BC1 Progeny Research Articles

Morphological characterization and genetic diversity analysis of interspecific hybrids of sugarcane

Interspecific hybrid derivatives involving Saccharum spontaneum, S. robustum and S. barberi were morphologically characterized with twenty two qualitative and six agronomic traits. Principal component analysis (PCA) of qualitative traits revealed that first nine principal components with eigen value > 1 accounted for a cumulative variance of 62.40%. The traits viz., ligule shape, auricle type, internode shape and its alignment, cane thickness, dewlap color, leaf blade width and curvature, leaf sheath hairiness, bud cushion and bud groove were identified as principal discriminatory characters which will be useful in preliminary screening and identification of interspecific hybrids. Cluster analysis of qualitative traits grouped hybrids into seven clusters. Maximum inter cluster distance was between cluster IV and VI followed by cluster I and III, III and VII and between VI and VII. Metroglyph analysis of agronomic traits categorized hybrids into ten groups. Groups III, IV, V, VIII and X with highest mean index scores were identified as genetically most distant. Thirty eight superior interspecific hybrids with high index score for agronomic traits (from metroglyph analysis) and wider inter cluster distance were identified as prebreeding stocks and utilized in further backcross programmes. BC1 progenies of SBH 12–45 x Co 0303 and SRH 12–275 x Co 0240 were significantly superior for single cane weight and brix %. Elite recombinants from back crosses SSH 12–158 x Co 0209, SSH 12–409 x Co 09014 and SRH 12–119 x Co 94008 surpassed commercial check for cane yield and were on par for quality.

Mismatch repair deficiency increases the transfer of antibiosis and antixenosis properties against Colorado potato beetle in somatic hybrids of Solanum tuberosum + S. chacoense.

Colorado potato beetle (CPB) has become the biggest enemy of cultivated potato worldwide. One of the most effective sources of resistance to CPB is Solanum chacoense, an accession with a high leptine glycoalkaloid content. The aim of our study was to assay the repellence and toxicity of S. chacoense, its somatic hybrids (SHs) and their backcross progenies (BC1 ) with potato for CPB adults and larvae. Transgenic S. chacoense, deficient in DNA mismatch repair (MMR), was also used to produce SHs, in order to increase homeologous recombination and hence introgression of wild-species DNA into the potato gene pool. Wild-type SH was highly resistant to CPB. Resistance to CPB of BC1 progenies showed a 1:3 inheritance pattern. MMR-deficient SHs performed better in the resistance analysis. Most MMR-deficient SHs had a similar toxicity as S. chacoense and an intensely repellent effect on CPB adults. Resistance of SHs and BC1 clones may be attributed to leptine biosynthesis, which was confirmed using a RAPD marker. This is the first report of SHs and their progenies exhibiting both antibiosis and antixenosis against CPB. Resistant SHs are an important step forward in combating this voracious pest of potato. © 2016 Society of Chemical Industry.

Efficient and heritable transformation of Phalaenopsis orchids.

Background Phalaenopsis orchid (Phal. orchid) is visually attractive and it is important economic floriculture species. Phal. orchids have many unique biological features. However, investigation of these features and validation on their biological functions are limited due to the lack of an efficient transformation method.ResultsWe developed a heritable and efficient Agrobacterium- mediated transformation using protocorms derived from tetraploid or diploid Phal. orchids. A T-DNA vector construct containing eGFP driven by ubiquitin promoter was subjected to transformation. An approximate 1.2–5.2 % transformation rate was achieved. Genomic PCR confirmed that hygromycin selection marker, HptII gene and target gene eGFP were integrated into the orchid genome. Southern blotting indicated a low T-DNA insertion number in the orchid genome of the transformants. Western blot confirmed the expression of eGFP protein in the transgenic orchids. Furthermore, the GFP signal was detected in the transgenic orchids under microscopy. After backcrossing the pollinia of the transgenic plants to four different Phal. orchid varieties, the BC1 progenies showed hygromycin resistance and all surviving BC1 seedlings were HptII positive in PCR and expressed GFP protein as shown by western blot.ConclusionsThis study demonstrated a stable transformation system was generated for Phal. orchids. This useful transformation protocol enables functional genomics studies and molecular breeding.Electronic supplementary materialThe online version of this article (doi:10.1186/s40529-016-0146-6) contains supplementary material, which is available to authorized users.

