BC1F1 Generations Research Articles

Marker assisted improvement of low soil phosphorus tolerance in the bacterial blight resistant, fine-grain type rice variety, Improved Samba Mahsuri

Improved-Samba-Mahsuri (ISM), a high-yielding, popular bacterial blight resistant (possessing Xa21, xa13, and xa5), fine-grain type, low glycemic index rice variety is highly sensitive to low soil phosphorus (P). We have deployed marker-assisted backcross breeding (MABB) approach for targeted transfer of Pup1, a major QTL associated with low soil P tolerance, using Swarna as a donor. A new co-dominant marker, K20-1-1, which is specific for Pup1 was designed and used for foreground selection along with functional markers specific for the bacterial blight resistance genes, Xa21, xa13, and xa5. A set of 66 polymorphic SSR marker were used for the background selection along with a pair of flanking markers for the recombination selection in backcross derived progenies and in BC2F2 generation, 12 plants, which are homozygous for Pup1, all the three bacterial blight resistance genes and possessing agro-morphological traits equivalent to or better than ISM were selected and selfed to produce BC2F3s. They were evaluated in plots with low soil P and normal soil P at ICAR-IIRR, Hyderabad for their low soil P tolerance, and bacterial blight resistance and superior lines were advanced to BC2F6. One of the lines, when tested at multiple locations in India was found promising under both normal as well as low soil P conditions.

Molecular mapping of a new recessive wheat leaf rust resistance gene originating from Triticum spelta

TSD276-2, a wheat genetic stock derived from the cross Agra Local/T. spelta 276 showed broad spectrum resistance against leaf rust pathogen. Genetic analysis was undertaken using F1, F2, F2:3 and BC1F1 generations derived from the cross TSD276-2/Agra Local. The results revealed a single recessive gene for leaf rust resistance, tentatively named as LrTs276-2, in TSD276-2. Molecular mapping of leaf rust resistance gene LrTs276-2 in TSD276-2 was done using SNP-based PCR and SSR markers. For Bulked Segregant Analysis (BSA), two bulks viz. resistant bulk and susceptible bulk, and the parents TSD276-2 and Agra Local were genotyped for SNPs using AFFYMETRIX 35K Wheat Breeders' AXIOM array. T. spelta 276 was also genotyped and used as a check. BSA indicated that the gene for leaf rust resistance in TSD276-2 is located on chromosome arm 1DS. Putatively linked SNPs on chromosome arm 1DS were converted into PCR-based markers. Polymorphic SSR markers on chromosome arm 1DS were also identified. Final linkage map was constructed using one SNP-based PCR and three SSR markers. The rust reaction and chromosomal location suggest that LrTs276-2 is a new leaf rust resistance gene which may be useful in broadening the genetic base of leaf rust resistance in wheat.

Gene Pyramiding for Achieving Enhanced Resistance to Bacterial Blight, Blast, and Sheath Blight Diseases in Rice.

Bacterial blight, blast, and sheath blight are the commonest diseases causing substantial yield loss in rice around the world. Stacking of broad-spectrum resistance genes/QTLs into popular cultivars is becoming a major objective of any disease resistance breeding program. The varieties ASD 16 and ADT 43 are the two popular, high yielding, and widely grown rice cultivars of South India, which are susceptible to bacterial blight (BB), blast, and sheath blight diseases. The present study was carried out to improve the cultivars (ASD 16 and ADT 43) through introgression of bacterial blight (xa5, xa13, and Xa21), blast (Pi54), and sheath blight (qSBR7-1, qSBR11-1, and qSBR11-2) resistance genes/QTLs by MABB (marker-assisted backcross breeding). IRBB60 (xa5, xa13, and Xa21) and Tetep (Pi54; qSBR7-1, qSBR11-1, and qSBR11-2) were used as donors to introgress BB, blast, and sheath blight resistance into the recurrent parents (ASD 16 and ADT 43). Homozygous (BC3F3 generation), three-gene bacterial blight pyramided (xa5 + xa13 + Xa21) lines were developed, and these lines were crossed with Tetep to combine blast (Pi54) and sheath blight (qSBR7-1, qSBR11-1, and qSBR11-2) resistance. In BC3F3 generation, the improved pyramided lines carrying a total of seven genes/QTLs (xa5 + xa13 + Xa21 + Pi54 + qSBR7-1 + qSBR11-1 + qSBR11-2) were selected through molecular and phenotypic assay, and these were evaluated for resistance against bacterial blight, blast, and sheath blight pathogens under greenhouse conditions. We have selected nine lines in ASD 16 background and 15 lines in ADT 43 background, exhibiting a high degree of resistance to BB, blast, and sheath blight diseases and also possessing phenotypes of recurrent parents. The improved pyramided lines are expected to be used as improved varieties or used as a potential donor in breeding programs. The present study successfully introgressed Pi54, and qSBR QTLs (qSBR7-1, qSBR11-1, and qSBR11-2) from Tetep and major effective BB-resistant genes (xa5, xa13, and Xa21) from IRBB60 into the commercial varieties for durable resistance to multiple diseases.

