Improvement Of Grain Yield Research Articles

Improving Nitrogen‐Use Efficiency in European Maize

Maize (Zea mays L.) cultivars with improved N‐use efficiency would be beneficial for low‐input production systems. Our objective was to estimate quantitative genetic parameters to optimize breeding programs for improving productivity under low N levels. Results of 21 field experiments with European breeding materials belonging to the flint and dent gene pool are presented. The study was performed during 1989 and 1999 at several locations in typical maize growing regions of Germany and France. All experiments were conducted at high (HN) and low (LN, no N fertilizer applied) N levels. Average grain yield was reduced by 37% at LN compared with HN. Coefficients of genotypic correlation between HN and LN were variable with an average of rG = 0.74 for grain yield and generally high for grain dry matter content. For grain yield, analyses of variance were computed from relative data, where plot values were expressed as percentage of the trial mean. Variances caused by genotype (G), G × location (L) interaction, and error effects were higher at LN compared with HN, with similar heritabilities at both N levels. For the untransformed data, components of variance were higher at HN than at LN. Genotype × N as well as G × L × N level interaction variances were significant in most experiments. Efficiency of improvement of grain yield at LN through indirect selection at HN was 70% compared with direct selection at LN. A trend toward increased efficiency of direct selection under LN conditions was evident with decreasing grain yield at LN.

Plant Breeding Scheme Effects on The Flower Number and Grain Yield Components in Bread Wheat

The increase of wheat production was mainly due to a considerable increment in growing areas and the improvements in grain yield through plant breeding programs. At present, ear analysis is one of the most relevant features in the development of new cultivars. The objectives of this study were to assess the effects of three cycles of recurrent selection of grain yield on the number of floret primordia and fertile florets per spikelet and to determine the relationship between grain number and the number of primordia and fertile florets. Forty eight families were evaluated in two running years (1997-1998) at the Ferreyra Experimental Station in COrdoba, Argentina (lat. 31° 29' S, long. 64° W). Five main shoots from each plot were divided in thirds for analysis. Results between cycles indicated that the most advanced cycle always had a higher mean value in the number of floret primordia per spikelet in 1997 than the values recorded for the other cycles. Statistical differences were observed in the number of fertile florets per spikelet between cycles in the lower and middle thirds both in 1997 and 1998. Significant differences were also observed in the kernel number per spikelet in the lower and upper third in 1998. Statistical analysis also showed that the number of floret primordia, fertile florets and kernels per spikelet increased mainly in the lower third during the microevolutive process. The mean values of all variables considered, regardless of cycle effects, were higher in the middle third than the other ones.

Selection for Reduced Carbon Isotope Discrimination Increases Aerial Biomass and Grain Yield of Rainfed Bread Wheat

Genetic gain is characteristically slow when selecting directly for increased grain yield under water‐limited conditions. Genetic increases in grain yield may be achieved through increases in aerial biomass following selection for greater transpiration efficiency (TE as aerial biomass/water transpired). Strong negative correlations between TE and carbon isotope discrimination (Δ) in wheat (Triticum aestivum L.) suggest that selection of progeny with low Δ may increase TE and aerial biomass under water‐limited conditions. This study investigated how early generation, divergent selection for Δ affected aerial biomass and grain yield among 30 low‐ and 30 high‐Δ, ‘Hartog’‐like, BC2F4:6 progeny and the recurrent, high‐Δ parent Hartog. Lines were evaluated in nine environments varying for seasonal rainfall (235–437 mm) and hence grain yield (1.3–6.2 Mg/ha). Selection for low Δ in early generation progeny was associated with significantly (P < 0.01) smaller Δ, higher grain yield (+5.8%), aerial biomass (+2.7%), harvest index (+3.3%), and kernel size (+4.8%) in tested lines. Kernel number was the same for low‐ and high‐Δ selected groups. Grain yield advantage of the low Δ group increased with reductions in environment mean yield (r = −0.89, P < 0.01) and total seasonal rainfall (r = −0.85, P < 0.01) indicating the benefit of low Δ, and therefore high TE for genetic improvement of grain yield in lower rainfall environments. Narrow‐sense heritability on a single‐plot basis was much greater for Δ (h2 = 0.63 ± 0.10) than for either aerial biomass (0.06 ± 0.05) or grain yield (0.14 ± 0.04). Strong genetic correlations between Δ and both aerial biomass (r g = −0.61 ± 0.14) and grain yield (−0.58 ± 0.12) suggest Δ could be used for indirect selection of these traits in early generations. Selection of low Δ (high TE) families for the advanced stages of multiple‐environment testing should increase the probability of recovering higher‐yielding wheat families for water‐limited environments.