Characteristics Analysis of F1 Hybrids between Genetically Modified Brassica napus and B. rapa.

A number of studies have been conducted on hybridization between transgenic Brassica napus and B. rapa or backcross of F1 hybrid to their parents. However, trait changes must be analyzed to evaluate hybrid sustainability in nature. In the present study, B. rapa and transgenic (BrAGL20) B. napus were hybridized to verify the early flowering phenomenon of F1 hybrids, and F1 hybrid traits were analyzed to predict their impact on sustainability. Flowering of F1 hybrid has been induced slightly later than that of the transgenic B. napus, but flowering was available in the greenhouse without low temperature treatment to young plant, similar to the transgenic B. napus. It is because the BrAGL20 gene has been transferred from transgenic B. napus to F1 hybrid. The size of F1 hybrid seeds was intermediate between those of B. rapa and transgenic B. napus, and ~40% of F1 pollen exhibited abnormal size and morphology. The form of the F1 stomata was also intermediate between that of B. rapa and transgenic B. napus, and the number of stomata was close to the parental mean. Among various fatty acids, the content of erucic acid exhibited the greatest change, owing to the polymorphism of parental FATTY ACID ELONGASE 1 alleles. Furthermore, F2 hybrids could not be obtained. However, BC1 progeny were obtained by hand pollination of B. rapa with F1 hybrid pollen, with an outcrossing rate of 50%.

English

Groundnut rosette disease is one of the most damaging diseases militating against groundnut production in sub-Saharan Africa. The disease cause up to 100% yield loss whenever epidemic occurs. The most effective, economic and environmental friendly method to control the disease is through genetic resistance. Knowledge on inheritance of resistance to the rosette disease is required to accelerate breeding of resistant varieties. A study was conducted to understand the nature and magnitude of gene effect of resistance to the disease. Thus F1, RF1, F2, RF2, BC1, RBC1, BC2, and RBC2 progenies were derived from crosses of Otuhia × Manipintar, Otuhia × Shitaochi, ICGV 01276 × Manipintar, and ICGV 01276 × Shitaochi along with their parents were evaluated in a randomized complete block design at CSIR - CRI, Fumesua, under artificial infection. Generation mean analysis revealed that additive gene action effect was predominant on the resistance to the disease in all the crosses. Additive by dominance was the only form of non-allelic interaction observed to be significant in ICGV 01276 × Manipintar cross. Reciprocal differences suggested the presence of maternal effect involved in the inheritance of resistance to groundnut rosette disease. Estimates of broad and narrow sense heritability indicated that genetic effect was larger than the environmental effects in this study. Disease diagnosis using TAS ELISA revealed the presence of groundnut rosette assistor virus (GRAV) antigens in the resistant samples analyzed. Resistant genotypes containing GRAV were considered to be resistant to the GRV and its Sat-RNA, but not the GRAV which causes no obvious symptoms by itself. Pure line breeding with selection from early generation is suggested for the improvement of resistance to rosette virus disease, because additive genetic effect contributed significantly in controlling the inheritance of resistance to groundnut rosette disease (GRD). Key words: Additive, dominance, heritability, inheritance, heterosis, rosette disease.

Molecular Mapping of Stripe Rust Resistance Gene Yr76 in Winter Club Wheat Cultivar Tyee.