Reduction of cadmium accumulation in the grains of male sterile rice Chuang-5S carrying Pi48 or Pi49 through marker-assisted selection.

To reduce cadmium (Cd) accumulation in the grains of rice Chuang-5S (C5S), a gene OsHMA3 and a QTL qlGCd3 related to low-Cd accumulation were separately introgressed into the recipient parent C5S (male sterile line) by molecular marker-assisted breeding. The recurrent parent C5S was then replaced by NIL (near-isogenic line)-C5S with the blast resistance gene Pi48 or Pi49 to construct the BC2F1 generation. Finally, two groups of improved materials of C5S, which pyramided the gene/QTL associated with low-Cd accumulation and blast resistance gene, were developed. The Cd accumulation, agronomic traits, genetic background and blast resistance of these improved C5S materials were evaluated. The results showed that the average Cd content of improved C5S material carrying OsHMA3 and qlGCd3 was, respectively, reduced by 52.8% and 50.8% compared with that of C5S, indicating that the gene related to low-Cd accumulation was, successfully, transferred to C5S with stable expression. The main agronomic traits of the improved materials were consistent with those of C5S. Besides, the improved C5S lines showed stronger blast resistance than C5S and more than 88% similarity to the genetic background of C5S. These two groups of improved materials may be further utilized for the breeding of advanced male sterile lines or superior hybrid rice.

Introgression of the Afila Gene into Climbing Garden Pea (Pisum sativum L.)

The pea (Pisum sativum L.) is one of the most important crops in temperate agriculture around the world. In the tropics, highland production is also common with multiple harvests of nearly mature seeds from climbing plant types on trellises. While the leafless variant caused by the afila gene is widely used in developing row-cropped field peas in Europe, its use for trellised garden peas has not been reported. In this study we describe a pea breeding program for a high-elevation tropical environment in the Department of Nariño in Colombia, where over 16,000 hectares of the crop are produced. The most widespread climbing varieties in the region are ‘Andina’ and ‘Sindamanoy’, both of which have high-biomass architecture with abundant foliage. They are prone to many diseases, but preferred by farmers given their long production season. This plant type is expensive to trellis, with wooden posts and plastic strings used for vine staking constituting 52% of production costs. The afila trait could reduce these costs by creating interlocking plants as they do in field peas. Therefore, our goal for this research was to develop a rapid breeding method to introduce the recessive afila gene, which replaces leaves with tendrils, into the two commercial varieties used as recurrent parents (RPs) with three donor parents (DPs)—‘Dove’, ‘ILS3575′ and ‘ILS3568′—and to measure the effect on plant height (PH) and yield potential. Our hypothesis was that the afila gene would not cause linkage drag while obtaining a leafless climbing pea variety. Backcrossing was conducted without selfing for two generations and plants were selected to recover recurrent parent characteristics. Chi-square tests showed a ratio of 15 normal leaved to one afila leaved in the BC2F2 plants, and 31:1 in the BC3F2 generation. Selecting in the last of these generations permitted a discovery of tall climbing plants that were similar to those preferred commercially, but with the stable leafless afila. The method saved two seasons compared to the traditional method of progeny testing before each backcross cycle; the peas reached the BC2F2 generation in five seasons and the BC3F2 in seven seasons. This is advantageous with trellised peas that normally require half a year to reach maturity. Leafless garden peas containing the afila gene were of the same height as recurrent parents and, by the third backcross, were equally productive, without the high biomass found in the traditional donor varieties. The value of the afila gene and the direct backcrossing scheme is discussed in terms of garden pea improvement and crop breeding.

