Transgressive Segregation Research Articles

Genetic variability and divergence studies to identify and isolate superior genotypes from European radish (Raphanus sativus) germplasm

The present study was carried during the winter (rabi) seasons of 2019–20 and 2020–21 at Dr. Y. S. Parmar University of Horticulture and Forestry, Nauni, Solan, Himachal Pradesh to identify and isolate superior genotypes from European radish (Raphanus sativus L.) germplasm. The experiment was laid out in randomized block design (RBD) comprising of 25 genotypes with three replications. These genotypes were evaluated for various horticultural and yield contributing traits, using the popular check cultivar Pusa Himani as a reference. The combined data from two years revealed significant differences among all the genotypes for the studied traits. Notably, genotypes UHF-SOL-RAD-3, UHF-SOL-RAD-1 and RKR-Sel-III exhibited higher yields compared to the check variety and performed well across most traits. The root top ratio demonstrated the highest phenotypic and genotypic coefficient of variability (34.79% and 34.64%, respectively). Traits such as total soluble solids (TSS), average root weight, root yield, gross plant weight, root top ratio (length basis), and root length exhibited moderate to high heritability along with moderate genetic advances. Based on Mahalanobis D2 statistics, five clusters were identified, with a majority of genotypes falling into cluster II. Cluster III displayed the highest intra-cluster similarity (51.18%), while clusters I, III, and V demonstrated greater diversity, thereby increasing the likelihood of obtaining favourable transgressive segregants through hybridization between genotypes in these clusters.

<i>SiDREB2</i>-based SNAP Marker-Assisted and Multi-Trait Selection in The Early Generation of Foxtail Millet (<i>Setaria italica</i> L. Beauv.)

Setaria italica L. or foxtail millet is known for its nutritious grains and adaptability to unfavorable environmental conditions. High productivity, early heading, medium stature, and tolerance to drought- or salinity stress are among the breeding objectives for foxtail millet. The objective of this study was to select F3 families of foxtail millet from the cross of Botok-10xICERI-6 by weighted selection index and assisted by SiDREB2-based SNAP marker. Genotyping of 178 F3 families using the SiDREB2-based SNAP marker resulted in 29 A/A genotypes, 121 A/G genotypes, and 28 G/G genotypes. Further evaluation was conducted on 48 F3 families consisting of 27 A/A genotypes and 21 A/G genotypes in an augmented randomized complete block design together with their parental genotypes (Botok-10xICERI-6) and three check genotypes (Mauliru-2, NTB-1, and Toraja). Plant height and heading time had high broad-sense heritability, whereas grain weight per plant had a moderate broad-sense heritability. Ten potential F3 families were selected based on a weighted selection index with 20% intensity, comprised of seven A/G genotypes and three A/A genotypes with a weighted selection index ranging from 0.84 to 3.76. The F3 family with pedigree numbers B10I6-15-136, B10I6-15-161, and B10I6-15-70 with A/A genotypes are considered putative transgressive segregants and could be continued to the next generation for further breeding process.

Multi-season-based estimation of genetic diversity, correlation and path analysis in spearmint (Mentha spicata L.) half-sib populations

Spearmint (Mentha spicata L.) is popular for its medicinal benefits and industrial uses, in this study forty-three half-sib progenies were evaluated over three seasons at CSIR-CIMAP, Research Centre Pantnagar to study genetic variability, correlation, path coefficient analysis and Mahalanobis D2 diversity by using five morphological and two biochemical traits. These forty-three half-sib populations were derived from nine commercially existing spearmint varieties through an intra-population improvement method. Results of correlation and path coefficient studies indicated the paramount importance of certain key traits in the selection process. Notably, traits such as herb yield per plot (kg), plant height (cm) and oil content (%) emerged as pivotal, exhibiting positive correlations, high heritability and moderate to high genetic advance. These attributes, therefore need primacy in the selection of superior lines. Furthermore, genotypes OPSP-106, OPSP-92, OPSP-47, OPSP-35 and OPSP-76 showed significant genetic divergence. These accessions hold promise as parent candidates for hybridization experiments aimed at finding transgressive segregants in later generations. Additionally, this study highlighted the presence of specific oil components, such as carvone and limonene, offering insights into potential avenues for targeted breeding efforts. This study provides a holistic view of the genetic makeup of Mentha spicata genotypes, enabling informed decisions in breeding programs. By prioritizing traits and maximizing genetic diversity, the results of this investigation will contribute to the development of improved spearmint varieties with enhanced morphological and biochemical characters, thus advancing the medicinal and industrial applications of spearmint.

