Six potential expected-differential bands were sequenced. Lengths of the expressed sequence tags ranged from 128 to 532 bp. Although these expressed sequences were likely associated with S. avenae resistance, there was one expressed sequence tag located on 7DL chromosome, and its potential function may associate with the ability to maintain photosynthesis in wheat. That serves as an active way for tolerant common wheat with resistant to S. avenae. Cloning the full length of these sequences would help us thoroughly understand the mechanism of wheat resistance to S. avenae and be valuable for breeding cultivars with S. avenae resistance.

Inheritance of acaricide resistance in inbreeding lines of two-spotted spider mite

Background: The two-spotted spider mite is one of the economically important crop pests. Its control has been and still is largely based on the use of acaricides. However, due to its short life cycle and abundant progeny it is able to develop resistance to acaricides very rapidly. The information on mechanisms of resistance is the aim of devising resistance management strategies. Materials and methods: A laboratory-selected susceptible and resistant inbreeding lines of the spider mite Tetranychus urticae Koch. were used to determine toxicological, cross-resistance, biochemical and genetic data. Mortality caused by acaricide in the F1 progeny and backcrosses with F1 females revealed striking differences in the mode of inheritance. Results: The resistance ratio (RR) calculated from the LC50s of selected susceptible and resistant to dimethoate, bifenthrin, abamectin and bromopropylate lines were 1000, 2600, 2000 and 2000-fold, respectively. Resistance to dimethoate is monogenic dominant inheritance associated with a strong increase in isoenzyme carboxylesterase activity and that could be considered as biochemical marker. Mortality caused by selecting by abamectin in the F1 and backcross progeny indicated that the mode of inheritance resistance is dominant digenic and by selecting bifenthrin and bromopropylate was incompletely recessive linked with two main genetic mutations. Conclusion: The biochemical/physiological mechanisms of resistance to acaricides can be categorized as target site insensitivity or regulatory changes in gene expression elevated some enzyme activity that determines the degree viability in arthropods.

Variability in microsatellite DNA markers in gynogenetic and backcross progenies obtained from ornamental (koi) carp (Cyprinus carpioL.) × goldfish (Carassius auratusL.) hybrid females

Inheritance and segregation at five microsatellite loci were studied in diploid gynogenetic and triploid backcross progenies obtained from koi × goldfish hybrid females, which produce diploid eggs. Gynogenetic and backcross progenies were obtained from three individual hybrid females by inseminating eggs with genetically inactivated and intact sperm of parental species respectively; no shock treatments were applied to the early embryos. Complete absence of paternally specific alleles at all investigated microsatellite loci has proven successful genetic inactivation of spermatozoa by irradiation and confirmed gynogenetic origin of progenies. Genotypic segregations at microsatellite loci showed almost complete homogeneity of gynogenetic progenies and their identity to female parents. These results correspond with previous cytogenetic data on the occurrence of premeiotic endomitosis in hybrid females producing diploid eggs. Fish from triploid backcross progenies had genotypes resulting from combination of entire diploid female genome and haploid genome from male.

Abnormal chromosome behavior during meiosis in the allotetraploid of Carassius auratus red var. (♀)×Megalobrama amblycephala (♂).

BackgroundAllopolyploids generally undergo bivalent pairing at meiosis because only homologous chromosomes pair up. On the other hand, several studies have documented abnormal chromosome behavior during mitosis and meiosis in allopolyploids plants leading to the production of gametes with complete paternal or maternal chromosomes. Polyploidy is relatively rare in animals compared with plants; thus, chromosome behavior at meiosis in the allopolyploid animals is poorly understood.ResultsTetraploid hybrids (abbreviated as 4nRB) (4n = 148, RRBB) of Carassius auratus red var. (abbreviated as RCC) (2n = 100, RR) (♀) × Megalobrama amblycephala (abbreviated as BSB) (2n = 48, BB) (♂) generated gametes of different size. To test the genetic composition of these gametes, the gynogenetic offspring and backcross progenies of 4nRB were produced, and their genetic composition were examined by chromosome analysis and FISH. Our results suggest that 4nRB can produce several types of gametes with different genetic compositions, including allotetraploid (RRBB), autotriploid (RRR), autodiploid (RR), and haploid (R) gametes.ConclusionsThis study provides direct evidence of abnormal chromosome behavior during meiosis in an allotetraploid fish.

