Pollen Sterility Research Articles

Impact of Gametocides on Pollen Sterility and Growth Traits in Chilli (Capsicum annuum L.)

This study, conducted at the College of Agriculture, Vellayani, Thiruvananthapuram during 2023-2024, investigated the effects of gametocides on pollen sterility and plant growth in two chilli varieties, Jwalamukhi and Ujwala. The experiment followed a Factorial Completely Randomized Design with 18 treatments (2 varieties x 9 gametocide concentrations x 3 stages), replicated thrice. Pollen sterility was significantly affected by gametocide treatments, with Maleic Hydrazide (MH) at 200 ppm applied at 20+40 days after transplanting (DAT) resulting in the highest sterility in both varieties. Plant height also varied significantly, with the highest growth observed in Jwalamukhi treated with GA3 at 2.5% in stage III. The study found that GA3 increased plant height and branching, while MH treatments, especially at higher concentrations, reduced plant height, with Ujwala showing the most pronounced effect. These findings highlight the potential of gametocide treatments in modifying pollen sterility and growth traits in chilli plants.

Past and future of cytoplasmic male sterility and heterosis breeding in crop plants.

Plant breeding needs to embrace genetic innovations to ensure stability in crop yields under fluctuating climatic conditions. Development of commercial hybrid varieties has proven to be a sustainable and economical alternative to deliver superior yield, quality and resistance with uniformity in a number of food crops. Cytoplasmic male sterility (CMS), a maternally inherited inability to produce functional pollen, facilitates a three-line system for efficient hybrid seed production strategies in crops. The CMS system has illustrated its potential as a robust pollination control mechanism to support the billion-dollar seed industry. In plants, CMS arises due to a genomic conflict between mitochondrial open reading frames (orfs) and nuclear-encoding restoration-of-fertility (Rf) genes, leading to floral abnormalities and pollen sterility. Research on pollen sterility and fertility restoration provides deeper insights into cytoplasmic-nuclear interplay in plants and elucidates key molecular targets for hybrid breeding in crops. More recently, programmable gene editing (e.g., TALEN, CRISPR-Cas) has emerged as a promising tool to functionally validate CMS and Rf genes and obviate the need for pollen donors or Rf-genes for hybrid breeding. Modern genomic prediction models have allowed establishment of high-performing heterotic groups and patterns for sustaining long-term gain in hybrid breeding. This article reviews latest discoveries elucidating the molecular mechanisms behind CMS and fertility restoration in plants. We then present our perspective on how evolving genetic technologies are contributing to advance fundamental knowledge of the CMS-Rf genetic system for producing crop hybrids with high heterosis.

Mitochondrial genome structural variants and candidate cytoplasmic male sterility-related gene in sugarcane

BackgroundSugarcane is a crucial crop for both sugar and bioethanol production. The nobilization breeding and utilization of wild germplasm have significantly enhanced its productivity. However, the pollen sterility in Saccharum officinarum restricts its role to being a female parent in crosses with Saccharum spontaneum during nobilization breeding, resulting in a narrow genetic basis for modern sugarcane cultivars. Mitochondria, often referred to as the intracellular “energy factories”, provide energy for plant life activities, and are also implicated in cytoplasmic male sterility (CMS).ResultsWe performed mitochondrial genome assembly and structural analysis of two Saccharum founding species. We discovered that the proportions of repeat sequences are the primary factor contributing to the variations in mitochondrial genome structure and size between the two Saccharum species. Heterologous expression of the mitochondrial chimeric gene ORF113, which is highly expressed in male-sterile S. officinarum flowers, significantly inhibits growth and ATP synthesis in yeast cells, making it a key candidate CMS-related gene in sugarcane. Furthermore, we developed two co-dominant simple sequence repeat (SSR) markers based on the mitochondrial genome, which can effectively distinguish the cytoplasmic types of the two Saccharum species.ConclusionIn this study, we identified structural variants and developed SSR molecular markers in the mitochondrial genomes of both S. officinarum and S. spontaneum. We also identified a novel mitochondrial chimeric ORF as a key candidate CMS-related gene. These findings offer valuable insights into variety identification, genetic resource development, and cross-breeding strategies in sugarcane.