Genetic Study and Temporal Dynamics of the Reaction to Ascochyta rabiei Epidemic in Improved Lines and Cultivars of Chickpea (Cicer arietinum L.)

ABSTRACTAscochyta blight is the most devastating worldwide disease of chickpea (Cicer arietinum L.). It is caused by Ascochyta rabiei (teleomorph: Didymella rabiei) an airborne pathogenic fungus which is common in rainy climates and warm temperatures. Despite the efforts deployed by genetic improvement to develop highly resistant varieties, a total resistance to Ascochyta blight is lacking in chickpea. From 2015 to 2019 season, a study was carried out to develop highly resistant lines at the experimental station of the National Agronomical Institute of Tunis (INAT).In this genetic program, four crosses were realized: Nour x ILC154986, Nour x ILC154445, Béja1x ILC155064, and Béja1x ILC154449. Nour and Béja1 varieties were respectively tolerant and susceptible to Ascochyta blight and were used as female parents. The genetic study showed a total of six genes controlling the resistance to Ascochyta blight. The disease progress was analyzed under inoculation in the field on seven dates, and the plant infection rate r was recorded on the parental cultivars and the lines developed from crosses. The temporal progress of the disease was studied by using statistical and mathematical tools. A logistic model was tested and then applied to describe the Ascochyta rabiei progress over time in the field. The fitting adequacy of the logistic model was estimated by the determination coefficient R2 which value exceeded 0.98 and justified this selection. The logistic curves analysis showed a slow blighting and an infection progress decrease of lines issued from Béja1 x desi1 and Nour x Kabuli1 crosses. These lines obtained by transgressive segregation in the Nour x Kabuli1 and Beja1 x Desi2 populations can develop a stable resistance and prevent its overcoming.

Genetic variability, association and diversity analysis of yield and its component traits in rice (Oryza sativa) germplasm

An experiment was conducted during winter (rabi) season of 2022 at ICAR-Indian Institute of Rice Research, Hyderabad, Telangana to evaluate extent of genetic variability, heritability, diversity and the relationship between yield and its component traits in a collection of 60 rice germplasm accessions. Results showed that germplasm accessions exhibited ample genetic variability and diversity for yield traits. Based on per se performance, inter crosses between the genotypes IC458483 with high grain yield, IC210775 with more panicle length, IC75919 with high 100-grain weight, IC75980 with more productive tillers and IC75965 with high protein content could produce positive transgressive segregants for improving respective traits. Plant height, total and effective tillers, grain yield and 100-grain weight traits which exhibited the highest heritability and genetic advance could be vital for selection in hybridization programmes. Crossing among genotypes of diverse clusters specifically VI, VII and VIII is suggested as this could create a broad variation useful for selecting genotypes with both high yield and long panicles.

