Characterization of <Emphasis Type="Italic">opaque2</Emphasis> modifier QTLs and candidate genes in recombinant inbred lines derived from the K0326Y quality protein maize inbred

Quality protein maize (QPM) is a high lysine-containing corn that is based on genetic modification of the opaque2 (o2) mutant. In QPM, modifier genes convert the starchy endosperm of o2 to the vitreous phenotype of wild type maize. There are multiple, unlinked o2 modifier loci (Opm) in QPM and their nature and mode of action are unknown. We previously identified seven Opm QTLs and characterized 16 genes that are differentially up-regulated at a significant level in K0326Y QPM, compared to the starchy endosperm mutant W64Ao2. In order to further characterize these Opm QTLs and the genes up-regulated in K0326Y QPM, we created a population of 314 recombinant inbred lines (RILs) from a cross between K0326Y QPM and W64Ao2. The RILs were characterized for three traits associated with endosperm texture: vitreousness, density and hardness. Genetic linkage analysis of the RIL population confirmed three of the previously identified QTLs associated with o2 endosperm modification in K0326Y QPM. Many of the genes up-regulated in K0326Y QPM showed substantially higher levels of expression in vitreous compared with opaque RILs. These included genes associated with the upstream regulation of the ethylene response pathway, and a gene encoding a regulatory subunit of pyrophosphate-dependent fructose-6-phosphate 1-phosphotransferase, an adaptive enzyme of the glycolytic pathway.     

Endosperm Protein Quality and Kernel Modification in the Quality Protein Maize Inbred Lines

Twenty-two selected quality protein maize (QPM) lines, including 13 lines developed in India (DMRQPM series) and nine lines released by CIMMYT, Mexico (CML series), were evaluated for their endosperm protein content and quality, besides kernel modification in terms of vitreousness. Endosperm protein contents in 13QPMlines were on par or better than that of the normal maize ‘checks’ (Trishulata and Parkash). The QPM endosperm proteins showed significantly higher % tryptophan as well as EF-1α (a multifunctional protein with a positive and highly significant correlation with lysine content in the endosperm) contents, in comparison with the normal maize genotypes. Evaluation of kernel modification revealed considerable scope for accumulation of endosperm modifiers in some of the QPM lines. Positive and highly significant correlation was revealed between tryptophan and EF-1α contents in the endosperm proteins, whereas the correlations between the quality parameters with kernel modification in the QPM genotypes were found to be non-significant. The study led to the identification of some promising QPM lines, such as DMRQPM-37, DMRQPM-44, CML176, CML142 and CML149, which could be effectively deployed in the QPM breeding programmes.     

Temporal profiling of essential amino acids in developing maize kernel of normal,opaque - 2 and QPM germplasm

Maize, an important cereal crop, has a poor quality of endosperm protein due to the deficiency of essential amino acids, especially lysine and tryptophan. Discovery of mutants such as opaque-2 led to the development of nutritionally improved maize with a higher concentration of lysine and tryptophan. However, the pleiotropic effects associated with opaque-2 mutants necessitated the development of nutritionally improved hard kernel genotype, the present-day quality protein maize (QPM). The aim of present study was to analyze and compare the temporal profile of lysine and tryptophan in the developing maize kernel of normal, opaque-2 and QPM lines. A declining trend in protein along with tryptophan and lysine content was observed with increasing kernel maturity in the experimental genotypes. However, opaque-2 retained the maximum concentration of lysine (3.43) and tryptophan (1.09) at maturity as compared to QPM (lysine-3.05, tryptophan-0.99) and normal (lysine-1.99, tryptophan-0.45) lines. Opaque-2 mutation affects protein quality but has no effect on protein quantity. All maize types are nutritionally rich at early stages of kernel development indicating that early harvest for cattle feed would ensure a higher intake of lysine and tryptophan. Two promising lines (CML44 and HKI 1105) can be used for breeding high value corn for cattle feed or human food in order to fill the protein inadequacy gap. Variation in lysine and tryptophan content within QPM lines revealed that differential expression of endosperm modifiers with varying genetic background significantly affects nutritional quality, indicating that identification of alleles affecting amino acid composition can further facilitate QPM breeding program.     