Virulence effectors encoded in the rice yellow dwarf phytoplasma genome participate in pathogenesis.

Bacteria-like phytoplasmas alternate between plant and insect hosts, secreting proteins that disrupt host development. In this study, we sequenced the complete genome of "Candidatus Phytoplasma oryzae" strain HN2022, associated with rice yellow dwarf (RYD) disease, using PacBio HiFi technology. The strain was classified within the 16Sr XI-B subgroup. Through SignalP v5.0 for prediction and subsequent expression analysis of secreted proteins in Nicotiana benthamiana and rice (Oryza sativa L.), we identified the key virulence effector proteins RY348 and RY378. RY348, a homolog of Secreted Aster Yellows Phytoplasma Effector 54 (SAP54), targets and degrades the MADS-box transcription factors MADS1 and MADS15, causing pollen sterility. Meanwhile, RY378 impacts the strigolactone and auxin signaling pathways, substantially increasing tillering. These findings offer insights into the interactions between plants and phytoplasmas.

Consistency in patterns of pollen sterility between floral morphs in distylous populations of Erythroxylum (Erythroxylaceae)

Consistency in patterns of pollen sterility between floral morphs in distylous populations of Erythroxylum (Erythroxylaceae)

Exogenous Melatonin Enhances Pollen Fertility of Drought‐Stressed Cotton (Gossypium hirsutum L.) by Improving Antioxidant Metabolism

ABSTRACTExogenous melatonin (MT) can aid crops in mitigating drought stress, yet its impacts on cotton pollen fertility under drought remain understudied. To address this, a study on the effects of exogenous MT on cotton pollen sterility and internal physiological metabolism under drought stress was conducted. Results showed that although antioxidant enzymes catalase (CAT), peroxidase (POD) and superoxide dismutase (SOD) activities increased in drought‐stressed anthers, yet this was insufficient to balance reactive oxygen species (ROS) levels, which led to higher hydrogen peroxide (H2O2) and superoxide anion (O2−) accumulation, resulting in oxidative stress, manifested by elevated malondialdehyde (MDA) and reduced pollen viability. Remarkably, the application of MT further bolstered the activities of CAT, POD and SOD in drought‐stressed anthers, effectively mitigating the accumulation of O2− and H2O2. This enhancement facilitated the antioxidant defence system under drought conditions. Simultaneously, the activity of ascorbate peroxidase (APX) was reduced, which prevented the reduction of dehydroascorbate (DHA) to ASA, and the ascorbic acid‐glutathione (AsA‐GSH) cycle was destroyed, leading to the accumulation of GSH. Nevertheless, MT application triggered upregulation of both GhDHAR and GhMDHAR expressions, promoting AsA synthesis and regeneration, respectively, thereby elevating AsA levels. Furthermore, MT revitalised APX activity, accelerating the removal of H2O2 through AsA‐mediated reduction, ultimately restoring the balance of the AsA‐GSH cycle and enhancing the overall antioxidant capacity of drought‐stressed anthers. In summary, exogenous MT can enhance the scavenging ability of ROS in drought‐affected anthers by elevating the activities of CAT, POD and SOD and by enhancing APX activity in the AsA‐GSH cycle, thereby alleviating drought‐induced oxidative stress and improving pollen fertility under water deficit stress.

Introgressing photoperiod/thermo-sensitive genic male sterile gene into Basmati 370 rice

