Heterotic Combinations Research Articles

Multivariate Analysis for Genetic Diversity Estimation in Lotus (Nelumbo nucifera gaertn.) Genotypes

Background: Lotus (Nelumbo nucifera Gaertn.) is a perennial rhizomatous aquatic plant naturally growing in India from Kashmir to Kanyakumari with enormous phenotypic diversity in shape, size and colour. It serves as a gene pool for breeding new, improved cultivars; nevertheless, plants’ natural habitat is disappearing daily due to rapid urbanization driven by population growth. Therefore, the current study was formulated to estimate the genetic diversity for upcoming breeding initiatives and further conservation of available germplasm of lotus. Methods: In the current study, in-situ morphological observations were recorded from thirty-three lotus genotypes between 2022 and 2023, from different locations of Bihar (India). Morphological data on 21 quantitative traits were recorded from selected natural lotus growing site with five replications. Result: Based on principal component analysis, six principal components were identified, which accounted for 88.97% of total genetic variation. In D2 analysis, genotypes were categorized into six different clusters. Cluster II consisted of the maximum number of genotypes (23) followed by cluster I (4). The highest intra-cluster distance was recorded for cluster II (184.40), while the inter-cluster distance was highest between cluster VI and III (5098.07). The study highlights the enormous genetic diversity among the genotypes of lotus and generates information about suitable breeding material(s) for future crop improvement programs. The genotypes from distant clusters may serve as potential genetic material for further selection or a superior heterotic combination for lotus breeding.

Genetic Diversity of Maize (Zea mays L.) Genotypes under Low Level of Nitrogen

Maize (Zea mays L.) is India's second most significant crop, behind rice. As a cross-pollinated crop, hybrid vigour is commonly used to achieve the best production potential. The selection of various genotypes is a primary goal in the maize hybrid breeding programme. Maize is a voracious feeder and requires a lot of fertiliser. The biggest limits on maize production in India are low soil nitrogen and high fertiliser costs. Jharkhand consumes only 82.5 kg of total fertiliser nutrients per acre. In order to discover genetically varied maize genotypes for nitrogen usage efficiency, the current study evaluated 121 maize genotypes in a randomised block design with two replications at low nitrogen levels. Plant height, days to 50% pollen shed, days to 50% silk, anthesis-silking interval (ASI), days to75% maturity, number of leaves per plant, root length, stover yield per plant, grain yield per plant, and harvest index were all recorded. Statistical analysis was performed using the morphological trait data. Analysis of variance revealed substantial (p≤0.05) variations in morphological features between maize genotypes. For statistical analysis, a clustering method was used to locate various genotypes with greater genetic distance in order to develop good heterotic combinations. One hundred twenty one genotypes were divided into six clusters using the dendogram-by-ward minimum variance approach. Cluster III and V had the greatest inter-cluster distance (79.26), followed by cluster III and VI (74.77) and cluster II and III (73.80). The many heterotic combinations developed from these clusters can be employed in subsequent breeding programmes to produce low nitrogen-requiring hybrids with a low yield penalty.

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.

F1 Hybrids in oil palm

F1 Hybrid production in oil palm (Elaeis guineensis) is a reality. F1 Hybrids have the potential to provide massive increases in yield as demonstrated in a range of crops. Verdant has the intellectual property and “know-how” to produce haploids and double them to give doubled haploids. Doubled haploids are fertile and 100% homozygous (genetically pure lines), making them ideal as parents for F1 Hybrids. There has been no genetic modification. Verdant now has a collection of Dura and Pisifera doubled haploids that span the genetic diversity of oil palm from which parents can be selected based on genetic contrasts (using Diversity Array Technology). The first F1 Hybrid crosses (Dura x Pisifera) were made in 2019 and field progeny trial testing started in 2021. Performance in the field is being monitored by a range of physiological tests, but ultimately on palm product yield per hectare plus commercially significant secondary traits, such as disease tolerance, will determine selection. The intention is to start commercial F1 Hybrid seed production in 2029. A phenomics nursery has been set up to correlate seedling physiological traits with yield with the aim of developing early indicators for yield potential and to screen for variation between crosses for 1) Ganoderma tolerance, 2) nutrient uptake, and 3) drought tolerance. Genotyping is also being deployed to identify and select heterotic combinations that result in hybrid vigour.

