Recurrent Selection For Grain Yield Research Articles

Response of locally adapted pearl millet populations to s1 progeny recurrent selection for grain yield and resistance to rust

In the semi-arid zones of Uganda, pearl millet ( Pennisetum glaucum (L.) R. Br.) is mainly grown for food and income; but rust ( Puccinia substriata var indica (L.) R. Br.) is the main foliar constraint lowering yield. The objective of the study was to genetically improve grain yield and rust resistance of two locally adapted populations (Lam and Omoda), through two cycles of modified phenotypic S 1 progeny recurrent selection. Treatments included three cycles of two locally adapted pearl millet populations, evaluated at three locations. Significant net genetic gain for grain yield (72 and 36%) were achieved in Lam and Omoda populations, respectively. This led to grain yield of 1,047 from 611 kg ha -1 in Lam population and 943 from 693 kg ha -1 in Omoda population. Significant improvement in rust resistance was achieved in the two populations, with a net genetic gain of -55 and -71% in Lam and Omoda populations, respectively. Rust severity reduced from 30 to 14% in Lam population and from 57 to 17% in Omoda population. Net positive genetic gains of 68 and 8% were also achieved for 1000- grain weight in Lam and Omoda, respectively. Traits with a net negative genetic gain in both populations were days to 50% flowering, days to 50% anthesis, days to 50% physiological maturity, flower-anthesis interval, plant height and leaf area. Key Words : Pennisetum glaucum, Puccinia substriata

Effect of Recurrent Selection on the Genetic Structure of Two Broad‐Based Spanish Maize Populations

ABSTRACTMaize (Zea mays L.) landraces are useful materials that can introduce new diversity into breeding programs, but they will need to be selected to maximize their agronomic performance. The objective of this study was to use molecular markers to investigate the changes in the genetic diversity and structure over the cycles of a maize breeding program that combined intra‐ and interpopulation recurrent selection for grain yield in two broad‐based Spanish maize composites. Using 76 polymorphic simple sequence repeat (SSR) markers and two flowering time related indels, this study looked at 10 populations derived from a breeding program designed to exploit the heterotic pattern northern Spain × southern Spain. Agronomic evaluations demonstrated that the selection effectively increased the yield of the composites and their crosses, but, as the molecular data from this study show, the improvement was at the expense of some variability. The genetic distance between populations increased with selection, which is accordant with the increment of heterosis found in the agronomic evaluation. The changes observed were consistent with a model in which genetic drift is the main force, although selection could also play a role in the changes observed in EPS7 and EPS13. Allele frequencies changed significantly for one marker during intrapopulation selection and three markers under interpopulation selection, pointing to regions 3.04, 7.03, 9.01, and 9.03 as quantitative trait loci (QTL) related to grain yield.

Estimation of genetic progress after eight cycles of recurrent selection for common bean grain yield

The objective of this study was to estimate the genetic progress of eight cycles of recurrent selection for common bean lines with high yield. The base population was obtained from 10 parents differing in several characters. To date, eight selection cycles have been performed. In each cycle the selection process continues after recombination, until lines are established, which are then evaluated more extensively in the experiment of evaluation of elite lines together with lines of other programs. The genetic progress was estimated based on the data of evaluations of these lines in each cycle over the years. The estimated genetic progress of 3.3 % per cycle allows the conclusion that recurrent selection for grain yield is efficient.