The emasculation of male gametes in pollen-recipient parents among self-pollinated crops (rice) is key to producing quality hybrid rice seeds. One of the emasculation tools in rice breeding is the photoperiod-thermo sensitive genic male sterility (P/TGMS) method, which ultimately requires long daylight length and high-temperature growth conditions to induce male gametes sterility. Using the P/TGMS method to produce hybrid Basmati rice seeds has been slow because no commercial line has been developed. Crossing the Basmati rice line with a non-aromatic rice line produces F1 with non-basmati quality traits. This study aimed to introgress the p/tgms12-1 gene into Basmati 370 by treating P/TGMS lines (IR-7327-2376-157S and IR-75589-31-27833S) with daytime temperatures (>33ºC) under a polythene greenhouse to emasculate pollen and cross-pollinating them with Basmati 370. Marker-assisted backcrossing was used to develop the BC1F2 Basmati breeding lines evaluated for pollen sterility and agro-morphological traits. Pollen sterility was tested by staining with 1% iodine potassium-iodide solution (I2KI), in which fertile and sterile pollen grains were stained with blue-black and yellow-pink dyes, respectively. The acquisition of near-complete pollen sterility among female parents is a manifestation of the greenhouse temperatures effectively emasculating pollen in P/TGMS parents and BC1F2. Analysis of variance on agro-morphological data showed significantly better agro-morphological traits in BC1F2 than the parents and significantly higher pollen sterility in P/TGMS lines than Basmati 370 (P≤0.05). The presence of the fgr gene in BC1F2 lines was confirmed using SSR markers, and the hybrids had both homozygous aromatic and heterozygous non-aromatic traits, the successful development of BC1F2 with p/tgms12-1 and fgr genes. The results obtained from this study are a major milestone towards improving Basmati rice yields in Kenya using hybrid seeds.

Differential Variability of Maize (Zea mays L.) Inbred Lines to Moisture-stress at Reproductive Stages and DNA Methylation Studies of Identified Contrasting Genotypes under Moisture-Stress Conditions

An investigation was undertaken to assess the effect of moisture stress during the reproductive initiation stage on the quality and quantity of pollen grains produced in eight inbred lines (UASBM22, UASBM13, UASBM09, UASBM11, UASBM06, UASBM14, UASBM02 and UASBM10) under greenhouse conditions in three blocks viz., well-watered, stress I (for 21 days from 28 days after sowing) and stress II (for 22 days from 32 days after sowing). Moisture stress significantly affected the number of pollen grains per anther and other plant growth-related traits. The moisture stress effect was not uniform across inbred lines. The inbred lines UASBM22, UASBM13, UASBM09 and UASBM11 recorded a significant reduction in the total number of pollen grains per anther and an increase in pollen sterility while in inbred lines, UASBM06, UASBM14, UASBM02 and UASBM10, the moisture stress effect was not significant. The changes in the DNA methylation pattern in leaves and immature anthers under moisture stress of the contrasting inbred lines (UASBM06 and UASBM13) were studied through methylation- sensitive random amplification polymorphism. An increase in total DNA methylation level in both leaves and anthers was observed in drought tolerant inbred line, UASBM06 under stress while the increase was only in the leaves of the susceptible inbred line UASBM13. Leaves and anthers of UASBM06 showed hypermethylation compared to UASBM13 in moisture-stress conditions. In maize, increased DNA methylation seems to be an important mechanism associated with drought responses which probably regulates the methylation-sensitive gene expression and acclimation responses in maize.

Environmentally acquired gut-associated bacteria are not critical for growth and survival in a solitary bee, Megachile rotundata.

