Heterotic groups for identifying of suitable combiners in sunflower using top-cross

The study was conducted in order to identify the suitable parental inbred lines using top cross method for improvement of new sunflower F1 single cross hybrids at research field of Seed and Plant Improvement Institute in Karaj, Iran during two Crop season (2018 and 2019). Experimental materials consisted of 31 restore lines and 43 cytoplasmic male sterile lines which were crossed with A1221 and R14 as the testers respectively. The developed F1 hybrids were evaluated for GCA of three breeding objectives i.e. flowering time, plant height and grain yield during two years replicated trials. Cluster analysis revealed two heterotic groups in which the restorer lines; R22, R24 and R38 (Grain yield of 33, 32 and 31 g head-1 respectively) and three CMS lines; A32, A370 and A110 (Grain yield of 47, 44 and 43 g head-1 respectively) were identified as the suitable restorer and cytoplasmic male sterile line for improvement of new sunflower single cross hybrids. Evaluation of specific combing ability of the resulted combinations will reveal the efficiency of this selection in the following generation.

Combining ability and heterosis in plant improvement

Information on combining ability and heterosis of parents and crossings is crucial in breeding efforts. Genetic variety is crucial to the effectiveness of yield improvement efforts because it helps to broaden gene pools in any given crop population. The genotype's ability to pass the intended character to the offspring is referred to as combining ability. As a result, information on combining ability is required to determine the crossing pairs in the production of hybrid varieties. Heterosis is the expression of an F1 hybrid's dominance over its parents in a given feature, as measured not by the trait's absolute value, but by its practical use. To put it another way, heterosis is defined as an increase in the character value of F1 hybrids when compared to the average value of both parents. A plant breeder's ultimate goal is to achieve desirable heterosis (hybrid vigor). In a variety of crop species, heterosis has been widely employed to boost output and extend the adaptability of hybrid types. A crucial requirement for discovering crosses with significant levels of exploitable heterosis is knowledge of the quantity of heterosis in different cross combinations. Any crop improvement program's success is contingent on the presence of a significant level of genetic diversity and heritability. The lack of a broad genetic foundation is the most significant constraint to crop improvement and a major bottleneck in breeding operations. Heterosis is a critical factor in hybrid generation, particularly for traits driven by non-additive gene activity. To get the most out of heterosis for hybrid cultivar production, germplasm must be divided into distinct heterotic groups. Similarly, knowledge on genetic diversity is critical for hybrid breeding and population improvement initiatives because it allows them to analyze genetic diversity, characterize germplasm, and categorize it into different heterotic groupings. In general, general combining ability is used to detect a line's average performance in a hybrid combination, whereas specific combining ability is used to find circumstances where definite combinations perform better or worse than expected based on the mean performance of the lines involved.

Formation of Potential Heterotic Groups of Oat Using Variation at Microsatellite Loci

An evaluation of polymorphism at the microsatellite loci was applied in distinguishing 85 oat (Avena sativa L.) genotypes selected from the collection of genetic resources. The set of genotypes included oats with white, yellow, and brown seeds as well as a subgroup of naked oat (Avena sativa var. nuda Koern). Variation at these loci was used to form potential heterotic groups potentially used in the oat breeding program. Seven from 20 analyzed microsatellite loci revealed polymorphism. Altogether, 35 microsatellite alleles were detected (2–10 per locus). Polymorphic patterns completely differentiated all genotypes within the subgroups of white, brown, and naked oats, respectively. Only within the greatest subgroup of yellow genotypes, four pairs of genotypes remained unseparated. Genetic differentiation between the oat subgroups allowed the formation of seven potential heterotic groups using the STRUCTURE analysis. The overall value of the fixation index (Fst) suggested a high genetic differentiation between the subgroups and validated a heterotic grouping. This approach can be implemented as a simple predictor of heterosis in parental crosses prior to extensive field testing or development and implementation of more accurate genomic selection.

Aflatoxin Accumulation in a Maize Diallel Cross Containing Inbred Lines with Expired Plant Variety Protection

In-field infection of maize (Zea mays L.) ears by the fungus Aspergillus flavus Link:Fr causes pre-harvest aflatoxin contamination of maize grain. Germplasm lines with host-plant resistance to aflatoxin accumulation are available to breeders, but these lines often possess undesirable agronomic characteristics. Commercial lines with expired plant variety protection (ex-PVP lines) are a potential source of elite germplasm available to public maize breeders. A diallel cross containing three aflatoxin-accumulation-resistant germplasm lines and seven ex-PVP lines were evaluated in replicated trials for aflatoxin contamination after artificial inoculation and for yield. The resistant germplasm lines Mp313E, Mp715, and Mp717 were the only lines with significant general combining ability (GCA) for reduced aflatoxin accumulation. Of the ex-PVP lines evaluated, the Stiff-Stalk line F118 was the most promising line to use in breeding crosses. Based on its GCA, it was the only ex-PVP line that did not significantly increase aflatoxin and the only ex-PVP line that significantly increased yield. Second-cycle breeding lines derived from crosses between F118 and the resistant donor lines will be valuable if they combine the donor lines’ disease resistance with F118’s earlier maturity while introgressing the disease resistance into a genetic background that aligns with the industry’s well-defined heterotic groups.

