Selection For Yield Improvement Research Articles

Principal component and correlation analyses study on fruit yield in cucumber (Cucumis sativus L.) genotypes

The degree of association between yield and its components can be identified using correlation and Principal Component Analyses (PCA). PCA also reveals key characteristics that explain most of the differences between genotypes. A study was formulated to evaluate the relationship between yield and its contributing traits in cucumber. The experiment was conducted with 16 cucumber genotypes in a Randomized Complete Block Design, with three replications. The correlation analysis revealed a strong and statistically significant relationship in number of pistillate flowers (r = 0.58**), number of branches (r = 0.43**), vine length (r = 0.69**), number of leaves (r = 0.73**), leaf area (r = 0.70**), number of fruits (r = 0.91**), fruit length (r = 0.40**), fruit girth (r = 0.39**), and fruit weight (r = 0.74**) with fruit yield. PCA revealed that PC1 accounted for 51.53% of the total variation, while PC2 explained 13.91% of the total variability. This study demonstrated that choosing traits such as number of pistillate flowers, number of branches, vine length, number of leaves, leaf area, number of fruits, fruit length, fruit girth, and fruit weight that have a strong positive correlation with fruit yield could be given priority in selection for yield improvement.

Relationship between yield and its component traits for enhancing grain yield in single cross hybrids of maize (Zea mays L.)

Sixty single cross hybrids of maize synthesised through Line × Tester mating design along with their sixteen parental lines were evaluated for their performance in the experimental field. Genetic parameters viz., genotypic and phenotypic correlation and path coefficients were estimated to understand the association among yield and its attributes in enhancing the grain yield. The observed thirteen biometric traits differed significantly in all the genotypes. Correlation studies concluded that cob weight (rg=0.994), the number of kernels per row (rg=0.897), plant height (rg=0.882), earheight (rg=0.841), and hundred seed weight (rg= 0.830) were strongly and significantly correlated with grain yield. Path analysis showed that cob weight (0.887) and shelling percentage (0.150) had the highest direct effects over yield which emphasized their importance during selection for yield improvement. Developmental traits viz., days to 50% flowering and days to 50% silking negatively contributed to yield, and hence the selection for these traits could be restricted.

Genetic Relationships and Principal Component Analysis in Elite Chickpea (Cicer arietinum L.) Genotypes for Seed Yield and Its Component Traits

Background: Chickpea (Cicer arietinum L.) is the important Rabi season food legume crop ranked third after common bean and field pea. The degree and extent of trait variability, genetic relationship and genetic diversity in promising chickpea genotypes should be known for possible yield improvement. Realizing the importance of genetic relationships and genetic diversity in key economic traits, the present investigation envisaged to measure the genetic relationships in the yield component traits to make effective selection for yield improvement in chickpea breeding programme. Methods: The experimental material comprised of 60 chickpea genotypes (both Desi and Kabuli types), grown in RBD with three replications at Pulses Section of Department of Genetics and Plant Breeding, CCSHAU, Hisar during Rabi 2014-15. The data on 11 quantitative traits was analysed for ANOVA, correlation coefficient, path coefficient, regression and principle component analysis. Result: The present study has led the understanding of many inter-related traits involved in the genetic variation of chickpea seed yield. This would certainly provide guidelines for selection of parents as well as effective selection of promising chickpea genotypes, and also have paramount importance in formulating plant model for selection of segregating generations in chickpea breeding programmes for development of high yielding varieties.

