The technique at the heart of the study is gynogenesis, the induction of embryo development from the female gametophyte without fertilization. When an unfertilized ovary is cultured on the right medium, the egg cell or an adjacent cell can be triggered to divide and form an embryo that carries only a single set of chromosomes. Such haploid plants are genetic blanks: every gene is present in just one copy. If breeders then double the chromosomes chemically, they obtain instantly homozygous, fully inbred lines in a single generation, a shortcut that in traditional breeding would demand six or more generations of selfing and selection. In speed-breeding programmes, gynogenesis is regarded as one of the fastest routes to haploid production, which is precisely why the IARI team focused on it.

Marigold, however, has been a reluctant participant. Earlier attempts in the same laboratory and elsewhere relied on androgenesis, culturing anthers or microspores to recover haploids from the male side, and on indirect gynogenesis, in which ovary explants first form callus that must then be coaxed to regenerate shoots. Indirect pathways carry a well-known penalty: callus phases introduce somaclonal variation, chromosome instability and genotype-dependent losses, so the plants that finally emerge are not always faithful copies of the mother line. The goal of the new work, published in the Indian Journal of Genetics and Plant Breeding, was to eliminate the callus stage altogether and regenerate haploid plantlets directly from cultured ovaries, something the authors describe as a first for this species.

The researchers worked with two hybrid genotypes of African marigold, DAMH-24 and DAMH-55, and systematically varied the two most influential levers in ovary culture: the hormonal composition of the medium and the stress pre-treatment applied to the buds before they entered culture. Unpollinated flower buds were excised and their ovaries placed on a modified Murashige and Skoog medium supplemented with the urea-derived cytokinin thidiazuron (TDZ) at five concentrations ranging from 0.25 to 1.50 mg per litre, combined with the auxin naphthaleneacetic acid (NAA) at either 0.20 or 0.50 mg per litre. TDZ is a potent morphoregulatory compound that mimics and often outperforms natural cytokinins, promoting cell division and organogenesis at remarkably low doses, which made it a logical candidate for triggering embryo-like divisions in the female gametophyte.

The second lever was cold shock. Before culturing, batches of buds were held at 4 degrees Celsius or 9 degrees Celsius for 0, 3, 7 or 10 days. Low-temperature pre-treatments are widely used in haploid induction because chilling appears to reprogramme gametophytic cells toward an embryogenic fate, partly by suspending normal developmental progression and partly by modulating stress-signalling pathways. In crops as diverse as sugar beet, onion, cucumber and cauliflower, cold pre-treatment has repeatedly improved the frequency of gynogenic or androgenic recovery, and the marigold study confirmed that the same principle applies on the female side of this ornamental species.

The winning combination was unambiguous. Ovaries of genotype DAMH-24 that were chilled at 4 degrees Celsius for seven days and then cultured on medium containing 0.75 mg per litre TDZ together with 0.20 mg per litre NAA produced the highest frequency of direct regeneration. In other words, the optimal recipe paired a moderate, sustained cold stress with a mid-range cytokinin dose and a low auxin level, a balance that appears to push the egg cell into division without diverting the explant into callus. Genotype mattered as well, a familiar theme in haploid work: responsiveness to gynogenesis is strongly heritable and varies dramatically between lines, which is why the two marigold hybrids were compared side by side from the outset.

Recovering plantlets is only half the battle; proving that they are genuinely haploid is the other half. The team deployed a three-tier verification strategy that is becoming standard in doubled-haploid research. First, stomatal guard cells were examined for chloroplast number, a rapid cytological proxy: albino or yellowish-green plantlets carried only 3 to 7 chloroplasts per guard cell, whereas vigorous green plantlets carried 10 to 14. Second, root-tip chromosome counts confirmed the division: putative haploids showed 2n = x = 12 chromosomes, exactly half the diploid complement of 2n = 2x = 24. Third, flow cytometry measured nuclear DNA content, with haploids displaying a 1 C value corresponding to a mean peak index of roughly 65 K, while diploids registered a 2 C value near 129 K. The concordance of all three markers left little doubt about the ploidy of each class of regenerant.