Field evaluation of early vigour for genetic improvement of grain yield in wheat

Improved early vigour in wheat (Triticum aestivum L.) has been proposed as an important trait for increasing grain yield through greater water-use efficiency in rainfed, Mediterranean-type environments. Three years of field trials were undertaken in Western Australia at 2 sites, Merredin (low rainfall, 244 mm in the growing season) and Wongan Hills (medium rainfall, 308 mm), to examine the influence of increased early vigour on crop growth and yield. The effect of breeding for greater early vigour was tested in 1998 and 1999 using 3 high vigour and 3 low vigour BC2:F5 lines of the cultivar Amery backcrossed to a 'high vigour' donor. Averaged across environments, the high vigour backcross lines had a 10% increase in early vigour (i.e. leaf area/plant) at 50 DAS compared with the low vigour lines. Differences in yield across environments were associated with variation in total rainfall, rainfall distribution, and soil properties. In the wetter of the 2 years (1999), greater early vigour translated to increased yield of c. 12%, averaged across environments, but there was no difference in yield in either environment in the drier year (1998). Potential deleterious effects of the recurrent parent on yield were eliminated in field trials in 1999 and 2000 by manipulating early vigour through varying grain size (25, 35, or 50 mg) or seeding density (50, 200, or 400 plants/m2) of Amery at sowing. Large grain increased the embryo size and early vigour at 50 DAS in both environments in 1999. This translated to greater biomass production at anthesis and maturity to increase grain yield at Wongan Hills in 1999. In contrast, there was no relationship between grain size, biomass production, and yield at Merredin in 1999 or at either site in 2000. Sowing density treatments also had no effect on yield in 2000. In conclusion, there is potential to increase yield of wheat by selecting for greater early vigour in a wheat breeding program. The expression of vigour in field conditions and the translation of this improvement to higher yields is, however, dependent on the environment. Current yield limitations arising through backcrossing with a high vigour, yet poor yielding donor, need to be addressed.

Selection for Reduced Carbon Isotope Discrimination Increases Aerial Biomass and Grain Yield of Rainfed Bread Wheat

Genetic gain is characteristically slow when selecting directly for increased grain yield under water-limited conditions. Genetic increases in grain yield may be achieved through increases in aerial biomass following selection for greater transpiration efficiency (TE as aerial biomass/water transpired). Strong negative correlations between TE and carbon isotope discrimination (Δ) in wheat (Triticum aestivum L.) suggest that selection of progeny with low Δ may increase TE and aerial biomass under water-limited conditions. This study investigated how early generation, divergent selection for Δ affected aerial biomass and grain yield among 30 low- and 30 high-Δ, ‘Hartog’-like, BC2F4:6 progeny and the recurrent, high-Δ parent Hartog. Lines were evaluated in nine environments varying for seasonal rainfall (235–437 mm) and hence grain yield (1.3–6.2 Mg/ha). Selection for low Δ in early generation progeny was associated with significantly (P < 0.01) smaller Δ, higher grain yield (+5.8%), aerial biomass (+2.7%), harvest index (+3.3%), and kernel size (+4.8%) in tested lines. Kernel number was the same for low- and high-Δ selected groups. Grain yield advantage of the low Δ group increased with reductions in environment mean yield (r = −0.89, P < 0.01) and total seasonal rainfall (r = −0.85, P < 0.01) indicating the benefit of low Δ, and therefore high TE for genetic improvement of grain yield in lower rainfall environments. Narrow-sense heritability on a single-plot basis was much greater for Δ (h2 = 0.63 ± 0.10) than for either aerial biomass (0.06 ± 0.05) or grain yield (0.14 ± 0.04). Strong genetic correlations between Δ and both aerial biomass (r g = −0.61 ± 0.14) and grain yield (−0.58 ± 0.12) suggest Δ could be used for indirect selection of these traits in early generations. Selection of low Δ (high TE) families for the advanced stages of multiple-environment testing should increase the probability of recovering higher-yielding wheat families for water-limited environments.