Genetics of white rust resistance in Indian mustard (Brassica juncea L.) and its validation on using molecular markers

White rust resistance loci (AcB1-A4.1 and AcB1-A5.1) associated with intron polymorphic (IP) markers i.e. At5g41560 and At2g36360, respectively, were used for validation of P1, P2, F1, F2, BC1F1 and BC2F1 generations. The donor parents namely, Bio-YSR and BEC-144 produced desired banding pattern of 430 and 750 bp while recipients viz., NRCHB 101 and DRMR-150-35 exhibited different pattern from donors confirming white rust resistance loci 4.1 and 5.1 with marker At5g41560 and At2g36360, respectively. Confirmation of these set of two IP markers in the parents and F1s lead us to further screening of selected F2, BC1F1 and BC2F1 populations. Available data on white rust reaction in different generations under study revealed that single dominant gene is responsible for white rust resistance. Potential of molecular markers in developing white rust resistant genotypes is proved under present study.

Biofortification of sweet corn hybrids for provitamin-A, lysine and tryptophan using molecular breeding

Traditional sweet corn is poor in provitamin-A, lysine and tryptophan, deficiency of which causes serious health problems. Here, parental lines of two shrunken2 (sh2) -based sweet corn hybrids viz., ASKH-1 and ASKH-2 were targeted for introgression of crtRB1 and opaque2 (o2) genes through marker-assisted backcross breeding. Gene-based markers; umc1066 (SSR) and 3′TE-InDel were utilized for foreground selection of o2 and crtRB1, respectively in BC1F1, BC2F1 and BC2F2 generations. Background selection employing 102–113 polymorphic SSRs led to >90% recovery of recurrent parent genome. Reconstituted hybrids recorded high mean provitamin-A (18.98 μg/g) with a maximum of 7.7-fold increase over original hybrids (3.12 μg/g). High mean lysine (0.39%) and tryptophan (0.10%) with an average enhancement of 1.71- and 1.79-fold, respectively was recorded among reconstituted hybrids over original versions (lysine: 0.23%, tryptophan: 0.06%). Improved hybrids exhibited high phenotypic resemblance with their original hybrids. The average cob yield (11.82 t/ha) and brix (17.66%) of improved hybrids was at par with their original versions (cob yield: 11.27 t/ha, brix: 17.04%). These biofortified sweet corn hybrids rich in provitamin-A, lysine and tryptophan hold immense significance as multinutrient-rich balanced food. This is the first report to stack sh2, crtRB1 and o2 genes to improve nutritional quality in sweet corn.

Introgression of drought tolerance QTLs through marker assisted backcross breeding in wheat (Triticum aestivum L.)

The present study reports the introgression of the genomic regions linked with drought tolerance traits viz., NDVI, staygreen, chlorophyll content/chlorophyll fluorescence and yield from a drought tolerant parent HI1500 in to a popular high yielding but drought susceptible wheat variety GW322 following the marker assisted backcross breeding. Background selection with 109 polymorphic SSR markers accelerated genome recovery of recurrent parent which ranged from 72.14 to 86.9% in BC1F1, 90.33 to 92.02% in BC2F1 and 91.6 to 94.95% with an average of 93.5% in BC2F2 generation. Eighteen homozygous BC2F3 progenies were found to be phenotypically superior for morpho-physiological and agronomic traits over the recurrent parent GW322.

A novel leaf rust resistance gene introgressed from Aegilops markgrafii maps on chromosome arm 2AS of wheat.

A novel leaf rust resistance gene, LrM, introgressed from Aegilops markgrafii and mapped on chromosome 2AS using SSR- and SNP-based PCR markers will aid in broadening the genetic base of rust resistance in wheat. A new leaf rust resistance gene tentatively named LrM was introgressed from the diploid non-progenitor species Ae. markgrafii (2n = 2x = 14, genome CC) into common wheat using the nulli-5B mechanism. The introgression line ER9-700 showed a high degree of resistance against a wide spectrum of Puccinia triticina pathotypes. Genetic analysis was performed using the F1, F2, F2:3 and BC1F1 generations derived from the cross ER9-700/Agra Local. The results showed a single dominant gene for leaf rust resistance. The resistance gene LrM was mapped on chromosome arm 2AS using SSR- and SNP-based PCR markers. Preliminary mapping with SSR markers in the F2:3 population from the cross ER9-700/Agra Local identified two SSR markers flanking the LrM. SNPs were identified in the genomic region flanked by SSR markers, and SNP-based PCR markers were developed to construct the final map. Three SNP-based PCR markers co-segregated and mapped closest to the resistance gene at a distance of 2cM. The gene LrM was distinguished from all the other genes designated and mapped on chromosome arm 2AS by molecular markers and rust reaction. All five markers used in the mapping amplified identical alleles in the donor Ae. markgrafii accession and introgression line ER9-700. The chromosomal location and rust reaction suggest that LrM is a novel leaf rust resistance gene that may be useful in broadening the genetic base of leaf rust resistance in wheat.

