The success of winter × spring wheat hybridization programmes depends upon the ability of the genotypes of these two physiologically distinct ecotypes to combine well with each other. Hence the present investigation was undertaken to study the combining ability and nature of gene action for various morpho-physiological and yield-contributing traits in crosses involving winter and spring wheat genotypes. Five elite and diverse genotypes each of winter and spring wheat ecotypes and their F
(spring × spring, winter × winter and winter × spring) hybrids, generated in a diallel mating design excluding reciprocals, were evaluated in a random block design with three replications. Considerable variability was observed among the spring and winter wheat genotypes for all the traits under study. Furthermore, these traits were highly influenced by the winter and spring wheat genetic backgrounds, resulting in significant differences between the spring × spring, winter × winter and winter × spring wheat hybrids for some of the traits. The winter × spring wheat hybrids were observed to be the best with respect to yieldcontributing traits. On the basis of GCA effects, the spring wheat parents HPW 42, HPW 89, HW 3024, PW 552 and UP 2418 and the winter wheat parents Saptdhara, VWFW 452, W 10 and WW 24 were found to be good combiners for the majority of traits. These spring and winter wheat parents could be effectively utilized in future hybridization programmes for wheat improvement. Superior hybrid combinations for one or more traits were identified, all of which involved at least one good general combiner for one or more traits in their parentage, and can thus be exploited in successive generations to develop potential recombinants through various breeding strategies. Genetic studies revealed the preponderance of additive gene action for days to flowering, days to maturity and harvest index, and non-additive gene action for the remaining six traits.
Brown planthopper (BPH) is one of the destructive insect pests causing significant yield losses in rice. BPH causes direct damage to the rice plants by sucking the sap from phloem, causing hopper burn and transmitting viral diseases like grassy and ragged stunt viruses. Several resistant donors have been identified from time to time, but the new biotypes of the pest arise to defeat the extended use of resistance genes in a single variety. This necessitates the regular identification of new resistant donors along with their nature of inheritance and gene action controlling the resistance. Knowing the inheritance pattern, gene action and number of genes controlling a trait helps the plant breeders to plan the effective breeding approaches for crop improvement. The present investigation was hence carried out to know the inheritance pattern, gene action and number of genes controlling BPH resistance in newly identified sources. The results indicated that the BPH resistance in PHS 29 genotype is under the control of single recessive gene. Whereas, it is controlled by two recessive genes in MRST 3 genotype. This reveals that relatively higher population size will be required to recover desirable segregants in the segregating populations involving MRST 3 genotype as one of the parents as compared to that involving PHS 29 genotype as parent. Since, the resistance in both the cases being recessive in nature, the trait will hence show significant additive effect, indicating that pure line development will be desirable for improvement of such a trait.
Authors:P. Sanjana Reddy, B. Reddy, and P. Srinivasa Rao
Sweet sorghum (Sorghum bicolor (L.) Moench) is a potential raw material for production of ethanol that on blending in petrol is expected to meet the energy demand and address the environmental issues. Well-developed hybrid technology will make the crop remunerative to the farmers. Hence, gene action and best combining female and male parents for sugar yield in sweet sorghum (Sorghum bicolor (L.) Moench) and the association of sugar yield with other agronomic traits was studied in 171 hybrids developed by crossing 19 female parents with nine male parents in line × tester design and evaluated during both rainy and postrainy seasons of 2006. The significant differences between the seasons for all the traits suggested that these traits are greatly influenced by the environment. The lines (female parents) ICSA 38, ICSA 479, ICSA 702, ICSA 675 and ICSA 474 and the restorers (male parents), SSV 74 and SSV 84 combined well for sugar yield during rainy season and the lines, ICSA 702, ICSA 38 and ICSA 474 and the restorers, ICSV 93046, SPV 1411 and ICSV 700 combined well during postrainy season. The magnitude of SCA variance was higher suggesting the importance of non-additive gene action in inheritance of all the traits though both additive and dominant genes controlled overall sugar yield during both the seasons. Hence, selection in early generation would be ineffective and recurrent selection with periodic intercrossing is advocated. However, breeding good combining restorer parents can fetch high sugar yield in postrainy season. There is an indication of existence of transgressive segregation for sugar yield that can be exploited. The sugar yield was weak though significantly correlated with high brix and poor grain yield during both the seasons requiring extensive crossing to improve these traits simultaneously. Keeping in view mean performance, SCA effects and heterobeltiosis, the hybrids, ICSA 474 × SSV 84, ICSA 24001 × ICSR 93046 and ICSA 474 × SPV 422 were identified promising for rainy season and the hybrids ICSA 24001 × SPV 1411 and ICSA 511 × ICSV 93046 were identified for postrainy season.