Social bees have been extensively studied for their gut microbial functions, but the significance of the gut microbiota in solitary bees remains less explored. Solitary bee, Megachile rotundata females provision their offspring with pollen from various plant species, harboring a diverse microbial community that colonizes larvae guts. The Apilactobacillus is the most abundant microbe, but evidence concerning the effects of Apilactobacillus and other provision microbes on growth and survival are lacking. We hypothesized that the presence of Apilactobacillus in abundance would enhance larval and prepupal development, weight, and survival, while the absence of intact microbial communities was expected to have a negative impact on bee fitness. We reared larvae on pollen provisions with naturally collected microbial communities (Natural pollen) or devoid of microbial communities (Sterile pollen). We also assessed the impact of introducing Apilactobacillus micheneri by adding it to both types of pollen provisions. Feeding larvae with sterile pollen + A. micheneri led to the highest mortality rate, followed by natural pollen + A. micheneri, and sterile pollen. Larval development was significantly delayed in groups fed with sterile pollen. Interestingly, larval and prepupal weights did not significantly differ across treatments compared to natural pollen-fed larvae. 16S rRNA gene sequencing found a dominance of Sodalis, when A. micheneri was introduced to natural pollen. The presence of Sodalis with abundant A. micheneri suggests potential crosstalk between both, shaping bee nutrition and health. Hence, this study highlights that the reliance on nonhost-specific environmental bacteria may not impact fitness of M. rotundata.IMPORTANCEThis study investigates the impact of environmentally acquired gut microbes of solitary bee fitness with insights into the microbial ecology of bee and their health. While the symbiotic microbiome is well-studied in social bees, the role of environmental acquired microbiota in solitary bees remains unclear. Assessing this relationship in a solitary pollinator, the leaf-cutting bee, Megachile rotundata, we discovered that this bee species does not depend on the diverse environmental bacteria found in pollen for either its larval growth or survival. Surprisingly, high concentrations of the most abundant pollen bacteria, Apilactobacillus micheneri did not consistently benefit bee fitness, but caused larval mortality. Our findings also suggest an interaction between Apilactobacillus and the Sodalis and perhaps their role in bee nutrition. Hence, this study provides significant insights that contribute to understanding the fitness, conservation, and pollination ecology of other solitary bee species in the future.

Temperature change regulates pollen fertility of a PTGMS rice line PA64S by modulating the ROS homeostasis and PCD within the tapetum.

Photoperiod and temperature-sensitive male sterility rice is an important line for two-line hybrid rice, and the changes in the cultivation temperature strictly control its pollen fertility. However, the mechanism by which temperature variation regulates pollen fertility is still unclear. This study obtained stable fertile PA64S(F) and sterile PA64S(S) rice from PA64S by controlling temperature changes. PA64S(F) shows a normal anther development and fertile pollen under low temperature (21°C), and PA64S(S) shows delayed degradation of the tapetum cells, leading to abnormal pollen wall formation and ubisch development under normal temperature (28°C). The accumulation of reactive oxygen species (ROS) positively correlates with the programmed cell death (PCD) process of tapetum cells. The delayed accumulation of ROS in the PA64S(S) tapetum at early stages leads to a delayed initiation of the PCD process. Importantly, we localized ascorbic acid (ASA) accumulation in the tapetum cells and determined that ASA is a major antioxidant for ROS homeostasis. ROS-inhibited accumulation plants (PA64S-ASA) demonstrated pollen sterility, higher ASA and lower ROS accumulation in the tapetum, and the absence of PCD processes in the tapetum cell. Abnormal changes in the tapetum of PA64S(S) rice disrupted metabolic pathways such as lipid metabolism, cutin and wax synthesis, sugar accumulation, and phenylpropane, affecting pollen wall formation and substance accumulation, suggesting that the timely accumulation of ROS is critical for male fertility. This study highlights the central role of ROS homeostasis in fertility alteration and also provides an avenue to address the effect of environmental temperature changes on pollen fertility in rice.

The mitochondrial genes orf113b and orf146 from Xinjiang wild rapeseed cause pollen abortion in alloplasmic male sterility

Nsa CMS, a type of cytoplasmic male sterility (CMS) in rapeseed, originates from the cross between Xinjiang wild rapeseed (Sinapis arvensis) and Xiangyou 15 (Brassica napus L.). Although this CMS variant shows promising applications, the factors contributing to its sterility and their underlying mechanisms remain unclear. To the best of our knowledge, we successfully assembled and analyzed the mitochondrial genome of 1258A (Nsa CMS) for the first time. This mitochondrial genome, spanning 263,010 bp, contains 91 genes, including 33 protein-coding and 36 orf genes. Our analysis identified a novel mitochondrial gene, orf113b, and a mutated, truncated gene, orf146, both likely linked to the sterility observed in 1258A. ORF113b and ORF146 were found to impede cell growth, disrupt gene expression associated with complexes I, III, and V of the mitochondrial oxidative phosphorylation pathway, and trigger reactive oxygen species (ROS) production. Additionally, transcriptome data analysis revealed key nuclear genes co-expressed with orf113b and orf146, suggesting that their aberrant expression may be influenced by retrograde signaling from the mitochondria. This signaling could lead to atypical programmed cell death (PCD) in the tapetum layer, resulting in pollen sterility. In conclusion, our study not only provides the first characterization of the Nsa CMS mitochondrial genome but also identifies orf113b and orf146 as crucial to pollen sterility. Furthermore, it suggests that ROS induced by these mitochondrial genes may play a central role in the abnormal regulation of nuclear genes essential for pollen development, offering new insights into the molecular mechanisms underlying Nsa CMS.

