Estimation of Gene Action for Seed Yield and Component Traits using Generation Mean Analysis in Pigeonpea [Cajanus cajan (L.) Millspaugh]

Background: For improvement of quantitative traits the information on nature of gene action is an important asset for plant breeders. However, the information on gene action for yield and its attributes is scanty in pigeonpea crop. Methods: The present experiment was carried out during kharif 2018-2020 at GBPUAT, Pantnagar, Uttarakhand. The experimental material consisted of six generations of three crosses viz., PADT-16 × PUSA 992, PADT-16 × UPAS 120 and PADT-16 × PAU 881. The observations were recorded on nine morphological characters. The gene action was estimated by three parameters model of Jinks and Jones if scaling tests were non significant and six parameters model of Hayman if scaling tests were significant. Result: For majority of traits in all three crosses, epistatic gene action was present as scaling tests were found to be significant. However, for traits number of primary branches, number of secondary branches and number of seeds per pod in cross PADT-16 × UPAS 120 a simple additive/dominance model was found to be adequate. In general, magnitude of dominance was found to be higher as compared to corresponding additive gene action. The high magnitude of dominance indicated that heterosis breeding is rewarding in these characters.

Heterosis and combining ability studies by Line × tester analysis for fruit biochemical, morpho-physiological, and yield traits governing shelf life in tomato (Solanum lycopersicum L.)

Improving tomatoes keeping quality is crucial for reducing post-harvest losses. Knowledge on heterosis, and combining ability is pre requisite for breeding high yielding and good shelf life heterotic hybrids. An investigation was undertaken with each of 3 lines, testers, and 9 hybrids to identify desirable parents and crosses for 20 fruit biochemical, morpho-physiological, and yield traits and to elucidate nature of gene action for shelf life and its contributing traits through Line × Tester analysis. The lines contributed to most of hybrids variability than testers and fruit quality traits had higher degree of SCA variance as compared to GCA variance. pH, ascorbic acid, fruit firmness, and plant height governed by additive gene action. Lycopene, titratable acidity, TSS, calcium, magnesium, pericarp thickness, pulp content, locule number, fruit length, diameter, weight, shelf life, number of branches, number of clusters, number of fruit/cluster, and yield/plant were under the control of non-additive gene action. All the lines and Arka Saurabh were best general combiners and IIHR 2349 × Arka Vikas, IIHR 2349 × Arka Saurabh, IIHR 2358 × Arka Ahuti and IIHR 2357 × Arka Ahuti were the best specific combiner in producing heterotic hybrids. IIHR 2349 × Arka Vikas and IIHR 2349 × Arka Saurabh were promising hybrids for high yield and shelf life. The crosses involved both parents with high, one parent with high and other with low and both parents with low good overall general combining ability status respectively indicated the additive, non-additive and epistatic gene action in fruit quality and yield traits inheritance.

Genetic Analysis of Yield and its Attributes in Bread Wheat (Triticum Aestivum L. Em. Thell) Under Irrigated and Rainfed Conditions

Experiments were conducted to study the genetics and combining ability for yield and its attributes under Irrigated (E1) and Rainfed (E2) conditions using F1 hybrids derived from Line X Tester mating design by crossing eleven lines with three testers. Significant differences were observed among all the genotypes for all the traits in both E1 and E2 environments as well as in pooled analysis. The σ2gca/σ2sca ratio indicated predominance of non-additive gene action for all the characters in both environments. Therefore, this component of variance can be utilize in breeding programme through exploitation of heterosis and the selection process for identification of superior plant type should be postponed to further generations like F4 or F5. VL3001 and KACHU*2//WHEAR/SOKOLL was identified as good general combiner in irrigated condition (E1) and in rainfed condition (E2), respectively for maximum number of traits. Parent VL3001 was also identified as good general combiner for maximum number of traits in case of pooled analysis. Cross BECARD/KACHU × WH1080, BOW/VEE/5/ND/VG9144//KAL/BBB/YACO/4/CHIL/6/CASKOR/3/… × WH1080 and C306 × WH1142 was identified as good specific combination for maximum number of traits in irrigated condition (E1), rainfed condition (E2) and in pooled analysis, respectively.