Identification of opaque-2 genotypes in segregating populations of Quality Protein Maize by analysis of restriction fragment length polymorphisms

Quality Protein Maize (QPM) is a name given to genetically modified opaque-2 maize with hard endosperm. The opaque-2 mutation conditions a reduction in the amount of zein seed storage protein; zeins are deficient in the essential amino acids lysine and tryptophan, and mutant seed have a higher nutritional value. To utilize the potential of opaque-2 maize, elite inbreds can be converted to o2/o2 forms and subsequently to hard endosperm opaque-2. Since opaque-2 is recessive and endosperm specific, conventional backcross procedures to convert elite inbreds to opaque-2 forms are inefficient. To alleviate this problem, a marker-assisted selection procedure was developed for the Texas A&M University Quality Protein Maize breeding program. Hybridization of an O2 cDNA probe to blots of DNA from plants carrying O2 and o2 alleles showed that restriction fragment length polymorphisms (RFLPs) exist between the W64A o2 allele and O2 alleles of Mo17 and TX5855 inbred lines. To identify the opaque2 genotypes in segregating populations, an RFLP marker assay combining the O2 cDNA probe and HindIII-digestion of genomic DNA was developed. The effectiveness of the O2 RFLP marker assay was tested under field conditions using F₂ and backcross populations of several hard endosperm opaque-2 lines. A comparison of the genotypes identified by RFLP analysis with the seed phenotypes of the next generation indicated that this procedure is accurate and can be used for identifying O2/O2, O2/o2, and o2/o2 genotypes of individual juvenile plants in breeding populations.     

Genetic analysis of opaque2 modifier loci in quality protein maize

Quality protein maize (QPM) was created by selecting genetic modifiers that convert the starchy endosperm of an opaque2 (o2) mutant to a hard, vitreous phenotype. Genetic analysis has shown that there are multiple, unlinked o2 modifiers (Opm), but their identity and mode of action are unknown. Using two independently developed QPM lines, we mapped several major Opm QTLs to chromosomes 1, 7 and 9. A microarray hybridization performed with RNA obtained from true breeding o2 progeny with vitreous and opaque kernel phenotypes identified a small group of differentially expressed genes, some of which map at or near the Opm QTLs. Several of the genes are associated with ethylene and ABA signaling and suggest a potential linkage of o2 endosperm modification with programmed cell death.     

Influence of genotype and texture on zein content in endosperm of maize grains

The effect of genotypes and texture on the content of proteins in maize grains was examined by assessing absolute amounts of six protein fractions in the whole endosperms of four wild‐type lines with high protein content and four quality protein maize (QPM) varieties and for hand‐dissected hard and soft endosperm regions from eight other lines. As previously reported for six wild‐type lines and their opaque‐2(o2) versions, zeins were predominant for all genetic backgrounds and all types of endosperms. From these data and others the amounts of zeins and true proteins (crude proteins free of non‐protein nitrogen) in developing and mature endosperms of wild‐type lines were correlated. The data points for zeins from hard endosperms lay between the regression line and the upper limit of confidence area. Those for zeins from soft endosperms were located at the lower part of confidence area and on a level with the points corresponding to the most immature endosperms. Furthermore, some data points for zeins from o2 and QPM samples lay near the lower limit while the others were outside the confidence area. This suggested an initial zein accumulation dependent on the genotype at a low relative rate, followed by an accumulation at higher rate. The conditions used for isolating and quantitating zeins are discussed.     