Understanding the role of P-type ATPases in regulating pollen fertility and development in pigeonpea.

The P-type ATPase superfamily genes are the cation and phospholipid pumps that transport ions across the membranes by hydrolyzing ATP. They are involved in a diverse range of functions, including fundamental cellular events that occur during the growth of plants, especially in the reproductive organs. The present work has been undertaken to understand and characterize the P-type ATPases in the pigeonpea genome and their potential role in anther development and pollen fertility. A total of 59 P-type ATPases were predicted in the pigeonpea genome. The phylogenetic analysis classified the ATPases into five subfamilies: eleven P1B, eighteen P2A/B, fourteen P3A, fifteen P4, and one P5. Twenty-three pairs of P-type ATPases were tandemly duplicated, resulting in their expansion in the pigeonpea genome during evolution. The orthologs of the reported anther development-related genes were searched in the pigeonpea genome, and the expression profiling studies of specific genes via qRT-PCR in the pre- and post-meiotic anther stages of AKCMS11A (male sterile), AKCMS11B (maintainer) and AKPR303 (fertility restorer) lines of pigeonpea was done. Compared to the restorer and maintainer lines, the down-regulation of CcP-typeATPase22 in the post-meiotic anthers of the male sterile line might have played a role in pollen sterility. Furthermore, the strong expression of CcP-typeATPase2 in the post-meiotic anthers of restorer line and CcP-typeATPase46, CcP-typeATPase51, and CcP-typeATPase52 in the maintainer lines, respectively, compared to the male sterile line, clearly indicates their potential role in developing male reproductive organs in pigeonpea.

Isolation and evaluation of novel male sterile and self‐incompatible mutant lines of mungbean (Vigna radiata L.)

AbstractHeterosis has long been harnessed in crop production, and while crop fertility lays the groundwork for leveraging heterosis, there remains a dearth of comprehensive data regarding genic male sterility in mungbean. Mungbean (Vigna radiata (L.) Wilczek), being a self‐pollinating crop, exhibits significant hybrid vigour in F1 hybrid seed yield, suggesting the potential for developing hybrid varieties to propel mungbean yield beyond existing plateaus. A new male sterile mutant was induced, isolated, stabilized and evaluated, via gamma irradiation at a rate of 600 Gy, identified in the M3 generation of the GM 4 accession. A uniform male sterile line was crossbred with the wild‐type parental plant to explore the inheritance pattern of male sterility. Pollen sterility was validated through the acetocarmine test, while stigma viability was ascertained using the hydrogen peroxide. While all F1 plants displayed fertile flowers, the F2 generation showed a clear 3:1 segregation ratio for fertile to male sterile plants, indicating the control of male sterility by a single recessive gene, mms. Also, a novel existence of a truncated stigma nestled within the anther column inhibits the effective reception of pollen during anthesis, offering potential in reducing emasculation time by a slight cut on the flower bud and enhancing cross pollination during hybrid seed production. The isolation of these two mutants is poised to significantly advance the global mungbean hybrid breeding programme.

Conversion of superior bread wheat genotype HD3209 carrying Lr19/Sr25 into CMS line for development of rust-resistant wheat hybrids

Hybrid development is one of the most promising strategies for boosting crop yields. Parental lines used to create hybrids must have good per se performance and disease resistance for developing superior hybrids. Indian wheat line HD3209 was developed by introducing the rust resistance genes Lr19/Sr25 into the background of popular wheat variety HD2932. The wheat line HD3209 carrying Lr19/Sr25 has been successfully and rapidly converted to the CMS line A-HD3209, with 96.01% background genome recovery, based on selection for agro-morphological traits, rust resistance, pollen sterility, and foreground and background analyses utilizing SSR markers. The converted CMS line A-HD3209 was completely sterile and nearly identical to the recurrent parent HD3209. Based on high per se performance and rust resistance, the study concludes that the derived CMS line A-HD3209 is promising and can be employed successfully in hybrid development.