Effect of crop residue incorporation and nitrogen on succeeding wheat (Triticum aestivum)

A field experiment was conducted during 1997 98 to 1999 2000 to work out the effect of residue incorporation of rice (Oryza safiva L.), soybean [Glycjne max (L.) Merr.] and groundnut (Arachis hypogaea L.) and nitrogen requirement of succeeding wheat (Triticum aestivum L. emend. Fiori Paol.) crop. An increasing trend was recorded in wheat yield and organic carbon content in soil with the incorporation of crop residue. Incorporation of groundnut residue showed higher rate of increase in grain yield of wheat than soybean and rice. Improvement in grain yield of wheat was observed with application of higher dose (150 kglha) of nitrogen. In general, positive improvement in soil fertility status was recorded with residue incorporation. The crop sequence of wheat followed by rice produced highest net return and benefit :cost ratio. Similar trend was also noticed with removal of residue and application of higher dose of nitrogen.

Weed control studies in pearlmillet (Pennisetum g1aucum)- pigeonpea (Cajanus cajan) intercropping system under rainfed condition

A field experiment was carried out during rainy (kharif) season of 1997 and 1998 to assess the production potential of intercropping of pearlmillet [Pennisetum glaucum (L.) R. Br. emend. Stuntz] with pigeonpea [Cajanus cajan (L.) Millsp.] in relation to various measures of weed control. Treatments consisted of 3 intercropping systems (sole pearlmillet, sole pigeonpea and pearlmillet+ pigeonpea) and 4 methods of weed control (control hand-weeding twice, fluchloralin @ 1.0 kg/ha and pendimethalin@ 1.0 kglha). lntercropping did not influence the population and dry-matter accumulation by weeds. Grain yield of pearlmillet did not vary significantly due to various methods of cropping. However, sole pigeonpea gave significantly higher yield than pearlmillet + pigeonpea intercropping. Highest total productivity in terms of pearlmillet equivalent was recorded with pearlmillet + pigeonpea intercropping system. Weeding caused significant reduction in weed infestation and improvement in grain yield of pearlmillet and pigeonpea and total productivity compared with the control. Best results were achieved with hand-weeding twice closely followed by fluchloralin @ 1.0 kgha.

Feasibility of applying all nitrogen and phosphorus requirements at planting of no-till winter wheat

The recent advances in no-till seeding technology are providing new N management options for crop production on the prairies. The objectives of this study were to evaluate the potential interaction between P and N fertilizer on winter wheat production in a one-pass seeding and fertilizing system and to determine the feasibility of side-banding all N requirements using urea or anhydrous ammonia at planting as compared with the current practice of broadcasting ammonium nitrate early in the spring. Three forms of N fertilizer (urea, anhydrous ammonia, ammonium nitrate), three rates of N (50, 75 and 100 kg ha–1) and three rates of P (0, 9 and 17 kg P ha–1) were investigated. Urea and anhydrous ammonia were applied during the seeding operation, whereas ammonium nitrate was broadcast the following spring. Applying P fertilizer to the side and below the seed at planting with rates &gt; 9 kg Pha–1 increased grain yield in 3 out of 6 site-years when ammonium nitrate was broadcast early in the spring. The positive yield response to P corresponded to soil test levels of 24 kg P ha–1. With soil test levels greater than 34 kg P ha–1, grain yield response to P fertilizer was not observed. When urea was banded at planting, together with P fertilizer, the yield increases with the increased P rates was shown only in 1 out of 6 site-years. At 5 of th e 6 site-years, grain protein concentration was not affected by P fertilizer; while for 1 site-year, the high rate of P fertilization decreased grain protein concentration. Responses of total grain N and P yields to P fertilization were parallel to the corresponding responses of P fertilization to grain yield, and were rarely associated with N or P concentrations in the grain. Applying N fertilizer at rates of 50 to 100 kg N ha–1 increased winter wheat grain yields by 3 to 8% in 3 out of 6 site-years. The high N rates increased grain protein concentrations in all 6 site-years. Grain protein concentration was 6% greater with N fertilizer applied as ammonium nitrate in early spring than when banding urea or anhydrous ammonia at planting. More consistent improvements in grain yield and grain protein concentration were obtained when the N fertilizer was applied as ammonium nitrate in the spring. Further research is required to determine the benefits of applying some of the crop’s N fertilizer requirements at planting, to reduce the risks of N stresses when the spring application is delayed because of adverse weather or soil conditions. Key words: Ammonium nitrate, anhydrous ammonia, grain yield, nitrogen timing, phosphorus, protein, urea

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.

