Heterosis For Yield Research Articles

Line × Tester analysis for kernel yield and component traits in maize (Zea mays L.)

Line × Tester analysis performed using 10 female and 4 male parental lines and their 40 hybrids in yellow maize. The analysis of variance showed that the enormity of sca variance was higher than the gca variance for all the traits except for days to tasseling, days to silking and ASI. The ratio of σ2gca/σ2sca was less than unity for all the characters except days to silking, which indicated predominance of non-additive gene action in the inheritance of these traits. Based on general combining ability (gca) effects, none of the parents was good general combiners for all the characters. Parental line IMR-33 was good general combiner for cob yield per plant, kernel yield per plant, plant height, ear height and cob length, while it was average for rest of the traits except days to dry husk. The cross combination VL-1032 × WNC 40218 exhibited highest significant positive sca effects for cob yield per plant (63.08) and kernel yield per plant (49.09). The cross BLD-329 × BLD-270 exhibited highest heterobeltiosis and standard heterosis for both cob yield per plant and kernel yield plant.

Combining Ability and Heterosis of Tolerance to Low Soil Nitrogen in Tropical Maize Cultivars Derived from Two Breeding Eras

Abstract Low soil nitrogen is one of the principal abiotic stresses affecting maize productivity in Sub-saharan Africa. Field studies were conducted at the International Institute of Tropical Agriculture (IITA), Ibadan during the cropping seasons for three years, from 2010 to 2012, with ten open pollinated maize varieties (OPVs) derived from two breeding eras (1 and 2). The ten OPVs and their crosses were evaluated under high-N and low-N conditions. The aim was to identify superior populations that may be useful sources genes for inbred line extraction and hybrid development for grain yield. Under low-N condition, mid and high parent heterosis for grain yield were low indicating the suitability of the hybrids for cultivation only in environments with high productivity index. Hybrid DMR-LSR-W (Era 1) × TZSR-Y-I (Era 2) had greatest mid and high-parent heterosis for grain yield under high-N and across the other four test environments. Parent AMATZBR-WC2B with higher general combining ability effects and mean values for grain yield, and cross combinations DMR-LSR-W (Era 1) x BR9928DMRSR (Era 2) and BR9922DMRSR (Era 2) x TZBRELD-4C0W (Era 2) with higher specific combining ability for grain yield under low-N environment are promising candidates for the development of nitrogen use efficient varieties for cultivation in low-N environments.

Estimation of heterosis for yield and its contributing traits in brinjal

Estimation of heterosis for yield and its contributing traits in brinjal

Estimation of Heterosis of Yield and Yield-Related Traits in the African Eggplant (Solanum Aethiopicum) Hybrids

African eggplant is an important fruit and leafy vegetable in Africa. Heterosis over mid and better parents was estimated in eight crosses of eggplant involving eight pure lines in a field experiment in 2012 and 2013 cropping seasons. The experiment was laid out using a randomized complete block design with three replications. Collected data was subjected to analysis of variance and significant differences were further subjected to Duncan Multiple Range Test. The aim of this study was to identify superior hybrids that can be advanced in the eggplant breeding program for improved yield and related traits. Significant variation was observed among all traits measured for the parents and hybrids. The highest fruit number was observed in NHS10-40 and in NHS 10-71 x NHS 10-40 among the parents and hybrids respectively. The highest heterosis was recorded in the cross between NHS10-71 x NHS10-40.