Marker assisted selection reveal SNP deletion mutation in gene associated with cytoplasmic male sterility in Solanumvillosum

Male sterility (MS) is powerful tool for improvement of various traits of economic importance. MS has not been characterized in Solanum villosum, and molecular mechanism underlying mutation change have not yet been studied. In this study, Sanger sequence platform was employed to amplify the MS genic region using mt ATPase marker. The molecular mechanism governing sterility was studied, and the results detected the amplification region at 1150bp. The sequence query was 97 % identical with atp subunit 6 gene loci. Significance mutation detected in this study was deletion GG (delGG) and deletion C (delC) occurring between 536bp and 542bp position in atp6 gene transcript. The mutation score was 16 for delGG and 17 for delC, with a 90 % mutation confidence interval. The study observed that SNP changes due to base deletions in the atp6 gene region were the main cause of male sterility in the studied mutants due to anticipated frameshifts of the open reading frame (ORF) of the mitochondrial atp6 gene, this is regarded as cytoplasmic male sterility type (CMS). Deformed and low pollen count was morphological changes confirmed this study that associated with sterility. Disruption of the ATP synthesis in mitochondria, limits the energy supply for pollen grain formation and anticipated pollen sterility however, mitochondria nuclear gene interaction governing the CMS should be further studied in case of S.villosum. These findings shed-light on molecular mechanism underlying the CMS and can be utilized as a molecular marker for agronomic traits improvement of S.villosum.

Floral deception in dioecious Actinidia polygama (Actinidiaceae) revealed by differential nitrogen investment in male organs

AbstractAnimal‐pollinated plants have evolved rewards and advertisements to attract pollinators, which learn to associate advertisements with rewards. Pollen‐collecting insects, such as bees, associate stamens with pollen (a reward) essential for brood rearing. In some dioecious plants, female flowers have stamens with sterile pollen grains to mimic male flowers. It is not yet fully understood whether females offer less nutritious pollen to pollinators in order to conserve nutrition. Here, we tested this hypothesis in a perennial vine, Actinidia polygama, which bears nectarless flowers. We quantified flower production and measured the dry mass of floral parts as well as carbon and nitrogen concentrations in floral parts and pollen in both sexes. Males produced more flowers per inflorescence and more inflorescences per shoot than females, while the dry mass of each flower was greater in females. The carbon allocation pattern was similar to that of biomass, but nitrogen allocation exhibited a remarkable reduction in sterile stamens and pollen of female flowers. In addition, as sterile pollen of females was sparse, when compared at the same volume, it was lighter than the pollen of males. Sterile pollen produced in female flowers appears to be as voluminous as that of male flowers but extremely poor in nutrients, especially in nitrogen, which clearly suggests that A. polygama females deceive pollen‐collecting pollinators for brood rearing.

Cytological Observation and RNA-Seq Analyses Reveal miR9564 and Its Target Associated with Pollen Sterility in Autotetraploid Rice.

