Early Generation Selection Research Articles

Genetic variation and response to selection for storage root dry matter and associated traits in a population of yam bean (Pachyrhizus spp.) interspecies crosses

The goal of yam bean improvement in Africa is to develop superior high yielding and high dry matter cultivars that are preferred for adoption. In this study, the estimates of variance components, heritability and response to selection were studied in F3 yam bean families selected from interspecies crosses targeting improvement of storage root dry matter and associated traits. Breeding populations were generated using North Carolina II (NC II) mating design involving high dry matter P. tuberosus chuin cultivar, low dry matter P. ahipa and the high yielding P. erosus yam beans. The progenies were advanced through selfing from F1 to F2 population and then exposed to selection at 10% selection intensity to obtain 83 high dry matter lines. The selected lines were evaluated in an F3 trial using a randomized complete block design (RCBD) with three replications at the National Crops Resources Research Institute (NaCRRI) Namulonge, in Central Uganda. The results revealed significant (P < 0.001) genetic variation for storage root dry matter (RDM), storage root fresh yield (RFY), storage root dry yield (RDY), vine yield (VNY), fresh biomass yield (FBY), harvest index (HI), starch (STA) and protein (PRO) content. High genotypic coefficient of variation (GCV) and phenotypic coefficient of variation (PCV) were obtained for VNY, RDY, FBY, RFY, RDM and STA. Narrow sense heritability was higher than 0.5 and response to selection was 15.5 to 33.1 for RDM, RFY, RDY, VNY, FBY and STA, indicating rapid genetic progress is achievable and early generation selection would be effective to improve these traits. Significant (P < 0.01) positive genetic correlations were observed between RDM, RDY, RFY, VNY, FBY and STA ranging from 0.422 to 0.963 implying that simultaneous improvement of these traits is possible in the current yam bean populations.

Genotyping crossing parents and family bulks can facilitate cost-efficient genomic prediction strategies in small-scale line breeding programs

Key messageGenomic relationship matrices based on mid-parent and family bulk genotypes represent cost-efficient alternatives to full genomic prediction approaches with individually genotyped early generation selection candidates.The routine usage of genomic selection for improving line varieties has gained an increasing popularity in recent years. Harnessing the benefits of this approach can, however, be too costly for many small-scale breeding programs, as in most genomic breeding strategies several hundred or even thousands of lines have to be genotyped each year. The aim of this study was thus to compare a full genomic prediction strategy using individually genotyped selection candidates with genomic predictions based on genotypes obtained from pooled DNA of progeny families as well as genotypes inferred from crossing parents. A population of 722 wheat lines representing 63 families tested in more than 100 multi-environment trials during 2010–2019 was for this purpose employed to conduct an empirical study, which was supplemented by a simulation with genotypic data from further 3855 lines. A similar or higher prediction ability was achieved for grain yield, protein yield, and the protein content when using mid-parent or family bulk genotypes in comparison with pedigree selection in the empirical across family prediction scenario. The difference of these methods with a full genomic prediction strategy became furthermore marginal if pre-existing phenotypic data of the selection candidates was already available. Similar observations were made in the simulation, where the usage of individually genotyped lines or family bulks was generally preferable with smaller family sizes. The proposed methods can thus be regarded as alternatives to full genomic or pedigree selection strategies, especially when pedigree information is limited like in the exchange of germplasm between breeding programs.

Inheritance of Drought Tolerance Using Six Populations Model in Two Bread Wheat Crosses

DROUGHT stress is the primary restricting factor of crop productivity in Egypt. The development of drought-tolerant lines is urgent. However, drought tolerance is a complex trait. So, this work aimed to reveal the genetic background and gene effects controlling of yield parameters and to discover the epistasis in two bread wheat crosses; Sakha 93 × pureline 5 and Gemmeiza 10 × pureline 42 under irrigated and drought conditions, utilizing seven generations viz. P1, P2, F1, BC1, BC2, F2 and F3.Genetic analysis revealed that additive and dominance effects are involved in the genetics for most traits in both crosses and conditions. Both additive x additive and additive x dominance effects were significant in most cases, supporting the presence of duplicate type of epistasis. Therefore, early generation selection would have failed.F1 hybrids (Drought susceptibility indexes were 0.278 in cross I and 0.295 in cross II), were less affected by drought stress conditions, displaying the presence of heterobeltiosis for drought tolerance. Broad-sense and narrow-sense heritabilities and genetic advance ranged from moderate to high for most of the studied traits and these two crosses could be selected to produce high yielding lines under drought conditions.