Effects of Recurrent Selection for Grain Yield and Striga Resistance in an Extra‐Early Maize Population

Effects of Recurrent Selection for Grain Yield and Striga Resistance in an Extra‐Early Maize Population

Effects of Recurrent Selection for Grain Yield and Striga Resistance in an Extra‐Early Maize Population

ABSTRACTStriga hermonthica (Del.) Benth threatens maize (Zea mays L.) production in sub‐Saharan Africa. In an extra‐early population, S1 families derived from four cycles of recurrent selection for grain yield and Striga resistance were evaluated with and without Striga infestation at three locations in Nigeria for 2 yr to determine relative changes in genetic variances, heritabilities, and genetic correlations for yield and other traits. Under infestation, yield was not correlated with other traits at C0 but was significantly correlated with ears per plant (EPP), Striga damage, and emerged Striga plants in advanced cycles. Genetic correlations between yield and most traits were significant in C0 when Striga‐free but was reduced in advanced cycles. Genetic variances and heritabilities for yield and ear aspect increased in advanced cycles. Genetic variances decreased with selection for emerged Striga counts and EPP under infestation. A response to selection for improved yield, Striga emergence and EPP is expected in subsequent cycles. Low genetic variances and heritabilities for Striga damage and low predicted gain cycle−1 for all traits except numbers of emerged Striga plants suggest a need to introgress novel resistance genes into the population for faster progress from selection for increased yield.

Performance of Early Maize Cultivars Derived from Recurrent Selection for Grain Yield and Striga Resistance

Maize (Zea mays L.) production in west and central Africa (WCA) is constrained by the parasitic weed Striga hermonthica (Del.) Benth and recurrent drought. Two early maize populations, TZE‐W Pop DT STR C0 (white) and TZE‐Y Pop DT STR C0 (yellow), developed from diverse genetic backgrounds, were subjected to three cycles of S1 recurrent selection under artificial Striga infestation. Inbreds and synthetic cultivars were developed from the different cycles of selection. The populations (C0), derived cultivars, and check cultivars were evaluated in 2002 and 2003 under Striga‐infested and Striga‐free environments in WCA. The objective was to assess the performance of the derived cultivars from the different cycles of selection. Under Striga infestation, ACR 94 TZE Comp5‐Y and ACR 94 TZE Comp5‐W, which were not from the selection program, were the highest‐yielding group (2158 and 2124 kg ha−1, respectively). The second group comprised six products of the selection program, with grain yield ranging from 1806 to 1954 kg ha−1 The third group, with grain yield of 1498 to 1759 kg ha−1 contained mostly Striga‐susceptible cultivars and the C0 of the selection program. Under Striga‐free conditions, the performance of several cultivars from the selection program was equal to or better than ACR 94 TZE Comp5‐Y and ACR 94 TZE Comp5‐W. The genotype plus genotype × environment interaction biplot analysis demonstrated that EV DT‐Y 2000 STR C1 and TZE‐W Pop DT STR C3 from the selection program, along with ACR 94 TZE Comp5‐W, had stable grain yield under Striga‐infested and noninfested conditions.

Originality of M3S maize population and changes in allele frequencies revealed by SSR markers after two cycles of selfed progeny recurrent selection

Maksimir 3 Synthetic (M3S) maize population was developed at the Faculty of Agriculture University of Zagreb by intercrossing inbred lines, whose origins trace back to several open-pollinated varieties and local populations from different regions of the former Yugoslavia. The population was subjected to two cycles of selfed progeny recurrent selection for grain yield. The objectives of this study were: (i) to determine genetic distances among the parental inbred lines of the M3S population (M3S progenitors), the M3S population before and after two cycles of recurrent selection, and elite inbred lines representing the BSSS and Lancaster heterotic group; and (ii) to examine the effect of two cycles of recurrent selection on allele frequency changes in the population. Nine M3S progenitors, three BSSS lines, and three Lancaster lines were genotyped at 24 SSR loci, out of which nine randomly chosen loci were used for genotyping 96 individuals from both C0 (the M3S population before selection) and from C2 (M3S population after two cycles of selection). A total of 101 alleles were detected across 24 loci in the 15 lines, whereas 83 alleles were found in the nine M3S progenitors. Among the latter 83 alleles 31 were unique, i.e. found only in one of the progenitors. Mean genetic distance among nine M3S progenitors was 0.61 indicating a broad genetic base of the M3S population. High mean genetic distance was found between M3S progenitors and BSSS lines (0.69) and M3S progenitors and Lancaster lines (0.71). This indicates that the M3S population represents a germplasm source unrelated to both the BSSS and Lancaster germplasm. Mean genetic distance between the M3S population and BSSS as well as Lancaster lines decreased slightly after two cycles of recurrent selection suggesting the need to introduce testers from both groups in future selection in the M3S population in order to maintain heterotic complementarity of the M3S population to these groups. A test of selective neutrality identified several non-neutral loci in the population whose allele frequency changes from the C0 to the C2 cannot be explained by genetic drift. The majority of non-neutral alleles, whose frequency increased after two cycles of selection, were present in at least one line from the BSSS or Lancaster heterotic group.