Grain Yield of Rice Cultivars and Lines Developed in the Philippines since 1966

Genetic improvement in grain yield has been intensively studied in wheat (Triticum aestivum L.), barley (Hordeum vulgare L.), oat (Avena sativa L.), maize (Zea mays L.), and soybean [Glycine max (L.) Merr.]. Such information is limited in rice (Oryza sativa L.). The objective of this study was to determine the trend in the yield of rice cultivars–lines developed since 1966. Twelve cultivars–lines were grown at the International Rice Research Institute (IRRI) farm and the Philippine Rice Research Institute farm during the dry season of 1996. Seven cultivars–lines were grown at IRRI farm in the dry season of 1998. Growth analyses were performed at key growth stages, and yield and yield components were determined at physiological maturity. Regression analysis of yield versus year of release indicated an annual gain in rice yield of 75 to 81 kg ha−1, equivalent to 1% per year. The highest yields obtained with the most recently released cultivars was 9 to 10 Mg ha−1, which is equivalent to reported yields of IR8 and other early IRRI cultivars obtained in the late 1960s and early 1970s at these same sites. Therefore, the 1% annual increase in yield may not represent genetic gain in yield potential. The increasing trend in yield of cultivars released before 1980 was mainly due to the improvement in harvest index (HI), while an increase in total biomass was associated with yield trends for cultivars–lines developed after 1980. Results suggest that further increases in rice yield potential will likely occur through increasing biomass production rather than increasing HI.

Correlation and path analysis in the F, generation of greengram (Vigna radiata (L.) Wilczek)

The correlation and path coefficients were worked out in seven parents and F, population of their 21 crosses in greengram for 13 characters. Seed yield had significant positive genotypic correlation with number of secondary roots at maturity, dry weighty of plants at maturity, plant height, clusters per plant, pods per plant, seeds per pod and hundred grain weight and harvest index. Number of pods, clusters per plant and harvest index showed high positive correlation on grain yield and also with each other. Path analysis revealed that pods per plant had the highest positive direct effect on grain yield followed by to hundred grain weight and number of seeds per pod. Plant height showed high indirect effect through number of pods, seeds per pod and hundred grain weight on grain yield. The study revealed that genetic improvement of grain yield is possible by selecting characters having high positive correlation and positive direct effect.

How can breeding contribute to more productive and sustainable rainfed lowland rice systems?

The contributions to this special issue have examined our current understanding of the adaptation of rainfed lowland rice to the abiotic stresses associated with drought, submergence and low soil fertility. Genetic variation has been identified for both broad adaptation across target rainfed lowland environments and specific adaptations to some of the abiotic stress environments, e.g. late season drought, and submergence during vegetative development. However, in general progress in genetic improvement of adaptation that contributes to higher and more stable yields has been extremely slow. The opportunities for increasing the rate of genetic improvement of grain yield is examined under the four headings: (1) the complexity of the target genotype–environment system; (2) the genetic resources available to the breeding programs; (3) clarity of the breeding objectives, capacity of the adopted breeding strategy to achieve the necessary genetic modifications and selection strategy; and (4) the physical and human resource capability to implement, evaluate and manage the necessary breeding strategies. Recommendations are made on priority research areas that are required to integrate the growing understanding of rainfed lowland rice adaptation and the needs of the breeding programs.

Mass Selection for Improvement of Grain Yield and Protein in a Maize Population

Increasing grain protein concentration in maize (Zea mays L.) has not been a major focus of most breeding programs, which mainly focus on yield, maturity, and resistance to stress. The objective of this study was to evaluate the effectiveness of three cycles of mass selection to improve simultaneously yield and grain protein in the maize population GR‐OP‐319, derived from the F2 generation of the single‐cross hybrid PX‐95. The two‐step selection procedure involved a stratified mass selection system that included check plants for environmental control. In the first step, plants having grain yield higher than 80% of the check‐plant mean and protein concentration greater than the check‐plant mean were selected. In the second step, the four plants within each selection grid having the highest protein concentration were selected, which resulted in a final selection intensity of 5%. Three cycles of selection were completed during 1991 to 1995. Response to selection was evaluated during the selection process and by direct field evaluation of the C0, C1, C2, and C3 populations in 1995 and 1996. The average response during the selection was 5.1% cycle−1 for yield, 0.8 g kg−1 cycle−1 for protein concentration, and 7.0% cycle−1 for protein yield. No measurable differences among cycles were observed in the direct field evaluation even though the trends in the means of the cycles followed the trends shown during selection. After three cycles, the mass selection system studied did not appear to be particularly effective.