Variability in Indian wheat germplasm for important quality and physiological traits

Knowledge of variability in wheat genotypes is important for proposing crosses intended for development of heterotic combinations with improved stability. The present study consists of 120 wheat genotypes comprised of landraces, genetic stocks, released varieties, and improved genotypes. For the research experiment was conducted field in two rabi seasons (2019–2020 and 2020–2021) at ICAR-IIWBR, Karnal and a total of 120 genotypes were assessed using a randomized block approach for four quality (Zinc, iron, protein content and nitrogen) and six different physiological traits (Normalized difference vegetation index [NDVI]-1, NDVI-2, Soil Plant Analysis development [SPAD]-1, SPAD-2, Canopy Temperature [CT]-1, and CT-2) beside grain yield (GY). The occurrence of significant genetic variability amongst the several genotypes for nutritional and physiological characters indicates the inevitability for utilization of a considerable degree of genetic variation through the process of selection. The genotypic and phenotypic coefficients of variation (Genotypic coefficient of variation and Phenotypic coefficient of variation) exhibited their peak values for the trait GY, tailed by, grain zinc content, nitrogen (%), and SPAD-2. The high heritability values, in conjunction with substantial genetic advances, are indicative of the significance of GY, zinc, nitrogen, and protein content are key traits that hold potential for crop enhancement purposes. The total set of 120 genotypes clustered into 12 discrete sets on the basis of quality and physiological traits using the clustering technique and principal component analysis program available in the Statistical Package for Agricultural Research. Principal components axis 1 to principal component axis 4 unveiled about 71.31% of the total variability. Based on the findings of this study, it can be inferred that the released varieties showed greater performance in terms of grain output, although some landraces displayed higher values for the quality features. Hence, to acquire a comprehensive range of superior quality (Zn, PC, N, and Fe) cum high-yielding segregants, the selected genotypes from clusters “C” and “L” could function as better lines of parentage to organize breeding plans.

Heterotic combinations among advanced breeding lines of brinjal (Solanum melongena L.)

The present study aimed to examine the performance of hybrids developed from advanced breeding lines in brinjal. Fifty F1 hybrids including three checks of different fruit groups were evaluated for yield and quality attributes in randomized block design with three replications. Analysis of variance indicated significant differences for different characters in small round, big round and long hybrids except fruit length among small round hybrids. Among small round hybrids, SR-5 × SR-9322 showed the highest heterosis for the number of fruits per plant (60.80%) and fruit yield per plant (6.17%) over the standard check PBH-3. Among big round hybrids, BR-15-2 × SR-9322, PC-123 × JG, BR-324 × SR-9322 and MR-494 × SR-6793 showed significant heterosis for a number of fruits per plant and fruit yield per plant in comparison to standard check PBHR-41. Among long hybrids, the hybrid combinations, BL-47 × MR-494, BL-47 × BR-21-6, BL-47 × MR-431, BL-47 × BR-1142 performed the best for fruit yield per plant overcheck hybrid PBH-5. For quality traits such as dry matter percentage, total phenols and anthocyanin, SR-5 × SR-9322 and MR-494 × SR-9322 (small round hybrids), BR-15-2 × SR-9322 and BR-1142 × SR-6793 (big round hybrids) and BL-214 × MR-319, BL-23 × MR-319 and MR-494 × BL-72 (long hybrids) performed better than their respective standard checks. The best-performing hybrids in the present investigation can further be exploited for commercial release