SONA SUPER BASMATI: A NEW EXTRA-LONG GRAIN HIGH YIELDING RICE VARIETY WITH EXCELLENT COOKING QUALITY

Abstract Rice crop feeds about half of the world’s population which is getting larger and hungrier with every tick of the clock. Basmati rice being a geographical speciality of Pakistan is widely proclaimed as one of the finest rice available throughout the world due to its unique aroma, taste, and texture. Changing consumer behavior and preferences for basmati rice i.e., extra-long grain length along with excellent cooking quality, reiterates the revitalization of rice breeding objectives to develop suitable basmati rice varieties. In this context, plant breeders at Rice Research Institute, Kala Shah Kaku identified a suitable transgressive segregant from F2 segregating population of a cross (PK 10436) between the famous basmati rice variety “Basmati 515” (female parent) and 99417 (male parent). The initial cross of PK 10436-4-2 was accomplished during Kharif, 2010 followed by its rigorous selection and purification in succeeding generations through the pedigree method till F4 generation in Kharif, 2014. After its development, PK 10436-4-2 was evaluated in Station Yield Trials (Kharif, 2016 - 2019) for various yields and its attributing traits in which it gave a cumulative 31.37 % yield advantage over the check variety (Super Basmati). Meanwhile, multi-locational yield evaluation was accomplished in Micro-plot Yield Trials and National Uniform Yield Trials for two consecutive years (Kharif, 2020 - 2021) at various locations across Pakistan; in which, PK 10436-4-2 out-yielded the check variety by 17.50 % and 19.75 % respectively. In addition to superior yield indices, PK 10436-4-2 showed excellent cooking quality i.e., extra-long grain length (AGL = 9.5 mm; CGL = 17.5 mm), with strong aroma. The aforementioned superior credentials of this candidate line led to its approval for general cultivation as “Sona Super Basmati” in the 56th meeting of the Punjab Seed Council, Punjab, Pakistan. In the future, prospects of cultivating Sona Super Basmati could create new vistas not only in local rice consumption but also in the basmati rice export of Pakistan.

Studies on Genetic Divergence in Cabbage Genotypes in the Mid Hills of Solan District, Himachal Pradesh, India

Cabbage (Brassica oleracea var. capitata L.) is one of the most important vegetables of the family Brassicaceae and is grown under temperate to tropical climatic conditions for its head in more than ninety countries throughout the world. The diversity in cabbage is immense due to the presence of variation in shape, size, weight and maturity of heads. The greater the variability in the available germplasm, more would be the chances for selecting superior genotypes for use in breeding programmes or direct use as cultivars. Twenty three genotypes of cabbage including check variety, Golden Acre were evaluated in a Randomized Complete Block Design (RCBD) with three replications. The results concluded that twenty-three diverse genotypes of cabbage were grouped into four clusters. The resultant four clusters showed genetic diversity and maximum number of genotypes were accommodated in cluster I (12) followed by II (7), IV (3) and III (1). The maximum inter cluster distance was recorded between cluster II and III, therefore, the hybridization between the genotypes of cluster II and III can be performed to get superior hybrids or recombinants in segregating populations for further breeding programmes. Based on the mean performance, genetic distance and clustering pattern, inter-varietal crosses can be made which may be advantageous in creating wider variability for better heterotic combinations and transgressive segregants in cabbage.

Selection of Saccharum spp. × Saccharum spontaneum progeny for sugar and biomass traits

ABSTRACT This study evaluated an interspecific hybrid (Saccharum spp. × S. spontaneum) population with the aim of developing germplasm for use in both sugar and bioenergy (biomass) production. Specific objectives were to determine the genetic variability and heritability among the interspecific hybrid progenies for traits of economic importance and to use the Best Linear Unbiased Predictions (BLUPs) to determine their genotypic values. The 46 interspecific hybrids used in this study originated from crossing commercial sugarcane cultivars (UT5, F152, and KK07–559) as female and S. spontaneum clones (THS98–41, THS98–91, THS98–95, THS98–94, and THS97–51) as male parents. There were significant residual variances, attributed to the small plot size, but the juice quality traits were measured with relatively higher precision than other traits. Selection recommendations varied for different traits, suggesting selection pressure could be moderate to high for juice quality traits and moderate for yield-related traits. No hybrid genotypes were found to outperform cultivar parents for traits such as commercial cane sugar and low fiber, necessitating further germplasm enhancement for improvement of varieties destined for sugar production. On the contrary, transgressive segregation was observed for cane yield and other traits influencing biomass yield. The production potential of these hybrids could be tested in larger plots across multiple locations.

Combining ability and multiple parent‐based approach to derive simultaneous transgressive segregants for multiple traits in cotton (Gossypium hirsutum L.)