A selection strategy for combining high grain yield and high protein content in South African wheat cultivars

Grain protein content is a major contributor to nutritional quality of wheat. Due to the negative relationship between yield and protein content, simultaneous improvement of these traits is very difficult. The aim of this study was to identify possible selection criteria to improve protein content and yield simultaneously. Six spring irrigated wheat cultivars were used as parent lines in a half diallel design. The F1 hybrid progeny and parents were used as experimental material. Both high and low protein wheat types translocated equal amounts of nitrogen to the grain. Phenotypic correlations re-emphasised the problems of simultaneous improvement of grain yield and protein content. The use of correlated response gave a better solution. If grain protein yield (highly significantly correlated with grain yield), was used as selection criterion, even protein per kemel showed a correlated response. It also had a relatively high narrow sense heritability. Grain protein yield selection therefore gave the only possible solution towards simultaneous improvement of grain yield, and grain protein content.

CHARACTER ASSOCIATION AND PATH ANALYSIS IN GRAIN SORGHUM (Sorghum bicolor (L.) moench)

Sixty hybrids of sorghum were evaluated to know the magnitude and direction of association between yield and component traits during rabi and summer seasons of 1994 in four locations. Positive and significant association was noticed between grain yield and component traits except days to 50 per cent flowering and days to maturity. Improvement in grain yield in sorghum would be possible through selection for stem thickness, number of rachis per panicle and 100 grain weight.

Genetic improvements in New Zealand forage cultivars

Substantial genetic gains have been achieved across a range of temperate forage grass and legume species in New Zealand during the past 60 years. The genetic gains reported here compare favourably with those achieved in cereals and with those achieved for similar species internationally. Substantial improvements in grain yield of cereal crops have been achieved through changes in harvest index; however, increases in yield of forage grasses and legumes reflect increases in total above ground biomass. Rates of genetic gain have been lower in lucerne (Medicago sativa L.) than in red clover (Trifolium pratense L.) and white clover (Trifolium repens L.) and lower in perennial ryegrass (Lolium perenne L.) than in annual ryegrass (Lolium multiflorum Lam.) and tall fescue (Festuca arundinacea Schreb.). Gains in forage yield and quality have often exceeded 1% per year and have led to significant (0.3 to 1.3% per year) increases in animal performance. Keywords: animal performance, forages, genetic improvement, quality, symbiotic associations, yield

Effects of the Fungicide Propiconazole on Agronomic and Quality Traits of Hulled and Hulless Barley

The hypocholesterolemic effect of hulless waxy barley (Hordeum vulgare L.) has increased its use in food products. Hulless cultivars currently grown in the Upper Midwest U.S. barley growing region are susceptible to a foliar disease, spot blotch, that can severely reduce yield. Spot blotch and kernel blight generally occur in the eastern area of the region; thus, hulless barley production is limited to the western area. Research on chemical control of spot blotch and kernel disease in hulless barley genotypes grown in the Upper Midwest has not been conducted. The objectives of this study were to determine whether natural field infections of the pathogen responsible for causing spot blotch and partly responsible for causing kernel blight similarly affect kernel and flour brightness of hulled and hulless barley genotypes, and to determine whether disease control with the fungicide propiconazole {1[[2-(2,4-dichlorophenyl)-4-propyl-1,3-dioxolan-2-yl]methyl]-1H-1,2,4-triazole} similarly affect agronomic and quality traits of hulled and hulless barley genotypes. Propiconazole reduced spot blotch severity. This resulted in increased yield and yield-related traits in hulled and hulless genotypes. Responses to propiconazole by the hulled and hulless genotypes were generally similar for spot blotch control, and similar for grain yield and 1000-kernel weight. The reduction in spot blotch severity did not result in brighter kernels or flour, nor did it affect mean total or soluble β-glucan content of hulled and hulless genotypes. Thus, hulless barley cultivars susceptible to spot blotch can be produced in the eastern area of the Upper Midwest barley growing region if they are protected with propiconazole.