The yield, while modest, is a genuine proof of concept. Out of 77 plants regenerated directly from cultured ovaries, the researchers randomly selected 30 for ploidy analysis and confirmed that 4 of them, or 13.33 percent, were true haploids. The remainder were diploids, which in ovary culture can arise either from spontaneous chromosome doubling during early embryo development or from the accidental inclusion of maternal somatic tissue in the regenerative event. The authors are candid that the haploid frequency remains low and that the protocol will need further refinement before it becomes a routine breeding tool, but the decisive point is that haploid plants were recovered through a direct, callus-free pathway, avoiding the genetic noise that indirect regeneration introduces.

Importantly, the team did not attempt chromosome doubling in this study. The confirmed haploid plants are being maintained in vitro at ICAR-IARI, and diploidisation to create homozygous parental lines for F1 hybrid development is planned as the next stage of the programme. That step will typically involve treating haploid plantlets or their explants with a mitotic inhibitor such as colchicine, allowing the single chromosome set to replicate without cell division and thereby producing fully homozygous doubled haploids. Once achieved, those lines could serve as stable, uniform parents for hybrid marigold seed production, compressing years of pedigree inbreeding into a single laboratory cycle.

The broader significance of the work extends beyond one flower. Doubled-haploid technology has transformed breeding in wheat, barley, rapeseed and many vegetables, but ornamental crops have lagged behind, partly because their reproductive biology resists the standard anther- and microspore-culture toolkits. By demonstrating direct gynogenesis in African marigold, and by defining the cold-shock and hormonal parameters that make it work, the IARI group has added a valuable entry to a growing list of gynogenic systems in species such as onion, sugar beet, cucumber, cassava and chrysanthemum. For a crop whose petals colour everything from egg yolks to industrial lutein extracts, a faster route to pure parental lines is not merely a laboratory curiosity; it is a potential accelerant for an entire industry. The bottleneck in marigold hybrid breeding has not been eliminated, but for the first time it has been clearly broken open.

Subject of Research: Direct haploid plant regeneration via in vitro gynogenesis in African marigold (Tagetes erecta L.) for accelerated hybrid breeding

Article Title: Breaking the Bottleneck in African Marigold (Tagetes Erecta L.) Hybrid Breeding: Direct Haploid Regeneration via Gynogenesis

Article References: Arzoo, E., Bhatia, R., Dubey, K., Singh, K. P., Panwar, S., Talukdar, A., Singh, B., & Rao, M. (2026). Breaking the Bottleneck in African Marigold (Tagetes Erecta L.) Hybrid Breeding: Direct Haploid Regeneration via Gynogenesis. Indian Journal of Genetics and Plant Breeding. https://doi.org/10.1007/s44489-026-00055-8

Image Credits: AI Generated

DOI: 10.1007/s44489-026-00055-8

Keywords: African marigold, Tagetes erecta, gynogenesis, haploid, doubled haploid, thidiazuron, cold shock pre-treatment, ovary culture, ploidy analysis, F1 hybrid breeding, plant tissue culture, ICAR-IARI

The hybrid is the product of a two-line hybrid rice breeding system, an approach that has become one of the most technically elegant solutions to a longstanding problem in crop genetics. Rice is predominantly self-pollinating, which makes the large-scale production of hybrid seed difficult: to create F1 hybrids, breeders need female plants that cannot self-fertilize, so that pollen from a chosen male parent produces the hybrid seed instead. Early hybrid rice programs relied on cytoplasmic male sterility, a three-line system requiring a sterile line, a maintainer line to propagate it, and a restorer line. The two-line system simplifies this architecture by using environment-sensitive genic male sterility, in which fertility is controlled by nuclear genes whose expression depends on growing conditions.

At the heart of Pusa Jawahar Rice Hybrid 56 is a thermosensitive genic male sterile (TGMS) line developed at ICAR-IARI. In a TGMS system, plants are male sterile when grown above a critical temperature threshold and fertile when grown below it. This temperature dependence gives breeders a practical switch: seed multiplication of the sterile line can be carried out in seasons or locations where temperatures remain low enough for the plants to be self-fertile, while hybrid seed production is carried out in warmer conditions or seasons in which the same line becomes fully male sterile and can accept pollen from a selected male parent. The result is a breeding pipeline in which a single genetic stock serves both the maintenance and hybridization phases, eliminating the need for separate maintainer lines and reducing the complexity and cost of commercial seed production.

