F3 Selection Research Articles

Genetic Enhancement of Yield Traits in Chickpea (Cicer arietinum L.): An Analysis of Selection in Early Segregating Generations

Background: Indirect selection for yield contributing traits in segregating generation is practiced to realize the potential yields. However, the effectiveness of selection either in early or late segregating generation is a debatable issue in self pollinated crops. The issue is addressed in chickpea by analyzing four segregating generations of a cross in the same season. Method: A bold seeded desi chickpea variety BGD 103 crossed with JAKI 9218. The segregating generations were advanced up to F5 without selection and retaining part of the seeds in each generation. The populations comprised of 162 F­2 plants, 162 F3, F4 and F5 progeny rows were evaluated during rabi 2018-19. The observations on seed traits were recorded and data was subjected to statistical analyses to estimate correlation among the traits in each generations, inter-generation correlation and heritability.Result: The range of variation for the traits narrowed with advancement of the generations. The heritability decreased for seed weight, increased for number of pods per plant and number of seeds per plant with the advancement of generation. In all the four generations, seed yields were associated with number of pods per plant, seeds per plant and seed weight. The change in association among seed traits different generations and estimates of inter-generation correlations suggest that simultaneous improvement of seed weight, seed number and seed yield could be achieved by selection in F3 and F4 generations.

Registration of ‘Acala 1517‐21’ Cotton Cultivar

AbstractThe New Mexico Agricultural Experiment Station announces the release of upland cotton (Gossypium hirsutum L.) cultivar ‘Acala 1517‐21’ (Reg. no. CV‐144, PI 693757). Acala 1517‐21 was derived from a single plant selection in F3 from a bi‐parental cross between LA05307029 and AU‐5491. This new cultivar was tested in eight replicated field trials in New Mexico in 2012–2017 and 21 tests across 12 states of the Cotton Belt in 2016–2017. In New Mexico, Acala 1517‐21 yielded similarly to medium‐staple cultivars or transgenic commercial Acala cultivars including ‘PHY 725 RF’, ‘PHY 755 WRF’, ‘PHY 764 WRF’, ‘FM 2322GL’, and ‘FM 1830GLT’. Compared with ‘Acala 1517‐08’, Acala 1517‐21 averaged 12.9% higher lint yield and 11.5% higher lint percentage, with a similar boll weight, fiber length, length uniformity, elongation, micronaire, and short fiber content. However, Acala 1517‐21 had similar or slightly lower fiber strength with significantly lower strength and elongation in one test. Compared with commercial transgenic and nontransgenic cultivars across the Cotton Belt, Acala 1517‐21 had consistently longer and stronger fibers or lower micronaire readings. Acala 1517‐21 represents a high‐yielding upland cotton cultivar with high lint percentage and a long staple.

Selection of a carotenoid-rich scallop strain, QN Orange, from the inter-specific hybrids between the bay scallop and the Peruvian scallop

In our previous study, we reported the selection of ‘Bohai Red’, a new scallop strain with improved performance in growth from the hybrids between the bay scallop and the Peruvian scallop. In this study, we selected another new strain, the ‘QN Orange’ scallop, with orange adductor muscles, from the same hybrid cohort as the origin of ‘Bohai Red’. In brief, during the selection of the ‘Bohai Red’ strain, a small F1 cohort was produced through mass spawning of a large cohort of the bay scallop-Peruvian scallop hybrids and reproduced consecutively to obtain the F2-F3 cohorts with size-selected brood stocks. About 500 scallops with orange adductor muscles and shells were selected from the F3 selection cohort to form the base selection cohort (G0). The G1-G6 cohorts were reproduced with size-selected brood stocks with orange adductor muscles and orange shells from the G0-G5 cohorts, respectively. The results showed that the percentage of scallops with orange adductor muscles was 88.9% in G1, 92.3% in G2, 92.0% in G3, 94.9% in G4, 96.6% in G5 and 97.4% in G6, respectively. No significant difference in growth was found between the new selection cohort and the control ‘Bohai Red’ selection cohort, however, compared with the control bay scallop cohort, the average shell height, whole weight and adductor muscle weight of the new selection strain were 4.5%, 30.4% and 16.3% higher in G1, 4.1%, 40.6% and 65.2% higher in G2, 20.3%, 50.3% and 88.9% higher in G3, and 17.7%, 73.9% and 80.8% higher in G4, respectively. Thus, through continuous selection, we have obtained a new scallop strain with orange adductor muscle/orange shell and improved growth from the bay scallop-Peruvian scallop hybrids, which was named ‘QN Orange’ scallop.