Genetic response to index selection for grain yield, kernel weight and per cent protein in four wheat crosses

AbstractQuantitative genetic theory was used to investigate selection differentials, expected and observed direct and correlated responses to simultaneous improvement of grain yield, kernel weight, and grain protein content in F3 and F4 populations of four spring wheat (Triticum aestivum L.) crosses. Selection in the F3 generation based on the Smith‐Hazel index (SH) and yield was found to be superior to the other methods studied in identifying high‐yielding lines, but resulted in substantial decrease in grain protein level. Consequently, a 1.0% increase in protein from selection for protein depressed grain yield as much as 536 kg/ha below the population mean, reducing the expected yield gains per generation selection cycle by 250%. The weight‐free indices (EW), particularly the index involving only yield and kernel weight (EW3) and its linear approximation (EW4), and the desired gains indices were effective in improving protein content but were less efficient in selecting top‐yielding lines. Selection in the opposite direction using truncation of the lowest 10% of the population based on weight‐free‐index involving yield, kernel weight and protein (EW2) reduced all traits significantly compared with the mean of the unselected population indicating the effectiveness of the unweighted selection index. The observed genetic gains (Ra) from selection based on yield, the SH, EW3 and EW4 indices were slightly lower than the expected advances per cycle (R) in populations from crosses ‘Sinton’בGlenlea’ (C1), ‘Glenlea’בNB505’ (C2), and ‘A2P5’בNB320’ (C6) (Ra/R = 70 to 85%) but were higher in cross ‘NB505’בA2P5’ (C5) (Ra/R = 126 to 143%). It was concluded that weight‐free and the desired gains indices can be used to improve wheat grain yield and grain protein simultaneously in F3 generation selection, as revealed by response to selection measured in the F4 generation.

Genetic Analysis for Stalk Lodging Resistance in Narrow‐Base Maize Synthetic Population ZPS14

Stalk lodging resistance and grain yield are the result of interactions of many traits expressed during maize (Zea mays L.) development. Determination of which traits influence stalk lodging resistance and grain yield might improve breeding program efficiency. The main objective of this study was to identify stalk traits that might relate to stalk lodging and grain yield, so that they can be selected as correlated traits for improving both grain yield and stalk quality. For this investigation, S1 progenies were randomly derived from the Yugoslavian maize synthetic population ZPS14. Correlations and path coefficient analysis showed stalk water content had the greatest impact on stalk lodging resistance and grain yield. Genotypic correlations (rg) revealed that stalk water content had a negative and significant influence on both percentage of lodged plants (rg = – 0.46*) and grain yield (rg = – 0.42*). Thus, improvement in grain yield and stalk lodging would be not expected from selection for stalk water content. However, a small number of S1 families with high stalk water content and above average grain yield were identified, suggesting some progress could be made in improving both traits simultaneously if the breeding population was large. A significant genotypic relationship was not found for grain yield and stalk lodging resistance (rg = 0.04). As shown by path analysis, direct effects of stalk lodging on grain yield were small and nonsignificant (P1.2 = 0.003). Breeding for better stalk quality, thus, will not affect future progress of selection for grain yield.

Selection Criteria for Combining High Grain Yield and High Grain Protein Concentration in Bread Wheat

This study was designed to identify selection criteria for the simultaneous improvement of grain yield and grain protein concentration in spring wheat (Triticum aestivum L.). Eight cultivars were selected. Six expressed contrasting levels of grain protein concentration and grain yield. Two, the cultivars ‘UM632’ and ‘UM684’, expressed high levels of both traits concurrently. Plants in replicated plots were sampled from anthesis to maturity over 2 yr and data were collected on traits related to nitrogen (N) and dry matter accumulation and remobilization. Grain protein concentration was not correlated with grain yield but was correlated with post‐anthesis N uptake (r = 0.66**), total plant N at maturity (r = 0.49**), and N harvest index (r = 0.87**), and was inversely correlated with vegetative N at maturity (r = −0.49**). Grain yield was correlated with both post‐anthesis N (r = 0.50**) and dry matter uptake (r = 0.58**), with total N (r = 0.78**) and dry matter (r = 0.77**) at maturity, and with harvest index (r = 0.83**). Grain protein yield was highly correlated with post‐anthesis N accumulation (r = 0.90**), total N at maturity (r = 0.98**) and the sum of N harvest index and harvest index (r = 0.93**). UM632 and UM684 coupled high post‐anthesis N uptake and total N at maturity with high remobilization efficiency and N harvest index, while maintaining harvest index. We concluded that grain protein concentration and grain yield could be improved simultaneously if selection was practiced for threshold levels of grain yield or protein concentration followed by selection for grain protein yield in populations constructed from crosses combining high total N at maturity, N harvest index and harvest index.