Tyee, one of the wheat cultivars used to differentiate races of Puccinia striiformis f. sp. tritici in the United States, was identified to have a single gene for all-stage resistance, tentatively named YrTye. To map the gene, Tyee was crossed with 'Avocet Susceptible' (AvS). Genetic analysis of the F1, F2, F2:3, and BC1 progenies confirmed a single dominant gene for resistance to race PSTv-37 that is avirulent to YrTye. A mapping population of 135 F2 plants was phenotyped with PSTv-37 and the derived F2:3 lines were tested with races PSTv-37, PSTv-40, and PSTv-79. The F2 mapping population was genotyped with simple sequence repeat (SSR) markers. A genetic map comprising 13 SSR markers located YrTye in chromosome 3AS flanked distally by SSR marker wmc11 and proximally by wmc532 at 2.6 and 3.4 cM, respectively. Amplification of Chinese Spring 3A deletion lines placed the gene in the distal bin 3AS4-0.45 to 1.00. Because YrTye is different from all formally named Yr genes in chromosomal location, we permanently name the gene Yr76. A near-isogenic line of spring common wheat was developed and selected by testing F3 lines derived from a AvS*4/Tyee cross with Tyee-avirulent and virulent races and the flanking markers. The specific SSR alleles flanking Yr76 were validated using cultivars and breeding lines with and without the gene, and showed high polymorphisms. The specificity of Yr76 is useful in differentiating P. striiformis f. sp. tritici races, and its tightly linked markers will be useful in developing resistant cultivars when combining the gene with other genes for resistance to stripe rust.

Introgression of clubroot resistance into an elite pak choi inbred line through marker‐assisted introgression breeding

AbstractClubroot is a soilborne disease that severely infects cruciferous species. Pak choi (Brassica rapa subsp. chinensis) is an economically important cruciferous crop cultivated throughout the world. However, no clubroot‐resistant germplasms have been identified in pak choi to date. To improve disease resistance, we used marker‐assisted selection (MAS) to introgress the clubroot resistance (CR) trait from the ‘CCR13685’ Chinese cabbage (B. rapa subsp. pekinensis) inbred line into an elite pak choi inbred line, ‘GHQ11021’. Genetic analysis of F2 and BC1 progeny showed that CR of ‘CCR13685’ was controlled by a single dominant gene. We designed nine candidate sequence‐characterized amplified region markers, K‐1 to K‐9, based on two molecular markers linked to the CR gene. We found that K‐3 co‐segregated with CR and an inoculation test confirmed that K‐3 could be used for MAS. Two introgression lines, BC3‐1‐4 and BC3‐2‐18, were developed using K‐3 for foreground selection. These lines displayed the same phenotypic properties as ‘GHQ11021’, but were highly resistant to clubroot, indicating that the CR gene of ‘CCR13685’ had been successfully introduced into pak choi.

Transferring clubroot resistance from Chinese cabbage (Brassica rapa) to canola (B. napus)

Clubroot, caused by Plasmodiophora brassicae, is one of the most important diseases of Brassica species worldwide, including vegetable and oilseed crops. A dominant clubroot resistance gene from B. rapa (Chinese cabbage) was previously fine mapped and molecular markers were developed in Chinese cabbage that could be used for marker-assisted selection (MAS) in other Brassica crops. To transfer this clubroot resistance gene to B. napus (canola), an interspecific hybridization was made between B. napus (canola) and B. rapa (Chinese cabbage). Subsequently, the F1 was backcrossed to the canola recurrent parent for three generations to produce BC1, BC2 and BC3 progenies. Using these populations, simple sequence repeat (SSR) markers flanking the clubroot resistance gene were used to perform MAS in canola. These molecular markers were then evaluated in 13 different canola and rapeseed quality genotypes in B. napus and B. rapa. These markers exhibited high reliability in identifying clubroot resistance in this diverse set of Brassica genotypes. Clubroot resistance also co-segregated with the SSR markers flanking the clubroot resistance gene in the BC3 and BC3S1. The segregation ratio of resistant and susceptible individuals in the BC3 supported the expected 1:1 ratio for the segregation of a single Mendelian gene. BC3S1 families with homozygous clubroot resistance were developed during this process, and should be valuable sources of clubroot resistance in B. napus breeding activities.