Assessment of Tomato Recombinant Lines in Conventional and Organic Farming Systems for Productivity and Fruit Quality Traits

It is estimated that more than 95% of organic agriculture is based on crop cultivars that were bred for the conventional high-input sector. Most selections were made through conventional breeding programs and lack important traits required under organic and low-input conditions. Hybrids are the most common type of cultivars used in tomato because of heterosis. In tomato, continuous selfing enabled homozygosity to exploit favorable additive genes, resulting in the so-called inbred vigor. This paper presented the possibility to express inbred vigor at a level equal to or greater than hybrid vigor in tomato when cultivated under organic low input conditions. The evaluation of the recombinant lines produced through classical reverse breeding from four F1 single cross hybrids was done at low- and high-input farming systems. The results show that, following the appropriate breeding process in early generation selection and under low-input conditions, it is possible to produce recombinant lines, demonstrating inbred vigor in yield potential and fruit quality. These genetic materials can stand as new dynamic cultivars intended for cultivation in organic, low-input, or high-input conditions, depending on their performance in different farming systems at the later stages of evaluation.

Assessment of National Performance Trials of Potatoes in Mid-Altitude Regions of Kenya

Potato is the second most important food crop in Kenya after maize. It is a valuable cash and food crop mainly grown by small-scale farmers. Potato is cultivated mainly under rainfed production conditions at altitudes between 1500 and 3000 metre above sea level (masl). Consequently, National Performance Trials (NPTs) test sites are located in these highlands. Recently, potato production has spread to the mid-highlands (1200-1500masl) mostly due to high food demand occasioned by population increase, and migration of small scale farmers from the densely populated highlands to the more spacious midlands. Consequently, there is increased need to breed potato varieties that can grow profitably in the warmer mid-altitudes. This development called for identification of new conventional NPT test sites located in the mid-altitudes. Six mid-altitude sites were identified and client-managed conventional NPTs carried out. Twenty six potato genotypes were evaluated for two seasons. First season crop was planted in 2016 while the second season crop was planted in 2017. There was a significant (p≤ 0.001) effect of genotypes, environments and genotype x environment interaction in the first season. Trans-Nzoia was the highest yielding site. All genotypes yielded between 10 and 25 ton/ha. In the second season, only environments showed significant (p≤ 0.001) effects. Again, Trans-Nzoia was the highest yielding site. Across the two seasons, Trans-Nzoia gave an average yield of 26.96 ton/ha followed by Kabete at 18. 21ton/ha. All the other four sites yielded less than 10 ton/ha. The high yields at Trans-Nzoia and Kabete could be due to higher altitudes in these two sites compared to the others. In order to develop potato varieties that can produce profitably in the warm mid-altitudes, breeding and early generation selections activities should be based in these areas.

Genomic Prediction of Rust Resistance in Tetraploid Wheat under Field and Controlled Environment Conditions