Molecular genetic approaches to developing quality protein maize

Since its development more than two decades ago, Quality Protein Maize (QPM) has been adopted for cultivation in many regions of the developing world. Given the potential benefits of widespread use of QPM, research to better understand the genetic and biochemical mechanisms responsible for its altered kernel texture and protein quality is important. Recent investigations into the improved protein quality of the opaque2 mutant and the genetic mechanisms that can suppress its starchy kernel phenotype provide new insights to support the continued improvement of QPM. Chief among these developments are the use of transgenic approaches to improve nutritional quality and the discovery that an important component of modified endosperm texture in QPM is related to altered starch granule structure.     

In vitro plant regeneration from quality protein maize (QPM)

Breeding efforts to obtain more nutritious maize materials aimed at alleviating dietary deficiencies in developing countries have resulted in an improved maize germplasm known as quality protein maize (QPM). Quality protein maize has higher contents of tryptophan, lysine, and leucine than common maize, but suffers from some major agronomic drawbacks found in common inbred maize lines, such as susceptibility to insect pests and fungal and bacterial diseases and herbicide sensitivity. The development of a reproducible and efficient protocol for tissue culture of QPM is expected to solve some of these deficiencies. In this work, we have evaluated different formulations for in vitro induction of morphogenic responses in three QPM lines developed by the International Maize and Wheat Improvement Center (CIMMYT): CML (CIMMYT maize line)-145, CML-176, and CML-186. Only CML-176 and CML-186 have proven to be responsive to the in vitro conditions considered in this work, with CML-176 showing the highest efficiency in regenerable callus formation and growth. N6C1 medium was found to be efficient for in vitro culture of QPM, whereas no plants could be regenerated by using MPC medium. From CML-176 embyogenic calli cultured on N6C1 medium, we were able to regenerate up to 0.3 plants per 500 mg fresh weight (FW) callus. Further modifications in this experimental protocol, including the replacement of 3,6-dichloro-o-anisic acid with 2,4-dichlorophenoxyacetic acid and modification of the N6C1 vitamin balance, significantly increased the regeneration response of the induced calli, with up to 16.8 and 9.3 plants recovered per 500 mg FW callus for CML-176 and CML-186, respectively.     

Genetic analysis of opaque2 modifier gene activity in maize endosperm

Modifier genes have been described that convert the soft endosperm of opaque2 mutants to a hard, vitreous phenotype. The mode of action and the components of the genetic system involved in this seed modification are poorly understood. We used genetic and biochemical analyses to investigate the number of opaque2 modifier genes, their mode of action and their relationship to the biochemical alterations in the modified endosperm. Using two inbred opaque2 lines, we showed that the activity of opaque2 modifier genes is influenced by the genetic background. Analysis of segregating progenies and recombinant inbred lines derived from crosses between opaque2 and modified opaque2 genotypes indicated two independent loci affecting seed opacity and density. Consistent association between endosperm modification and enhanced accumulation of the gamma-zein storage protein suggested that either this protein is directly involved in the process of seed modification, or else that a modifier gene could be tightly linked to the genes responsible for gamma-zein synthesis.     

