Comparison of Genetic Parameters among Selfed Lines and Random Mated Population A (PDM 53 x PDM 4441) and Population B (HKI 1105 x HKI 323) and Identification of Transgressive Segregants

The present study was conducted to compare the genetic variability parameters among selfed lines of population A (PDM 53 x PDM 4441) and population B (HKI 1105 x HKI 323) and also random mated population A (PDM 53 x PDM 4441) and random mated population B (HKI 1105 x HKI 323) using original inbred parents and three commercial checks, HM-4 (National check), CPB 468 and TENDER (Private check). High heritability coupled with high genetic advance was observed for number of cobs per plant, husked cob weight, dehusked cob weight, baby corn yield with and without husk per plant among selfed populations and a similar trend was observed in random mated populations except for ear length and days to 50 % silking. In total the variability observed was more in random mated populations than selfed lines because allelic frequency differences occur in random mated populations and the pool of gametes originating from male and female is different when compared to the pollen source in selfed populations. The frequency of transgressive segregants were more in random mated Population A (PDM 53 x PDM 4441) and the most promising transgressive segregant identified can be used in the further breeding programmes.

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.

Transgressive Segregants in F2 Populations of Three Superior Crosses viz., ML 267×LGG 528, MGG 390×LM 95, LM 95×EC 362096 in Mungbean

Background: Among several reasons for low productivity in mungbean, various biotic and abiotic factors play a major role. Although intensive research work has been done on genetic architecture of yield and yield attributes of mungbean but limited work was done on yield attributes along with water use efficiency (WUE) and heat stress tolerance related traits. The present study is aimed to identify the genetic potential of mungbean genotypes with high yield and drought and heat stress tolerance. Methods: The F2 seed was harvested from selfed F1 population during 2017-18 from three superior crosses viz., ML 267×LGG 528, MGG 390×LM 95 and LM 95×EC 362096. These crosses were selected based on their per se performance of yield, yield attributes and WUE related traits. Genetic analysis was carried out in F2 populations of three crosses for fourteen quantitative characters to identify the number of transgressive segregants in desirable direction. Result: A good number of transgressive segregants in desirable direction were observed for plant height, number of pods per cluster, harvest index, SLA, SLW and relative injury in the cross ML 267×LGG 528: for plant height, number of branches per plant, SCMR, SLA, SLW and relative injury in the cross MGG 390×LM 95 and for plant height, number of pods per cluster, number of pods per plant SCMR, SLA, SLW, relative injury and seed yield in the cross LM 95×EC 362096.

Gene Action Studies for Yield and its Related Traits by using Generation Mean Analysis in Mungbean [Vigna radiata (L.) Wilczek]

Background: Mungbean is one of the most important legume crop with high nutritional value and is consumed in various forms in different parts of India. In order to meet its growing demand, there is a need to increase the yield through adoption of breeding approaches like heterosis breeding and breeding for high yielding varieties. This demands a critical study of the gene action involved in regulation of yield and yield attributing traits which can be achieved through generation mean analysis. Methods: In the present study, generation mean analysis was undertaken using five parameter model to estimate the nature and magnitude of gene action of yield and its component traits in six crosses of greengram. Result: Magnitude of dominance gene effect was reported to be higher than additive gene effect in most of the crosses. Either one or both the interaction components were found significant for all the traits besides number of branches per plant and hundred seed weight. It was evident from the study that the yield components could be improved by exploiting both additive and non-additive gene effects. The transgressive segregants thus produced will prompt the development of desirable high yielding genotypes.

Studies on Heterosis, Residual Heterosis and Inbreeding Depression for Yield and Related Traits in Sorghum (Sorghum bicolor L.)

Background: Selection of genotypically superior parents is most challenging task for the development of potential hybrids. In conventional plant breeding, magnitude of heterosis and inbreeding depression has been proved very effective in identifying vigorous parental combinations. Methods: The present investigation was carried out to study the heterosis, residual heterosis and inbreeding depression of forty sorghum crosses (F1s and F2s) obtained by crossing of eight restorer lines with five cytoplasmic male sterile lines in Line x Tester mating design in 2013 and 2014. Observations were recorded on morphological traits viz. days to 50% flowering, days to maturity, plant height, flag leaf length, flag leaf width, panicle length, panicle width, panicle weight,1000 seed weight and grain yield per plant. Result: Among all crosses, ICSA467 x UPC2 and MR750A2 x UPC2 were found to be best for most of the characters. Inbreeding depression was recorded as significantly positive for plant height for most of the crosses indicates the occurrence of transgressive segregants in F2 generation.

Identification of Transgressive Segregants and Variability Studies in Segregating Generations of Four Crosses in Chickpea

Background: An impressive progress has been made in development and promotion of extra-large kabuli chickpea varieties in India during the past decade. As a result, India has become from importer to exporter of kabuli chickpea. The breeding programmes need to continue efforts on enhancing genetic gain in breeding kabuli chickpea varieties through increasing genetic variability and precision and efficiency of selection. This study was aimed at evaluating early segregating generations of chickpea to assess genetic variability for various important traits. Methods: Four large-seeded kabuli chickpea genotypes (JGK 2, KAK 2, KRIPA and ICC 17109); were crossed with a common small-seeded kabuli genotype (ICC 16644). F1, F2 and F3 along with parents were evaluated under normal field conditions and observations were recorded on various phenological, morphological and yield traits. Data was analysed to estimate genetic variability, heritability and genetic advance in the segregating populations.Result: Considerably high variability was observed in F2 and F3 populations of all the crosses. Heritability estimates in broad sense were high coupled with high genetic advance as per cent of mean for days to first flower, days to pod initiation, number of pods per plant, number of seeds per plant and 100-seed weight which indicated the presence of additive gene action for these traits. Large number of transgressive segregants was identified for number of seeds per plant followed by number of pods per plant and yield per plant. The most promising transgressive segregants could be used in future breeding programme.

Genetic Diversity in Fiber Related Traits of Tossa Jute (Corchorus Olitorius L.) Germplam

Genetic diversity of twenty-one genotypes of tossa jute was studied through Mahalanobis D2 statistic and principal component analysis for 15 quantitative traits related to yield at the research farm of Sher-e-Bangla Agricultural University, Dhaka, Bangladesh. The genotypes were grouped into four clusters. Cluster III contained the highest number of genotypes (nine), while cluster II had the lowest number of genotypes (three). The inter-cluster distances were higher than intra-cluster distances indicating wider genetic diversity among the genotypes of different clusters. The intra-cluster distances were lower in all the cases reflecting homogeneity of the genotypes within the cluster. The highest intra-cluster distance was noticed for the cluster I and the lowest for cluster IV. The genotypes from cluster I could be selected as parents for hybridization for producing transgressive segregants. The highest inter-cluster distance was found between clusters I and IV followed by clusters I and III and the lowest was between clusters III and IV. Cluster IV recorded the highest mean value for plant height, base diameter, root length, leaf area, fresh weight with and without leaves, dry fiber weight and dry stick weight. In the total divergence, the highest contribution was recorded in plant height (65.1%) followed by base diameter (16.6%). The first two principal components, whose eigen values were greater than one, accounted for 81.7% of the total variations among the genotypes for fifteen fiber related traits. Considering the magnitude of cluster distance, cluster means for different characters and contribution of characters towards divergence, the genotypes G17, G18 from cluster IV; G1, G2, G5, G10, G16 from cluster I and G4 from cluster III could be selected as promising parents for hybridization program. SAARC J. Agri., 18(2): 27-37 (2020)