Transcriptome and DNA methylome reveal insights into yield heterosis in the curds of broccoli (Brassica oleracea L var. italic)

BackgroundCurds are the main edible organs, which exhibit remarkable yield heterosis in F1 hybrid broccoli. However, the molecular basis underlying heterosis in broccoli remains elusive.ResultsIn the present study, transcriptome profiles revealed that the hybridization made most genes show additive expression patterns in hybrid broccoli. The differentially expressed genes including the non-additively expressed genes detected in the hybrid broccoli and its parents were mainly involved in light, hormone and hydrogen peroxide-mediated signaling pathways, responses to stresses, and regulation of floral development, which suggested that these biological processes should play crucial roles in the yield heterosis of broccoli. Among them, light and hydrogen peroxide-mediated signaling pathways represent two novel classes of regulatory processes that could function in yield or biomass heterosis of plants. Totally, 53 candidate genes closely involved in curd yield heterosis were identified. Methylome data indicated that the DNA methylation ratio of the hybrids was higher than that of their parents. However, the DNA methylation levels of most sites also displayed additive expression patterns. These sites with differential methylation levels were predominant in the intergenic regions. In most cases, the changes of DNA methylation levels in gene regions did not significantly affect their expression levels.ConclusionsThe differentially expressed genes, the regulatory processes and the possible roles of DNA methylation modification in the formation of curd yield heterotic trait were discovered. These findings provided comprehensive insights into the curd yield heterosis in broccoli, and were significant for breeding high-yield broccoli varieties.

Standard heterosis for grain yield in maize hybrids

Determination of heterosis in maize hybrids is necessary for their commercial exploitation. Data derived from several experiments, namely, Coordinated Varietal Trial-Hybrid (CVTH), Diallel Crosses, Observation Nurseries (OBN), Top Crosses and Test Crosses conducted at Rampur (Chitwan) and Parwanipur (Bara), Nepal were complied to determine heterosis and identify high yielding hybrids. The maize hybrids, namely, RML-4/RML-7, RML-5/NML-1, NML-2/RML-6, RML-6/RML-7, RML-5/RL-47, RML-8/RL-47, RML-5/RML-8, NML-1/RML-17, RML-7/RML-18, RML-6/RML-18 and RML-5/NML-1 produced high heterosis (greater than 40%) indicating these hybrids superior for commercial cultivation.

Mean Performance and Heterosis for Yield and Fruit Traits of Tomato under Drought Conditions

Mean Performance and Heterosis for Yield and Fruit Traits of Tomato under Drought Conditions

Gene Expression Analysis in Sorghum Hybrids and Their Parental Lines at Critical Developmental Stages in Relation to Grain Yield Heterosis by Exploiting Heterosis-Related Genes from Major Cereals

Relative expression levels of selected genes from the Heterosis-Related Gene Database exhibiting more than 90% homology with sorghum were studied in hybrids and their respective parental lines for a better understanding on the molecular basis of heterosis. A high (27A × RS 673) and a low heterotic hybrid (7A × CB 26) of sorghum along with their parental lines were used for this purpose. Twenty (15 maize and 5 rice) genes exhibiting more than 90% homology with that of sorghum were identified. The maize genes ZmHG13, ZmHG16, and ZmhG19 exhibited more than fourfold increase over the male parent (RS 673) of high heterotic hybrid during booting stage, which started decreasing during flowering stage. Similarly, the rice genes OsHG1 and OsHG12 recorded > 2.5-fold increase. However, these genes recorded less than twofold increase during the same stage of the plant in the low heterotic hybrid. Notably, among the genes that exhibited higher expression in the highly heterotic hybrid were those coding for proteins, which were known to play crucial roles in the manifestation of heterosis in plants.

Heterosis and combining ability studies for economic traits in garden pea (Pisum sativum L.)

A line × tester analysis comprising of 7 promising lines and three testers having wider genetic base was carried out for pod yield and related horticultural traits in garden pea (Pisum sativum L.) Among parents, line 17, line 14 and Palam Triloki were observed as best general combiners for pod yield and majority of component traits. Cross, line 17 x Arkel showed high heterosis and SCA effects for pod yield and related horticultural traits. The cross combination line 17 x Palam Triloki was most promising for early flowering and green pod picking. For most of the traits including pod yield per plant non-additive gene actions were of prime importance.

Combining ability and Heterosis analysis for grain yield and yield associated traits in Pea (Pisum sativum L.)