Introgression of the bmr6 allele in biomass sorghum lines for bioenergy production

Sorghum bicolor (L.) Moench is a crop that has high potential to be used for bioenergy generation. The objective of this study was to introgression of the bmr6 allele in elite lines of biomass sorghum and to obtain experimental “brown midrib” hybrids. Three genetic materials belonging to the Embrapa Maize and Sorghum Breeding Program were used. Two backcross programs were conducted separately, in which the CMSXS170 line was the donor of the bmr6 allele and the CMSXS652 and IS23777 lines were the recurrent ones. Through molecular markers specific for the bmr6 allele, the assisted selection was utilized for the brown midrib characteristic in the BC1F1 and BC2F1 generations. Polymorphic SNP markers were distributed throughout the genome of sorghum to accelerate the recovery of the recurrent genome. After the confirmation of the bmr genotypes, the lines were crossed with line A (female), to obtain the hybrid seeds and evaluated under field conditions. As result, it was possible to perform the introgression of the bmr6 allele in lines of biomass sorghum. The SNPs markers were efficient in identifying individuals with a higher rate of recurrence of the recurrent genome. Experimental “brown midrib” hybrids were obtained and demonstrated satisfactory potential for bioenergy production.

Transfer of the ph1b gene of ‘Chinese Spring’ into a common wheat cultivar with excellent traits

In wheat/alien species hybrids, pairing homoeologous (Ph1) suppresses the pairing and recombination of wheat and alien chromosomes. Ph1b has been found to be the most effective allele in inducing meiotic homoeologous pairing/recombination and is widely used in gene introgression from wild Triticeae species into wheat. However, due to the poor agronomic traits of the ‘Chinese Spring’ ph1b (CS ph1b) mutant, which is more susceptible to disease, the application of CS ph1b is limited. In this study, we transferred the ph1b gene from the CS mutant to a commercial cultivar Shumai 126 (SM126), which has excellent agronomic traits, by crossing and continuous backcrossing. The results showed that the ph1b was present in 11 lines in the BC2F2 generation and was transferred to SM126. Further study indicated that seven homozygous ph1b mutant allele lines were identified from the BC2F3 generation. Two of these lines, SM126ph1b line 1 and 24, are homozygous at loci encoding high molecular weight glutenin subunits (HMW-GS) and the Wx protein, and the line 24 possesses the excellent agronomic traits of SM126. The results of meiotic metaphase I pairing showed that the SM126ph1b pollen mother cells (PMCs) are slightly higher pairing than the level of the original CSph1b stock. A progeny line of wild cross between wheat and Aegilops sharonensis was crossed with CSph1b and line 24 of SM126ph1b, respectively; the results of ND-FISH further proved that SM126ph1b and CSph1b have same effect on inducing homoeologous pairing/recombination, which will facilitate the use of wheat alien chromosome recombinations in wheat improvement.

Validation of QTLs for seed weight in a backcross population derived from an interspecific cross in soybean [Glycine max (L.) Merr.

Soybean [Glycine max (L.) Merr.] is a major oilseed crop of India. Seed weight is an important yield component trait which should be suitably optimized in soybean varieties to maximize productivity. To validate 100-seed weightquantitave trait loci (QTL), a backcross population of soybean was developed from a cross between wild species Glycine soja (Sieb. and Zucc.) and Indian soybean cultivar JS 335. The BC2 backcross population was evaluated for three yield component traits, namely 100-seed weight, number of seeds/plant and seed yield/plant in BC2F2, BC2F3 and BC2F4 generation. Six QTLs reported to be associated with 100-seed weight in soybean were selected for QTL validation. SSR markers linked with two major QTLs for 100-seed weight could be validated successfully. One QTL, on linkage group D1a between Satt580-Satt179, identified for 100-seed weight explained 19.18% ofphenotypic variance for combined data of three years. The second QTL for 100-seed weight was identified on linkage group C2 between marker Sat_251 and Sat_238 which contributed 10.97 and 9.28% of phenotypic variance in year 2015 and 2016, respectively.