Development of a Set of Chromosome Segment Substitution Lines in Pearl Millet [Pennisetum glaucum (L.) R. Br.

ABSTRACTThe detection of minor quantitative trait loci (QTL) with conventional mapping populations can be complicated by the overshadowing effect of major QTL as well as by interactions between QTL. To overcome these constraints, we developed a set of chromosome segment substitution lines (CSSLs) by introgression of overlapping chromosome segments from 863B into ICMB 841 background for use in QTL detection, fine mapping, and trait mechanism studies, especially for complex traits. Since each CSSL carries one or a few donor segments in the genetic background of the recurrent genotype, the QTL interaction is confined to genes present on small homozygous substituted segments. Advanced generation backcross progenies (1492), expected to provide coverage across the mapped length of each of the seven pearl millet linkage groups (LGs), were genotyped at 74 marker loci [(48 simple sequence repeats (SSRs), 21 single strand conformation polymorphism‐single nucleotide polymorphism (SSCP‐SNP), and 5 sequence tagged sites (STSs)] identifying 124 segment introgression homozygotes (13 for LG1, 9 for LG2, 10 for LG3, 41 for LG4, 23 for LG5, 11 for LG6, and 17 for LG7). These CSSLs consisted of 1–3 homozygous introgression segments substituted from 863B in the genetic background of the recurrent parent ICMB 841 and among them, 54 represent unique lines with the donor chromosome segment averaging 100.69 cM. These CSSLs developed here provide a nearly ideal set of genetic stocks for mapping and fine mapping the multitude of traits for which their parents differ.

Broadening the genetic base of Abyssinian mustard (Brassica carinata A. Braun) through introgression of genes from related allotetraploid species

Brassica carinata (BBCC, 2n=34) has still to emerge as a major oilseed crop owing to poor agronomic attributes like long stature, long maturity duration and low seed yield. The restricted amount of genetic variability available in natural B. carinata necessitates utilization of new sources of variability for broadening its genetic base. Interspecific hybridization followed by selection in selfed and back cross progenies was employed to generate useful variability into B. carinata cv ˈPC5ˈ from elite lines of Brassica napus (AACC, 2n=38) and Brassica juncea (AABB, 2n=36). The morphological evaluation of 24 stable introgressed progenies revealed wide range of variability for key economic traits. The progenies with mean maturity duration of 161 ± 2.1 days, short stature of 139.5 ± 6.5 cm and seed yield per plant of 18.6 ± 2.0 g in comparison to the corresponding figures of 168 ± 4.6 days, 230.6 ± 12.7 cm and 12.0 ± 2.4 g in ˈPC5ˈ (recurrent parent) were recovered. Diversity analysis at morphological level revealed that 22 out of 24 stable introgressed progenies were grouped with B. carinata ˈPC5ˈ at average taxonomic distance of 1.19. The diversity at molecular level using 25 polymorphic and reproducible RAPD primers revealed that 19 out of 21 introgressed progenies grouped with B. carinata ˈPC5ˈ at a similarity coefficient of 0.68. The clusters in general represent a wide range of genetic diversity in the back cross lines of B. carinata as a result of introgression of genes from elite lines of B. napus and B. juncea parents.

Quantitative trait Loci for resistance to the congenital nephropathy in tensin 2-deficient mice.