Genomic selection can increase the rate of genetic gain in crops through accumulation of positive alleles and reduce phenotyping costs by shortening the breeding cycle time. We performed genomic prediction for resistance to wheat rusts in tetraploid wheat accessions using three cross-validation with the objective of predicting: (1) rust resistance when individuals are not tested in all environments/locations, (2) the performance of lines across years, and (3) adult plant resistance (APR) of lines with bivariate models. The rationale for the latter is that seedling assays are faster and could increase prediction accuracy for APR. Predictions were derived from adult plant and seedling responses for leaf rust (Lr), stem rust (Sr) and stripe rust (Yr) in a panel of 391 accessions grown across multiple years and locations and genotyped using 16,483 single nucleotide polymorphisms. Different Bayesian models and genomic best linear unbiased prediction yielded similar accuracies for all traits. Site and year prediction accuracies for Lr and Yr ranged between 0.56–0.71 for Lr and 0.51–0.56 for Yr. While prediction accuracy for Sr was variable across different sites, accuracies for Yr were similar across different years and sites. The changes in accuracies can reflect higher genotype × environment (G × E) interactions due to climate or pathogenic variation. The use of seedling assays in genomic prediction was underscored by significant positive genetic correlations between all stage resistance (ASR) and APR (Lr: 0.45, Sr: 0.65, Yr: 0.50). Incorporating seedling phenotypes in the bivariate genomic approach increased prediction accuracy for all three rust diseases. Our work suggests that the underlying plant-host response to pathogens in the field and greenhouse screens is genetically correlated, but likely highly polygenic and therefore difficult to detect at the individual gene level. Overall, genomic prediction accuracies were in the range suitable for selection in early generations of the breeding cycle.

THE ROLE OF NON-ALLELIC INTERACTION IN INHERITANCE OF SOME ECONOMIC TRAITS IN G. BARBADENSE

The triple test cross analysis was used to study different components of genetic variation by using 75 triple test cross families and their parents, F1 and F2 in one cotton cross (Giza 95 x Australy) for yield, its components and fiber quality traits. The 75 TTC families (25L1, 25L2 and 25L3) were sown at Sakha Experimental Station; Agriculture Research Center, Kafr El-Sheikh government; Egypt. Mean squares between L1, L2 and L3 were highly significant for all traits studied, while between L1 and L2 Families found to be significant for boll weight, lint percentage, lint index, fiber length and micronaire reading. Overall epistatic gene effects were highly significant differences for all traits studied except for fiber length and fiber strength. The (i) fixable type (additive × additive) was the most important epistatic effect than j and 1 non-fixable type for all traits. Both additive and dominance components were highly significant for all the traits studied. The degree of dominance was less than unity and confirmed the presence of partial dominance for all traits studied except for lint yield/plant; lint index and seed index were over-dominance. The Additive gene action played an important role in controlling inheritance for all traits studied than dominance one except for lint yield/plant; lint index and seed index. Direction of dominance (r) was non-significant for most traits indicating absence of dominance directional. Due to influence of (i) type of epistatic effects for the majority of the studied traits selection in early generations may be recommended. Genotypic correlation was positive and significant between yield traits and its components. This could help cotton breeder to use indirect selection to increase yield traits. All the studied traits showed higher proportion of recombinants inbreds falling outside parental range nearly 40%. So, these higher values of prediction revealed that it would be feasible to predict as early as possible for transgressive segregation which can surpass parental range for most studied traits.

THE ROLE OF NON-ALLELIC INTERACTION IN INHERITANCE OF SOME ECONOMIC TRAITS IN G. BARBADENSE

The triple test cross analysis was used to study different components of genetic variation by using 75 triple test cross families and their parents, F1 and F2 in one cotton cross (Giza 95 x Australy) for yield, its components and fiber quality traits. The 75 TTC families (25L1, 25L2 and 25L3) were sown at Sakha Experimental Station; Agriculture Research Center, Kafr El-Sheikh government; Egypt. Mean squares between L1, L2 and L3 were highly significant for all traits studied, while between L1 and L2 Families found to be significant for boll weight, lint percentage, lint index, fiber length and micronaire reading. Overall epistatic gene effects were highly significant differences for all traits studied except for fiber length and fiber strength. The (i) fixable type (additive × additive) was the most important epistatic effect than j and 1 non-fixable type for all traits. Both additive and dominance components were highly significant for all the traits studied. The degree of dominance was less than unity and confirmed the presence of partial dominance for all traits studied except for lint yield/plant; lint index and seed index were over-dominance. The Additive gene action played an important role in controlling inheritance for all traits studied than dominance one except for lint yield/plant; lint index and seed index. Direction of dominance (r) was non-significant for most traits indicating absence of dominance directional. Due to influence of (i) type of epistatic effects for the majority of the studied traits selection in early generations may be recommended. Genotypic correlation was positive and significant between yield traits and its components. This could help cotton breeder to use indirect selection to increase yield traits. All the studied traits showed higher proportion of recombinants inbreds falling outside parental range nearly 40%. So, these higher values of prediction revealed that it would be feasible to predict as early as possible for transgressive segregation which can surpass parental range for most studied traits.