The development of the TGMS line itself, credited in the article’s author contributions to M. Nagarajan and Gopala Krishnan Subbaiyan, involved successive generations of selection to fix the sterility response while preserving agronomic quality. A TGMS line must satisfy competing demands: it must be completely and stably sterile under hybrid seed production conditions, so that no selfed seed contaminates the commercial hybrid, yet reliably fertile under multiplication conditions, so that breeder seed can be produced economically. It must also carry good plant type, flowering duration and outcrossing characteristics, because hybrid seed yield depends on how effectively the sterile female plants receive pollen from the male parent rows planted alongside them in production fields. Traits such as panicle exsertion, staggered flowering between male and female rows, and glume openness all influence how much hybrid seed a hectare of production plot yields.

Once the sterile line was stabilized, the evaluation of testcross hybrids fell to Nagarajan and K. K. Vinod, who screened candidate crosses for the combination of yield, maturity, plant height and grain quality that Indian rice markets demand. Hybrid vigor, or heterosis, in rice can deliver substantial yield advantages over inbred varieties, frequently in the range of fifteen to twenty-five percent under favorable management, but the advantage is only worth commercializing if the hybrid also meets expectations for grain dimensions, cooking quality and consumer preference. In India, where market classes range from long slender grains to aromatic basmati types, a hybrid’s grain profile can determine whether it is adopted at all, regardless of its yield performance in trials.

Confirmation of performance came through multilocation trials conducted by a network of collaborating institutions. The author contributions record that G. K. Koutu, Sanjay Kumar Singh, Uttam Bisen and Gopala Krishnan Subbaiyan carried out the multilocation evaluation of the hybrid, drawing on facilities at JNKVV in Jabalpur, Madhya Pradesh, and the wider ICAR-IARI system. Multilocation testing is the crucible in which any new variety must prove itself: a hybrid that performs brilliantly at one station but collapses under the disease pressure, soil conditions or temperature regimes of another region is of limited value. Only genotypes showing consistent superiority across environments and seasons advance to notification, the formal process by which India’s varietal release system authorizes a genotype for cultivation in identified zones.

Parallel to the yield testing, Rakesh Seth at the ICAR-IARI Regional Station in Karnal conducted DUS characterization, the systematic recording of distinctness, uniformity and stability traits that serves as the botanical identity card of a new variety. DUS testing examines a defined set of morphological markers, from leaf angle and auricle coloration to grain shape and lemma-palea color, and establishes that the candidate variety is distinguishable from all existing varieties, uniform across plants, and stable across generations. This characterization underpins plant variety protection and seed certification, giving the hybrid a legal identity that allows seed producers and farmers to verify authenticity in the marketplace.

The collaborative structure of the program reflects the geography of Indian rice improvement. Alongside the core team at ICAR-IARI in New Delhi, the effort drew on M. Nagarajan’s work at the Rice Breeding and Genetics Research Centre in Aduthurai, Tamil Nadu, a station whose location in the Cauvery delta provides conditions suited to TGMS line multiplication and evaluation; Rajeev Rathour’s contribution to characterization and multiplication of the TGMS line at CSHPKVV in Palampur, Himachal Pradesh, where cooler hill conditions serve the fertility-restoration phase of the two-line cycle; and the Jabalpur team’s role in hybrid testing across central India. This division of labor, in which different agroclimatic stations handle different phases of the breeding cycle, is a hallmark of the two-line system’s practical deployment and illustrates why hybrid rice development is inherently a multi-institution enterprise.

The notification article itself is brief, as varietal notification records typically are, but its significance lies in what it enables. Notification under India’s Seeds Act brings a variety into the formal seed chain: it can be included in state and national seed production programs, certified by seed testing agencies, and recommended for specific cultivation zones. Germplasm registration, the second component of the publication, protects the parental lines as genetic resources, documenting their distinctive traits in the national registry so that other breeders can legitimately access and use them in future crossing programs. In this way, a single notification article feeds two streams at once: the immediate commercialization of one hybrid, and the longer-term enrichment of the breeding pool from which the next generation of hybrids will be drawn.