INHERITANCE OF OIL YIELD AND ITS COMPONENTS IN SAFFLOWER (Carthamus tinctorius L.)

In this research, a diallel cross consisting of genetically diverse six parents (Es-8517, Emek-16, Ekak-7, Emek-21, Ekay-1, Emek-24) was used, aimed to obtain estimates of the gene action in terms of plant height, first branches height, head diameter, 1000 seed weight, oil content, oil yield of per plant in safflower by using Jinks-Hayman type analyses. This study was conducted Transitional Zone Agricultural Research Institute Eskisehir, Turkey during 2016 and 2017. According to the results of all diallel crosses, environmental variance (E), additive gene variance (D), dominance gene variance (H1), (H2) and the value of interaction of additive x dominance gene variance effect (F) were found significant statistically studied traits expect head diameter. Of all the traits studied, being larger dominant gene variances (H1) than the additive gene variances (D) and negative D-H1 value indicated the more important role of dominant genes. Beside of these, positive F value shows that dominant alleles are greater than the number of recessive alleles. Result of Wr, Vr graphics indicated partial dominancy for the first branch height, head diameter, and over dominancy for the rest of the studied traits. It was determined that plant height, first branches height, head diameter, 1000 seed weight, oil content, oil yield of per plant had low narrow heritability values. According to results to obtain superior plants in this hybrid population to perform single plant selection in F3 and F4 generations would be more appropriate.

Impacts of Selection for Spike Length on Heat Stress Tolerance in Bread Wheat (Triticum aestivumL.)

Two consecutive cycles of selection were imposed on five F2 populations of bread wheat. The first cycle was a divergent selection for spike length conducted in favorable environment (optimal sowing date) and the response was measured under favorable and heat stress conditions of a late sowing date. Positive responses to selection for longer spikes were obtained under favorable (13.43%) heat stress (8.66%) conditions, whereas the responses for shorter spikes were 2.24 and 5.02% in the two environments, respectively. The realized heritability of spike length was greater under favorable conditions (0.25-0.56) than under heat stress (0.18- 0.41). Concurrent positive responses to selection for longer spikes were obtained in grain yield per spike under favorable (25.35%) and heat stress (13.65%) environments. Selection for greater number of grains per spike imposed on F3 plants selected for spike length under heat stress resulted in significant responses (14.65%). Selection for greater number of grains per spike resulted in correlated responses in grain yield per spike (17.64%). The concurrent positive responses produced in spike length in F4 with selection for number of grains per spike (averaged 9.20%) was almost equal to that produced by the direct selection in F3 (8.66%), indicating that selection advance effected in F3 has been maintained in F4. High F4/F3 regression was obtained for spike length under heat stress (b = 0.85 ± 0.07), indicating high heritability. In conclusion, phenotypic selection for longer spikes under heat stress followed by a cycle of selection for number of grains per spike was capable of improving heat tolerance in wheat.

Extreme QTL mapping of germination speed in Arabidopsis thaliana.