Genetic Variability, Heritability, Genetic Advance and correlation studies for seed yield and yield components in early segregating lines (F3) of Greengram [Vigna radiata (L.) Wilczek

The present investigation was conducted with the F3 breeding lines derived from three crosses viz., DGGV-7 × V-02-709, DGGV-7 × V-02-802, DGGV-2 × SML-1815 along with their parents used as checks. The progeny lines were evaluated for estimation of genotypic coefficient of variation (GCV), phenotypic coefficient of variation (PCV), heritability and genetic advance. The correlation study was undertaken among the ten selected quantitative characters. The analysis of variance showed, the progeny lines derived from the cross DGGV-7 × V-02-709, recoded very high significant variation for the characters like the number of branches per plant (2.988), pod length (2.363) and seed yield per plant (13.007g). The 100 seed weight (4.7g) was observed in the cross derivative of DGGV-2 × SML-1815 with high heritability 73.26 per cent and moderate genetic advance under mean (19.65). The breeding lines of DGGV-7 × V-02-709 have recorded mean seed yield 3.7 g with the range of 3.22 to 4.65 g and the PCV (17.35%), GCV (14.23%) was moderate with high heritability (72.12%) coupled with moderate genetic advance over mean (17.45%). There is a positive significant correlation was observed between plant height, number of clusters per plant, number of pods per plant, number of seeds per pod and seed yield per plant. Therefore, these characters should give higher priority at the time of selection for improvement of yield in greengram.

Selection for Yield Improvement in Bambara Groundnut (Vigna subterranea L. Verdc.)

Selection as the most practical and economical way of improving yield in an extreme autogamous crop was carried out in a Randomized Complete Block Design (RCBD) with three replications, with thirty three accessions of Bambara groundnut {Vigna subterranea (L.) Verdc}. Qualitative characters displayed a reasonable range of variation except for eye pattern, seed shape, pod texture and growth habit. The result on the analysis of variance (ANOVA) showed significant differences (p0.05) for all traits except for plant height, number of leaves per plant and seed length that were statistically insignificant. The principal component analysis result revealed that eight components (Eigen values ≥ 1) accounted for 78.36 % of the phenotypic variance, and quantitative traits revealed more phenotypic variation among the accessions Pearson’s correlation coefficient showed that petiole length (r= 0.64), vigour index (r= 0.49), seed length (r=0.53), canopy width (r=0.38), and internode length (0.58). had a high positive correlation with seed yield. Ranking of the accessions based on significantly strong correlated traits with yield using the rank summation index (RSI) method, and the selection of the best top 5% of the entries identified accessions TVSU 1688 and 1638 with RSI scores of 31 and 43 respectively as the best high yielding Bambara groundnut lines. Correspondingly, accessions TVSU 1688 and 1638 had the highest mean seed yield per plant of 1150.5g and 720.8g respectively in the 3-year field evaluation; which further confirmed the precision of the ranking and selection result. Invariably these two accessions were inherently high yielding Bambara groundnut accessions.

Study of Genetic Variability in Cucumber

Twenty three genotypes of cucumber along with two checks (Pant Khira-1 and Pant Khira3) were studied for extent of genetic variability, character association and path coefficient analysis with respect to yield and yield contributing traits at Vegetable Research Center, NDUAT, Faizabad. Analysis of variance indicated substantial variability among the progenies for all the traits. Highest genotypic and phenotypic coefficient of variation was exhibited by number of fruits per plant (54.22 and 55.93, respectively) and lowest in days to first fruit harvest (8.75 and 10.05, respectively). High heritability with high genetic advance (GA) was observed for fruit yield per plant followed by number of fruits per plant, which is an indicative of greater proportion of additive genetic variance and consequence a high genetic gain from selection. Correlation analysis revealed that number of fruits per plant had significant positive correlation for fruit yield/plant. Path analysis revealed that number of fruits per plant had highest positive direct effect on fruit yield/plant followed by average fruit weight on fruit yield per plant at both genotypic and phenotypic level indicating for greater emphasis on these traits during selection for improvement of yield.

Association of bulb yield and its attributing traits under different environments in garlic (Allium sativum L.)

Fifteen genotypes of garlic were grown under seven environments. these environments were created by different dose of organic and inorganic fertilizers. Correlation coefficients among yield and its contributing traits were estimated for each environment. Significant positive association of bulb yield was observed with bulb diameter and leaf length in all the environments. the results also revealed that plant height, number of leaves per plant and number of cloves per bulb showed significant positive correlation with yield. Bulb diameter, bulb weight and number of cloves were positively correlated with each other over all the environments. the study has revealed the importance of bigger cloves, thick, broad and flat leaves during selection to achieve maximum efficiency during selection for yield improvement with enhanced probability to develop genotype with lesser susceptibility to pests and diseases.