Map-Based Functional Analysis of the GhNLP Genes Reveals Their Roles in Enhancing Tolerance to N-Deficiency in Cotton.

Nitrogen is a key macronutrient needed by plants to boost their production, but the development of cotton genotypes through conventional approaches has hit a bottleneck due to the narrow genetic base of the elite cotton cultivars, due to intensive selection and inbreeding. Based on our previous research, in which the BC2F2 generations developed from two upland cotton genotypes, an abiotic stress-tolerant genotype, G. tomentosum (donor parent) and a highly-susceptible, and a highly-susceptible, but very productive, G. hirsutum (recurrent parent), were profiled under drought stress conditions. The phenotypic and the genotypic data generated through genotyping by sequencing (GBS) were integrated to map drought-tolerant quantitative trait loci (QTLs). Within the stable QTLs region for the various drought tolerance traits, a nodule-inception-like protein (NLP) gene was identified. We performed a phylogenetic analysis of the NLP proteins, mapped their chromosomal positions, intron-exon structures and conducted ds/dn analysis, which showed that most NLP genes underwent negative or purifying selection. Moreover, the functions of one of the highly upregulated genes, Gh_A05G3286 (Gh NLP5), were evaluated using the virus gene silencing (VIGS) mechanism. A total of 226 proteins encoded by the NLP genes were identified, with 105, 61, and 60 in Gossypium hirsutum, G. raimondii, and G. arboreum, respectively. Comprehensive Insilico analysis revealed that the proteins encoded by the NLP genes had varying molecular weights, protein lengths, isoelectric points (pI), and grand hydropathy values (GRAVY). The GRAVY values ranged from a negative one to zero, showing that proteins were hydrophilic. Moreover, various cis-regulatory elements that are the binding sites for stress-associated transcription factors were found in the promoters of various NLP genes. In addition, many miRNAs were predicted to target NLP genes, notably miR167a, miR167b, miR160, and miR167 that were previously shown to target five NAC genes, including NAC1 and CUC1, under N-limited conditions. The real-time quantitative polymerase chain reaction (RT-qPCR) analysis, revealed that five genes, Gh_D02G2018, Gh_A12G0439, Gh_A03G0493, Gh_A03G1178, and Gh_A05G3286 were significantly upregulated and perhaps could be the key NLP genes regulating plant response under N-limited conditions. Furthermore, the knockdown of the Gh_A05G3286 (GhNLP5) gene by virus-induced silencing (VIGS) significantly reduced the ability of these plants to the knockdown of the Gh_A05G3286 (GhNLP5) gene by virus-induced gene silencing (VIGS) significantly reduced the ability of the VIGS-plants to tolerate N-limited conditions compared to the wild types (WT). The VIGS-plants registered lower chlorophyll content, fresh shoot biomass, and fresh root biomass, addition to higher levels of malondialdehyde (MDA) and significantly reduced levels of proline, and superoxide dismutase (SOD) compared to the WT under N-limited conditions. Subsequently, the expression levels of the Nitrogen-stress responsive genes, GhTap46, GhRPL18A, and GhKLU were shown to be significantly downregulated in VIGS-plants compared to their WT under N-limited conditions. The downregulation of the nitrogen-stress responsive genes provided evidence that the silenced gene had an integral role in enhancing cotton plant tolerance to N-limited conditions.

Pentaploid Apomicts by Interspecific Hybridization between Diploid Urochloa ruziziensis and Tetraploid Apomictic U. decumbens

ABSTRACTUrochloa species are a rich source of quality forage in the tropical and subtropical areas, and cultivated species are predominantly facultative apomictic. They are well adapted to poor soil conditions, resistant to heavy grazing, and drought tolerant, but some Urochloa species produce poor pasture and seed yield. Therefore, it is important to complement and to combine characteristics of different species in breeding programs. We have conducted interspecific crosses between diploid U. ruziziensis (R. Germ. & C. M. Evrard) Crins ‘Kennedy’ (2n = 2x = 18) with apomictic tetraploids U. decumbens (Stapf) R. D. Webster ‘Basilisk’ (2n = 4x = 36) and U. brizantha (Hochst. ex A. Rich.) R. D. Webster ‘Marandu’ (2n = 4x = 36). Diploid, triploid, and tetraploid plants were obtained from these crosses. The triploid plants were further crossed with ‘Basilisk’ to produce a BC1F1 generation. Although no seeds were produced by self‐pollination of the F1 triploid hybrids, backcrossing eventually produced triploid, tetraploid, and pentaploid plants (BC1F1). Only the pentaploid plants produced seeds by self‐pollination. This is the first report of the production of apomictic pentaploid progenies from interspecific crosses in Urochloa.