BREEDING AND GENETIC FEATURES OF SOYBEAN VARIETIES BASED ON THE MANIFESTATION OF TRAITS IN F1 HYBRIDS IN TOPCROSSES

Further increase in gross soybean production requires the introduction of new varieties with an optimal combination of elements of the crop structure. Hybridization in soybeans is the main effective method of creating new varieties. Increasing the efficiency of hybridization in obtaining heterotic offspring is possible when using parental forms with high combinational ability in crosses. In the study, a two-tester analysis of topcrosses of soybean varieties differing in economically valuable traits was used. Based on the results of the combinational ability assessment, the value of soybean varieties was determined by the elements of the yield structure. Heterotic combinations in first-generation hybrids were identified, from which it is more likely to select highly productive forms in later hybrid populations F2-F4. The high effects of ZKZ and SCZ on plant height in varieties Medea, Kyivska 97, Sawyer 2-95 and KiVin tester; on the height of lower bean attachment in varieties Sawyer 2-95, Ustia, Kharkivska skoroglya and KiVin tester; on the number of productive nodes - in varieties Kyivska 97 and Goverla tester; by the number of beans per plant - in varieties Sawyer 2-95, Kyivska 97 and tester Goverla; by the number of seeds per plant - in varieties Medea, Kyivska 97 and tester KiVin; by the weight of 1000 seeds - in varieties Sawyer 2-95, Kyivska 97 and tester Goverla; by the weight of grain per plant - in varieties Sawyer 2-95, Kyivska 97 and tester Goverla. It was found that additive effects of genes were predominant in the genetic control of plant height and lower bean attachment, elements of yield structure and grain weight per plant, but there is a smaller influence of non-additive effects. The manifestation of true heterosis (dominance in 100% of cases) in hybrids (F1) was found in crosses with both testers for the number of productive nodes, number of beans and seeds per plant, and grain weight per plant.

Studies on Promising Restorer Lines for Yield and Yield Components in Rice (Oryza sativa L.)

The present investigation was carried out at Regional Agricultural Research Station, Maruteru with a set of 30 experimental hybrids developed by crossing three male sterile lines with 10 testers in Line × Tester mating design during kharif, 2022. The resultant 30 hybrids were evaluated in Randomized Block Design with two replications along with the parents and hybrid check, HRI-174 during rabi, 2022-23. Analysis of variance for yield and yield components revealed significant differences among the genotypes, parents, hybrids and parents vs. crosses for most traits, indicating significant differences among parents and hybrids, in addition to significant levels of heterosis for the traits studied. In general, the hybrids had recorded higher grain yield per plant, compared to the lines and were observed to be early and relatively tall with a more number of productive tillers per plant and increased panicle length compared to the parents. The hybrids, APMS 15A×RGL 5613, APMS 15A×MTU 1213, APMS 17A×RGL 5613 and APMS 17A ×MTU 2055had recorded significant and positive relative heterosis, heterobeltiosis and standard heterosis of more than 25 per cent for grain yield per plant and were identified as promising heterotic combinations for further evaluation and commercial exploitation.

Prediction of heterotic combinations using correlation between genetic distance, heterosis and combining ability in yellow sarson (Brassica rapa var. yellow sarson Prain)

Prediction of heterotic combinations using correlation between genetic distance, heterosis and combining ability in yellow sarson (Brassica rapa var. yellow sarson Prain)

Morphological characterization, combining ability and heterosis for important horticultural traits in snowball cauliflower (B. oleracea var. botrytis L.)