Seed germination is a key life history transition for annual plants and partly determines lifetime performance and fitness. Germination speed, the elapsed time for a nondormant seed to germinate, is a poorly understood trait important for plants' competitiveness and fitness in fluctuating environments. Germination speed varied by 30% among 18 Arabidopsis thaliana populations measured, and exhibited weak negative correlation with flowering time and seed weight, with significant genotype effect (P<0.005). To dissect the genetic architecture of germination speed, we developed the extreme QTL (X-QTL) mapping method in A.thaliana. The method has been shown in yeast to increase QTL mapping power by integrating selective screening and bulk-segregant analysis in a very large mapping population. By pooled genotyping of top 5% of rapid germinants from ~100000 F3 individuals, three X-QTL regions were identified on chromosomes 1, 3 and 4. All regions were confirmed as QTL regions by sequencing 192 rapid germinants from an independent F3 selection experiment. Positional overlaps were found between X-QTLs and previously identified seed, life history and fitness QTLs. Our method provides a rapid mapping platform in A.thaliana with potentially greater power. One can also relate identified X-QTLs to the A.thaliana physical map, facilitating candidate gene identification.

Matrix based system of isotretinoin as nail lacquer to enhance transungal delivery across human nail plate

The project was aimed at development of isotretinoin nail lacquer and assessment of its penetration efficiency across human nail plate. Preliminary studies (hydration enhancement factor and SEM) aided the selection of thioglycolic acid as permeation and eugenol was selected as local anesthetic in the formulation. The nail lacquer was optimized by 32 factorial design and a total of nine formulations were prepared and screened. In vitro adhesion and ex vivo permeation (cumulative drug permeation per unit area (CDP/A)=6.61±0.57mg/cm2) across bovine hoof guided the selection of F3 as optimized formulation that was improvised. Viscosity adjustments to improve handling characteristics were affected by incorporation of ethyl cellulose (6%; F3M1) that scaled the viscosity to 312.681 cp and insignificantly (p>0.05) affected CDP/A (6.32±0.45mg/cm2). In comparison to marketed preparation (Retino-A cream) F3M1 afforded two fold increase in CDP/A. The permeation characteristics were defined by Higuchi model (r2=0.964) and flux value of 176μg/cm2/h. Confocal laser scanning microscopy, after 72h of nail lacquer application, revealed extensive distribution of the fluorescent tracer across the human nail plate in comparison to control that was confined to the top layer. Conclusively, an efficacious and stable nail lacquer of isotretinoin was developed for potential clinical topical use to target the drug to nail bed in treatment of nail psoriasis.

Response to Early Generation Selection for Resistance to Rice Kernel Fissuring

ABSTRACTThe value of milled rice (Oryza sativa L.) depends on the percent whole versus broken kernels after milling. Kernel fissures caused by pre‐ or postharvest stresses are the leading cause of breakage on milling. ‘Cypress’ is known to be more fissure resistant (FR) than most cultivars, but breeding success has been limited by a lack of ability to identify FR among F2 and F3 progeny. An induced‐fissuring method wherein small samples of seed are evaluated for fissure rates after controlled exposure to humid laboratory conditions can distinguish FR among pure‐breeding rice cultivars. To measure the efficacy of the induced‐fissuring system for evaluating FR among segregating breeding progeny, we applied divergent selection for FR and fissure susceptibility (FS) on seed harvested from ∼300 Cypress (FR) × ‘LaGrue’ (FS) F2 plants and evaluated selection success using seed from F2:3 plants grown in Arkansas and Texas. A second round of divergent selection was made among F3 progeny followed by F3:4 progeny testing. Fissure susceptible F2:3 progeny fissured twice as much as FR progeny, with an average response to selection of 13.5%. Response to F3 selection was smaller (averaging 2.6%), suggesting some fixation of alleles due to the F2 selections. Narrow‐sense heritabilities (h2) were 0.54 and 0.73 for the FR and FS F2 selections, respectively. This study documented successful early‐generation selection for FR, opening new opportunity for breeders to develop rice cultivars improved for this important trait.