A major QTL for resistance to Gibberella stalk rot in maize

Fusarium graminearum Schwabe, the conidial form of Gibberella zeae, is the causal fungal pathogen responsible for Gibberella stalk rot of maize. Using a BC₁F₁ backcross mapping population derived from a cross between ‘1145’ (donor parent, completely resistant) and ‘Y331’ (recurrent parent, highly susceptible), two quantitative trait loci (QTLs), qRfg1 and qRfg2, conferring resistance to Gibberella stalk rot have been detected. The major QTL qRfg1 was further confirmed in the double haploid, F₂, BC₂F₁, and BC₃F₁ populations. Within a qRfg1 confidence interval, single/low-copy bacterial artificial chromosome sequences, anchored expressed sequence tags, and insertion/deletion polymorphisms, were exploited to develop 59 markers to saturate the qRfg1 region. A step by step narrowing-down strategy was adopted to pursue fine mapping of the qRfg1 locus. Recombinants within the qRfg1 region, screened from each backcross generation, were backcrossed to ‘Y331’ to produce the next backcross progenies. These progenies were individually genotyped and evaluated for resistance to Gibberella stalk rot. Significant (or no significant) difference in resistance reactions between homozygous and heterozygous genotypes in backcross progeny suggested presence (or absence) of qRfg1 in ‘1145’ donor fragments. The phenotypes were compared to sizes of donor fragments among recombinants to delimit the qRfg1 region. Sequential fine mapping of BC₄F₁ to BC₆F₁ generations enabled us to progressively refine the qRfg1 locus to a ~500-kb interval flanked by the markers SSR334 and SSR58. Meanwhile, resistance of qRfg1 to Gibberella stalk rot was also investigated in BC₃F₁ to BC₆F₁ generations. Once introgressed into the ‘Y331’ genome, the qRfg1 locus could steadily enhance the frequency of resistant plants by 32–43%. Hence, the qRfg1 locus was capable of improving maize resistance to Gibberella stalk rot.     

Molecular genetic mapping of a high-lysine mutant gene (<Emphasis Type="Italic">opaque-16</Emphasis>) and the double recessive effect with <Emphasis Type="Italic">opaque-2</Emphasis> in maize

The lysin content in maize endosperm protein is considered to be one of the most important traits for determining the nutritional quality of food and feed. Improving the protein quality of the maize kernel depends principally on finding a mutant with a higher lysine content. Two high-lysine mutant lines with opaque endosperm, QCL3024 and QCL3021, were isolated from a self-cross population derived from Robertsons Mutator stocks. The gene controlling this mutation is temporarily termed opaque-16 (o16). In order to illuminate the genetic locus and effect of the o16 gene, two F_2:3 populations, one developed from a cross between QCL3024 and QCL3010 (a wild type line) and another from a cross between Qi205 (opaque-2 line) and QCL3021, were created, and F₃ seeds from the F₂ plants in the two populations were evaluated for lysine content. The distributions of lysine content and tests for their normality indicate that the lysine content in the two populations is regulated by the major gene of o16 and genes of o2 and o16, respectively. Based on two data sets of the linkage maps of the F₂ plant marker genotypes and the lysine content of F₃ seeds originating from the two F_2:3 populations, the o16 gene was located within 5 cM, at either 3 or 2.2 cM from umc1141 in the interval between umc1121 and umc1141 on the long arm of chromosome 8, depending on the recombination rate in the two populations as determined by composite interval mapping. According to the data of the F_2:3 population constructed from the o2 and o16 lines, the double recessive mutant effect was analyzed. The average lysine content of the F₃ o2o2o16o16 families identified by the umc1066 and umc1141 markers was approximately 30% higher than that of the F₃ o2o2 and o16o16 families, respectively. The lysine content of seven F₃ families among nine F₃ double recessive mutant families showed different increments, with an average increase of some 6% compared with that of the maternal o2 line. The potential application of the o16 mutant for maize high-lysine breeding may be to combine it with the o2 mutant bearing modifier genes, thus obtaining a mutant with much higher lysine content. For the purpose of pyramiding the o16 with o2 genes, the availability of closely linked markers of the o16 and o2 loci will facilitate marker-assisted selection and greatly reduce breeding time and effort.     