AbstractCauliflower is an important vegetable crop grown worldwide. Development and characterization of suitable cytoplasmic male sterile (CMS) lines and male fertile inbreds is instrumental in developing heterotic hybrids. A study was undertaken to estimate heterosis and combining ability in snowball cauliflower lines through line × tester analysis involving five Ogura CMS lines and seven male fertile testers. The assessment of F1s along with their parental lines for different horticultural traits revealed a wide range of heterosis. Ogu-13-01 was the best general combiner for leaf length, leaf width and plant height, Ogu-13-85 for number of leaves/plant, Ogu-101 for days to 50% curd initiation, days to 50% curd maturity and net curd weight and Ogu-119 for harvest index. The lines with better general combining ability (GCA) were involved in majority of the heterotic hybrids. The tester Kt-18 was the best general combiner for leaf width, DB-1305 for number of leaves/plant and DB-187 for leaf length, plant height, gross plant weight and days to 50% curd initiation. However, GCA alone was not sufficient to determine and identify the potential parental lines. Hybrids Ogu-101 × DB-1305 and Ogu-119 × Suprimax Late were the best specific combinations for marketable curd weight, marketable curd yield, net curd weight and net curd yield. The hybrid Ogu-119 × Suprimax Late was the best heterotic combination for marketable curd weight, marketable curd yield, net curd weight and net curd yield, followed by Ogu-101 × DB-1305, Ogu-119 × Sel-26 and Ogu-101 × DB-187. Our findings will be instrumental to identify suitable parental lines and developing heterotic F1 hybrids in cauliflower.

Heterosis studies for grain yield and yield attributes in rice (Oryza sativa. L) hybrids

In the current study, 20 elite rice genotypes were crossed with four CMS lines- CMS 23A, CMS 59A, CMS 64A and JMS 13A in a line x tester mating design and assessed alongside standard controls (JKRH 3333 and MTU 1001) to determine the best heterotic combinations in terms of grain yield and yield component characters at the Rice Research Centre, Rajendranagar. Eight restorer lines were found in Kharif 2018–19 based on pollen and spikelet fertility (MTU 1153, RNR 26015, RNR 28355, JGL 25960, MTU 1010, IET 27253, RNR 26085 and JAYA). The resulting 32 hybrids of 8 restorer lines and their corresponding CMS lines are studied for combing ability and heterosis. The degree of heterosis varied between traits. Three of the 32 hybrids under study had considerable standard heterosis for grain yield viz., JMS 13A x MTU 1153, CMS 59A x RNR 26015 and CMS 64A x MTU 1153, which outperformed the best checks JKRH 3333 and MTU 1001. The best experimental hybrid, JMS 13A x MTU 1153, yielded the most grain yield per plant, 62.89g (Table 1). Further testing of these three experimental hybrids will take place in areas conducive to extensive commercialization. Keywords: Rice, Heterosis, Heterobeltiosis, Standard heterosis, Grain yield, Line x Tester

Heterosis Studies in Snake Gourd (Trichosanthes Cucumerina Var. Anguina L.)

An investigation was carried out on snake gourd at the research farm of the Department of Horticulture, Bangabandhu Sheikh Mujibur Rahman Agricultural University (BSMRAU), Bangladesh during March to June 2019. Significant heterosis was observed for most of the characters studied to find out high heterotic combination for better hybrids. Both positive and negative heterosis were found for different characters of the F1 hybrids over better parents. The best better parent heterotic performance was exhibited by early flowering and fruit fly infestation in P2 x P7 and P6 x P7, respectively while P3 x P7 for higher individual fruit weight; P1 x P3, P2 x P6, P3 x P7, P4 x P6 for number of fruit bearing; P1 x P3, P2 x P3, P2 x P7, P3 x P7, for higher fruit yield per plant and hectare; P1 x P3, P2 x P3, P2 x P6, P3 x P7 for maximum fruit length P2 x P6, P4 x P6, P4 x P7 for fruit diameter as well as for increasing 100-seed weight the cross combinations were P2 x P3, P4 x P6. Based on all the characters and heterotic performance, the crosses combinations viz., P1 x P3, P2 x P6, P3 x P7 and P6 x P7 can be selected to exploit improved hybrid lines.
 Bangladesh J. Agril. Res. 47(1): 1-12, March 2022

Deciphering variability for heat tolerance index in maize hybrids and identification of stress resilient heterotic combinations