Recurrent Selection for Grain Yield in Two Spanish Maize Synthetic Populations

Recurrent Selection for Grain Yield in Two Spanish Maize Synthetic Populations

Recurrent Selection for Grain Yield in Two Spanish Maize Synthetic Populations

Crop Sci. 41:15–19 (January–February 2001) There is an error in Table 2; grain yield for EPS7(S)C0 should be 5.1—not 15.1, as printed.

Evaluation of U.S. and Yugoslavian Maize Populations as Sources of Favorable Alleles

Choice of an appropriate donor of alleles for use in reselection programs of existing inbred lines of maize (Zea mays L.) is crucial to the success of such programs. Well‐adapted local populations or exotic improved populations might be used as donors to improve a target genotype. The objectives of this study were to: (i) evaluate U.S. and Yugoslav maize populations as donors of favorable alleles for improvement of two single cross hybrids, (ii) estimate Dudley's relationship values to determine which inbred parent should be improved, and (iii) compare four estimators of the value of populations: Dudley's minimally biased estimators (Lplμ*), minimum upper bound (UBND), predicted three‐way cross (PTC), and net improvement (NI). Lplμ*, UBND, PTC, and NI showed significant differences among donors for grain yield. The highest values of favorable alleles were detected in populations, which had already undergone some type of family‐based recurrent selection for grain yield. The evaluation of Dudley's relationships between donors and parents of elite hybrids generally agreed with pedigree information. The improvement of both hybrids should be done with populations EP1, BS12C8, BS26, and ZPSyn1. The population EP1 can be used for comparative improvement of all three traits in the hybrid B73 × Mo17. Simultaneous improvement of grain yield and ear length in the hybrid A82/9 × L155 can be achieved with several donor populations. Rank correlations among applied estimators were positive and generally highly significant. The largest correlation values for grain yield were detected between Lplμ* and PTC.

Recurrent Selection for Grain Yield in Two Spanish Maize Synthetic Populations

The most common maize (Zea mays L.) heterotic pattern in Europe is European flint × U.S. dent. Northern Spain × southern Spain has been proposed as an alternative heterotic pattern. Three maize synthetic populations, namely EPS6 from northern Spain, EPS7 from southern Spain, and EPS10 formed by early American populations, were produced in Pontevedra, Spain. Because of their low yield, the two Spanish synthetic populations were subjected to three cycles of intrapopulation S1 recurrent selection for grain yield. Our objectives were to evaluate the effect of selection on grain yield and other agronomic traits, and to determine the changes in heterosis and general (GCA) and specific (SCA) combining ability brought about by selection. The three original synthetic populations, the three cycles of selection of the two Spanish synthetic populations, and the crosses among the original and the improved cycles were evaluated in two locations in northwest Spain in 1994 and 1995. Yield significantly increased with selection in both Spanish synthetic populations. The GCA improved with selection in both EPS6 and EPS7. Heterosis and SCA did not change significantly with selection. The third cycles of each Spanish synthetic would be the most appropriate maize populations to start a reciprocal recurrent selection to improve the heterotic pattern northern Spain × southern Spain.