Hybrid rice occupies a growing share of India’s rice area, and the technical refinements embodied in Pusa Jawahar Rice Hybrid 56, from its TGMS-based seed production system to its multilocation-validated performance, illustrate the steady engineering that underlies that expansion. The research received no special funding, according to the article’s funding statement, and the authors declare no competing interests. Correspondence for the work is handled by Gopala Krishnan Subbaiyan of ICAR-IARI. As climate variability tightens the margins of rice production across South Asia, hybrids that combine heterosis with stable seed production systems offer breeders a lever that inbred varieties cannot match, and each notified hybrid extends the reach of that lever to new farmers, new seasons and new soils.

Subject of Research: Notification of the two-line hybrid rice variety Pusa Jawahar Rice Hybrid 56 developed with a TGMS male sterile line at ICAR-IARI

Article Title: Pusa Jawahar Rice Hybrid 56

Article References: Nagarajan, M., Subbaiyan, G. K., Vinod, K. K., Bhowmick, P. K., Bollinedi, H., Ellur, R. K., Seth, R., Rathour, R., Koutu, G. K., Singh, S. K., Bisen, U., & Singh, A. K. (2026). Pusa Jawahar Rice Hybrid 56. Indian Journal of Genetics and Plant Breeding, 86(3), 383-384. https://doi.org/10.1007/s44489-026-00036-x

Image Credits: AI Generated

DOI: 10.1007/s44489-026-00036-x

Keywords: rice hybrid, Pusa Jawahar Rice Hybrid 56, TGMS, two-line hybrid breeding, ICAR-IARI, male sterility, heterosis, multilocation trials, DUS testing, germplasm registration, varietal notification, plant breeding

What sets Pusa Rice Hybrid 60 apart from the majority of commercial rice hybrids is its genetic architecture. The hybrid was created by crossing Pusa 1S, a thermo-sensitive genic male sterile line, with PRR 418, an aromatic rice genotype. Thermo-sensitive genic male sterility, commonly abbreviated as TGMS, is a genetic system in which the male parent becomes sterile under certain temperature conditions, allowing breeders to produce hybrid seed without the need for a separate maintainer line. This is the defining feature of two-line hybrid rice technology, which simplifies seed production considerably compared with the conventional three-line system that relies on a sterile line, a maintainer line and a restorer line. By eliminating one parent from the seed multiplication chain, the two-line approach reduces the cost and complexity of producing hybrid seed, a factor that can translate directly into more affordable seed for farmers and faster commercial scaling for seed producers.

The agronomic credentials of the new hybrid are substantial. Across three years of evaluation in Bihar and Uttar Pradesh, Pusa Rice Hybrid 60 recorded an average grain yield of 59.24 quintals per hectare, a figure that places it among the more productive short-duration options available to farmers in the region. In comparative trials conducted under the All India Coordinated Research Project on Rice, the hybrid outperformed the national hybrid check US 314 by 11.6 percent, demonstrating that its advantage extends beyond comparison with inbred varieties and holds up against established commercial hybrids. Against the national varietal check CO 51, a widely grown cultivar, the hybrid delivered a 25.3 percent yield advantage. Most strikingly, it showed a 40.8 percent superiority over the zonal check in the coordinated trials, underscoring the magnitude of the genetic gain achieved by the ICAR-IARI breeding team.

Equally important for the eastern Indo-Gangetic plains is the hybrid’s maturity duration. Pusa Rice Hybrid 60 matures in approximately 120 days, placing it firmly in the short-duration category. This characteristic carries profound implications for cropping intensity, a critical consideration in a region where land holdings are small and farmers depend on squeezing multiple harvests from the same plot each year. A rice crop that matures early can be harvested in time for a timely sowing of the following wheat crop, preserving the integrity of the rice-wheat rotation that dominates agriculture across Bihar and Uttar Pradesh. Early maturity also reduces the crop’s exposure to late-season pests and terminal heat stress, and it can lower irrigation requirements by shortening the period over which the crop must be maintained in the field.

Yield alone rarely determines the commercial success of a rice variety in India, where grain quality commands a decisive premium in the market. Here too, the new hybrid performs impressively. Pusa Rice Hybrid 60 produces long-slender grains, a grain type strongly preferred by consumers in much of northern and eastern India, and it combines this with aromatic quality inherited from the PRR 418 parent. The hybrid achieved a milling recovery of 69.8 percent and a head rice recovery of 61.6 percent, both indicators of a grain that withstands processing without excessive breakage. Head rice recovery in particular is a measure of the proportion of intact kernels remaining after milling, and higher values translate into better prices for millers and, ultimately, for farmers. The hybrid also possesses intermediate amylose content, a starch characteristic associated with grains that cook to a tender, non-sticky texture, and the breeders report excellent overall cooking and eating quality.