AbstractPlant breeders are always in pursuit of desirable genes and gene complexes, leading to identification of potential and promising individuals/segregants often exhibiting traits with higher intensity. Identifying segregants with desirable combination of multiple traits would enable a breeder to develop superior cultivars. In this study, combining ability and multiple parent‐based approach was employed to derive segregants simultaneously superior for multiple traits. Single and double crosses were developed by crossing 11 parental lines in half diallel fashion and were evaluated under seven environments. To create crosses, the parental lines with the highest positive gca effects were selected in addition to desirable yield and fibre quality traits (SCYP, NOBP, BW, GOT, UHML and FS). The positive and significantly higher gca effects in these parents is an evidence of prominence of additive and additive × additive component of genetic variance. To identify desirable segregants, six F2 populations derived from four single and their two double crosses were evaluated by raising an optimal population size of 910–935 and 3040–3055 plants for single and double crosses, respectively. In each population, proportion of desirable and simultaneous transgressive segregants was estimated. A total of 19 (2.87%), 22 (3.32%) and 24 (3.60%) plants were transgressive in nature simultaneously for multiple traits in single crosses, namely, RAHH‐1755 and RAHH‐455, and double cross, namely, RHDC‐1933, of Group I, respectively. While in Group II, 22 (3.32%), 22 (3.32%) and 24 (3.60%) plants showed simultaneous transgressive segregation in RAHH‐1702, SHH‐818 and RHDC‐1940, respectively. The per cent simultaneous transgressive segregants were found to be higher in the double crosses compared with their respective single crosses, possibly for the reason that double crosses involve more number of parents owing to increased recombination. Hence, breeding for desirable segregating recombinants using diallel and multiple parent‐based approach paves the way towards directional selection based on combining ability making it more efficient compared with conventional means of hybridization followed by selection.

Extension of the Eeigenvalue-Based Selection Index Method for Fixation of Multiple Trait-Transgressive Segregates in Mungbeans (Vigna radiata L. Wilczek)

The selection of the early generation is a viable strategy for the rapid development of new plant varieties. In mungbeans (Vigna radiata L. Wilczek), the selection process is carried out to obtain high seed yield, early maturity, and sufficiently large seed size. To enhance this process, the extension of the combined-eigenanalysis selection index method (CESIM) with transgressive segregation variables can be used to fix multiple-trait transgressive segregates. Therefore, this research aimed to (1) develop an eigenvalue-based selection index method in information from relatives analysis capable of fixing multiple-trait transgressive segregates in the early generation, (2) predict expected and realized multiple-trait selection responses, and (3) verify the presence of multiple-trait transgressive segregates in the early generation of mungbeans. The material used consisted of the F3 generation population and its selection outcomes in F4, originating from the crossbreeding of mungbean varieties Gelatik × Lasafu Lere Butsiw. The empirical breeding values (EBV) between and within families were obtained using the BLUP values of the F3 generation from the mixed linear model with a nested design and log-normal distribution. The EBV values between families and dummy variables of transgressive segregate families were used in the selection process with CESIM. Furthermore, analysis of variance in EBV values within families in the F4 generation was applied to verify the presence of multiple-trait transgressive segregates. The results showed that the selection from the best CESIM equation yielded index scores with a determination coefficient R2 = 97.76% and an expected selection response of 136.62. The verification process confirmed the presence of 9 families as multiple-trait transgressive segregate families in the early generation.

QTL Analysis of β-Glucan Content and Other Grain Traits in a Recombinant Population of Spring Barley.

Barley with high grain β-glucan content is valuable for functional foods. The identification of loci for high β-glucan content is, thus, of great importance for barley breeding. Segregation mapping for the content in β-glucan and other barley grain components (starch, protein, lipid, ash, phosphorous, calcium, sodium) was performed using the progeny of the cross between Glacier AC38, a mutant with high amylose, and CDC Fibar, a high β-glucan waxy cultivar. The offspring of this cross showed transgressive segregation for β-glucan content. Linkage analysis based on single-nucleotide polymorphism (SNP) molecular markers was used for the genotyping of the parents and recombinant inbred lines (RILs). Two Quantitative Trait Loci (QTL) for β-glucan content and several QTL for other grain components were found. The former ones, located on chromosomes 1H and 7H, explained 27.9% and 27.4% of the phenotypic variance, respectively. Glacier AC38 provided the allele for high β-glucan content at the QTL on chromosome 1H, whereas CDC Fibar contributed the allele at the QTL on chromosome 7H. Their recombination resulted in a novel haplotype with higher β-glucan content, up to 18.4%. Candidate genes are proposed for these two QTL: HvCslF9, involved in β-glucan biosynthesis, for the QTL on chromosome 1H; Horvu_PLANET_7H01G069300, a gene encoding an ATP-Binding Cassette (ABC) transporter, for the QTL on chromosome 7H.