Aim: High temperature at any critical stage for a prolonged duration is documented to negatively affect the growth and yield related processes in maize. Therefore, the present study was planned to identify resilience of different heterotic combinations to heat stress under field conditions. Methodology: A set of 20 parental lines were used as parents and 21 single cross hybrids raised in kharif 2020 using 16 lines as female parent and four lines as male parent along with three commercial checks using randomized block design under two regimes: Normal Sownin mid of February, i.e., timely sown condition (spring season crop) and late sown in mid of March (heat stress crop). Data was recorded for yield and its contributing traits. Results: Heat stress led to early onset of flowering, thus resulting in shortening of vegetative phase. Consequently, days to grain filling period was found to be reduced (84-106 days) under late sown as compared to 100-123 days under normal sown condition. Amongst the top performing six hybrids in both normal sown and late sown conditions, three hybrids were common viz., JH 20003, JH 20015 and JH 20018, though with different ranking, inferring their wider adaptability and tolerance to heat stress. Under late sown conditions, days to grain filling (r2=0.55) and thousand seed weight (r2 =0.50) showed significantly positive correlation with grain yield while as highly significant and negative association was observed between anthesis silking interval and grain yield (r2 = -0.76). Among the 21 hybrids, three hybrids (JH 20001, JH 20004, and JH 20015) showed greater potential under heat stress conditions on the basis of yield performance under stress, percent yield reduction and heat tolerance index. Interpretation: Based on multiple selection criteria, three hybrids viz., JH 20001, JH 20004, and JH 20015 were suggested for commercial utilization after validation. This study also led to identification of donor inbreds which can contribute to breeding for heat stress tolerance. Key words: Grain yield, Heat tolerance index, Heat stress, Maize, Percent yield reduction

Genetic Diversity Analysis for Yield and Quality Traits in Rice Cultivars of Manipur and Assam

The North–Eastern region of India is blessed with wide variability in rice. The present investigation was carried out with 41 diverse cultivars of rice collected from the farmers’ fields of Manipur and Assam to estimate the nature and magnitude of genetic divergence among the genotypes using Mahalanobis D2 statistics. The germplasm consisted of the popular black rice and some glutinous and non-glutinous rice which are commonly grown in both regions. The experimental materials were evaluated during the Kharif season of 2020-2021, following a randomized block design with three replications at the experimental field of BN College of Agriculture, Biswanath Chariali, Assam. The genotypes exhibited significant differences for all 24 characters under study. The cluster analysis indicated that 41 genotypes were grouped under 12 different clusters and cluster IV was the largest comprising the maximum number of genotypes with 12 genotypes, followed by cluster V with eight genotypes, cluster X with five genotypes, clusters II and XII with four genotypes each, cluster I with two genotypes and clusters III, VI, VII, VIII, IX & XI with one genotype each. Among all the characters studied, grain length exhibited maximum contribution towards divergence followed by kernel length after cooking, grain breadth, 100-grain weight and kernel breadth after cooking. Clusters X and XII showed the maximum inter-cluster distance and the maximum intra-cluster distance was exhibited by cluster XII, indicating the existence of a significant amount of variability within the cluster. The intra-cluster distance ranged from zero (clusters III, VI, VII, VIII, IX, XI) as they consist of a single genotype each to 1146.89 (cluster XII). Hybridization among the genotypes of clusters X and XII is expected to produce better heterotic combinations.

Combining Ability Analysis and Marker-Based Prediction of Heterosis in Yield Reveal Prominent Heterotic Combinations from Diallel Population of Rice