Seedling root characteristics and drought resistance of wheat in Shanxi province

<p indent=0mm>Wheat root morphology at the seedling stage is the basis of root distribution at the adult stage. It is closely related to stress resistance and yield. A comprehensive understanding of the root system characteristics at seedling stage and drought resistance is of great significance for the excellent germplasm utilization and early screening of drought resistance. Using 239 wheat varieties (lines) from Shanxi province, the root traits at seedling stage and their response to water stress were evaluated. The results showed that under normal growth, Shanxi wheat had a great variation in root traits at seedling stage, with the greatest variation in landraces. The maximum root length (MRL) tended to decrease slightly with the years, while other root traits were first increased and then decreased. There were differences among the root traits in response to water stress. The total root length (TRL) is the most sensitive to water, followed by root surface area (RSA), root volume (RV) and root biomass. The maximum root length (MRL) and the average number of roots (RN) were insensitive. The drought resistance of seedling roots showed a trend of decreasing first and then increasing with the years. Landraces and varieties released from 1970 to 1979 had moderately resistance to water stress, varieties released from 1980 to 1999 had lower drought resistance, and varieties released after 2000 had the better resistance, of which the dryland varieties were the best resistance. Correlation analysis of the seedling root characteristics and yield related traits suggested that the maximum root length, total root length, root volume and root biomass were significantly positively correlated with 1000-kernel weight and yield under rain-fed conditions, and the maximum root length and root biomass were also significantly positively correlated with adult plant drought resistance. The present study suggests that the maximum root length and root biomass at the seedling stage can be used as early generation selection parameters for drought resistance and yield in dryland breeding in semi-arid areas.

Aerial High‐Throughput Traits Improve Early‐Generation Selection

CSA NewsVolume 65, Issue 12 p. 16-16 SOCIETY SCIENCE Aerial High-Throughput Traits Improve Early-Generation Selection First published: 21 September 2020 https://doi.org/10.1002/csan.20282Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume65, Issue12December 2020Pages 16-16 RelatedInformation

Shortening the sugarcane breeding cycle at early selection stages and relevance of selection in ratoons

ABSTRACT Selection of sugarcane (Saccharum L. spp. hybrids) for commercial exploitation is a lengthy, laborious, and expensive process. The program can span more than 15 years in Mauritius. This study aimed at shortening the cycle by evaluating the relevance of testing in ratoons in early generation selection trials and eliminating the least efficient crop cycles or stages without undue loss of information. At the second and third clonal selection stages (Stages 3 and 4), genotypes are evaluated for two and 3 years, respectively. Stage 3 comprises trials with unreplicated genotypes and replicated controls, whereas Stage 4 entails classical replicated trials. Historical selection data available since 1986 for Stage 3 and since 1973 for Stage 4 were analyzed. Simulations made with standard selection threshold for sugar yield for individual crop cycles showed low coincidence of selected populations between plant cane (PC) and ratoon crops. More than 50% of genotypes selected in PC were rejected in ratoons. Heritability, genetic coefficient of variance and correlation values were in favor of ratoon crops. Using crop cycle as environment, the environment-centered GGE biplot analyses confirmed the higher disparity between PC and ratoon crops and a high degree of similarity between first (1R) and second (2R) ratoon crops. The performance of released commercial varieties as test candidates in early stages pointed to a higher reliability of 1R results than those of PC crop. These findings support the policy of maintaining selection in ratoon to ensure high precision.