Analysis of Heterosis and Stability in Brinjal at Multi-locations of Gujarat for Yield and its Attributing Traits

Background: Brinjal is the important vegetable crop. The extensive use of heterosis in vegetable crops has led to the creation of numerous high-yielding hybrid cultivars. Newly developed hybrids should also be tested across environments to develop region specific hybrids or hybrid for all the regions. Methods: The purpose of the present experiment was to develop region-specific brinjal (Solanum melongena L.) hybrids through line ´ tester design and to gather information on heterosis and stability for fruit yield and associated characters at multiple locations of viz., Sardarkrushinagar, Jagudan and Bhiloda under the jurisdiction of S.D.A.U. in late rabi 2021–2022. Result: There were noticeable genetic differences in the material for the majority of the traits. Several crosses were identified which showed desirable heterosis for at least one yield component in individual and pooled over locations. Fruit yield per plant is the most important trait. Hybrid ‘ISD-006 × GOB-5’ showed the highest fruit yield and maximum standard heterosis for fruit yield per plant, fruit girth, fruit weight, total soluble solids and chlorophyll content index. The interaction of G × E was highly significant for the majority of characters suggesting the differential response of experimental material to the varied locations. Stability analysis suggested ‘ISD-006 × GAB-6’, ‘JDNB-16-1 × GOB-1’ and ‘ABSR-2 × GAB-6’ as the top three stable crosses for fruit yield per plant. Overall, ‘ISD-006 × GRB-5’ appeared to be an outstanding cross for fruit yield and its attributing traits in terms of heterobeltiosis and standard heterosis in individual and pooled environments. As well as it was found to be average stable for four major traits and stable in favourable environments for fruit weight and yield per plant. Also, incorporating hybrids identified in this experiment might potentially result in transgressive segregants in brinjal.

Adult‐plant resistance to net form net blotch in barley (Hordeum vulgare L.): Durability and genetic control

AbstractThe research reported here was conducted to follow up on observations of durable adult‐plant resistance to net form net blotch in several Australian varieties of barley (Hordeum vulgare L.). Over 11 years, isolates of Pyrenophora teres f. teres were collected and used to inoculate barley varieties. The resistance of five varieties (Clipper, Schooner, Sloop SA, Buloke and Scope) endured until the ninth year. To investigate the genetic control of this durable resistance, doubled haploid lines developed from the F1 generation of a cross between Sloop SA and the susceptible variety Fathom were inoculated with an isolate that appeared fully virulent on Fathom and were evaluated for adult plant resistance. Six quantitative trait loci were mapped: three with resistance from Sloop SA and three with resistance from Fathom. Effects were additive across loci and transgressive segregation provided a few lines with better resistance than Sloop SA. Although the resistance investigated here is no longer effective, insights gained from this research could help guide ongoing efforts in resistance breeding and disease control.

New lentil variety RKL 58F-3715: a case study depicting the emergence of desirable transgressive segregants

Lentil is one of the world’s most important cool-season grain legumes. The frequency of natural recombinants and segregants under natural conditions is very low in lentil due to their cleistogamous flower. The present investigation depicted the emergence of desirable transgressive segregants obtained from spontaneous mutation. Exploiting these hypervariable mutants, a highyielding lentil variety RKL 58F-3715 (Kota Masoor 4; KM 4) was developed from the progeny of a natural variant. The identified single deviated plant from the seed production plot of DPL 62 was probably a spontaneous mutation. During generation advancement, the progenies showed hypervariable segregants, especially for seed morphological traits, such as size, shape, colour and texture. The breeding cycles following rigorous selection under modified pedigree and single seed descent delivered the high-yielding stable genotype KM 4. Hypervariable progenies were obtained from natural mutants, distinguished in morphological traits such as earliness, light foliage colour, and prominent tendrils from the parent variety. The national weighted mean over locations over the year of KM 4 for grain yield was 1865 kg/ha, with yield superiority of 22.80% over national check DPL 62. Considerable resistance against major diseases, i.e., wilt and rust, makes it a durable genotype for commercial cultivation in major lentil-growing areas of India.