Study of Combining Ability and Heterosis in Quality Protein Maize using Line x Tester Mating Design

Background: High protein content with good quality maize is likely to gain wider acceptance if hybrids are produced that have agronomic performance similar to normal hybrids and retain an enhanced nutritional quality. Thus, an attempt was made to develop quality protein maize hybrids for the benefit of different sections of society depending on maize. Methods: During the Rabi season of 2016-17 (hybrids were obtained crossing ten inbred lines and four testers following Line x Tester mating design) and 2017-18 (evaluation of hybrids and parents involved along with two commercial checks based on different agro-morphological traits). Result: Highly significant differences were observed among lines, testers and crosses. Combining ability revealed SCA variances was higher indicating preponderance of non-additive gene action. The contribution of line x tester interaction was higher suggesting parents used in this study can provide high heterotic cross combinations. The parents CML 508, CML 163-D and CML 169 were superior general combiners, indicating their efficacy as parents in future maize breeding programs. Heterosis identified superior yield advantage of the crosses namely, CML508 x CML154-2, CML170 x CML169 and CML163-D x DMRQPM103 over the standard commercial checks HQPM1 and 900 M Gold.

Genetic Analysis of Early White Quality Protein Maize Inbreds and Derived Hybrids under Low-Nitrogen and Combined Drought and Heat Stress Environments

An increase in the average global temperature and drought is anticipated in sub-Saharan Africa (SSA) as a result of climate change. Therefore, early white quality protein maize (QPM) hybrids with tolerance to combined drought and heat stress (CDHS) as well as low soil nitrogen (low-nitrogen) have the potential to mitigate the adverse effects of climate change. Ninety-six early QPM hybrids and four checks were evaluated in Nigeria for two years under CDHS, low-nitrogen, and in optimal environments. The objectives of this study were to determine the gene action conditioning grain yield, assess the performance of the early QPM inbred lines and identify high yielding and stable QPM hybrids under CDHS, low-nitrogen and optimal environment conditions. There was preponderance of the non-additive gene action over the additive in the inheritance of grain yield under CDHS environment conditions, while additive gene action was more important for grain yield in a low-nitrogen environment. TZEQI 6 was confirmed as an inbred tester under low N while TZEQI 113 × TZEQI 6 was identified as a single-cross tester under low-nitrogen environments. Plant and ear aspects were the primary contributors to grain yield under CDHS and low-nitrogen environments. TZEQI 6 × TZEQI 228 and the check TZEQI 39 × TZEQI 44 were the highest yielding under each stress environment and across environments. Hybrid TZEQI 210 × TZEQI 188 was the most stable across environments and should be tested on-farm and commercialized in SSA.

Heritability and Genetic Advance as Genetic Indicators for Improvement in Two Cotton Crosses

The primary breeding goal for the Egyptian cotton breeding program is how to genetically improve both yield and fibre quality traits, while most of these agronomically traits are biometric traits. The objective of the present study is to evaluate variability and estimate frequency of transgressive segregants in order to isolate early superior individual plants which exceeding the better parent for some yield and fiber quality traits in two intraspecific cotton crosses in early transgressive segregating generation (F2 ). The F1 was highly significant superior than the better parent (Giza 97 and Giza 94) of the two crosses for all the studied traits except boll weight and lint %. Most of the studied traits in F2 generation showed high values of broad sense heritability coupled with low GAM % indicated that these traits controlled by non-additive gene action. All the studied traits had positive skewness sign except for lint %. Presley index and uniformity index for the two cotton crosses and upper half mean for cross II showed negative skewness. The negative skewness indicated that the population had more plants frequency with higher mean values than population mean and controlled by dominancy alleles. While, the traits that had positive skewness are controlled by additive gene action. The two cotton crosses showed transgressive segregants for all the studied traits. Cross I has higher transgressive index for yield traits than cross II, while cross II has the same trend for fiber quality traits than cross I. These results indicated that the both parents of the two cotton crosses had different alleles and genes governing the respective studied traits, which will help cotton breeder to combine beneficial alleles into a single genotype by rigorous selection process. This strategy could be used to improve many economic biometric traits by using better and stringent selection procedure to enhance Egyptian cotton productivity which is major concern in Egypt. The breeder can use transgressive segregation as an indicator of genetic variability to select the most superior plants.