Core circadian clock and light signalling genes brought into genetic linkage across the green lineage

The circadian clock ensures that biological processes are phased to the correct time of day. In plants the circadian clock is conserved at both the level of transcriptional networks as well as core genes. In the model plant Arabidopsis thaliana, the core circadian singleMYB (sMYB) genes CCA1 and RVE4 are in genetic linkage with the PSEUDO-RESPONSE REGULATOR (PRR) genes PRR9 and PRR7 respectively. Leveraging chromosome-resolved plant genomes and syntenic ortholog analysis it was possible to trace this genetic linkage back to the basal angiosperm Amborella and identify an additional evolutionarily conserved genetic linkage between PIF3 and PHYA. The LHY/CCA1-PRR5/9, RVE4/8-PRR3/7 and PIF3-PHYA genetic linkages emerged in the bryophyte lineage and progressively moved within several genes of each other across an array of higher plant families representing distinct whole genome duplication and fractionation events. Soybean maintains all but two genetic linkages, and expression analysis revealed the PIF3-PHYA linkage overlapping with the E4 maturity group locus was the only pair to robustly cycle with an evening phase in contrast to the sMYB-PRR morning and midday phase. While most monocots maintain the genetic linkages, they have been lost in the economically important grasses (Poaceae) such as maize where the genes have been fractionated to separate chromosomes and presence/absence variation results in the segregation of PRR7 paralogs across heterotic groups. The evolutionary conservation of the genetic linkage as well as its loss in the grasses provides new insight in the plant circadian clock, which has been a critical target of breeding and domestication.

Germoplasma de porumb utilă la crearea liniilor consangvinizate timpurii

The evolution of germplasm incorporated into 477 inbred lines of early maize developed in 1981-2019 years are presented here. It is concluded that for modern maize breeding more useful germplasm are alternative heterotic groups Euroflint mixt, Reid Iodent, BSSS-B37 and Lancaster. A comparative study of 20 inbred lines from 3 heterotic groups demonstrated the performance of Reid Iodent germplasm as seed, female parents. In the mentioned period 35 original inbred lines used as parents of registered hy-brids have been created.

Using of GGE biplot in determination of genetic structure and heterotic groups in wheat (Triticum aestivum L.)

The present study was undertaken to analyze diallel data using GGE biplot model to gather information about genetic interrelationships among parents and identification of heterotic combinations for yield and yield components in bread wheat varieties. For this purpose, 8 bread wheat genotypes tested across in half-diallel crosses design, GGE biplot technique was used. Parents included the genotypes of Kouhdasht, Karim, Ehsan, Mehregan, N-92-9, Line 17, N80-19 and Atrak. The hybrids obtained from the one-way cross (28 hybrids) in agricultural years of 2016-17 were evaluated as randomized complete block design in two replications on the research farm of Gonbad Kavous University. The evaluated traits included the grain yield, weight of spike grains, number of grains in spike and number of spikes. Additive main effects and genotype × environment interaction (GGE) were employed in the evaluation of genotypes; analyses showed significant (P< 0.01) G × E, (genotype × environment interaction) with respect to plant seed yield. GGE biplot analysis showed that Karim was as the best general combiners for grain yield, number grain per spike and grain weight per spike, whereas Ehsan had the highest GCA effects for number of spikes. Ehsan and Karim had higher specific combining ability than other genotypes. The studied genotypes for this trait were divided into two heterotic groups where the first group included the genotypes of Kouhdasht, N-92-9, N80-19 and Atrak and the second group contained the genotypes of Line 17, Mehregan and Karim. Mehregan line had a weak combining ability with all testers and N-92-9 had also more power than others. Based on the biplot, the Karim genotype with high general adaptation was introduced as the ideal genotype in terms of grain yield, spike number, grain number per spike and grain weight, so the Karim genotype can be adapted to obtain high yield hybrids.

Gene Action, Heterotic Patterns, and Inter-Trait Relationships of Early Maturing Pro-Vitamin a Maize Inbred Lines and Performance of Testcrosses Under Contrasting Environments

Vitamin A deficiency is the leading cause of night blindness, total blindness, maternal and childhood mortality in developing countries. Drought, low soil nitrogen and Striga hermonthica parasitism are major constraints to maize production in sub-Saharan Africa (SSA). Thus, the development of multiple stress tolerant maize varieties with elevated levels of PVA is an economically feasible approach to simultaneously tackle malnutrition and food insecurity in SSA. The objectives of this study were to determine the gene action modulating the inheritance of grain yield and other traits, group the inbred lines, investigate inter-trait relationships among grain yield and other traits and assess the performance and stability of single-cross hybrids derived from a set of inbred lines under stress and non-stress environments. One hundred and ninety diallel crosses plus six hybrid checks were evaluated under managed drought at Ikenne during the 2016/17 and 2017/18 dry seasons, low soil N conditions at Mokwa and Ile-Ife, Striga infestation at Abuja and Mokwa, and optimal management conditions at Ikenne, Kadawa, Abuja, Bagauda and Mokwa during the 2016 and 2017 growing seasons. Both additive and non-additive gene actions were prominent in the inheritance of grain yield and other measured traits under stress and optimal management conditions. However, additive gene action was preponderant over the non-additive. The PVA inbreds were classified into three heterotic groups with TZEI 25 and TZEIOR 164 identified as inbred testers for heterotic groups 2 and 3, respectively. Plant and ear heights, ears per plant, plant and ear aspects were identified as reliable secondary traits for genetic enhancement of grain yield under both stress and non-stress conditions. Hybrids TZEIOR 4 x TZEIOR 158 and TZEIOR 119 × TZEIOR 158 were outstanding in performance and should be tested extensively for possible commercialization to combat malnutrition and food insecurity in SSA.