The ICR-derived glomerulonephritis (ICGN) mouse is a chronic kidney disease (CKD) model that is characterized histologically by glomerulosclerosis, vascular sclerosis and tubulointerstitial fibrosis, and clinically by proteinuria and anemia, which are common symptoms and pathological changes associated with a variety of kidney diseases. Previously, we performed a quantitative trait locus (QTL) analysis to identify the causative genes for proteinuria in ICGN mice, and found a deletion mutation of the tensin 2 gene (Tns2nph, MGI no: 2447990). Interestingly, the congenic strain carrying the Tns2nph mutation on a C57BL/6J (B6) genetic background exhibited milder phenotypes than did ICGN mice, indicating the presence of several modifier genes controlling the disease phenotype. In this study, to identify the modifier/resistant loci for CKD progression in Tns2-deficient mice, we performed QTL analysis using backcross progenies from susceptible ICGN and resistant B6 mice. We identified a significant locus on chromosome (Chr) 2 (LOD = 5.36; 31 cM) and two suggestive loci on Chrs 10 (LOD = 2.27; 64 cM) and X (LOD = 2.65; 67 cM) with linkage to the severity of tubulointerstitial injury. One significant locus on Chr 13 (LOD = 3.49; approximately 14 cM) and one suggestive locus on Chr 2 (LOD = 2.41; 51 cM) were identified as QTLs for the severity of glomerulosclerosis. Suggestive locus in BUN was also detected in the same Chr 2 region (LOD = 2.34; 51 cM). A locus on Chr 2 (36 cM) was significantly linked with HGB (LOD = 4.47) and HCT (LOD = 3.58). Four novel epistatic loci controlling either HGB or tubulointerstitial injury were discovered. Further genetic analysis should lead to identification of CKD modifier gene(s), aiding early diagnosis and providing novel approaches to the discovery of drugs for the treatment and possible prevention of kidney disease.

Genomic analysis of the appearance of ovarian mast cells in neonatal MRL/MpJ mice.

In MRL/MpJ mice, ovarian mast cells (OMCs) are more abundant than in other mouse strains, and tend to distribute beneath the ovarian surface epithelium at birth. This study investigated the factors regulating the appearance of neonatal OMCs in progeny of the cross between MRL/MpJ and C57BL/6N strains. F1 neonates had less than half the number of OMCs than MRL/MpJ. Interestingly, MRLB6F1 had more neonatal OMCs than B6MRLF1, although they were distributed over comparable areas. Furthermore, in MRL/MpJ fetuses for which parturition was delayed until embryonic day 21.5, the number of OMCs was significantly higher than in age-matched controls at postnatal day 2. These results suggest that the number of OMCs was influenced by the environmental factors during pregnancy. Quantitative trait locus analysis using N2 backcross progeny revealed two significant loci on chromosome 8: D8Mit343–D8Mit312 for the number of OMCs and D8Mit86–D8Mit89 for their distribution, designated as mast cell in the ovary of MRL/MpJ 1 (mcom1) and mcom2, respectively. Among MC migration-associated genes, ovarian expression of chemokine (C-C motif) ligand 17 at mcom1 locus was significantly higher in MRL/MpJ than in C57BL/6N, and positively correlated with the expression of OMC marker genes. These results indicate that the appearance of neonatal OMCs in MRL/MpJ is controlled by environmental factors and filial genetic factors, and that the abundance and distribution of OMCs are regulated by independent filial genetic elements.

Detection of QTL for forage yield, lodging resistance and spring vigor traits in alfalfa (Medicago sativa L.)

Alfalfa (Medicago sativa L.) is an internationally significant forage crop. Forage yield, lodging resistance and spring vigor are important agronomic traits conditioned by quantitative genetic and environmental effects. The objective of this study was to identify quantitative trait loci (QTL) and molecular markers associated with increased forage yield, resistance to lodging, and spring vigor. A backcross population composed of 128 progeny was developed by crossing the breeding parents DW000577 (lodging susceptible) and NL002724 (lodging-resistant) and back-crossing an individual F1 plant to the maternal parent (i.e. DW000577). A linkage map of NL002724 was developed based upon the segregation of 236 AFLP, SRAP, and SSR markers among the backcross progeny. The markers were distributed among 14 linkage groups, covering an estimated recombination distance of 1497.6 centiMorgans (cM). Replicated clones of both parents and backcross progeny were evaluated in the field for estimated forage yield, lodging, and spring vigor in Washington and Wisconsin during 2007 and 2008. Significant QTL were found for all three traits. In particular, two QTL for lodging resistance were identified that explained ≥14 % of trait variation, and were significant in all years and locations. Major QTL explaining over 25 % of trait variation for forage yield were detected in multiple environments at two separate locations on chromosome III. Several QTL for spring vigor were located in the same or similar positions as QTL for forage yield, possibly explaining the significant correlation between these traits. Molecular markers associated with the aforementioned QTL were also identified.