Genetic control of fruit shelf life and yield in crossbreeding of Sletr1-2 mutant with Indonesian tropical tomatoes

Postharvest losses are a significant concern for tomato breeding associated with their short fruit shelf life. Sletr1-2 is a new ethylene receptor mutant that has a prominent character in a prolonged fruit shelf life. This research aimed to estimate the combining ability of Sletr1-2 mutant and determine the selection method for future breeding associated with the fruit shelf-life and yield. Four lines of tropical tomato, i.e., 'Intan,' 'Mirah,' 'Ratna' and 'Mutiara,' were crossed with the wild type Micro-Tom (WT-MT) and Sletr1-2 mutant tomato using a line x tester mating design. A randomized complete block design with four replications was used to evaluate twelve F1 and their parents. The study revealed significant differences in the GCA of the line and tester but not for SCA. The lines and testers contributed more to total variance than their interaction. 'Intan' and Sletr1-2 mutants had the greatest fruit shelf-life combiners, with additive gene action being the most prevalent. Simple phenotypic selection or pure line selection from selected crosses in advanced generations would be preferable. 'Mutiara' was the best combiner for yield and plant growth, with non-additive gene action was the most common. The breeding strategy that considered dominance, overdominance, and epistasis was preferred.

Genetic Investigation in Segregating Generation of Brinjal (Solanum melongena L.)

The genetic variability studies indicated that the prevalence of sufficient genetic variation among the genotypes for all the characters. The high Genotypic co-efficient of variation and Phenotypic co-efficient of variation were observed for the number of primary branches and number of fruits per plant. High heritability coupled with high Genetic Advance as per cent of Mean was observed for plant height, number of primary branches, plant spread from North to South, plant spread from East to West, fruit length, fruit diameter, average fruit weight, number of fruits per plant, fruit yield per plant and Total Soluble Solids indicating that these characters are governed by additive gene action. Hence, direct selection may be followed for the improvement of brinjal by assessing these characters.

Evaluating Adaptability and Genetic Variability of Improved Maize Varieties

Maize is one of the most important cereals broadly adapted worldwide. Though, a number of improved maize varieties have been released, each micro-environment has not been touched that is why the study carried out. The experiment was conducted using seven maize varieties in RCB design with three replications. The analysis of variance signifies the presence of significant difference (p<0.05) among the seven maize varieties evaluated. High value of genetic (GCV) and phenotypic coefficient of variation (PCV) for grain yield (25.1 and 37.8%) were estimated and this infers less influence of environment. Additionally, moderately high heritability (44.2%) and high genetic advance in percent mean (34.4%) were estimated for grain yield which indicate the trait governed by additive gene action and could be improved via selection based on phenotypic performance. However, traits (male and female flower) with high heritability and moderate genetic advance in percent mean inherited mostly by non-additive gene action and heterosis breeding could be useful. Regarding agronomic performance, Hora maize variety provided highest grain yield (5.0 t/ha) followed by Kuleni (4.1 t/ha), Melkasa 2 (4.0 t/ha) and check (4.0 t/ha). Hora, Melkasa 2, Melkasa 4 and check flowered earlier as compared to the other and could be used as parent for generating early flowering varieties. In summary, Hora maize variety was better performing both statistically and in eyes of farmers and need seed multiplication and distribution to farming community. Moreover, the variability observed among the maize varieties could be utilizing in future breeding activities.

Genetic behavior analysis for phytochemical traits in coriander: Heterosis, inbreeding depression and genetic effects

Increasing fruit yield, fatty acids and essential oils content in coriander are the main objectives. Reaching them need to understand the nature of gene action and quantifying the heterosis and inbreeding depression. Six genetically diverse parents, their 15 F1 one-way hybrids and 15 F2 populations were evaluated under different levels of water treatments. Beside the water treatment and genotype effects, the genetic effects of general (GCA) and specific (SCA) combining ability and their interactions with water treatment were significant for all traits. Water deficit stress decreased all traits in both F1 and F2 generations except for essential oil content which were significantly increased due to water deficit stress. Under water deficit stress, a non-additive gene action nature was predominant in F1 generation while an additive gene action nature was more important in F2 generation for all the traits except fruit yield under severe water deficit stress. There was a positive high heterosis for the traits examined in some hybrids. Also, in F2 generation even after inbreeding depression, some promising populations displayed appropriate mean performance. These show that the parents used for crossing had rich gene pool for studied traits. Therefore, selection between the individuals of relevant F2 populations could be led to develop high yielding hybrids or transgressed lines.