Flower color and pigments in yellow-flowered hybrid progeny raised from the interspecific cross Pelargonium quinquelobatum × white-flowered geraniums

The aim of this study was to produce a yellow-flowered geranium (Pelargonium×hortorum Bailey). Interspecific crosses between white-flowered geraniums and Pelargonium quinquelobatum Hochst. ex A. Rich. were performed. Unilateral incompatibility was observed, such that normal seeds were obtained when P. quinquelobatum was used as the seed parent, whereas no seeds were obtained when P. quinquelobatum was used as the pollen parent. The F1 progeny produced sterile pollen; therefore, genome doubling of the F2 progeny was induced by colchicine treatment to ensure fertile pollen; F3 progeny were also produced. The F3 progeny were crossed with tetraploid geraniums to produce BC1 and BC1F2 progeny. The flower color of the hybrid progeny were pale yellow, ranged from green–yellow 1D to yellow 3C, according to the Royal Horticultural Society Color Chart, and became increasingly the value of the colorimetric parameter b* with advancing generations. The pigmentation of the pale yellow flowers involved a large amount of flavonols and a small amount of carotenoids: the main pigments were kaempferol or quercetin. The quercetin contents were significantly correlated with the b* value (r=0.82, P<0.001), whereas no correlation was found between the kaempferol or carotenoids contents and the b* value. Furthermore, the b* value was unaffected by the aluminum content or the pH value in the petals.

Genetic transmission of Solanum demissum (2n = 6x = 72) chromosomes from a pentaploid hybrid of S. tuberosum (2n = 4x = 48) into the aneuploid BC1 progeny

Solanum demissum is a homozygous, hexaploid wild species (2n = 6x = 72, AADDDdDd) that has long been used as a source of late blight resistance by repeated backcrossing with S. tuberosum (2n = 4x = 48, AAAtAt). To understand how S. demissum germplasm is incorporated to S. tuberosum through backcrosses, a linkage analysis of 590 DNA markers from S. demissum-specific simplex alleles was performed in an aneuploid population of 87 BC1 plants. Five hundred eighty-one markers were mapped to 38 linkage groups, of which 37 were assigned to potato chromosomes using markers of known location. Three homoeologous chromosomes were distinguished for each of the 12 potato chromosomes. Approximately 50 % of the markers were transmitted to the BC1 progeny except for chromosomes 2c, 3b and 6c, which were significantly under-represented. Two of the three homeologous chromosomes in at least nine of the chromosomes were transmitted to the BC1 progeny with negative correlations, which demonstrated that the two homeologous chromosomes paired at meiosis in the F1 parent then separated into different gametes. Therefore, we suggest that the two negatively correlated chromosomes were the slightly differentiated genomes cytologically designated D and Dd genomes, while the remaining one was the one cytologically designated A genome of S. demissum. The S. demissum genome map will be useful in analyzing intra-locus interaction of qualitative and quantitative traits among homoeologous chromosomes and analyzing allelic variation of homeolog expression.

GENERATION MEAN ANALYSIS FOR YIELD AND YIELD COMPONENTS IN SESAME (Sesamumindicum L.)

Two parents with contrasting characters were used, viz; Gd2002SPSN.29 and Ziraa-9 described as (P1) and (P2) respectively. They were selected from the sesame breeding program, Gedarif Research Station, ARC, Sudan. In season 2004 the two parents were crossed to produce F1 hybrid. In season 2005 parents and their F1 were grown. Part of the F1 was selfed to produce F2 and the other part was back crossed to both parents to produce Bc1 and Bc2 progenies. In season 2006 the parents (P1, P2), and their F1and F2 and back crosses (Bc1, Bc2) populations were evaluated in a randomized complete block design with three replicates. A wide range of variability was exhibited for most of the characters. The highest seed yield was obtained by the BC2 (714 Kg.ha-1), while the lowest was obtained by the BC1 (286 Kg.ha-1). Considering the nature and magnitude of gene action, improvement of days to 50% flowering, days to maturity, plant height, number of branches plant-1, height to first branch, height to first capsule, capsule length and 1000-seed weight could be achieved through simple pedigree method while hybrid breeding would be most effective for seed yield plant-1 and seed yield.ha-1International Journal of Environment Volume-4, Issue-3, June-August 2015Page: 111-120

Characterization of Chromosome Inheritance of the Intergeneric BC2 and BC3 Progeny between Saccharum spp. and Erianthus arundinaceus.