Selection for Phytophthora field resistance in the F2 generation of organic outdoor tomatoes

Tomatoes are the most important vegeta- ble, globally as well as in Germany. Outdoor tomato production is seriously impaired due to increasing infections with evolving late blight (Phytophthora infestans) populations. Within organic agriculture, research is being conducted to develop regionally adapted and open pollinated cultivars of outdoor tomatoes with late blight field resistance. In the present experiment, three crosses, including wild, cocktail, and beefsteak tomatoes, were selected for field resistance against late blight in F2 at one location per cross. The comparison of positive and negative selection in F3 revealed the selection of single F2 plants to be efficient in all three crosses. F2 selection has proved to be a robust and efficient tool for breeding programs. The correlated response to selection in other traits, including yield, fruit weight, days to maturity, harvest period, and plant height, depended on the cross. It was evident that selection for desired traits combined with field resistance against late blight is promising, even in wide crosses. The most undesired attribute of wild tomatoes is the formation of shoots on leaves and in inflorescences. No correlation was observed between field resistance and shoot formation, allowing the selection of genotypes with improved field resistance and yield, but without morphological disadvantages.

EVALUATION OF SOME BREEDING METHODS IN DURUM WHEAT

Four breeding methods representing different cycles of phenotypic selection were evaluated using durum wheat (Triticum durum L.) crosses. This included ; 1) pedigree method (PM) with three cycles of selection in F3, F, and F5, 2 ) modified bulk' (MB5) two cycles of selection in F., and F5, 3) modified bulk2 (M32) where only one cycle of selection in F3 was exercised, 4 ) bulk method (EM) where only natural breeding or selection was involved. This study was conducted at the farm of Et-Giza Agric. Res. Station, ARC, Egypt, during four successive seasons from 2005/2006 through 2008/2009 to evaluate the efficiency of four different breeding methods in improving grain yield potentiality and some other agronomic traits in six durum wheat crosses. The lines derived from various selection cycles were evaluated in terms of number of spikes/plant, number of kernels/spike, 100-kernel weight and grain yield/plant Results of analysis of variance for every cross showed significant differences among breeding methods in all crosses. Moreover, the genotypes showed significant differences in number of spikes/plant except crosses No. 1, 2 and 5, number of kemels/spike, except cross No. 1, 100-kernel weight except cross No. 2 and grain yield/plant for all crosses. The interaction between genotypes and methods of breeding was significant in all characteristics studied for all crosses except number of spikes/plant in cross No. 5, number of kernels/spike in cross No. 4, 100-kernel weight in crosses No. 1 and 6 and grain yield/plant for all crosses. Combined analysis for all methods of breeding crosses and genotypes showed significant differences for crosses (C), methods of breeding (M), genotypes (G), (C x M), (M x G) and (C x M x G). The best methods of breeding for all studied traits were pedigree method (PM) followed by modified bulk 2 (MP2) .Results revealed that the six durum wheat crosses differed in all studied characteristics. Cross No. 5 had the highest number of spikes/plant, cross No. 2 had the highest number of kemds/spike, cross No. 3 had the highest 100-kernel weght and cross No. 5 the highest grain yield/plant.

Comparison of the formant frequencies F3 and F4 on a three-dimensional vowel chart.

We have developed a three-dimensional vowel chart that should fit into a quadrilateral IPA vowel chart better and later we have added more visually effective functions to it. On the chart we can see not only the locations of F1 and F2 with two scales of x and y, where x is F1 and y F2, but also F1, F2, and F3 as well, with three scales of x, y, and z, where x is F1, y F2, and z F3. Thus, this enables us to compare the vowel locations of any language (multilingual vowel presentations), vowels uttered by male with those of female (thus, gender difference), vowels of adults with those of children (thus, age difference), foreign language learners with target vowels, or vowels uttered by the same language learners. This time, we focus more on the roles of the respective formants, particularly on the roles of F3 and F4. It has been clarified that F3 is more related to lip-spreading. We want to show that F4 may be more related to lip-protrusion. For this purpose, we have further added a selection of F3 and F4 functions to the chart. [Work supported by JSPS and Chubu University Grant (A).]