Caracterização fenotípica de três seleções de maracujazeiro-roxo (Passiflora edulis Sims)

O interesse pelo cultivo do maracujazeiro-roxo vem crescendo no centro-sul do País, visando à exportação. Observa-se um número significativo de formas selvagens, nativas, compatíveis entre si, propagadas por sementes de polinização aberta, ampliando a variabilidade natural da fruteira. Com o objetivo de identificar cruzamentos com características comerciais desejáveis e disponibilizar sementes de matrizes selecionadas aos produtores, foram realizados estudos de caracterização agronômica, morfológica e citogenética, envolvendo seleções do Banco de Germoplasma de Passifloras do IAC, denominadas 'Roxinho-Miúdo', 'Paulista' e 'Maracujá-Maçã'. Durante duas safras consecutivas, foram analisados cerca de 350 flores e 150 frutos de cada seleção. A maior amplitude de variação ocorreu na massa e no tamanho dos frutos (de 21 a 193 g por fruto), seguidos pelo teor de sólidos solúveis (de 15,2 a 21,4º Brix), produção por planta (11,5 a 30,8 kg) e número de sementes por fruto (de 39 a 261 sementes). A viabilidade polínica variou de 77 a 94,5%, enquanto o teste de germinação do pólen em ágar apresentou índices de 65,5 a 86%, contribuindo para o diferencial em produtividade observado. Todas as seleções apresentaram características comerciais desejáveis. 'Roxinho-Miúdo' possui fruto redondo, pequeno, com 4 cm de diâmetro, doce e de coloração roxo-intensa, adequando-se à preferência internacional. A seleção 'Paulista' apresentou frutos ovais, destacando-se pela dupla finalidade, podendo atender também à agroindústria. O 'Maracujá-Maçã' distinguiu-se pelo maior tamanho, formato arredondado e casca rosada, apto para um segmento diferenciado de mercado, que comercializa frutas por unidade e privilegia a qualidade.

Identification of quantitative trait loci under drought conditions in tropical maize. 2. Yield components and marker-assisted selection strategies

In most maize-growing areas yield reductions due to drought have been observed. Drought at flowering time is, in some cases, the most damaging. In the experiment reported here, trials with F3 families, derived from a segregating F2 population, were conducted in the field under well-watered conditions (WW) and two other water-stress regimes affecting flowering (intermediate stress, IS, and severe stress, SS). Several yield components were measured on equal numbers of plants per family: grain yield (GY), ear number (ENO), kernel number (KNO), and 100-kernel weight (HKWT). Correlation analysis of these traits showed that they were not independent of each other. Drought resulted in a 60% decrease of GY under SS conditions. By comparing yield under WW and SS conditions, the families that performed best under WW conditions were found to be proportionately more affected by stress, and the yield reductions due to SS conditions were inversely proportional to the performance under drought. Moreover, no positive correlation was observed between a drought-tolerance index (DTI) and yield under WW conditions. The correlation between GY under WW and SS conditions was 0.31. Therefore, in this experiment, selection for yield improvement under WW conditions only, would not be very effective for yield improvement under drought. Quantitative trait loci (QTLs) were identified for GY, ENO and KNO using composite interval mapping (CIM). No major QTLs, expressing more then 13% of the phenotypic variance, were detected for any of these traits, and there were inconsistencies in their genomic positions across water regimes. The use of CIM allowed the evaluation of QTL-by-environment interactions (Q×E) and could thus identify “stable” QTLs CIMMYT, Apartado Postal 6-641, 06600 Mexico D.F., Mexico across drought environments. Two such QTLs for GY, on chromosomes 1 and 10, coincided with two stable QTLs for KNO. Moreover, four genomic regions were identified for the expression of both GY and the anthesis-silking interval (ASI). In three of these, the allelic contributions were for short ASI and GY increase, while for that on chromosome 10 the allelic contribution for short ASI corresponded to a yield reduction. From these results, we hypothesize that to improve yield under drought, marker-assisted selection (MAS) using only the QTLs involved in the expression of yield components appears not to be the best strategy, and neither does MAS using only QTLs involved in the expression of ASI. We would therefore favour a MAS strategy that takes into account a combination of the “best QTLs” for different traits. These QTLs should be stable across target environments, represent the largest percentage possible of the phenotypic variance, and, though not involved directly in the expression of yield, should be involved in the expression of traits significantly correlated with yield, such as ASI.