This experiment was conducted to determine the general and specific combining abilities and heterosis for grain yield and yield associated traits in pea as a source of protein through line x tester analysis. Grain yield and its inheritance were carried out for investigation through a 12 x 3 line x tester analysis. Experimental materials comprising 15 parents and their 36 hybrids. The materials were planted in a randomized block design with three replications. The general combining ability and Specific combining ability effects were significant indicating the presence of both additive and non-additive types of gene actions. Heterosis was determined as the superiority over mid parent heterosis as well as better parent (HBP). Grain yield showed highly significant heterosis ranging from -36.29 to 8.77and relative heterosis ranged from -25.85 to 13.19 respectively.

Estimation of combining ability and heterosis for yield and yield attributing traits in Indian mustard (Brassica juncea)

Indian mustard [Brassica juncea (L) Czern. and Coss.] is an important oilseed crop which occupies leading position in oilseed sector of Indian agriculture. Development of high yielding genotypes with high oil content in Indian mustard has been a major breeding objective owing to high edible oil import in India. Present study was conducted with a set of 53 genotypes, that included 40 crosses and 13 parents evaluated for pooled estimation of combining ability and heterosis for yield and yield attributing traits during rabi 2014-15 under timely sown, late sown and extra late sown environmental conditions. The crosses were developed in line × tester design involving 8 lines and 5 testers during rabi 2013-14. The genotype × environment interaction was significant for almost all the traits studied indicating differential response of genotypes to the change in environments. The pooled analysis of variance over environments revealed sufficient differences among environments, parents, hybrids and parent vs. hybrids for most of the traits studied. Importance of both additive and non-additive types of gene actions was observed for seed yield and yield attributing traits. Estimates of GCA effects indicated that NRCHB-101, Pusa Bold and RGN-73 were good general combiners for seed yield/plant and yield attributing traits, i.e. 1000-seed weight, siliqua length, number of primary branches and number of secondary branches. The parent, Pusa Mustard-25 showed good combining ability for dwarfness and early maturity. The hybrids, viz. NRCHB-101 × EC552577, NRCHB-101 × BPR543-2, Pusa Mustard-25 × EC552577, BAUM-2007 × EC552577 and BAUSM 92-1-1 × RGN-73 had significantly high SCA effects, >15% heterobeltiosis and high per se performances for seed yield per plant. The parents showing good combining ability would be identified as promising genotypes and the hybrids having high SCA effects with high heterobeltiosis could give transgressive segregants for seed yield and yield attributing traits under different sowing conditions.

Heterosis for Fruit Yield and Heat Tolerance Traits in Tomato (Lycopersicon Lycopersicum Mill.) Under Field Conditions

Field experiments were conducted at the National Horticultural Research Institute, Bagauda in the Sudan Savannah and Institute for Agricultural Research, Samaru in the Northern Guinea Savanna ecological zones of Nigeria between July-October, 2014 rainy season to estimates heterosis for fruit yield and heat tolerance traits of tomato under field conditions. The experiment comprised two heat tolerant (Icrixina and Rio Grande) and four heat susceptible tomato (Tima, Tropimech, Petomech and Roma Savana) which were crossed using half diallel mating design in the screen house. The resultant 15 hybrids, their parental lines along with four checks were laid out in partially balanced lattice design with three replications. Analysis of variance revealed significant variation among the genotypes for all traits except fruit diameter and cell membrane thermostability, indicating sufficient variability existed among the genotypes. The cross combinations Icrixina × Rio Grande, Icrixina × Tima, Icrixina × Roma Savana and Icrixina × Petomech were found heterotic over better parent for fruit yield and heat tolerance traits (Number of branches per plant, number of clusters per plant, number of flowers per cluster, number of fruits per cluster, number of fruits per plant, percentage fruit set and chlorophyll content) among the hybrids. These hybrids were superior over better parent have the potentiality to be exploited for developing commercial heat tolerant tomato hybrid under field conditions.