Mapping QTL controlling maize deep-seeding tolerance-related traits and confirmation of a major QTL for mesocotyl length

Deep-seeding tolerant seeds can emerge from deep soil where the moisture is suitable for seed germination. Breeding deep-seeding tolerant cultivars is becoming increasingly important in arid and semi-arid regions. To dissect the quantitative trait loci (QTL) controlling deep-seeding tolerance traits, we selected a tolerant maize inbred line 3681-4 and crossed it with the elite inbred line-X178 to generate an F₂ population and the derivative F_2:3 families. A molecular linkage map composed of 179 molecular markers was constructed, and 25 QTL were detected including 10 QTL for sowing at 10 cm depth and 15 QTL for sowing at 20 cm depth. The QTL analysis results confirmed that deep-seeding tolerance was mainly caused by mesocotyl elongation and also revealed considerable overlap among QTL for different traits. To confirm a major QTL on chromosome 10 for mesocotyl length measured at 20 cm depth, we selected and self-pollinated a BC₃F₂ plant that was heterozygous at the markers around the target QTL and homozygous at other QTL to generate a BC₃F₃ population. We found that this QTL explained more phenotypic variance in the BC₃F₃ population than that in the F₂ population, which laid the foundation for fine mapping and NIL (near-isogenic line) construction.     

Marker-assisted selection and evaluation of high oil in vivo haploid inducers in maize

Doubled haploid technology, which is used to rapidly purify genetic resources, is one of the key technologies in modern maize breeding. In a previous study, the major quantitative trait locus qhir1, which influences in vivo haploid induction, was narrowed down to a 243-kb region, which made it feasible to use marker-assisted selection (MAS) for inducer development. Recently, a new method was developed for haploid identification using oil content (OC). The objective of this study was to develop high oil inducer lines using MAS of the qhir1 locus. We constructed an F₂ population, two backcross populations that were backcrossed to the inducer CAU5 (BC₁F₁-CAU5) and the high oil inbred line GY923 (BC₁F₁-GY923), respectively, which was derived from the cross GY923 × CAU5, and subjected continuous selfing to develop high oil inducer lines. In each cycle, three different parameters including kernel OC, marker genotype at qhir1 and haploid induction rate (HIR) were used for pedigree selection. Three candidate high oil inducer lines were developed, with an OC of approximately 8.5 %, an HIR of approximately 8 % and superior agronomic performance, which are suitable values for the application of these lines to haploid identification by OC. Our results confirm the notion that HIR selection combined with MAS for qhir1 is an effective approach to haploid inducer breeding. In addition, we determined that the accuracy of haploid identification by OC is influenced by the female germplasm resource and the high oil inducer and that appropriate critical points for OC can balance the false discovery rate and false negative rate.     

Transformation to telephonic genetic counselling during SARS-CoV-2 pandemic: challenges and suggested protocol in Indian scenario

To combat the dreaded diseases in rice like bacterial blight (BB) and blast, host plant resistance has been advocated as the most suitable and sustainable method. Through the present study, we have successfully incorporated three major BB resistance genes, namely Xa21, xa13 and xa5 into NLR3449, a high yielding, blast resistant, fine-grain type, popular rice variety through marker-assisted backcross breeding. Foreground selection was carried out using polymerase chain reaction based, gene-specific markers, namely pTA248 (Xa21), xa13prom (xa13) and xa5FM (xa5) at each generation of backcrossing, while 127 polymorphic SSR markers spanning on 12 chromosomes were used for background selection and backcrossing was limited to two rounds. At BC₂F₁ generation, a single plant (NLR-87-10) with 89.9% recovery, possessing all the three BB resistance genes was forwarded to BC₂F₂ generation. A solitary BC₂F₂ plant, namely NLR-87-10-106 possessing all the three resistance genes and 96% genome recovery was identified and advanced through selfing until BC₂F₄ generation by adopting pedigree-method of selection. Three best BC₂F₄ lines, possessing high level of resistance against BB and blast, and equivalent or superior to NLR 34449 in terms of yield, grain quality and agro-morphological traits were identified and advanced for multi-location trials.