Registration of three soft red winter wheat germplasm lines with exceptional milling and cookie baking performance

AbstractThe release of soft red winter wheat (Triticum aestivum, L.) germplasm lines VA11DH‐P46xTrib‐28 (Reg. no. GP‐1048, PI 691656), VA11DH‐P46xTrib‐99 (Reg. no. GP‐1049, PI 691657), and VA11DH‐P46xTrib‐103 (Reg. no. GP‐1050, PI 691658) is intended to provide breeders with genetic material having exceptional milling and baking quality performance. The quantitative nature of milling and baking performance makes improvement and early generation selection difficult. Marker assisted and genomic selection breeding schemes can be improved by introducing breeding material with superior end‐use quality and use of known predictive DNA markers. These three lines have acceptable agronomic performance with grain yields (4605–5733 kg ha−1) similar to or higher than those of Pioneer ‘26R46’ (4568 kg ha−1). The lines have exceptional milling and baking performance with mean flour yields (733–736 g kg−1), softness equivalence (550–573 g kg−1), flour protein (89–94 g kg−1), solvent retention capacity for lactic acid (1162–1189 g kg−1) and sodium carbonate (672–697 g kg−1), and cookie diameters (19.1–19.5 cm) that are better than or similar to (p &lt; .05) those of Pioneer 26R46 (721 g kg−1, 531 g kg−1, 93 g kg−1, 1221 g kg−1, 703 g kg−1, and 18.9 cm).

G × E interactions in QTL introgression lines of Spanish-type groundnut (Arachis hypogaea L.)

Multi-environment testing at five locations for rust and late leaf spot (LLS) resistance with 41 introgressed lines (ILs) bred using marker-assisted backcross breeding in the genetic background Spanish-type groundnut varieties identified significant genotype, and genotype × environment interactions (GEI) for LLS disease resistance and yield parameters. Significant GEI effects suggest the need to identify location specific breeding lines to achieve gains in pod yield and LLS resistance. The observed variable LLS disease reaction among the ILs in part suggests influence of background genotype on the level of resistance. A breeding scheme with early generation selection using molecular markers followed by phenotyping for LLS, and multi-location testing of fixed breeding lines was optimized to enhance selection intensity and accuracy in groundnut breeding. The ILs, ICGVs 14431, 14436 and 14438 with pooled LLS score at 90 DAS of 3.5–3.7 were superior to respective recurrent parent for pod yield, with early maturing similar to recurrent parents. The pod yield advantage in ILs is attributed by more number of pods, besides resistance to LLS that contributes to better filling.

Breeding wheat for increased potential yield: Contrasting ideas from Donald and Fasoulas, and the case for early generation selection under nil competition

The paper refers to spring wheat breeding for potential yield, yield in the absence of manageable stresses, under irrigated low latitude conditions, representing a major environment for wheat production. Initially it discusses two propositions both over 50 years old. Donald argued that for greater yield, early generation selection should target uncompetitive plant traits or “communal” plants. In contrast, Fasoulas proposed the opposite, namely selection of plants with high yield under nil-competition, aided by the use of a honeycomb design to control for soil variation. Despite some promising results, the absence of definitive proof of the relevance to yield breeding of either concept, wheat breeders have generally opted for an intermediate approach with focus on measuring yield in plots as early as possible. They have been successful but yield progress is slowing. The advent of seeding machinery permitting regular planting patterns through seed singulation, and the reporting of optimal densities for maximum yield per hectare as low as 20 plants/m2 under irrigation and excellent management in northwest Mexico (Fischer et al., 2019), suggest that Fasoulas’s method needs reinvestigating at least for wheat. Yield crossovers (i.e. genotype rank changes) with increasing plant density from the very low density for nil-competition (around 1.4/m2) are expected to be less likely if the target crop density is as low as say 20/m2. There are enough unknowns in the physiology of the wheat crop response to density to suggest that this is quite possible. The approach opens up new possibly more efficient strategies for early generation (e.g. F2) selection for potential yield and could give greater yield progress per unit cost. It would be especially suited for hybrid wheat breeding and production systems. Finally the paper discusses, in the light of the advances in precision agriculture, the opportunities for the agronomy of crops and breeding-nurseries based on low-density honeycomb planting. The major challenge, namely weed control, is manageable.

Multifamily QTL analysis and comprehensive design of genotypes for high-quality soft wheat.