Heterosis and combining ability analysis of quality protein maize (Zea mays L.) inbred lines adapted to mid-altitude sub-humid agro-ecology of Ethiopia

Generation of information on heterosis and combining abilities of newly developed maize inbred lines is necessary for a successful hybrid and synthetic maize varieties development. Accordingly, this study was conducted to estimate the combining ability of QPM inbred lines for grain yield and yield related traits and to determine the magnitudes of standard heterosis for grain yield and yield related traits in line × tester QPM hybrids. Fifty test crosses together with two standard checks were evaluated using alpha lattice design with three replications at three mid-altitude sub humid trial sites (Bako, Hawassa and Jimma) in Ethiopia during 2016 main cropping season. Combined analysis of variance showed highly significant differences among the three locations for all the studied traits indicating the presence of considerable variation among locations for genotype performance. The interaction between sites and genotypes were highly significant and significant (P<0.05) for grain yield and ear height, indicating that the performances of the genotypes and crosses were not consistent for these traits. The significance of both general combining ability (GCA) and specific combining ability (SCA) mean square for some traits indicates the role of additive and non-additive gene action in the inheritance of the traits. However, for all the traits, the contribution of GCA variance was greater than the contribution of SCA variance, revealing the predominance of additive gene action in the inheritance of all the traits studied. L1 and L3 had significant positive GCA effects and are considered as good combiners for grain yield. In addition, L1 and L9 were good combiners for earliness. In this study, none of the crosses showed positive and significant standard heterosis for grain yield. Key words: General combining ability, grain yield, specific combining ability, standard heterosis.

Stability factor and heterosis for yield and yield determinants over environments in Indian rapeseed, Brassica rapa var. yellow sarson

Forty-four yellow sarson hybrids developed by line x testers mating design (3 pistillate lines x 9 male parents) were studied along with parents and a standard check for heterosis of yield determinant characters in two environments [Genetics and Plant Breeding Farm (E1), Kumarganj and CRS, Masodha (E2)]. Significant desired heterobeltiosis ranged from 4.52 to 44.86 per cent in E1 and 13.42 to 62.07 per cent in E2 while, standard heterosis ranged from -6.64 to 23.01 per cent in E1 and -6.30 to 21.85 per cent for seed yield plant-1 . Other characters also showed considerable heterosis over better parent and standard check. The crosses L2 x T1 and L3 x T1 were identified as potential for commercial exploitation of heterosis both for seed yield plant-1 and oil content. High heterotic hybrids in both the environments viz., L8 x T1 and L9 x T1 showed stability in performance for nine characters including seed yield plant-1 where as among parent NDYS-141 showed near unity ratio of stability factor for five characters. L9 x T1 followed by L8 x T1 could be identified as most promising crosses on the basis of stability, per se performance, standard heterosis, high GCA and significant SCA effects.

English

English

Heterosis in cucumber (Cucumis sativus L.)

Heterosis for quantitative characters in 39 cucumber genotypes (19 parents and 20 F1 s) were investigated at the farm of Department of Genetics and Plant Breeding in Bangabandhu Sheikh Mujibur Rahman Agricultural University during March-November, 2013. Analysis of variance revealed highly significant differences among the parents and hybrids for 19 characters studied. Considerable coefficient of variation were observed for branches per plant, flesh thickness, placental thickness, fruit length ,fruit width, male and female flowers per plant, leaf length, leaf breadth, vine length, fruits per plant , fruit yield per plant indicating the scope of selection for those characters. The characters like branches per plant, male and female flowers per plant, fruit length, fruit weight, fruits per plant, fruit yield per plant contributed the maximum variability towards divergence among cucumber genotypes. Heterosis study depicted that the crosses Sobujsathi × Baromashi, Sobujsathi × Khira, Himaloy × Khira, exhibited significant positive heterosis for 50 % female flowering; Himaloy × Baromashi, Baromashi× Greenking for fruit length; Baromashi × Hero, Yuvraj × Khira for single fruit weight. Where Sobujsathi × Baromashi, Shila× Khira , Modhumoti × Hero and Modhumoti × Khira exhibited significant positive heterosis and heterobeltiosis for yield per plant. The highest positive heterotic effect for no. of fruits per plant was observed in Modhumoti × Baromashi (20%). The highest heterobeltiosis effect was found in hybrid Himaloy × Yuvraj (24.5%) followed by Sobujsathi× Khira (11.2 %), Modhumoti × Baromashi (10.0 %). Four crosses exhibited significant positive better parent heterotic effect for this trait and the combination Sobujsathi × Baromashi had the maximum heterosis on yield (47.6%). The maximum heterobeltiosis effect was found in Shila × Khira (27.73 %) followed by Modhumoti × Hero (15.14%) and Modhumoti × Khira (10%) for fruit yield.Bangladesh J. Agril. Res. 42(4): 731-747, December 2017