To identify an efficient pollen source for maize mediated system of chromosome elimination, wheat genotypes (10 F1s) were pollinated with eight diverse Himalayan maize genotypes. Among these, two were composite varieties Early Composite (Check) and Bajaura Makka (L 201) and rest six were locally grown traditional open pollinated maize varieties collected from diverse regions of North-west Himalaya. The data were recorded for three haploid induction parameters viz. pseudo seed formation, embryo formation and regeneration. In most of the crosses, haploid embryos were produced, asserting the potential of wheat × maize system as a genotype non-specific system as compared to androgenesis and bulbosum technique, where the genotype specificity limits the development of haploid plants. Frequencies of all the three haploid induction parameters in different crosses of wheat × maize clearly indicated that both wheat and maize genotypes were behaving differently for different crosses. The line × tester analysis also revealed significant influence of crosses, wheat, maize and their interaction on all the three haploid induction parameters. The results obtained suggest association of both additive and dominance gene action with all the haploid induction parameters. Over all proportional contribution of tester for embryo formation and regeneration parameters was found to be more, followed by line × tester interaction. On the basis of haploid formation efficiency (HFE) as well as general combining ability (GCA), Bajaura Makka has emerged to be the best general combiner among maize genotypes and also superior to the earlier identified variety, Early Composite. Also, HPW 155 × VL 852 and HPW 155 × HPW 211 were the top general combiners among wheat genotypes. Correlation between various haploid induction parameters revealed negative correlation between pseudo seed formation and embryo formation whereas embryo formation and regeneration were found to be significantly positively correlated; however the magnitude of correlation was not very high.
Authors:S. Sareen, N. Bhusal, G. Singh, B.S. Tyagi, V. Tiwari, G.P. Singh, and A.K. Sarial
Heat stress is a matter of a great concern for the wheat crop. Heat stress usually either hastens crop development or shortens the grain filling duration, which severely reduces grain yield. Being a complex trait, understanding the genetics and gene interactions of stress tolerance are the two primary requirements for improving yield levels. Genetic analysis through generation mean analysis helps to find out the nature of gene actions involved in a concerned trait by providing an estimate of main gene effects (additive and dominance) along with their digenic interactions (additive × additive, additive × dominance, and dominance × dominance). In the present investigation, we elucidated the inheritance pattern of different yield contributing traits under heat stress using different cross combinations which could be helpful for selecting a suitable breeding strategy. Thus six generations of five crosses were sown normal (non-stress, TS) and late (heat stress, LS) in a randomized block design with three replications during two crop seasons. The model was not adequate for late sown conditions indicating the expression of epistatic genes under stress conditions. The traits i.e. Days to heading (DH), Days to anthesis (DA), Days to maturity (DM), Grain filling duration (GFD), Grain yield (GY), Thousand grain weight (TGW), Grain weight per spike (GWS) and Heat susceptibility index (HSI) under heat stress conditions were found under the control of additive gene action with dominance × dominance interaction, additive gene action with additive × dominance epistatic effect, dominance gene action with additive × additive interaction effect, additive and dominance gene action with dominance × dominance interaction effect, additive gene action with additive × dominance epistatic effect, additive gene action with additive × additive interaction effect and dominance gene action with additive × additive interaction effect, respectively.
Authors:V. Muthusamy, F. Hossain, N. Thirunavukkarasu, S. Saha, P.K. Agrawal, and H.S. Gupta
Carotenoids are important micronutrients required by humans for growth and development. Yellow maize among cereals possesses sufficient carotenoids, and thus, it is important to genetically dissect such traits for proper utilization in breeding programme. Twenty-one maize hybrids generated using novel inbreds with rare allele of β-carotene hydroxylase (crtRB1) that enhances kernel β-carotene, were evaluated at two diverse maize growing locations. Lutein, zeaxanthin and β-cryptoxanthin were positively correlated, while β-carotene showed negative correlation with other carotenoids. Grain yield did not show association with carotenoids. Preponderance of additive gene action was observed for lutein, zeaxanthin, β-cryptoxanthin and β-carotene. Experimental hybrids were much superior for kernel β-carotene compared to commercial hybrids. Based on SCA effects, high yielding experimental hybrids were identified for provitamin A and non-provitamin A carotenoids. These novel hybrid combinations of maize possessing rare allele of crtRB1 hold promise in maize biofortification programme to alleviate vitamin A deficiency and degenerative diseases in humans.