Erianthus arundinaceus (E. arundinaceus) has many desirable agronomic traits for sugarcane improvement, such as high biomass, vigor, rationing ability, tolerance to drought, and water logging, as well as resistance to pests and disease. To investigate the introgression of the E. arundinaceus genome into sugarcane in the higher generations, intergeneric BC2 and BC3 progeny generated between Saccharum spp. and E. arundinaceus were studied using the genomic in situ hybridization (GISH) technique. The results showed that the BC2 and BC3 generations resulted from n + n chromosome transmission. Furthermore, chromosome translocation occurred at terminal fragments from the E. arundinaceus chromosome in some progeny of Saccharum spp. and E. arundinaceus. Notably, the translocated chromosomes could be stably transmitted to their progeny. This study illustrates the characterization of chromosome inheritance of the intergeneric BC2 and BC3 progeny between Saccharum spp. and E. arundinaceus. This work could provide more useful molecular cytogenetic information for the germplasm resources of E. arundinaceus, and may promote further understanding of the germplasm resources of E. arundinaceus for sugarcane breeders to accelerate its progress in sugarcane commercial breeding.

Micropollen Formation in F1 Hybrids and Backcrosses of Waterhemp (Amaranthus tuberculatus) X Smooth Pigweed (A. hybridus) as a Quick Method for Determination of Interspecific Hybridization Events

Various weedy amaranths have demonstrated the possibility of genetic exchange via interspecific hybridization. Normal meiotic events lead to the formation of normal tetrads and normal pollen while abnormal meiosis results in abnormal segregation of chromosomes in the tetrads resulting in macro and micropollen. Thus, pollen size can be used as an indirect measure of meiotic integrity. The purpose of this study was to examine the frequency of micropollen from putative F1, BC1, and BC2 progeny of waterhemp and smooth pigweed crosses to determine if infertility in the hybrids could be attributed to abnormal meiosis. Significant variation was observed with respect to the occurrence of micropollen. The F1 hybrids had the highest occurrence of micropollen, and highest percentage of abnormal tetrad formation. Problems in meiosis could be causing decreased fertility, but not complete sterility. However, backcrossing resulted in progeny with smaller percentages of micropollen, consistent with previous reports that fertility is restored in these progeny. This method allows for quick and cost effective method for determination of interspecific hybridization events.

Genomic Characterization of Interspecific Hybrids and an Admixture Population Derived from Panicum amarum × P. virgatum.

Switchgrass (Panicum virgatum L.) and its relatives are regarded as top bioenergy crop candidates; however, one critical barrier is the introduction of useful genetic diversity and the development of new cultivars and hybrids. Combining genomes from related cultivars and species provides an opportunity to introduce new traits. In switchgrass, a breeding advantage would be achieved by combining the genomes of intervarietal ecotypes or interspecific hybrids. The recovery of wide crosses, however, is often tedious and may involve complicated embryo rescue and numerous backcrosses. Here, we demonstrate a straightforward approach to wide crosses involving the use of a selectable transgene for recovery of interspecific [P. virgatum cv. Alamo × Panicum amarum Ell. var amarulum or Atlantic Coastal Panicgrass (ACP)] F1 hybrids followed by backcrossing to generate a nontransgenic admixture population. A nontransgenic herbicide-sensitive (HbS) admixture population of 83 F1 BC1 progeny was analyzed by genotyping-by-sequencing (GBS) to characterize local ancestry, parental contribution, and patterns of recombination. These results demonstrate a widely applicable breeding strategy that makes use of transgenic selectable resistance to identify and recover true hybrids.

The recipient potato cultivar influences the genetic makeup of the somatic hybrids between five potato cultivars and one cloned accession of sexually incompatible species Solanum bulbocastanum Dun.