A New Recessive Allele at the C Locus for Seedcoat Color in Common Bean

The inheritance of a new allele, cv, at the C locus for seedcoat color was studied in common bean (Phaseolus vulgaris L.) using plant introduction (PI) accession 527774 as the source of cv. The cross PI 527774 (yellow-brown seed) x v BC25-593 (mineral-brown seed) genetic tester stock was studied in F1 and F2 progeny. An F3 selection from the above cross, designated F3 cv G b v, was crossed to 5-593 (a Florida breeding line with black seeds), and the F1, and F2 progeny were analyzed for color segregation. The second hackcross [S-593 x F1 (F3 cv G b v x 5-593)] was investigated in selfed progenies from 32 random BC2-F1 parents. Two of the BC2-F2 progenies were further tested in BC2,-F3. A third hackcross of cv to 5-593 was made and analyzed, and an allelism test of cv B V BC2-F35-593 with the cartridge huff cu BC3 5-593 genetic tester stock confirmed that cv is an allele at C. The gene symbol, cv, is proposed for the new allele because it is only expressed with V and gives a grayish-brown seedcoat. Genotypes with C/cv do not show heterozygous mottling with G B v or G b v, and there is no difference in seedcoat color between C G B v and cv G B v, or between C G b v and cv G b v.

Early generation selection in wheat. I. Yield potential

F3 single plant traits were tested as possible selection criteria for increasing yield potential. F3 plants were grown spaced in a glasshouse, while yield was measured in southern New South Wales under irrigation and optimum management. Thc population studied comprised 220 F1-derived lines taken at random from a multiple convergent cross amongst 16 parents representing elite CTMMYT germplasm of the mid 1970s but containing diversity for major dwarfing genes, maturity, leaf angle and other traits. More than 50 traits were determined, comprising numerical components of yield, size and morphology, partitioning ratios, development rates and physiological activities. All F3 traits showed significant genotypic variation which was usually greater for progeny lines than for parents although only occasionally significantly so. Broad sense heritability was generally moderate to high.F3 lines were advanced by single seed descent for replicated F7 and F8 yield experiments, two in each of 1982 and 1983. In each experiment 60-68 progeny lines chosen at random were tested; 44 lines were common to all experiments. Plot size was 8 rows X 5 m, and edge rows and plot ends were discarded. Yield levels were high (mean yield 5.9 t h a 1 at 10Yo moisture) and largely free of interference from lodging and disease. The progeny main effect on grain yield was highly significant, but no progeny line significantly outyielded the best parent. Best correlations with progeny grain yield were given by F3 plant height (r= -0.31 to -0.50 across experiments), F3 kernel weight (r= -0.03 to -0.44), F3 harvest index (r = 0.18 to 0.5 l), F3 leaf angle (r = -0.13 to -0.40, erect leaves favouring high yicld) and F3 spike number (r=0.08 to 0.40). Retrospective selection in F3 using these traits singly at a selection intensity of 25% gave increases in population mean yield (0 to + 12%) and in the proportion of high yielding lines (doubled in some cases), but only selection in F3 for reduced stature is considered worthwhile for advancing yield potential. It is suggested that the ineffectiveness of F3 selection is largely due to genotype by environment interaction, along with the complex multigenic nature of grain yicld.