Genetic Variation within Maize Breeding Populations

Proper choice of germplasm determines the ultimate success of selection for genetic improvement. Germplasm included in maize (Zea mays L.) breeding has evolved from the original landrace cultivars to F2 populations of elite line crosses. Objectives of our study were to determine the mean and genetic variability (σ2G) of yield and other traits within three F2 populations (B73 × B84, B90 × Mo17, and B73 × Mo17), within three genetically narrow‐base synthetics (NBS) [BS14, Mol7‐Syn., and H73‐Syn.], and within three genetically broadbase synthetics (BBS) [BSll(FR)C9, BSCBI(R)C9, and BSSS(R)C9]. Fifty S1 progenies for each of the nine populations were evaluated at three locations for 2 yr. Differences among S1 progenies within each population were significant for most traits. Estimates of σ2G were determined from the S1 component of variance, and average estimates of σ2G for grain yield were similar for F2 and BBS populations, whereas the average estimate of σ2G for NBS populations was 40% smaller. Within population types, the related line cross (B73 × B84)F2 had 50% less σ2G for grain yield than the other two F2 populations. BS14, H73‐Syn., and BSCBI(R)C9 had smaller estimates of σ2G for grain yield than the other synthetic populations. Estimates of σ2G suggest selected F2 and BBS populations have greater potential for improved gains than the NBS populations. The related line (B73 × B84)F2 had 50% less 62G than either (B90 × Mo17)F2 or (B73 × Mo17)F2. (B90× Mo17)F2 and (B73 × Mo17)F2 had similar estimates of σ2G, although B90 and Mo17 are in the same heterotic group, whereas B73 and Mo17 are in different heterotic groups [Reid Yellow Dent (B73) and Lancaster Sure Crop (Mo17)]. Selection for improvement of yield would be more effective within the (B90 × Mo17)F2 than within (B73 × B84)F2 and more useful than within (B73 × Mo17)F2.

Variation among Full‐sib Families of Corn for Different Generations of Inbreeding

Recurrent selection for improvement of yield of corn (Zea mays L.) germplasm emphasizes early testing of either S0 or S1 progeny testcrosses. On the basis of early testing information, progenies are selected and intermated to form populations for continued selection. This study was conducted to determine if early testing was effective in identifying superior full‐sib families of S0 plants in reciprocal fullsib selection. The effectiveness of early testing was investigated by comparing the relative genetic variability and genetic correlations of 136 full‐sib families for the S0 S1, S2, S3, and S4 generations of in breeding. Full‐sib families and six hybrid checks were evaluated in three environments for each generation for grain yield and five other agronomic traits. The among full‐sib component of variance for grain yield tended to increase with inbreeding of the parents, and there was evidence that variability among full‐sib families was reduced in stress environments. Genetic correlations for yield between generations of inbreeding ranged from 0.87 for S0‐S1 generations to 0.31 for S0‐S4 generations. Genetic correlations decreased as the number of intervening generations increased. Selection of the 20 highest and lowest‐yielding S4 full‐sib families included only three and four, respectively, of the 20 highest‐ and lowest‐yielding S0 full‐sib families. None of the 20 lowest‐yielding S1 full‐sib families, however, was included in the 20 highest‐yield S4 full‐sib progenies. The objective of early testing in reciprocal full‐sib selection was achieved because none of the poorer performing families was included for intermating.