Milling properties and flour color are essential selection criteria in soft wheat breeding. However, high phenotypic screening costs restrict selection to relatively few breeding lines in late generations. To achieve marker-based selection of these traits in early generations, we performed genetic dissection of quality traits using three doubled haploid populations that shared the high-quality soft wheat variety Kitahonami as the paternal parent. An amplicon sequencing approach allowed effective construction of well-saturated linkage maps of the populations. Marker-based heritability estimates revealed that target quality traits had relatively high values, indicating the possibility of selection in early generations. Taking advantage of Chinese Spring reference sequences, joint linkage maps of the three populations were generated. Based on the maps, multifamily quantitative trait locus (QTL) analysis revealed a total of 86 QTLs for ten traits investigated. In terms of target quality traits, 12 QTLs were detected for flour yield, and 12 were detected for flour redness (a* value). Among these QTLs, six for flour yield and nine for flour a* were segregating in more than two populations. Some relationships among traits were explained by QTL collocations on chromosomes, especially group 7 chromosomes. Ten different ideotypes with various combinations of favorable alleles for the flour yield and flour a* QTLs were generated. Phenotypes of derivatives from these ideotypes were predicted to design ideal genotypes for high-quality wheat. Simulations revealed the possibility of breeding varieties with better quality than Kitahonami.

Genome-wide transcriptome and physiological analyses provide new insights into peanut drought response mechanisms

Drought is one of the main constraints in peanut production in West Texas and eastern New Mexico regions due to the depletion of groundwater. A multi-seasonal phenotypic analysis of 10 peanut genotypes revealed C76-16 (C-76) and Valencia-C (Val-C) as the best and poor performers under deficit irrigation (DI) in West Texas, respectively. In order to decipher transcriptome changes under DI, RNA-seq was performed in C-76 and Val-C. Approximately 369 million raw reads were generated from 12 different libraries of two genotypes subjected to fully irrigated (FI) and DI conditions, of which ~329 million (90.2%) filtered reads were mapped to the diploid ancestors of peanut. The transcriptome analysis detected 4,508 differentially expressed genes (DEGs), 1554 genes encoding transcription factors (TFs) and a total of 514 single nucleotide polymorphisms (SNPs) among the identified DEGs. The comparative analysis between the two genotypes revealed higher and integral tolerance in C-76 through activation of key genes involved in ABA and sucrose metabolic pathways. Interestingly, one SNP from the gene coding F-box protein (Araip.3WN1Q) and another SNP from gene coding for the lipid transfer protein (Aradu.03ENG) showed polymorphism in selected contrasting genotypes. These SNPs after further validation may be useful for performing early generation selection for selecting drought-responsive genotypes.

Genetic Analysis of Morphological Traits in Wheat Hybrids Based on the Additive-Dominance Model

Present study carried out in a randomized complete block design with three replications for determining additive, dominance and cytoplasmic effects on inheritance of yield and some of agro-morphological traits in bread wheat. The highest value of grain yield (265.5 g m–1) was obtained in p6. Dominance variance was larger than additive variance for grain-filling period (GFP), plant height (PH), spike length (SL), flag leaf exit (FLE), canopy temperature (CT), early growth vigor (EGV), grain length (GL) and thousand-grain weight (TGW). Whereas, the additive variance was larger than dominance one for days to heading (DH), days to maturity (DM), peduncle length (PL), SPAD and grain yield (GY). Therefore, for these traits selection in early breeding generations could be effective to bring positive changes in these traits. There were significantly positive additive effects (A) of P1 on GFP, CT, GL and TGW; of P3 on DH and DM; P4 on PL, FLE, SPAD and GY and of P6 on PH, SL and EGW. The crosses containing g3 × g4, g4 × g5 and g4 × g6 were indicated positive and significant heterosis for grain yield. P6 were desirable parent for reducing days to heading and maturity and increasing plant height, spike length and early growth vigor.