Characterization of a fertile backcross progeny derived from inter-specific hybrid of Momordica dioica and M. subangulata subsp. renigera and its implications on improvement of dioecious Momordica spp

A fertile female backcross progeny was produced from an inter-specific hybrid [teasel gourd (Momordica subangulata Blume subsp. renigera (G. Don) WJJ de Wilde)×spine gourd (Momordica dioica Roxb)] by backcrossing the F1 with the female parent. Agro morphological and biochemical traits of the first generation backcross (F1 ♀ BC) confirmed interchanges of genetic material. The F1 ♀ BC bear more resemblance to maternal parent than the paternal parent and exhibited substantial heterosis for number of flowers and yield per plant. In F1 ♀ BC, fruit set was significantly higher when pollinated with teasel gourd (84%) while the fruit set was very low upon sibbing (36%) and pollination with spine gourd (64%). The fruits of F1 ♀ BC had little variation for shape from teasel gourd when pollinated with teasel gourd pollen, while fruits obtained from sibbing and dusting of spine gourd pollen were deformed and smaller in size. The proximate and phytochemical analysis revealed that the F1 ♀ BC was intermediate between the original parents in its biochemical traits and antioxidant activity while mineral content was found to be higher or similar to its parents. The present study shows the potential for improving Momordica species through inter-specific hybridization followed by restoration of fertility by backcrossing.

Introgression of phenoxy herbicide resistance from Raphanus raphanistrum into Raphanus sativus

AbstractPhenoxy herbicides such as 2,4‐dichlorophenoxy acetic acid (2,4‐D) and 4‐chloro‐2‐methylphenoxy acetic acid (MCPA) are selective herbicides used extensively in agriculture for weed control. Wild radish (Raphanus raphanistrum) is a problem weed across the globe and heavily infests crop fields in Australia. Phenoxy herbicides are used to selectively control dicot weeds, including wild radish. As a result of selection, phenoxy‐resistant wild radish populations evolved in Western Australia. In this research, introgression of phenoxy resistance from wild radish to cultivated radish (Raphanus sativus) was investigated following classical breeding procedures. F1 progeny were generated by crossing MCPA‐resistant R. raphanistrum and MCPA‐susceptible R. sativus. F1 hybrids were screened for MCPA resistance. The MCPA‐resistant F1 hybrids were used to produce three generations of backcross progeny. Genetic analyses of F1 and backcross progeny demonstrated introgression of the MCPA‐resistant trait from wild radish to cultivated radish. Implications of phenoxy resistance introgression into cultivated radish include potential development of herbicide‐tolerant radish cultivars or other members of the Brassicaceae family.

Characterization of B chromosomes in Lilium hybrids through GISH and FISH

Supernumerary (B) chromosomes and small aberrant chromosomes were detected in Lilium hybrids and characterized through genomic in situ hybridization (GISH) and florescence in situ hybridization (FISH). Two small, supernumerary or B chromosomes were detected as extra chromosomes in a tetraploid plant derived from chromosome doubling of a hybrid (2n = 2x = 24) between a cultivar of the Longiflorum (L) and the Trumpet (T) group. When this tetraploid LLTT hybrid was crossed with a triploid LLO hybrid (O = Oriental), the B chromosome was transmitted to 73.4 % of the progenies. Based on GISH and FISH characterization, it was shown that the B chromosome consisted of two identical arms, with 5S rDNA hybridizing to the majority of it, which were flanked by normal telomeres, suggesting that this is an isochromosome. In another population, which is a backcross progeny between a F1 hybrid of Longiflorum × Asiatic (LA) and its Asiatic parent, the former produced functional 2n gametes which resulted in a triploid LAA progeny (2n = 3x = 36), in which three exceptional plants possessed 35 normal chromosomes and a small aberrant chromosome instead of the expected normal number of 36. In all three cases, the small aberrant chromosomes were isochromosomes which had obviously originated during the first backcross generation. These three chromosomes showed normal telomeres and mitosis. In addition, one of the new generated chromosomes possessed two 45S rDNA sites in the proximal positions. These new arisen isochromosomes were proposed to originate from centric breakage and fusion of two short arms of the missing chromosome in three genotypes, respectively, based on the comparison of arm lengths as well as rDNA loci. Their relevance to the origin of Bs is discussed.