Assessment of Transgressive Segregants for Yield and its Component Traits in French Bean (Phaseolus vulgaris L.)

Background: Extreme phenotypes carried on by transgressive segregation are, moreover, heritably stable in contrast to heterosis. It has been hypothesized that the development of extreme or “transgressive” traits in segregating hybrid populations assists in the adaptive divergence of hybrid taxa. The investigation on French bean was experimented to evaluate transgressive segregants generated in the F2 generation for yield and related traits. Methods: The present study on French bean was conducted during rabi 2019 to 2022 to elicit data on transgressive segregants produced for yield and related traits in F2 generation. Fertile F1 hybrids were developed from three crosses: IC 632961 × Arka Sukomal, IC 632961 × Arka Arjun and Arka Arjun × IC 63296. Heterosis was estimated for yield and related traits in these hybrids. The F2 progeny were evaluated in open field condition. Mean, standard deviation and percentage of transgressive segregants were estimated for quantitative traits under investigation. Result: Transgressive segregants were observed in all three crosses, with the highest number of transgressive segregants for yield traits found in the progeny of the cross IC 632961 × Arka Sukomal. The identification and isolation of such transgressive segregants indicate that the parents possess favourable alleles and genes governing the traits of interest, which can be consolidated into a single or a few genotypes through stringent selection. Superior and desirable transgressive segregants were observed for all sixteen yield and its component traits, except for leaf length, in the two cross combinations Arka Arjun × IC 632961 and IC 632961 × Arka Arjun. The highest percentage of transgressive segregation was observed for the number of inflorescences per plant (79.49%), followed by the number of pods per plant (78.46%) and pod yield per plant (75.61%) in the F2 generation.

Identification of Transgressive Segregation for Yield and Resistance to Yellow Stem Borer (Scirpophaga incertulas Walker) in F2 Segregating Generation of Six Rice Crosses (Oryza sativa L.)

The research investigation on the occurrence of transgressive segregation in F2 populations derived from six rice crosses namely: ADT 43 X TKM 6, ADT 43 X ASD 12, ADT 45 X TKM 6, ADT 45 X ASD 12, ASD 16 X TKM 6 and ASD 16 X ASD 12 with the aim of identifying superior genotypes for yield and resistance to the yellow stem borer (Scirpophaga incertulas). This research was conducted through series of field observations for transgressive segregants at Plant Breeding Farm, Department of Genetics and Plant Breeding, Faculty of Agriculture, Annamalai University during Kharif season of 2022. The crosses involved high-yielding but susceptible female parents (ADT 43, ADT 45, ASD 16) and YSB resistant but low yielding male parents (TKM 6, ASD 12). In the F2 generation, a wide range of phenotypes was observed for yield-related traits and YSB resistance. Twelve superior transgressive segregants were identified in each cross, exhibiting increased grain yield per plant, number of productive tillers, and number of grains per panicle, coupled with high levels of resistance to YSB. The results suggest that the parents carried different alleles and genes governing yield and its component traits, allowing the accumulation of favorable alleles in the F2 progeny through recombination. The identification of these high-performing transgressive segregants provides opportunities for further evaluation and potential use in rice breeding programs to develop improved cultivars with enhanced yield and biotic stress resistance.

Transgressive gene expression and expression plasticity under thermal stress in a stable hybrid zone.

Interspecific hybridization can lead to myriad outcomes, including transgressive phenotypes in which the hybrids are more fit than either parent species. Such hybrids may display important traits in the context of climate change, able to respond to novel environmental conditions not previously experienced by the parent populations. While this has been evaluated in an agricultural context, the role of transgressive hybrids under changing conditions in the wild remains largely unexplored; this is especially true regarding transgressive gene expression. Using the blue mussel species complex (genus Mytilus) as a model system, we investigated the effects of hybridization on temperature induced gene expression plasticity by comparing expression profiles in parental species and their hybrids following a 2-week thermal challenge. Hybrid expression plasticity was most often like one parent or the other (50%). However, a large fraction of genes (26%) showed transgressive expression plasticity (i.e. the change in gene expression was either greater or lesser than that of both parent species), while only 2% were intermediately plastic in hybrids. Despite their close phylogenetic relationship, there was limited overlap in the differentially expressed genes responding to temperature, indicating interspecific differences in the responses to high temperature in which responses from hybrids are distinct from both parent species. We also identified differentially expressed long non-coding RNAs (lncRNAs), which we suggest may contribute to species-specific differences in thermal tolerance. Our findings provide important insight into the impact of hybridization on gene expression under warming. We propose transgressive hybrids may play an important role in population persistence under future warming conditions.