Understanding the regulation of autotetraploid sterility is essential for harnessing the strong advantages in genomic buffer capacity, biodiversity, and heterosis of autotetraploid rice. miRNAs play crucial roles in fertility regulation, yet information about their reproductive roles and target genes in tetraploid rice remains limited. Here, we used three tetraploid lines, H1 (fertile), HF (fertile), and LF (sterile), to investigate cytological features and identify factors associated with autotetraploid sterility. LF showed abnormal meiosis, resulting in low pollen fertility and viability, ultimately leading to scarce fertilization and a low-seed setting compared to H1 and HF. RNA-seq revealed 30 miRNA-candidate target pairs related to autotetraploid pollen sterility. These pairs showed opposite expression patterns, with differential expression between fertile lines (H1 and HF) and the sterile line (LF). qRT-PCR confirmed that miR9564, miR528, and miR27874 were highly expressed in the anthers of H1 and HF but not in LF, while opposite results were obtained in their targets (ARPS, M2T, and OsRPC53). Haplotype and expression pattern analyses revealed that ARPS was specifically expressed in lines with the same haplotype of MIR9564 (the precursor of miR9564) as LF. Furthermore, the Dual-GFP assay verified that miR9564 inhibited the fluorescence signal of ARPS-GFP. The over-expression of ARPS significantly decreased the seed setting rate (59.10%) and pollen fertility (50.44%) of neo-tetraploid rice, suggesting that ARPS plays important roles in autotetraploid pollen sterility. This study provides insights into the cytological characteristic and miRNA expression profiles of tetraploid lines with different fertility, shedding light on the role of miRNAs in polyploid rice.

Is <i>Nymphaea rubra</i> Roxb. Ex Andrews-An Apomict?

Studies on several populations of Nymphaea rubra in the Howrah, Hooghly and 24-Parganas districts in West Bengal and Barisal district in Bangladesh reveal that this species, claimed to be a native of Bengal, never sets fruit in nature. The plant propagates though stolons and vegetative buds and, in exceptional cases, by proliferation of flowers. The report of meiotic irregularity and high incidence of polysomaty and pollen sterility is indicative of its apomictic nature. The nomenclature of the plant has been discussed.

Meiotic chromosomal behaviour of Artemisia amygdalina Decne: A critically endangered medicinal plant, endemic to the North-western Himalaya

The limited geographic distribution of endemic species renders them more susceptible to extinction risks stemming from a myriad of factors. One such factor could be meiotic constraints, which may directly or indirectly impact the reproductive success of the endemic plant species. Thus, comprehensive research on meiotic behaviour is essential for implementing species conservation measures. This study represents the first report on the male meiotic behaviour of Artemisia amygdalina Decne., a critically endangered endemic medicinal plant species of the Kashmir Himalaya. We procured the plant material from three different locations in the Kashmir Himalaya, and the chromosome number of the species from all sites was found to be 2n=18 (x = 9, n = 9), indicating its diploid nature. Various types of chromosomal abnormalities were found in these populations, including stickiness, univalents, out-of-plate bivalents, laggards, bridges, disturbed telophase, micronuclei, abnormal pollen grains formation and seed set formation. The overall percentage of chromosomal abnormalities varied among the populations, from 8.58 % to 25.16 %. Pollen sterility also varied among different populations, with maximum pollen sterility of 23.21 % and a minimum of 5.96 % across populations. The present findings will not only help in updating the chromosome atlas with the addition of a new report on chromosome number but also contribute to the understanding of the reproductive success of A. amygdalina. Further ecological and reproductive studies can facilitate the creation of effective management and conservation strategies for this species.

Use of irradiated pollen technique to recover haploids in bitter gourd

Haploids play a crucial role in plant breeding as they contain only one set of chromosomes, facilitating the rapid development of homozygous lines. Parthenogenetic haploids have been successfully produced using the irradiated pollen technique. Embryo rescue facilitates the development of an underdeveloped or lethal embryo into a viable plant. Inbred development through embryo culture has yet to be utilized in bitter gourd (Momordica charantia L.). An investigation was undertaken in a bitter gourd to recover haploids through the 60Co gamma-irradiated pollen technique, and an efficient protocol for embryo culture was standardized. Male flowers of bitter gourd genotype MC-139 irradiated at different gamma-ray doses were used for artificially pollinating female flowers. Intact seeds and excised embryos were cultured in E20A medium supplemented with 0.01 mg l-1 IAA, which was found as the most suitable medium for embryo induction and subsequent culture. The use of intact seeds extracted 15 days after pollinating with 60Co gamma irradiated (90 Gy) pollen resulted in a mutant plant. A significant difference was observed in the size of the guard cell, pollen grain diameter and chloroplast number per guard cell for the plant under T9 (90 Gy) compared to the plants under other treatments. The plant (T9) produced only sterile pollen, and the seed set was not observed when self-pollinated