Construction of a complete set of alien chromosome addition lines from Gossypium australe in Gossypium hirsutum: morphological, cytological, and genotypic characterization

Key message We report the first complete set of alien addition lines of G. hirsutum . The characterized lines can be used to introduce valuable traits from G. australe into cultivated cotton. Gossypium australe is a diploid wild cotton species (2n = 26, GG) native to Australia that possesses valuable characteristics unavailable in the cultivated cotton gene pool, such as delayed pigment gland morphogenesis in the seed and resistances to pests and diseases. However, it is very difficult to directly transfer favorable traits into cultivated cotton through conventional gene recombination due to the absence of pairing and crossover between chromosomes of G. australe and Gossypium hirsutum (2n = 52, AADD). To enhance the transfer of favorable genes from wild species into cultivated cotton, we developed a set of hirsutum–australe monosomic alien chromosome addition lines (MAAL) using a combination of morphological survey, microsatellite marker-assisted selection, and molecular cytogenetic analysis. The amphidiploid (2n = 78, AADDGG) of G. australe and G. hirsutum was consecutively backcrossed with upland cotton to develop alien addition lines of individual G. australe chromosomes in G. hirsutum. From these backcross progeny, we generated the first complete set of chromosome addition lines in cotton; 11 of 13 lines are monosomic additions, and chromosomes 7Ga and 13Ga are multiple additions. MAALs of 1Ga and 11Ga were the first to be isolated. The chromosome addition lines can be employed as bridges for the transfer of desired genes from G. australe into G. hirsutum, as well as for gene assignment, isolation of chromosome-specific probes, flow sorting and microdissection of chromosome, development of chromosome-specific ‘‘paints’’ for fluorochrome-labeled DNA fragments, physical mapping, and selective isolation and mapping of cDNAs for a particular G. australe chromosome.Electronic supplementary materialThe online version of this article (doi:10.1007/s00122-014-2283-1) contains supplementary material, which is available to authorized users.

A genetic map of Peromyscus with chromosomal assignment of linkage groups (a Peromyscus genetic map)

The rodent genus Peromyscus is the most numerous and species-rich mammalian group in North America. The naturally occurring diversity within this genus allows opportunities to investigate the genetic basis of adaptation, monogamy, behavioral and physiological phenotypes, growth control, genomic imprinting, and disease processes. Increased genomic resources including a high quality genetic map are needed to capitalize on these opportunities. We produced interspecific hybrids between the prairie deer mouse (P. maniculatus bairdii) and the oldfield mouse (P. polionotus) and scored meiotic recombination events in backcross progeny. A genetic map was constructed by genotyping of backcross progeny at 185 gene-based and 155 microsatellite markers representing all autosomes and the X-chromosome. Comparison of the constructed genetic map with the molecular maps of Mus and Rattus and consideration of previous results from interspecific reciprocal whole chromosome painting allowed most linkage groups to be unambiguously assigned to specific Peromyscus chromosomes. Based on genomic comparisons, this Peromyscus genetic map covers ~83% of the Rattus genome and 79% of the Mus genome. This map supports previous results that the Peromyscus genome is more similar to Rattus than Mus. For example, coverage of the 20 Rattus autosomes and the X-chromosome is accomplished with only 28 segments of the Peromyscus map, but coverage of the 19 Mus autosomes and the X-chromosome requires 40 chromosomal segments of the Peromyscus map. Furthermore, a single Peromyscus linkage group corresponds to about 91% of the rat and only 76% of the mouse X-chromosomes.