Somatic hybridization is a biotechnological tool, which allows the transfer of multiple resistance genes from sexually incompatible Solanum species into cultivated potato. Here we report the effect of the recipient commercial tetraploid potato cultivar on the genetic make-up of the somatic hybrids (SHs) with an accession of the incongruent diploid species Solanum bulbocastanum Dun. The SHs were produced by mesophyll protoplast electrofusion. The analysis of ploidy by flow cytometry was first used to select hexaploid putative SH shoots but SSR and AFLP markers, DAPI staining and later flow cytometry evaluation of ploidy reveals symmetric and asymmetric SH plants regeneration in proportions that depend on the potato cultivar. The growth and fertility of the SHs support the effect of recipient cultivar. Out of five different fusion combinations, the highest number of SHs and tuberosum morphology was recorded for the combinations: blb41 (+) ‘Delikat’ 235 SHs (104 symmetric and 131 asymmetric) and blb41 (+) ‘Rasant’ 33 SH plants (22 symmetric, 11 asymmetric). There were fertile SHs of these combinations and BC1 and BC2 progenies were obtained. Less successful were the combinations: blb41 (+) ‘Quarta’ 64 SHs (57 symmetric and 7 asymmetric), blb41 (+) ‘Baltica’ 25 SHs (16 symmetric and 9 asymmetric), which were infertile and blb41 (+) ‘Agave’ with only one highly asymmetric non-viable SH plant. The production of a large number of SHs with diverse commercial cultivars is a prerequisite for further selection of useful pre-breeding material. The causes of nuclear constitution asymmetry and somatic incompatibility of the two species are also discussed.

Inheritance and molecular mapping of stripe rust resistance genes in Chinese winter wheat Zhongliang 16

Stripe rust, caused by Puccinia striiformis f. sp. tritici (Pst), is one of the most widespread diseases of wheat worldwide. Resistance breeding is constantly pursued for decades to tackle the variations of prevalent Pst races. Zhongliang 16 has wide adaptability, strong resistance to abiotic stresses, excellent biological characteristics, and higher resistance to stripe rust. In this study, Zhongliang 16 was crossed with a susceptible genotype, Mingxian 169, to identify the resistance gene(s). Seedlings of the parents, F1, F2, F2:3, and BC1 progenies were tested for resistance with Chinese Pst race CYR29 and CYR30 in greenhouse conditions. Zhongliang 16 possessed different dominant genes for resistance to each race, temporarily designated as Yrzhong16-1 and Yrzhong16-2. Yrzhong16-1 conferring resistance to CYR29 was flanked by Xbarc212 and Xwmc177 on the short arm of 2A at genetic distances of 5.4 and 6.6 cM; and Yrzhong16-2 conferring resistance to CYR30 was flanked by Xgwm644 and Xbarc95 on the long arm of 7B at genetic distances of 2.3 and 3.5 cM, respectively. Chromosomal locations and race and allelism tests indicated that the two genes are different from previously reported stripe rust resistance genes. These genes and their flanking markers should be useful in marker assisted selection-breeding programs against wheat stripe rust.

GISH analyzed progenies generated from allotriploid lilies as female parent

Allotriploid lilies can produce aneuploid or euploid functional female gametes and can be used as the maternal parents in lily introgression breeding. In this study, the genome composition of 14 allopolyploid progenies, including 5 progenies which were derived from LLO×TTTT, 5 progenies which were derived from LLO×OTOT, and 4 BC2 progenies which were derived from MAD×AA/AAAA, were analyzed using genomic in situ hybridization (GISH) technique. The GISH results indicated that all of the 10 progenies which were derived from LLO×TTTT/OTOT were aneuploids, 4 BC2 progenies were euploids. Moreover, LLO always produced aneuploid functional female gametes, giving rise to aneuploid progenies, and MAD produced euploid functional female gametes including n or 2n gametes. Most interestingly, T/O recombinant chromosomes, which were caused by abnormal meiosis, were observed in 2 progenies of LLO×OTOT. Based on the analysis, we proposed that aneuploids might provide a promising approach for lily breeding.

Evaluation of cotton leaf curl virus resistance in BC1, BC2, and BC3 progenies from an interspecific cross between Gossypium arboreum and Gossypium hirsutum.