Combining ability along with heterosis was elucidated in the 21 F1 hybrid population of rice derived from a 7 × 7 diallel mating design. Furthermore, to formulate a strategy for marker-based prediction of heterosis, the molecular genetic diversity (GD) was then surveyed among the seven parental lines with RAPD markers. Analysis of combining ability revealed significant GCA and SCA variances and the ratio between the aforesaid genetic parameter was more than unity for most of the traits signifying the preponderance of additive gene action. Hybrid combination Double Rice × Pokkali was the best specific combiner for the traits pollen fertility percentage (%), panicle length (cm), filled grains/panicle (no.) and grain yield/hill (g) while Muktagacha × BRRI dhan29 and Basmati × Double Rice were the best specific combiners for grain length (mm) and 1000-grain weight (g), respectively. Regarding the magnitude of heterosis, Double Rice × Pokkali exhibited maximum heterobeltiosis for panicle length (33.33%) and the number of filled grains/panicle (144.01%). Furthermore, Pokkali × Chinigura was verified for producing the highest heterobeltiosis for tillers/hill (173.17%), as well as grain yield/hill (71.05%). The heatmap relying on molecular genetic diversity exposed the highest genetic distance between Chinigura and Pokkali followed by Muktagacha and Pokkali. Unweighted neighbor-joining trees clustered the parental lines into three groups indicating the presence of considerable genetic diversity among those seven parental genotypes. A positive and significant correlation was explored between molecular GD with specific combining ability as well as heterosis for all of the traits revealing the huge potentiality of hybrid performance prediction using RAPD markers with the present set of individuals. Thus, exploration of definite genomic regions underlying the candidate genes for respective traits relying on such RAPD-generated data following an advanced molecular marker approach would pave the path of mining out yielder heterotic combinations.

Heterosis and combining ability for yield traits and its relationship with gene action in muskmelon (Cucumis melo)

Twenty-one F1 hybrids were developed from seven diverse parental lines of muskmelon (Cucumis melo L.) from two horticultural groups, viz. inodorous and cantalupensis through half-diallel mating system and evaluated at ICARIndian Agricultural Research Institute, New Delhi, during 2017 and 2018. The component of variance for sca (σ2s) was higher than gca component of variance (σ2g) for all the characters, except average fruit weight, which indicated the importance of non-additive gene action for improvement of many traits. The predictability ratio and average degree of dominance was less than 0.5 and more than 1 for all the yield related traits, except average fruit weight, which further confirmed the predominant role of non-additive component of variance. The parent DHM-163 (P1) was identified as good general combiner for earliness, whereas parent DCM-31 (P4) for fruit length, average fruit weight and yield per plant. The parent Pusa Madhuras (P5) also exhibited highest gca effects for number of fruits per plant, number ofprimary branches per plant, fruit diameter and negative gca effects for days to first fruit harvest. The hybrid DCM-31 × Kashi Madhu (P4 × P6) exhibited highest heterotic value for days to first male flower anthesis, days to first female flower anthesis and days to first fruit harvest. Three crosses, DMM-159 × Pusa Madhuras (P3 × P5), DHM-163 × Kashi Madhu (P1 × P6) and DMM-159 × DCM-31 (P3 × P4) were found to be best heterotic combinations for yield related traits. These promising heterotic hybrid combinations may be tested under multi-location trials to assess their potential as commercial hybrids.

Phenotypic Diversity Analysis of Lens culinaris Medik. Accessions for Selection of Superior Genotypes

Knowledge of genetic diversity in lentil is imperative for selection of parental genotypes that could yield heterotic combinations. The aim of the present study was to investigate the genetic diversity among 43 diverse lentil genotypes to identify complementary and unique genotypes for breeding programmes. Field experimentation was carried out in two winter seasons (2019–2020 and 2020–2021) in Hisar (29°10′ N, 75°46′ E) using randomized block design (RBD) with three replications. The chi-square test analysis showed significant genotypic variation for qualitative traits. There was substantial genetic variation among the genotypes for most quantitative traits, connoting the need to exploit a high degree of genetic variation through selection. Multiple-trait selection would also be beneficial, as seed yield was positively associated with most quantitative traits. The principal component analysis recognized seed yield (SY), days to 50% flowering (DTF), days to maturity (DTM), number of pods per plant (NPP), number of primary branches (NPB), plant height (PH) and biological yield (BY) as target traits that prominently described variation within lentil genotypes. The cluster analysis discriminated the lentil genotypes into five discrete clusters. Cluster III and V were the most distant groups, implying wider diversity among the genotypes of these groups. Furthermore, cluster analysis identified genotypes IPL 316, LH 17-19, LH 18-04, LH 17-17, IPL 81 and Pant L-8 as high-yielding genotypes, while L 4717 was identified as an early-maturing genotype. Therefore, to obtain a broad spectrum of early-maturing high-yielding segregants, the selected genotypes may serve as superior parental lines for structuring breeding strategies.