Inheritance of seed yield and yield-related traits in sunflower

ABSTRACTTo determine the genetic control of seed yield and yield-related traits by using Hayman’s approach, and to estimate the proportion of dominant and recessive genes controlling traits in each parent, five genetically divergent genotypes of sunflower (Helianthus annuus L.) were crossed using a half-diallel mating design (excluding reciprocal crosses). The parents along with their half-diallel crosses were evaluated using a randomized complete block design with three replicates at Kafr El-Hamam/Sharkia and Al-Arish/North Sinai Agricultural Research Stations, Agricultural Research Center, Egypt. Significant differences were observed among genotypes for all studied traits at individual locations and across locations. Magnitude of additive gene effects was larger than that for dominance effects for all studied traits (except for seed weight plant−1) when the ratio [(a/b) & (H1/D) 0.5] was greater than unity at both locations, as also confirmed by high narrow-sense heritability. Hence, selection in early generations would be effective at both locations for these traits. Parents L1031, L1033, and Miak were desirable for early flowering and maturity as well as for short stature and increased proportion of seed oil, whereas Giza 102 and L24 were promising parents for improving number of green leaves plant−1, head diameter, 100-seed weight, and hence seed weight plant−1.

Spectral Vegetation Indices to Track Senescence Dynamics in Diverse Wheat Germplasm.

The ability of a genotype to stay green affects the primary target traits grain yield (GY) and grain protein concentration (GPC) in wheat. High throughput methods to assess senescence dynamics in large field trials will allow for (i) indirect selection in early breeding generations, when yield cannot yet be accurately determined and (ii) mapping of the genomic regions controlling the trait. The aim of this study was to develop a robust method to assess senescence based on hyperspectral canopy reflectance. Measurements were taken in three years throughout the grain filling phase on >300 winter wheat varieties in the spectral range from 350 to 2500 nm using a spectroradiometer. We compared the potential of spectral indices (SI) and full-spectrum models to infer visually observed senescence dynamics from repeated reflectance measurements. Parameters describing the dynamics of senescence were used to predict GY and GPC and a feature selection algorithm was used to identify the most predictive features. The three-band plant senescence reflectance index (PSRI) approximated the visually observed senescence dynamics best, whereas full-spectrum models suffered from a strong year-specificity. Feature selection identified visual scorings as most predictive for GY, but also PSRI ranked among the most predictive features while adding additional spectral features had little effect. Visually scored delayed senescence was positively correlated with GY ranging from r = 0.173 in 2018 to r = 0.365 in 2016. It appears that visual scoring remains the gold standard to quantify leaf senescence in moderately large trials. However, using appropriate phenotyping platforms, the proposed index-based parameterization of the canopy reflectance dynamics offers the critical advantage of upscaling to very large breeding trials.

Bazı Melez Patates Kombinasyonlarında Yapılan Fenotipik Erken Generasyon Seleksiyonları

Seleksiyon çalışmalarında temel hedef, melez kombinasyonlardan oluşan vasyasyondan üstün özelliklere sahip genotipleri seçmektir. Bu araştırmada, üç farklı melez patates kombinasyonundan gelen melez tohumlar kullanılarak elde edilen varyasyon ile fide ve birinci klonal generasyon aşamaları yürütülmüştür. Çalışma Tokat/Kazova‘da 2017-2018 yıllarında fide generasyonu tül sera, birinci klonal generasyon ise arazi koşullarında yürütülmüştür. Araştırmada, beş farklı ebeveyn kullanılarak oluşturulan üç kombinasyondan gelen (A3/15×Bafana, T5/4×Bafana, Başçiflik Beyazı ×Lady Olympia) 5500 adet melez tohum kullanılmıştır. Bu melez tohumlar 13×8‘lik viyollere ekilmiş, dikim olgunluğuna gelen fideler (10-15 cm), 15×24 cm‘lik saksılara şaşırtılmıştır. Fidelerden elde edilen melez klonlar ıslahçı tercihine göre seleksiyona tabi tutularak, devam edilmesi uygun görülen klonlar (1380 adet) ile birinci klonal generasyon aşamasına geçilmiştir. Dikimler, arazi koşullarına 70×50 mesafe olacak şekilde yapılmıştır. Hasattan sonra klonların (1380 adet) her biri ayrı ayrı incelenmiş yumruların fenotipik özellikleri dikkate alınarak yapılan negatif seleksiyon sonucunda 1100 adet klon seçilmiştir.