Identifying Hybridisation in Pinus Species Using near Infrared Spectroscopy of Foliage

Near infrared (NIR) spectra from foliage of the tropical pine species Pinus caribaea var. hondurensis, P. elliottii var. elliottii and their hybrids have been used to classify the extent of hybridisation for the F1 and backcross progeny. Comparison of results for F1 hybrids with simulated hybrids, made from admixtures of pure parent foliage samples, showed increased variation in the NIR spectra of the F1 hybrids as evidenced by greater scatter in the principal component analysis scores plot. Both partial least-squares–discriminant analysis and soft independent modelling of class analogy using the foliage spectra provide identification of the hybrid individuals from the parent taxa. In addition, it is possible to visualise the extent of genetic additive effect in hybrid-parent backcrosses. NIR spectra from foliage samples of P. radiata, a temperate pine species, were clearly discriminated from P. elliottii and P. caribaea. Near infrared spectroscopy has the potential to confirm and assess the extent of hybridisation in softwood species. In extreme situations whereby trial records are lost or trial plot labelling is missing, it might be possible to use NIR spectra from foliage to recover taxon information of seedlings.

Combined Selection in Backcross Population of Papaya (<i>Carica papaya</i> L.) by the Mixed Model Methodology

The selection of superior genotypes based on the simultaneous response to several characteristics of agronomic importance is a key strategy to overcome the scarcity of available varieties of papaya. This study aimed to apply the combined selection by using distinct selection indexes based on both the genetic values obtained by the REML/BLUP methodology and the real measured values to select agronomically superior genotypes of papaya within backcross progenies. The combined selection was carried out based on genetic and phenotypic values, original and standardized, multiplied by the agronomic weights. The results of the analysis of genetic parameters indicate that the evaluated progenies have expressive genetic variability for the considered traits, and that there are real possibilities of genetic progress with the selection. Among the analyzed indexes, the one based on standardized genetic value presented greater consistency in the ranking of genetic material, demonstrating the advantage of data standardization. Five progenies belonging to the BC1 generation, and five to the BC3 generation were selected using this index. A total of 27 plants ag-ronomically superior were selected within the top five progenies and recommended for generation advance, 23 being selected by combined selection and 4 using the direct selection for the four mainly characters in papaya breeding program: production, pulp and fruit firmness and soluble solids. Beyond the selection of superior genotypes for the development of future inbred lines, this study also allowed defining the best strategy to apply the combined selection in papaya using pre-dicted breeding values obtained by BLUP. This strategy may allow higher accuracy in the selection process, thus increasing the chances of success of the breeding programs.

Evidence to support natural hybridization between Anopheles sinensis and Anopheles kleini (Diptera: Culicidae): possibly a significant mechanism for gene introgression in sympatric populations

BackgroundMalaria caused by Plasmodium vivax is still a public health problem in the Republic of Korea (ROK), particularly regarding the recent re-emergence of this malarial species near the demilitarized zone in northwestern Paju City, Gyeonggi-do Province. Currently, at least 4 species (An. kleini, An. pullus, An. belenrae and An. lesteri) of the Hyrcanus Group are reported as possible natural vectors of vivax malaria in the ROK, and An. sinensis, which is the most dominant species, has long been incriminated as an important natural vector of this P. vivax. However, An. sinensis was ranked recently as a low potential vector. According to the discovery of natural hybrids between An. sinensis (a low potential vector for P. vivax) and An. kleini (a high potential vector for P. vivax) in Paju City, intensive investigation of this phenomenon is warranted under laboratory conditions.MethodsMosquitoes were collected during 2010-2012 from Paju City, ROK. Hybridization experiments used iso-female line colonies of these anophelines together with DNA analysis of ribosomal DNA [second internal transcribed spacer (ITS2)] and mitochondrial DNA [cytochrome c oxidase subunit I (COI)] of the parental colonies, F1-hybrids and repeated backcross progenies were performed intensively by using a PCR-based assay and pyrosequencing technology.ResultsThe results from hybridization experiments and molecular investigations revealed that the mitochondrial COI gene was introgressed from An. sinensis into An. kleini. The An. sinensis progenies obtained from consecutive repeated backcrosses in both directions, i.e., F2-11 progeny [(An. sinensis x An. kleini) x An. sinensis] and F3-5 progeny [(An. kleini x An. sinensis) x An. kleini] provided good supportive evidence.ConclusionsThis study revealed introgression of the mitochondrial COI gene between An. sinensis and An. kleini through consecutive repeated backcrosses under laboratory conditions. This new body of knowledge will be emphasized in reliable promising strategies in order to replace the population of An. kleini as a high potential vector for P. vivax, with that of a low potential vector, An. sinensis, through the mechanism of gene introgression in nature.