Assessment of Breeding Potential of Taro (Colocasia esculenta L.) Genotypes Using D2 Analysis under Hill Zone of Karnataka

Using Mahalanobis D2 statistics, the genetic diversity of 20 genotypes of taro for 21 characteristics was assessed as part of a breeding work to increase production potential. Five clusters were formed from the genotypes, indicating a significant level of genetic variation in the material being studied. With eight genotypes, Cluster I was the largest, followed by Cluster II with seven, and Cluster III with three. Each of the solitary clusters IV and V has a single genotype. The clusters that exhibit the greatest number of genotypes are indicative of limited genetic diversity. The intra-cluster distance was highest in cluster III and lowest in clusters IV and V. Clusters I and V have the highest inter-cluster distance, followed by II and V. These clusters could potentially be used as prospective genotypes for a hybridization programme. Tuber yield/plot (13%) showed the largest contribution to the overall divergence, followed by Corm yield/plant (12.20%) and Tuber yield/plant (11.43%). The finding that clusters V and III showed high cluster means for plant height, number of leaves per plant, leaf breadth, leaf area, leaf area index, tuber yield per plant, tuber yield per plot, and estimated tuber yield is noteworthy. These clusters can be effectively used in hybridization programmes to obtain desired transgressive segregants.

Genetic gains underpinning a little-known strawberry Green Revolution

The annual production of strawberry has increased by one million tonnes in the US and 8.4 million tonnes worldwide since 1960. Here we show that the US expansion was driven by genetic gains from Green Revolution breeding and production advances that increased yields by 2,755%. Using a California population with a century-long breeding history and phenotypes of hybrids observed in coastal California environments, we estimate that breeding has increased fruit yields by 2,974-6,636%, counts by 1,454-3,940%, weights by 228-504%, and firmness by 239-769%. Using genomic prediction approaches, we pinpoint the origin of the Green Revolution to the early 1950s and uncover significant increases in additive genetic variation caused by transgressive segregation and phenotypic diversification. Lastly, we show that the most consequential Green Revolution breeding breakthrough was the introduction of photoperiod-insensitive, PERPETUAL FLOWERING hybrids in the 1970s that doubled yields and drove the dramatic expansion of strawberry production in California.

Genetic Attributes for Selection and Assessment of Yield Enhancement in Paddy (Oryza sativa L.)

The present investigation was conducted in the Agricultural and Horticultural Research Station, Kathalagere. The experiment comprised sixty-seven advanced breeding lines of paddy. The experiment was conducted in three replications with 4mx3m of plot size. The observations are recorded on days to fifty per cent flowering, Days to maturity, Plant Height(cm), Panicles per sqm, Grain yield per plot(kg) and Grain yield per hectare (Kg). The data is subjected to analysis for genetic variability and diversity parameters (Key factors of plant breeding). Higher Genetic coefficient of variability (GCV) and Phenotypic coefficient of variability (PCV) are Days to fifty per cent flowering, Days to maturity, Plant height(cm), Panicles per square meter and grain yield per plot (Kgs) should be considered at the time of selecting the genotypes/varieties/breeding lines for progressing and prospering in the yield and yield contribution towards the varietal performance. Genetic diversity studies proved that the traits viz., days to 50 per cent flowering, Days to maturity, Panicles per square meter, Plant height and Grain yield per plot are prompt traits that contributed maximum divergence to the genotypes. Some clusters are composed of superior genotypes that may contribute to the several crossing studies to improve through transgressive segregants with high genetic yield potential and early maturity.