Allelic Frequency Change of P1 Gene in Maize Population After Recurrent Selection for Grain Yield

Full‐sib family recurrent selection for grain yield was conducted for four cycles in maize (Zea mays L.). The source population was the F2 of A632 (with red cob) ×195 (with white cob). Objectives of this research were to evaluate the change in allelic frequency at the P1 gene (determining cob color), to assess whether this change was due to random drift only, and to detect whether allelic frequencies were correlated with grain yield responses. The source and the four selected populations were crossed to two inbred lines with white cob (recessive trait). The frequency of red cob allele increased with selection following a highly significant linear trend (b = 0.066 cycle−1), suggesting the effect of directional selection. Correlation between allelic frequency and grain yield was significant for populations as S2 generation (r = 0.938), and as testcrosses (r = 0.886), and could be ascribed to fight linkage, to pleiotropy, or both.

Continued response through seven cycles of recurrent selection for grain yield in oat (Avena sativa L.)

Long-term selection experiments provide germplasm to study the effects of selection in a closed population. Recurrent selection to enhance grain yield in oat has been ongoing at the University of Minnesota since 1968. The objectives of this study were: (i) estimate the GCA and SCA effects for three agronomic traits in the seventh cycle of selection, (ii) assess the effect of the current methods of selection on parental contribution and unselected traits, and (iii) determine the direct and indirect responses to seven cycles of recurrent selection for grain yield. Progeny of the Cycle 6 parents and parents for Cycles 0 through 7 were grown in two separate tests. Grain yield, heading date and plant height were evaluated in each test. Grain yield was increased by 21.7% after seven cycles of selection. Evaluation of Cycle 6 progeny showed that GCA effects were significant for all three traits studied, and SCA effects were significant only for grain yield. Four Cycle 6 parents did not have any progeny selected as Cycle 7 parents. Results from this study indicate that long term recurrent selection has continued to increase grain yield. Alternative selection strategies may be necessary to maintain the genetic variability in this population, particularly when improvement of secondary traits is required.

Characterization of Interpopulation Genetic Variability in Three Hybrid Maize Populations

A cross-classification (North Carolina Design II) mating design was used to produce half-sib and full-sib families in three hybrid maize (Zea mays L.) populations: BSSSC0 × BSCB1C0, BSSS(R)C9 × BSCB1(R)C9, and BS13(S)C3 × BSCB1(R)C9. Families were evaluated in a replications-within-sets, randomized incomplete block design with two replications at five locations. Data were collected for grain yield, grain moisture, root and stalk lodging, dropped ears, plant and ear height, days from planting to anthesis and silking, and number of tassel branches. The objective was to estlmate genetic variance components, heritabilities, genetic correlations, and genetic gains for the three hybrid populations. The additive genetic variance component was the most important component of genetic variability for all traits. Except for grain yield, additive by environment interpopulation variance estimates were smaller than their corresponding additive variances. For grain yield, the additive variance components increased with selection; however, the original population cross showed greater additive by environment interaction variance than the improved population crosses. The estimates of additive genetic variance increased for plant and ear height and decreased for root and stalk lodging with reciprocal recurrent selection for grain yield. Except for grain yield, all traits exhibited a decrease in estimates of the dominance variance component after recurrent selection. The BSSS additive genetic contribution to the total interpopulation additive variance became more important with selection except for days to anthesis, days to silking, and number of tassel branches. Heritability estimates for grain yield increased with recurrent selection. Heritablity estimates of the original and selected cross populations were similar for the other traits. Grain yield had positive genotypic correlations with grain moisture, plant height, and ear height and negative correlations with stalk lodging. Correlations between traits were not affected by selection for yield. The results suggest that reciprocal recurrent selection was an effective method for improving the population cross for yield without decreasing genetic variability.