Evaluation of maize varieties for their potential as breeding populations

A 7-variety diallel of synthetic varieties that have not had selection for yield improvement and a 10-variety diallel of synthetic varieties that either resulted from recurrent selection for yield improvement or from the introgression of exotic germ plasm into adapted varieties were evaluated in six environments for yield and five other agronomic traits. The specific objective was to determine the relative potential of the synthetic varieties as germ plasm sources for breeding programs. Recurrent selection improved population yield in ‘BSSS CO’, ‘BSK CO’, and ‘Alph CO’ in the varieties and also in crosses with other varieties. ‘BSSS(R)C6’ and ‘BSSS(HT)C7’ yielded 11.4% and 16.1% more than ‘BSSS CO’, and the variety crosses of ‘BSSS(R)C6’ and ‘BSSS(HT)C7’ yielded 21.6% and 22.0% more than the variety crosses of ‘BSSS CO’. Recurrent selection also improved stalk-lodging resistance for ‘BSSS(R)C6’ and ‘BSSS(HT)C7’, but root lodging for ‘BSSS(HT)C7’ was significantly higher. ‘BS15’ had 61.0% higher yields than ‘Alph CO’, with 9.3% less stalk lodging. Average heterosis of the 10-variety diallel was 1120 kg/ha (19.6%) and ranged from 800 kg/ha (13.7%) for ‘BSK(S)C5’ to 1770 kg/ha (39.4%) for ‘BS12(HI)C5’. The heterosis expressed among individual variety crosses ranged from 4.3% for ‘BSK(S)C5’ x ‘BSTE(FR)C1’ to 37.6% for ‘BSSS(R)C6’ x ‘BS12(HI)C5’, which approached the yield of the two highest yielding single-cross checks. In the 7-variety diallel of unselected varieties, ‘BSTE CO’ and ‘Late Rootworm Synthetic’ were superior as varieties and in crosses for yield and stalk quality. Average heterosis for the 7-variety diallel was 950 kg/ha (18.5%). Stalk lodging was important in the performance of varieties with poor stalk quality. Although recurrent selection improved yield, development of superior breeding populations also will require selection for general agronomic performance. The performance of ‘BS16’ and the yields of ‘BSTL’ and ‘Teozea’ and their crosses suggest that exotic germ plasm should receive greater attention.

Breeding of maize for low rainfall areas of Kenya:1. The reliability of yield of early and later maturing maizes

SUMMARYA trial to compare the reliability of yield of a quick maturing maize (Taboran) with the medium maturity local maize was carried out at two low rainfall sites in Southern Province, Kenya, from 1957 to 1961. Each variety was grown at two spacings, giving plant densities of 1·8 and 3·6 pl./m2. Results showed a consistent difference in ‘days to 50% silking’, Taboran being on average 17 days earlier than Local White. There was no overall difference between varieties or spacings in yield per ha. There were highly significant interactions of seasons with varieties and with spacings. These were interpreted in terms of different linear yield/rainfall relationships for each variety and each spacing. A variety/spacing interaction was also demonstrated.Analysis of components of yield showed that similar linear relations between rainfall and each yield component obtained. There were significant differences between varieties and between spacings in both mean number of cobs per plant and yield per cob. Taboran had a higher mean number of cobs per plant and Local White a higher mean yield per cob. Seasons x varieties interactions were again interpreted in linear regression terms. Earliness of the Taboran variety often enabled plants to produce silks before development was arrested by drought and so was responsible for its relatively high mean number of cobs per plant in low rainfall seasons, giving it an advantage over Local White in yield per unit area in such circumstances. Taboran was shown to have a potential value in local agriculture, because of its consistency of yield. The expected advantage or disadvantage of Taboran over Local White was calculated for an area of known rainfall from the respective yield/rainfall regressions and the seasonal rainfall probabilities.Selection for earliness was shown to be of basic importance in a breeding programme for the low rainfall areas. Within a specified early maturity range, selection for yield improvement through the yield per cob component could be practised. A maturity length similar to Taboran would ensure a high value of mean cobs per plant in low rainfall season, i.e. confer the necessary reliability of yield.