Combining Ability, Heterosis, and Heritability of Storage Root Dry Matter, Beta-Carotene, and Yield-related Traits in Sweetpotato

Orange-fleshed sweetpotato (OFSP) is an effective, low-priced, and sustainable source of β-carotene (provitamin A). However, most OFSP varieties have low storage root dry matter content (DMC), which influences their acceptance by small-scale farmers and hence needs to be improved. The objective of the study was to determine the combining ability, type of gene action, heterosis and heritability of storage root DMC, β-carotene content, and yield-related traits of selected sweetpotato clones for further evaluation and breeding. Crosses were conducted using a 7 × 7 half-diallel mating design and a total of 28 genotypes (seven parents and 21 crosses) were evaluated at four locations in Ethiopia using a 7 × 4 alpha lattice design with two replications. The performance of the genotypes was significantly different (P &lt; 0.01) across the four locations for storage root DMC, β-carotene content, sweetpotato virus disease (SPVD) reaction, storage root yield, and harvest index (HI). The general combining ability (GCA) and specific combining ability (SCA) mean squares were significant (P &lt; 0.01) for all traits except the SCA effect of storage root DMC. The GCA to SCA variance ratios were 0.96, 0.94, 0.74, 0.96, and 0.97 for storage root DMC, β-carotene content, SPVD, fresh storage root yield, and HI, respectively, indicating that the inheritance of these traits was controlled mainly by additive genes. Progenies of crosses involving Ukerewe × Ejumula, Ukerewe × Pipi, Resisto × Pipi, and Ejumula × Pipi exhibited high levels of positive heterosis for storage root DMC. Similarly, progenies of crosses including Resisto × Pipi and Resisto × Ogansagan had higher positive heterosis for fresh storage root yield, reflecting the breeding value of these parents. Relatively high narrow sense heritability (h2) was obtained for β-carotene content (79.8%) and HI (48.6%). However, the h2 estimates of storage root DMC, SPVD, and fresh storage root yield were relatively low at 19.0%, 14.9%, and 20.4%, respectively. Crosses with high β-carotene content such as Ukerewe × Resisto, Resisto × Ogansagan, Eumula × Pipi, and NASPOT 1 × Temesgen exhibited high storage root DMC. These families also had medium-to-high mean fresh storage root yield. Therefore, progenies derived from these families are good candidates to develop improved OFSP varieties with high storage root DMC.

Parental Expression Variation of Small RNAs Is Negatively Correlated with Grain Yield Heterosis in a Maize Breeding Population.