Disease and pest reactions are a further dimension of the hybrid’s evaluation profile. In testing, Pusa Rice Hybrid 60 exhibited reactions to major insect pests that were comparable to those of standard checks, meaning that it does not carry unusual susceptibility that would require farmers to depart from established pest management practices. While the hybrid is not described as carrying specific resistance genes, parity with existing checks ensures that it can be integrated into current crop protection routines without added risk, an important practical consideration for the smallholder farmers who dominate rice cultivation in the target states.

The development of the hybrid reflects a coordinated effort across multiple ICAR-IARI stations and partner institutions. M. Nagarajan, based at the Rice Breeding and Genetics Research Centre at Aduthurai, is the lead developer of the hybrid, working alongside co-developers including Gopala Krishnan Subbaiyan and A. K. Singh of the Division of Genetics in New Delhi. The team’s division of labour illustrates the technical depth behind a modern variety release: Nagarajan and Subbaiyan drove the development of the TGMS line, while K. K. Vinod participated in the evaluation of both the sterile lines and the resulting hybrids. Data analysis was handled by Vinod, P. K. Bhowmick, Haritha Bollinedi and Ranjith K. Ellur, Rajeev Rathour of CSHPKVV Palampur contributed to the characterization and multiplication of the TGMS line, and Rakesh Seth at the institute’s Karnal regional station carried out the distinctness, uniformity and stability characterization required for formal registration. The work was published in the Indian Journal of Genetics and Plant Breeding as part of a report on varietal notification and germplasm registration.

The significance of the release extends beyond the performance figures themselves. India’s hybrid rice programme has historically been dominated by three-line systems, and the adoption of two-line technology has been slower than in China, where two-line hybrids occupy a large share of the hybrid rice area. Each successful Indian two-line hybrid strengthens the case for the approach, demonstrating that TGMS-based systems can deliver competitive yields and superior grain quality under Indian conditions. The registration of the Pusa 1S TGMS line and its deployment in a notified commercial hybrid also adds to the publicly available germplasm base, giving other breeding programmes access to proven genetic material for their own hybrid development pipelines. In a period when rice research worldwide is grappling with the twin pressures of shrinking land and water resources and rising demand, hybrids that combine early maturity with quality traits are increasingly viewed as a strategic asset.

For farmers in Bihar and Uttar Pradesh, the practical arithmetic is straightforward. A hybrid that yields roughly a quarter more grain than the leading varietal check, matures early enough to protect the following wheat crop, produces aromatic long-slender grain that fetches premium prices, and can be propagated through a simplified two-line seed system addresses nearly every major constraint in the region’s rice economy. The combination of high productivity, profitability and the potential for increased cropping intensity is precisely the package that agricultural planners have sought for the eastern Indo-Gangetic plains, a region that lags the northwestern states in productivity but holds vast untapped potential. As seed production of Pusa Rice Hybrid 60 scales up following its notification, the hybrid is positioned to become a promising cultivar for millions of rice farmers, and a showcase for what advanced two-line hybrid breeding can achieve in one of the world’s most important rice-growing regions.

Subject of Research: Development and evaluation of the two-line aromatic rice hybrid Pusa Rice Hybrid 60 for release in eastern India

Article Title: Pusa Rice Hybrid 60

Article References: Nagarajan, M., Subbaiyan, G. K., Vinod, K. K., Bhowmick, P. K., Bollinedi, H., Ellur, R. K., Seth, R., Rathour, R., & Singh, A. K. (2026). Pusa Rice Hybrid 60. Indian Journal of Genetics and Plant Breeding, 86(3), 381-382. https://doi.org/10.1007/s44489-026-00035-y

Image Credits: AI Generated

DOI: 10.1007/s44489-026-00035-y

Keywords: Pusa Rice Hybrid 60, hybrid rice, TGMS, two-line hybrid technology, ICAR-IARI, rice breeding, aromatic rice, grain yield, Bihar, Uttar Pradesh, short-duration rice, Indo-Gangetic plains