Recurrent Selection for Grain Yield in Durum Wheat

Considerable improvements of durum wheat (Triticum turgidum L. var. durum) genotypes with better yield have been achieved with different breeding methods. Because of several constraints in its application in small cereals, recurrent selection in durum wheat has not been used extensively. The objectives of this research were to evaluate two cycles of recurrent selection for grain yield and to assess effects of selection on other agronomic and yield‐component traits. Nineteen semidwarf durum wheat genotypes selected for high yield and broad genetic diversity, were intercrossed to form the base population. Fifty‐five randomly selected S2 lines from three cycles of selection and a set of four checks were planted in two 1989 and three 1990 environments, respectively. Genotype × environment interactions were generally of magnitude rather than of rank order changes for traits evaluated and therefore a combined analysis across environments was performed. Regression analysis indicated an average increase in yield of 0.25 ± 0.03 Mg ha−1 per cycle of selection. Cycle 2 (C2) produced lines with grain yield higher than any line in Cycles 0 (C0) or 1 (Cl). Test weight and plant height increased 8.39 ± 2.01 Kg m−3 and 2.62 ± 0.3 cm per cycle, respectively. Recurrent selection for grain yield did not affect spikelets per spike and kernels per spike. Kernel weight increased 2.8 mg from C0 to C2. When calculated as a percentage of the total variance, the genetic variance of most of the evaluated traits decreased slightly. Genotype × environment variance was the most important component of variances of five of the evaluated traits. The efficiency of recurrent selection for yield was demonstrated. Indications are that recurrent selection solely for yield did not have any negative correlated response to unselected traits.

Effects of Recurrent Selection for Grain Yield on Oat Kernel Morphology

Kernel size, as it is related to kernel weight, is an important yield component in oat (Avena saliva L.). The main objective of our research was to evaluate the changes in kernel morphology following five cycles of recurrent selection for grain yield. Parents of Cycles 0, 1, 3, and 5 and seven check cultivars were grown in row and hill plots at St. Paul and Rosemount, MM, in 1989. Kernel area, perimeter, length, and width were measured on 100‐kernel samples from each plot using digital image analysis (DIA). Grain yield, kernel weight, and kernel number were also evaluated in these experiments. Grain yield was enhanced by 26.8 and 55.3% following five cycles of recurrent selection as measured in row and hill plots, respectively. Kernel area increased by 9.8 and 10.1% in row and hill plot samples, respectively. Kernel perimeter, length, and width increased by 4.8, 5.7, and 4.6%, respectively, in row plot samples. In hill plot samples, kernel perimeter, length, and width increased by 5.5, 6.8, and 3.7%, respectively. There were no significant difference among cycles for two derived shape factors, FCIRCLE (4 π [kernel area]/[kernel perimeter]2) and kernel width/length ratio. Values for kernel area, perimeter, length, and width from hill plot samples were significantly larger than those from row plots; however, selection responses in the two plot types were quite similar. In this study, environmental influences on kernel morphology were minor. Kernel weight was positively correlated with the two size measurements, kernel area and width. Results from our study indirectly suggest that increased kernel size, and not kernel density, largely accounts for the observed increases in kernel weight. These experiments also demonstrate the utility of DIA in agronomic research.

Recurrent Selection for Increased Grain Yield in Oat

Grain yield is a primary consideration in choosing oat (Avena sativa L.) cultivars. This research examines gain from five cycles of recurrent selection for grain yield in oat, and compares the yield responses when evaluated in hill and row plots. A secondary goal was to examine the yield components that contributed to the yield gains in the two plot types. Parents of all five cycles of recurrent selection and the checks ‘Don’, ‘Hazel’, ‘Moore’, ‘Noble’, ‘Ogle’, ‘Starter’, and ‘Steele’ were grown in hill and row plots in 1988 and 1989 at St. Paul and Rosemount, MN. Experimental design for both experiments was a randomized complete block and data were recorded on grain yield (g m−2), seed weight (g 100 seed−1) and seed number (seed m−2). Grain yield gain per cycle, as measured by weighted linear regression, was 15.1 g m−2 in hill plots and 12.8 g m−2 in row plots. Examination of the yield components seed weight and seed number indicated that the grain yield gain resulted from an increase in both traits. The relationship between seed weight and seed number was numerically different in the two plot types, with seed weight showing a larger increase per cycle in row plots and seed number a larger increase per cycle in hill plots. Phenotypic correlations of parent performance in the two plot types were 0.85 for grain yield, 0.81 for seed weight and 0.69 for seed number (P < 0.01). The large gain in grain yield per cycle and the excellent agreement in performance of the parents of all five cycles in hill and row plots indicate the effectiveness of recurrent selection in oat.