Early generation selection in wheat. II. Grain quality

In order to test early-generation selection for grain quality, random F1-derived progeny from a multiple convergent cross of 16 high-yielding bread wheats were grown in F3 generation, along with the parents, as spaced plants in a glasshouse under optimal conditions. Progeny lines were then advanced without selection to F7 when 58 random lines were sown with the parents in a replicated yield experiment at Griffith under irrigation and optimal management. Small-scale grain quality tests were performed on grain from the F3 plants, the F7 plots and the parents. The tests comprised particle size index (PSI), grain and flour protein content (GP, FP), sodium dodecyl sulfate sedimentation volume (SDS), Pelshenke wheatmeal fermentation time (PEL) and flour milling yield (MY).There were significant genotypic effects for all quality traits in each generation. Phenotypic correlations in F3 and in F7 showed positive correlations between protein content and SDS and PEL, and in F7 a strong negative correlation between grain yield and grain quality (GP, FP, SDS, PEL). Across generations (F3 versus F7), the relationship was strong for PSI, moderate for SDS and PEL, but nonsignificant for the other traits.The realized heritability was high for PSI (77%), moderate for SDS (44%) and PEL (47%), but low (18-24%) in the other cases. Selection at an intensity of 26% for the first three mentioned traits did not significantly change grain yield, plant height or flowering date, although for GP and FP it did lower grain yield by 7%. Desirable quality types were defined within the three hardness (PSI) classes, namely, hard, intermediate, and soft (gluten type not biscuit type). Retrospective selection in F3 for desirable types significantly and markedly increased the frequency of desirable types in each class by three- to eight-fold. It is concluded that in wheat early generation selection for PSI, SDS and PEL, even when practised upon glasshouse-grown plants, gives useful progress without prejudicing grain yield.

Selection for High and Low Harvest Index in Three Winter Wheat Populations1

Low heritability of grain yield in wheat (Triticum aestivum L.) often results in a slow response to selection. Selection criteria other than grain yield per se are being sought by wheat breeders. Harvest index (HI), the ratio of grain yield to total biomass yield, may be a useful selection trait for yield improvement. A study was undertaken to estimate the heritability of HI and to determine the response to selection for high and low HI in three genetically diverse populations of winter wheat. Selections were made in the F3 generation and selected progenies were evaluated in replicated tests in the F4 generation. Realized heritability estimates for HI were intermediate in magnitude (0.44 to 0.60). Selection in F3 for high and low HI was effective in identifying F4 lines with high and low HI, respectively. Also, selection for high HI resulted in shorter plants with earlier heading dates and lower biomass yield. Genotypic correlations (rG) between HI and grain yield were low (rG = 0.04 to 0.23). Phenotypic correlations between HI and grain yield were relatively high in the F3 but much lower in the F4. Harvest index was negatively correlated with plant height and days to heading, while correlations between HI and biomass yield were mostly nonsignificant. Simple correlation coefficients between F3 and F4 means were higher for HI than for grain yield. Results indicated that HI in the F3 generation was a good predictor of HI in the F4, but a poor predictor of grain yield in the F4.

Evaluation of Early Generation Testing in Chickpea1)

AbstractInter‐generation correlations between F2‐F3, F2‐F4 and F3‐F4 in six crosses of chickpea were calculated by using individual plant/progeny means. In general, correlation values in case of plant height, seeds per pod and 100‐seed weight were higher between F3 and F4 than those between F2 and F3 and F2 and F4. However, inter‐generation correlations were mostly non‐significant in case of pods per plant and grain yield. These results clearly show that selection in F3 can be fruitful for seeds per pod and 100‐seed weight. However, selection for pods per plant and grain yield in early generations may not show any relationship with later generation performance for these traits.

Reproductive Duration and Date of Maturity in Populations of Three Wide Soybean Crosses1