Introgression of Root and Water Use Efficiency Traits Enhances Water Productivity: An Evidence for Physiological Breeding in Rice (Oryza sativa L.)

BackgroundSemi-irrigated aerobic cultivation of rice has been suggested as a potential water saving agronomy. However, suitable cultivars are needed in order to sustain yield levels. An introgression of water mining and water use efficiency (WUE) traits is the most appropriate strategy for a comprehensive genetic enhancement to develop such rice cultivars.ResultsWe report a novel strategy of phenotyping and marker-assisted backcross breeding to introgress water mining (root) and water use efficiency (WUE) traits into a popular high yielding cultivar, IR-64. Trait donor genotypes for root (AC-39020) and WUE (IET-16348) were crossed separately and the resultant F1s were inter-mated to generate double cross F1s (DCF1). Progenies of three generations of backcross followed by selfing were charatcerised for target phenotype and genome integration. A set of 260 trait introgressed lines were identified. Root weight and root length of TILs were 53% and 23.5% higher, while Δ13C was 2.85‰ lower indicating a significant increase in WUE over IR-64. Five best TILs selected from BC3F3 generation showed 52% and 63% increase in yield over IR-64 under 100% and 60% FC, respectively. The trait introgressed lines resembled IR64 with more than 97% of genome recovered with a significant yield advantage under semi-irrigated aerobic conditions The study validated markers identified earlier by association mapping.ConclusionIntrogression of root and WUE into IR64, resulted in an excellent yield advantage even when cultivated under semi-irrigated aerobic condition. The study provided a proof-of-concept that maintaining leaf turgor and carbon metabolism results in improved adaptation to water limited conditions and sustains productivity. A marker based multi-parent backcross breeding is an appropriate approach for trait introgression. The trait introgressed lines developed can be effectively used in future crop improvement programs as donor lines for both root and WUE.

Segregation distortion in cotton

A BC2F1 population was developed from the cross between Gossypium hirsutum (AADD), the most widely cultivated cotton species, and G. armourianum, a non-progenitor D-genome wild species, (using G. hirsutum as the recurrent parent) in order to transfer some useful characteristics from G. armourianum. Here, we report the pattern of transmission of the donor G. armourianum alleles in the backcross derivatives. Of the 100 SSR markers used to document polymorphism between the parents, 52 were observed to be polymorphic. Eight (15.4%) of these 52 markers were amplified in the BC1F1 plant in contrast to the expected Mendelian ratio of 50%, thus showing segregation distortion. The range of transmission of these markers in BC2F1 generation varied from 38.1% through 75.0%. Two SSR markers namely TMB 1271 and NAU 6316 followed non-Mendelian segregation and were transmitted in higher frequency than expected in the BC2F1 progeny.

Assessment of genetic variability, heritability and genetic advance in backcross population of BC1F1, BC2F1 and BC2F2 in maize

Genetic variability, heritability and genetic advance are the important factors which provides the knowledge about the nature of traits in breeding programme. The aim of this study is to estimate the genetic variability, heritability, and genetic advance in the backcross population of UMI1200β+ × HKI163 and UMI1230β+ × HKI163 to identify the individuals in the population with superior agronomic traits. Fourteen biometrical traits were analysed and thus revealed that all the backcross (BC1F1, BC2F1) and selfed (BC2F2) generations, phenotypic coeffiecient of variation is higher than the genotypic coefficient of variation. Highest heritability combined with genetic advance as percent of mean was observed in BC2F2 generation for 100 kernel weight (UMI1200β+ × HKI163) and single plant yield (UMI1230β+ × HKI163). Hence, the genetic gain of the individuals in the population are controlled by additive gene action.