     

Fine-mapping of <Emphasis Type="Italic">qRfg2</Emphasis>, a QTL for resistance to <Emphasis Type="Italic">Gibberella</Emphasis> stalk rot in maize

Stalk rot is one of the most devastating diseases in maize worldwide. In our previous study, two QTLs, a major qRfg1 and a minor qRfg2, were identified in the resistant inbred line ‘1145’ to confer resistance to Gibberella stalk rot. In the present study, we report on fine-mapping of the minor qRfg2 that is located on chromosome 1 and account for ~8.9% of the total phenotypic variation. A total of 22 markers were developed in the qRfg2 region to resolve recombinants. The progeny-test mapping strategy was developed to accurately determine the phenotypes of all recombinants for fine-mapping of the qRfg2 locus. This fine-mapping process was performed from BC₄F₁ to BC₈F₁ generations to narrow down the qRfg2 locus into ~300 kb, flanked by the markers SSRZ319 and CAPSZ459. A predicted gene in the mapped region, coding for an auxin-regulated protein, is believed to be a candidate for qRfg2. The qRfg2 locus could steadily increase the resistance percentage by ~12% across different backcross generations, suggesting its usefulness in enhancing maize resistance against Gibberella stalk rot.     

Developmental expression of genetically defined peptidases in maize

The activities of genetically defined amino- and endopeptidases of maize were compared in pericarp, endosperm, and embryonic tissue of the maize kernel from 5 days postpollination until harvest. Activities were highest in the immature stages and declined as drying progressed. The expression of some of the peptidase genes contributed by the pollen parent was examined during early endosperm development in an F₁ cross. The paternally contributed peptidase variants could first be detected 7 days after pollination.     

Some genetic and biochemical characteristics of a new source of maize opaque-2 mutant

Summary The opaque kernels separated from the F₁ of crosses of our opaque-2 strains with normal inbred lines contained 45, 50 and 74 percent more lysine in the whole kernel than the translucent kernels from the same ear. The opaque kernels from these crosses contained almost the same level of lysine as the parental opaque-2 strains.Some of our opaque-2 strains contain 63 to 122 percent more lysine than the tested dent or flint normal inbred lines. In comparison with opaque-2 Purdue, four opaque-2 strains had almost the same lysine content and a strain labelled as SP-1 No. 15 contained 25 percent more lysine and 73 percent more tryptophan. Some of our opaque-2 strains contained 55 to 100 percent more tryptophan in the whole kernel than opaque-2 Purdue.In contrast to lysine content, the transmission of the tryptophan content from opaque-2 strains to opaque kernels from their crosses shows variability.We found weak positive correlation (r = +0,3057) between lysine and tryptophan content in opaque-2 kernels.Our opaque-2 strains had a higher lysine content in the endosperm than did opaque-2 Purdue 22.1 – 36.6% more, and compared with normal lines they had 109.5 – 142.6% more.It is apparent that a new source of opaque-2 mutant gene, which has the same genetic and biochemical characteristics as the opaque-2 mutant discovered by Mertz, Bates and Nelson (1964), has been found in a completely new, genetically divergent, strain derived from a large number of populations.

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Zusammenfassung Die vorgenommenen Prüfungen haben gezeigt, daß undurchsichtige Körner, die nach F₁-Kreuzung unserer Opaque 2-Linien mit Normallinien ausgelesen wurden, 45, 50 und sogar 74% mehr Lysin im ganzen Korn als normale durchsichtige Körner desselben Maiskolbens enthalten. Der Lysingehalt der undurchsichtigen Körner aus diesen Kreuzungen entspricht annähernd dem der Opaque 2-Elternlinien.Einige unserer Opaque 2-Linien enthalten 63 bis 122% mehr Lysin als die untersuchten normalen Inzuchtlinien. Im Vergleich zu Opaque 2 — Purdue weisen unsere 4 Opaque 2-Linien einen etwa gleichen Lysingehalt auf, während die SP-1 No. 15 25% mehr Lysin und 73% Tryptophan enthält. Unsere Opaque 2-Linien zeigen im ganzen Korn 55 bis 100% mehr Tryptophan als Opaque 2 — Purdue.Im Unterschied zum Lysingehalt zeigt die Übertragung des Tryptophangehalts von Opaque 2-Linien auf undurchsichtige Körner bei den Kreuzungen Variabilität.Wir fanden eine schwach positive Korrelation (r = + 0,3057) zwischen dem Lysin- und Tryptophangehalt bei den Opaque 2-Köinern.Unsere Opaque 2-Linien hatten mehr Lysin im Endosperm als Opaque 2-Purdue, und zwar 22,1 bis 36,6% bzw. 109,5 bis 142,6% im Vergleich zu den normalen Linien.Offensichtlich ist eine neue Quelle für das mutante Opaque 2-Gen in einer ganz neuen, genetisch unterschiedlichen Synthese einer großen Anzahl von Populationen entdeckt worden. Die neue Quelle hat dieselben genetischen und biochemischen Merkmale wie die Opaque 2-Mutante, die von Mertz, Bates und Nelson (1964) aufgefunden wurde.