Recurrent selection for grain yield in early generations of two barley populations

Two spring barley composites, one based on eight West-European two-rowed cultivars (A) and one, the predominantly six-rowed composite XXI, based on several thousands of barley cultivars (B), formed the starting point of a recurrent selection procedure. The aim was to study whether recurrent selection in early generations is an effective procedure to improve barley populations for agronomic characteristics, especially grain yield.

Evaluation of the Performance and Combining Ability of Selected Lines Derived from Improved Maize Populations1

Seven cycles of reciprocal recurrent selection for grain yield were completed in maize (Zea mays L.) populations ‘Iowa Stiff Stalk Synthetic’ (BSSS) and ‘Iowa Corn Borer Synthetic No. 1’ (BSCB1). Also, seven cycles of recurrent selection based on half‐sib progeny performance and one cycle based on S2 line performance have been completed for BSSS. Populations BSSS(R)C5 and BSCB1(R)C5 were crossed and random‐mated to give BS6. Then, BS6 had two cycles of recurrent selection based on half‐sib progeny performance. Crosses of the improved populations and four selected S2 lines from each improved population crossed in design II's (six sets) were evaluated for grain yield and moisture and for root and stalk lodging. The average yields for four sets of S2 crosses were not significantly different from their respective population crosses; one set of S2 crosses yielded significantly less than its population cross, BSSS(R)C7 ✕ BS6(RS)C2; and one set of S2 crosses yielded significantly higher than its population cross, BSCB1(R)C7 ✕BS6(RS)C2. Generally, sets of crosses had less grain moisture and better resistance to root and stalk lodging than did their respective population crosses. General combining‐ability effects accounted for 76% of the total genetic variation for yield among S2 ✕ S2 line crosses. Compared with five single‐cross checks, no S2 ✕ S2 line cross yielded as well as the highest‐yielding check, but one had a performance index equal to the best check, and several had performance indices similar to four checks.

Recurrent Selection for Grain Yield in a Maize Population1

Mass selection for improved grain yield was conducted in the ‘Krug’ (BSK) maize (Zea mays L.) population. Effectiveness of 14 cycles of mass selection for grain yield in BSK was measured in nine environments using the original (CO) and the even‐numbered cycles of selection (Cn) as populations per se and two sets of testcrosses (Cn ✕ CO and Cn ✕ B73). Unselected S1 lines derived from the original, the 14th cycle of mass selection, and the eighth cycles of half‐sib and S1 progeny selection were evaluated in four environments to estimate the effect of the three recurrent selection procedures on genetic variability and on grain yield improvement of S1 progenies per se. Linear response per cycle of mass selection for grain yield was obtained for the populations per se (0.024 ± 0.009 Mg ha−1) and testcrosses with the CO population (0.026 ± 0.010 Mg ha−1) and B73 (0.028 ± 0.010 Mg ha−1). Average yield response to mass selection in BSK per se was 0.49% per cycle or 6.9% after 14 cycles of mass selection. Increased yield was accompanied by later flowering, increased root and stalk lodging, increased grain moisture at harvest, and higher ear placement. The mass selection methods we used for improving grain yield in BSK apparently require modification to include selection for other agronomic traits, but such modifications would increase the complexity of mass selection and perhaps reduce gain for yield. Estimates of genetic variability among S1 progenies for grain yield showed a decrease in genetic variance for the S1 and half‐sib derived populations for most traits and no change for the mass‐selected population.