Heterotic grouping of Indian baby corn lines based on combining ability

The present study involved estimating the combining ability effects and heterotic grouping to increase the efficacy of parental selection for successful hybrid development. A total of 52 F1 hybrids were generated by Line × Tester mating design by crossing 26 diverse maize inbred lines with two testers, namely, HKI 323 and HKI 1105. The 26 baby corn inbred lines were classified into a different heterotic group based on the specific combining ability (SCA) effects and heterotic groups specific and general combining ability (HSGCA). The SCA effects and HSGCA of baby corn yield without husk (BCY) classified the inbred lines into five and four groups, respectively. This is the first study of heterotic’s grouping for baby corn germplasm considering BCY based on SCA and HSGCA methods. The information generated through heterotic grouping may be used to derive new inbred lines and develop different heterotic combinations for further utilization in breeding programs.

Heterosis response and combining ability (variance and effect) analysis for seed yield and its components in Indian mustard (Brassica juncea L.) under timely sown condition

Diallel analysis excluding reciprocal crosses comprising of seven parents and their 21 specific hybrids was carried out to identifyhigh heterotic combinations and their relationship in terms of general and specific combining ability (GCA and SCA) in Indian mustard. Highest economic heterosis for yield was observed in crosses namely; NRCHB-101 x Pusa M-21, Urvashi x Pusa Bold, NRCDR-2 x Urvashi, Maya x Pusa Bold, and Maya x NRCDR-2. The economic parents Urvashi, Pusa Bold, NRCHB-101, Pusa M-21, NRCDR-2, Maya and RGN-73 were the best parents for majority of the characters with Urvashi and Pusa Bold being the best economic parents for seed yield/plant and its contributing characters as their GCA and per se performances were high. Analysis of variance for GCA and SCA signified differences for majority of the characters. Ratio of GCA and SCA variances was below unity for majority of the characters except Days to 50% flowering and Days to maturity, which suggested superior role of non-additive genetic variance in the inheritance of these traits. The crosses namely Maya x NRCDR-2, Maya x Pusa Bold, NRCDR-2 x Urvashi, NRCHB-101 x Pusa M-21 and Urvashi x Pusa Bold showed high per se performance as well as SCA effects for seed yield and its contributing characters. The above best parents and best crosses could be used in hybridization and heterosis breeding respectively.

Genetic analysis of parental lines and identification of heterotic hybrid combinations in rice (Oryza sativa L.)

Thirty hybrids along with their parents (B and R lines) and standard checks viz., MTU 1001 and 27P63 were evaluated for grain yield and related traits to study combining ability and heterosis in rice. The mean performance of the hybrids for most of the characters was found higher than that of parents. The analysis of variance revealed significant differences among lines, testers and hybrids for most of the characters studied. SCA variances were found lower than GCA variances for most of the characters and average degree of dominance was far from unity indicating the predominance of additive gene action for these traits. However, for effective bearing tillers and spikelet fertility the average degree of dominance was very near to unity inferring the predominance of non-additive genetic components for these traits. The gca effects revealed that the lines, RNR 25783 and RP 5980-109-12-9-27 had significant gca effects in desired direction for yield and yield attributing traits whereas the tester, CMS 59A was a good general combiner. SCA effects showed that the hybrid, JMS 13A × RNR 19361 was found to be good specific combiner for grain yield per plant and spikelet fertility. Similarly, the hybrids, CMS 59A × SYE 503-78-34-2, CMS 46A × WGL 347 and JMS 13A × RP 5980-109-12-9-27 were identified as good specific combiner for grain yield and yield contributing characters. Based on heterotic estimates, five hybrids viz., CMS 59A × RNR 25783, CMS 59A × WGL 14, JMS 13A × RNR 25783, CMS 59A × RNR 25776, JMS 13A × RP 5980-109-12-9-27 were identified as promising with more than 5% and 20% yield advantage over hybrid and varietal checks, respectively.