Cotton leaf curl virus disease (CLCuD) is an important constraint to cotton production. The resistance of G. arboreum to this devastating disease is well documented. In the present investigation, we explored the possibility of transferring genes for resistance to CLCuD from G. arboreum (2n = 26) cv 15-Mollisoni into G. hirsutum (2n = 52) cv CRSM-38 through conventional breeding. We investigated the cytology of the BC1 to BC3 progenies of direct and reciprocal crosses of G. arboreum and G. hirsutum and evaluated their resistance to CLCuD. The F1 progenies were completely resistant to this disease, while a decrease in resistance was observed in all backcross generations. As backcrossing progressed, the disease incidence increased in BC1 (1.7–2.0%), BC2 (1.8–4.0%), and BC3 (4.2–7.0%). However, the disease incidence was much lower than that of the check variety CIM-496, with a CLCuD incidence of 96%. Additionally, the disease incidence percentage was lower in the direct cross 2(G. arboreum)×G. hirsutum than in that of G. hirsutum×G. arboreum. Phenotypic resemblance of BC1 ∼BC3 progenies to G. arboreum confirmed the success of cross between the two species. Cytological studies of CLCuD-resistant plants revealed that the frequency of univalents and multivalents was high in BC1, with sterile or partially fertile plants, but low in BC2 (in both combinations), with shy bearing plants. In BC3, most of the plants exhibited normal bearing ability due to the high frequency of chromosome associations (bivalents). The assessment of CLCuD through grafting showed that the BC1 to BC3 progenies were highly resistant to this disease. Thus, this study successfully demonstrates the possibility of introgressing CLCuD resistance genes from G. arboreum to G. hirsutum.

Unexpected inheritance pattern of Erianthus arundinaceus chromosomes in the intergeneric progeny between Saccharum spp. and Erianthus arundinaceus.

Erianthus arundinaceus is a valuable source of agronomic traits for sugarcane improvement such as ratoonability, biomass, vigor, tolerance to drought and water logging, as well as resistance to pests and disease. To investigate the introgression of the E. arundinaceus genome into sugarcane, five intergeneric F1 hybrids between S. officinarum and E. arundinaceus and 13 of their BC1 progeny were studied using the genomic in situ hybridization (GISH) technique. In doing so, we assessed the chromosome composition and chromosome transmission in these plants. All F1 hybrids were aneuploidy, containing either 28 or 29 E. arundinaceus chromosomes. The number of E. arundinaceus chromosomes in nine of the BC1 progeny was less than or equal to 29. Unexpectedly, the number of E. arundinaceus chromosomes in the other four BC1 progeny was above 29, which was more than in their F1 female parents. This is the first cytogenetic evidence for an unexpected inheritance pattern of E. arundinaceus chromosomes in sugarcane. We pointed to several mechanisms that may be involved in generating more than 2n gametes in the BC1 progeny. Furthermore, the implication of these results for sugarcane breeding programs was discussed.

Genetic and Molecular Mapping of Stripe Rust Resistance Genes in Wheat Cultivar Zhongliang 12

AbstractStripe rust, caused by Puccinia striiformis f.sp. tritici (Pst), is one of the most widespread and destructive diseases of wheat worldwide. Resistance breeding is constantly pursued for decades to tackle the variations of prevalent Pst races. Zhongliang 12 has strong resistance to abiotic stresses, wide adaptability, higher resistance to stripe rust and excellent biological characteristics. To identify the resistance gene(s) against stripe rust, Zhongliang 12 was crossed with stripe rust susceptible genotype Mingxian 169, and F1, F2, F2 : 3 and BC1 progenies were tested with Chinese Pst race CYR30 and CYR31 in seedling stage in greenhouse. Zhongliang 12 possessed different dominant genes for resistance to each race. Linkage maps were constructed with four simple sequence repeats (SSRs) markers, Xwmc695, Xcfd20, Xbarc121 and Xbarc49, for the gene on wheat chromosome 7AL conferring resistance to CYR30 (temporarily designated as Yrzhong12‐1) with genetic distance ranging from 3.1 to 10.8 cM and four SSR markers, Xpsp3003, Xcfd2129, Xwmc673 and Xwmc51, for the gene on wheat chromosome 1AL conferring resistance to CYR31 (temporarily designated as Yrzhong12‐2) with genetic distance ranging from 3.9 cM to 9.3 cM. The molecular markers closely linked to each gene should be useful in marker‐assisted selection in breeding programmes for against stripe rust.