Lai tạo và tuyển chọn các dòng lúa chịu mặn từ tổ hợp lai hồi giao OM238/Pokkali

The hybridization and selection of salt tolerant and good quality rice varieties are the criteria for the current situation of climate change such as the present. Therefore, this study have transferred salinity tolerant genes of Pokkali to a good quality rice OM238 to determine the rice lines having both salinity tolerance and good quality. This study was caried out to: (1) to evaluate salinity tolerance phenotype by screening in artificial saline medium, (2) to test salinity tolerance gene by SSR technique, (3) to evaluate agronomic characteristics and grain quality based on International Rice Research Institute (IRRI) method. Breeding and selection to BC3F3 generation, then planted to tested at salty fields in BC3F4 and BC3F5 generations. The result revealed that two rice lines in the BC3F6 generation with both the salinity tolerant genes of Pokkali by RM1287 and high iron content in rice, amylose content £ 20%, gel consistency at group 1 (soft rice), low chalikiness of endosperm £ 8%, the long and slender rice grain to develop salinity tolerance and good quality rices.

Genome composition and pollen viability of Jatropha (Euphorbiaceae) interspecific hybrids by Genomic In Situ Hybridization (GISH).

Interspecific hybridization is required for the development of Jatropha curcas L. improved cultivars, due to its narrow genetic basis. The present study aimed to analyze the parental genomic composition of F1 and BC1F1 generations derived from interspecific crosses (J. curcas/J. integerrima and J. curcas/J. multifida) by GISH (Genomic In Situ Hybridization), and the meiotic index and pollen viability of F1 hybrids. In F1 cells from both hybrids, 11 chromosomes of each parental was observed, as expected, but chromosome rearrangement events could be detected using rDNA chromosome markers, suggesting unbalanced cells. In the BC1F1, both hybrids had 22 chromosomes, suggesting that only n = 11 gametes were viable in the next generation. However, GISH allowed the identification of three and two alien chromosomes in J. curcas//J. integerrima and J. curcas//J. multifida BC1F1 hybrids, respectively, suggesting a preferential transmission of J. curcas chromosomes for both hybrids. Pollen viability in F1 hybrids derived from J. curcas/J. integerrima crosses were higher (82-83%) than those found for J. curcas/J. multifida (68%), showing post-meiotic problems in these last hybrids, with dyads, triads, polyads, and micronuclei as post-meiosis results. The here presented cytogenetic characterization of interspecific hybrids and their backcross progenies can contribute to the selection of the best genotypes for future assisted breeding of J. curcas.

Distribution of genes producing phenol colour reaction in grains of wheat and its related species, mode of inheritance and breeding for low polyphenol activity

One of the important chapati quality traits pertains to the darkening of whole meal dough and its subsequent effect on browning of chapatis (unleavened Indian bread). The grain pericarp of most of the bread wheat varieties grown in India reacts to phenolic compounds and produce dark brown or brown colour. The present investigation undertook a most intriguing challenge to breed a variety, which do not react to phenol and does not darken the dough. A large number of wild wheat species, bread wheat cultivars, durum wheat and synthetic hexaploid (SH) wheat were screened to identify wheat genotype(s) with negative reaction to phenol. A variety of phenol reactions were recorded among the wheat species having different genomes. Most of the Aegilops squarrosa and Triticum timopheevi accessions showed negative colour reaction. Two phenol non-reactive (-ve) SH wheats (SH26 and SH32) were crossed with hexaploid bread wheat variety, HD 2851 with positive reaction (+ve) to phenol. Phenol test of F1 grains reacted positively and produced dark brown colour on pericarp indicating that the phenol colour reaction is a dominant trait. The F2 population segregated into two categories where the grains of 746 plants developed colour and 13 were non reactive (-ve colour or no colour). The Chi-square analysis revealed that development of phenol colour in grains is governed by three dominant alleles as the observed frequency of plants fit well into theoretical ratio of 63 (+ve) : 1 (-ve). The subsequent BC1-F2 and BC2-F2 generations were simultaneously tested with phenol to facilitate selection of the genotypes with –ve reaction. A few genetic stocks and selections derived from multi-parent-cross did not develop colour upon testing with polyphenol. These genetic stocks have been improved further in respect of other agronomic traits. In Addition, an alternative chemical to phenol was discovered, which gave comparable results, safer to use, would not affect germinability adversely and thus amenable to high through put application in breeding programme.