Greater seed yield may be related to a longer reproduction period (RP) in soybean [Glycine max (L.) Merr.]. Unique combinations of genes controlling photoperiod sensitivity may allow selection for longer RP without delaying date of physiological maturity (R7). Three single‐cross populations of F2‐derived soybean lines were made from a diallel crossing of two photoperiod‐insensitive determinate plant introductions, PI317.334B and PI317.336, and an indeterminate cv. Harosoy 63 in an attempt to develop populations in which the correlations of date of R7 with length of the seed‐filling period (SFP) and RP are small. Genetic variability and response to selection of these traits were also studied. Time from beginning of flowering (R1) to beginning of rapid seed filling (RS) of determinate lines averaged 12.6 days and 7.3 days shorter than those of indeterminate lines in two crosses, while SFP, days from R5 to R7, averaged 11.2 and 6.7 days longer for determinate lines than for indeterminate lines. These results are likely due to the difference in estimating stage R5 (seeds 3 mm long in one of the top four plant nodes) between determinate and indeterminate lines rather than biological differences in SFP between determinates and indeterminates. Associations of SFP and RP with R7 in crosses of Harosoy 63 with either plant introduction were weaker than those previously reported for US‐adapted germplasm. Estimates of realized heritabilities of RP ranged from 0.63 to 1.17, even when RP was adjusted for differences in R7. Realized heritability estimates of SFP ranged from 0.40 to 1.02, except for indeterminates where considerably less genetic variance was observed. Reproduction period and SFP of selected F4 populations were lengthened by F3 selection up to 6.4 and 6.1 days, respectively, relative to population means, without significantly changing R7. These results suggest that selections from two of the three crosses should be useful for incorporation of longer SFP and RP into adapted germplasm to enhance yield potential without delaying date of R7.

Selection Strategy in Breeding of Self-fertilizing Crops : IV. The Sizes of F2 and F3 Populations in Consideration of Selection

The sizses of F2 and F3 populations are investigated based on the two criteria, i. e., the probability that promising genotypes are selected in the F2 and F3 Selection, and the economic advantage which is expected to be gained by obtaining the promising genotypes. In formulating these criteria, a selection system is assumed where within and among cross selection is made in F2 regarding qualitative and some highly heritable continuous charaters, selection for these and other less heritable characters being operated in F3. The optimurn. sizes of the populations are differently estimated according to the quantity of breeding cost and the number of cross combinations available for the breeding programme at issue, but it may be safely adopted as a standard in a routine selection work that several hundred and a few to several thousand plants are grown for the F2 and. F3 selection respectively. The genetic potentiality of individual crosses may not be fully tested in this scale of selection, but the economic advantage in the long run will be enlarged. Only one out of hundreds of crosses can lead to a new variety in highly improved crops such as rice and wheat. With such a poor identification of desirable crosses, spending a large cost for a limited number of crosses may cause a serious waste of breeding cost unless the crosses are pre-confirmed to be more promising than others.

Selection for Apparent Photosynthesis and Related Leaf Traits in Early Generations of Soybeans1

Evidence suggests that photosynthate production may be yield‐limiting in soybeans [Glycine max (L.) Merr.]. This study was designed to estimate potential for selection of CO2‐exchange rate (CER), specific leaf weight (SLW), leaf thickness (LT), and leaf density (LD) in early generations of soybeans.Two crosses (‘Amsoy’ ✕ ‘Ford;’ ‘Corsoy’ ✕ ‘Hawkeye’) involving adapted cultivars high (Amsoy, Corsoy) and low in leaf CER were used. CER, SLW, LT, and LD were measured in parents, F1s and F2s. CER was measured in selected F3 and F4 lines of one cross, whereas the other variables were measured in all F3 and F4 lines.All traits showed quantitative inheritance without dominance effects. Broad‐sense heritability, based on parental, F1 and F2 variances, was low to moderate for CER (0.36, 0.56); it was low to very low for the other variables. Selection for either high or low CER in the F2 or F3 was ineffective. Gain from hypothetical selection for SLW was about 596 in the F2 and 5‐11% in the F2. Gain from hypothetical F3 selection in LT was about 5%. LD showed poor gain.Use of pure lines from advanced generations may give an entirely different picture of the potential for direct selection for increased photosynthesis than that shown by this study.

Selection for yield in wheat breeding

If selection based on F3 yield tests is to be effective, the yield tests must be successful in discriminating among yield genotypes. The available literature indicates that simple tests with limited or no replication are not very effective, although more extensive, replicated tests may be. Data from an experiment comparing F3 yield tests with a single seed descent procedure showed that F3 selection based on a two-replicate test with single seed descent procedure did not justify the extra work involved.