     

Identification and fine-mapping of a bacterial brown spot disease resistance gene in maize

Bacterial brown spot (BBS) in maize (Zea mays L.) is caused by Pseudomonas syringae pv. syringae Van Holl (Pss). In China, this disease is not prevalent in maize at present. Here, we report the identification and fine mapping of the gene, referred to as Psy1, which confers resistance to BBS. An F₂ population, derived from the cross P25/F349, was used for linkage analysis and mapping of the resistance gene Psy1. Analysis of a BC₈F₂ population, derived from the same parents, confirmed that Psy1 was located on chromosome 10L and inherited as a single dominant gene. For fine mapping of Psy1, two introgression lines, X41 and X44, homozygous at the resistant gene locus, were introduced to hybridize with the susceptible parent P25 respectively, and developed a mixed BC₁ population. We found the closest markers to Psy1 are EST1 and FG29-3, which located on two adjacent BACs respectively, based on the B73 BAC sequence. Sequence analysis of these two BAC sequences (~300 kb) revealed the presence of a homologous sequence of receptor-like kinase. Also a co-segregation marker was developed based on this homologous sequence. These results will be useful for cloning of Psy1 and for transferring or pyramiding Psy1 through MAS in maize breeding programs.     

Analysis of transgene(s) (psy+crtI) inheritance and its stability over generations in the genetic background of indica rice cultivar Swarna

Rice the major staple food crop which feeds more than half of the world’s population but, lacks pathway to synthesize and accumulate provitamin A in endosperm therefore rice eaters particularly children, and pregnant women suffer due to vitamin A deficiency. The pathway for provitamin A synthesis in rice endosperm has been engineered and transgenic rice lines have yellow endosperm, called ‘Golden Rice’. The present study aimed at studying the inheritance of transgene(s) in six transgenic events of ‘Golden Rice’ and transfer of provitamin A trait from transgenic lines to a widely grown mega rice variety Swarna. The events E1, R1 and W1 showed normal Mendelian inheritance in F₂, BC₁F₁ and BC₁F₂ generations. The event W1 was studied in BC₁F₃ as well and showed normal Mendelian inheritance of 3:1. The inheritance pattern in L1 event in BC₁F₁ and BC₁F₂ showed normal Mendelian inheritance following expected ratio 1:1 and 3:1 respectively. The two events G1 and T1 showed distorted segregation in BC₁F₂ and BC₂F₂ respectively in Swarna genetic background. In G1 event, transgene inheritance showed segregation distortion in BC₁F₂ in favour of transgene negative plants. In T1 event, inheritance followed expected Mendelian segregation in BC₁F₁, BC₂F₁ and BC₂F₂, generations. However, when tested against co-dominant inheritance 1:2:1 pattern in BC₂F₂, segregation distortion was observed with less than the expected transgene homozygotes. While against 3:1 ratio, it showed the expected segregation pattern in BC₂F₂ generation. Segregation distortion probably due to differential transmission of transgene positive/negative gametes through either/both parents which needs further study.