Heterosis refers to a quantitative phenomenon in which F1 hybrid trait values exceed the mean of the parental values in a positive direction. Generally, it is dependent on a high degree of heterozygosity, which is maintained in hybrid breeding by developing parental lines in separate, genetically distinct heterotic groups. The mobility of small RNAs (sRNAs) that mediate epigenetic regulation of gene expression renders them promising candidates for modulating the action of combined diverse genomes in trans–and evidence already indicates their contribution to transgressive phenotypes. By sequencing small RNA libraries of a panel of 21 maize parental inbred lines we found a low overlap of 35% between the sRNA populations from both distinct heterotic groups. Surprisingly, in contrast to genetic or gene expression variation, parental sRNA expression variation is negatively correlated with grain yield (GY) heterosis. Among 0.595 million expressed sRNAs, we identified 9,767, predominantly 22- and 24-nt long sRNAs, which showed an association of their differential expression between parental lines and GY heterosis of the respective hybrids. Of these sRNAs, 3,485 or 6,282 showed an association with high or low GY heterosis, respectively, thus the low heterosis associated group prevailing at 64%. The heterosis associated sRNAs map more frequently to genes that show differential expression between parental lines than reference sets. Together these findings suggest that trans-chromosomal actions of sRNAs in hybrids might add up to a negative contribution in heterosis formation, mediated by unfavorable gene expression regulation. We further revealed an exclusive accumulation of 22-nt sRNAs that are associated with low GY heterosis in pericentromeric genomic regions. That recombinational suppression led to this enrichment is indicated by its close correlation with low recombination rates. The existence of this enrichment, which we hypothesize resulted from the separated breeding of inbred lines within heterotic groups, may have implications for hybrid breeding strategies addressing the recombinational constraints characteristic of complex crop genomes.

The Environment Strongly Affects Estimates of Heterosis in Hybrid Sweet Sorghum

Sweet sorghum [Sorghum bicolor (L.) Moench] has potential as a biofuel feedstock, but hybrid cultivars are needed to support an industry based on this crop. The purpose of this study was to compare five inbred sweet sorghum lines and 15 hybrids derived from them and to determine the extent of environmental effects on estimates of hybrid vigor (heterosis) and heritability for various agronomic traits. The test was repeated across 2 years (2013 and 2015) and three planting dates each year (April, May, and June) at Tifton, GA, USA. Environmental conditions were highly variable, and thus, estimates of heterosis for various traits, as well as correlations between hybrids and midparents (average of the inbred parents), were also variable. In the 2015 season, a new insect pest, sugarcane aphid (Melanaphis sacchari Zehntner), appeared to cause reduced juice Brix in the April planting. Hybrids generally flowered earlier than their inbred male-parent lines, and flowering time was highly correlated between midparents and hybrids. Hybrids frequently had greater lodging percentage than inbreds, but lodging was also correlated between midparents and hybrids in four environments. Heterosis for juice Brix and sugar yield was uncommon, while heterosis for panicle (grain) yield was frequently observed. Based on this study, it will be difficult to predict hybrid performance for juice Brix, sugar yield, and panicle yield based on inbred performance. Testing in multiple environments will be essential for the development of sweet sorghum hybrids, and there is a critical need for sweet sorghum cultivars with resistance to sugarcane aphids.

Can spelt wheat be used as heterotic group for hybrid wheat breeding?

Spelt wheat is a distinct genetic group to elite bread wheat, but heterosis for yield and protein quality is too low for spelt to be recommended as heterotic group for hybrid breeding in wheat. The feasibility to switch from line to hybrid breeding is currently a hot topic in the wheat community. One limitation seems to be the lack of divergent heterotic groups within wheat adapted to a certain region. Spelt wheat is a hexaploid wheat that can easily be crossed with bread wheat and that forms a divergent genetic group when compared to elite bread wheat. The aim of this study was to investigate the potential of Central European spelt as a heterotic group for Central European bread wheat. We performed two large experimental field studies comprising in total 43 spelt lines, 14 wheat lines, and 273 wheat-spelt hybrids, and determined yield, heading time, plant height, resistance against yellow rust, leaf rust, and powdery mildew, as well as protein content and sedimentation volume. Heterosis of yield was found to be lower than that of hybrids made between elite wheat lines. Moreover, heterosis of the quality trait sedimentation volume was negative. Consequently, spelt wheat does not appear suited to be used as heterotic group in hybrid wheat breeding. Nevertheless, high combining abilities of a few spelt lines with elite bread wheat lines make them interesting resources for pre-breeding in bread wheat. Thereby, the low correlation between line per se performance and combining ability of these spelt lines shows the potential to unravel the breeding value of genetic resources by crossing them to an elite tester.