Selection For Dry Matter Yield Research Articles

Developing genomic selection for dry matter yield in white clover

Genomic selection (GS) integrates DNA marker and trait data to develop a model that enables prediction of trait performance (genomic-estimated breeding values; GEBVs) based on genotype data alone. GS has been shown to improve the efficiency and effectiveness of breeding programmes, especially for complex traits such dry matter yield (DMY). DMY data were generated from a training population of 200 white clover half-sibling (HS) families assessed in multi-location field trials for two years. We generated a GS prediction model after integrating genotyping-by-sequencing marker data from parents of the HS families with the HS DMY data. We then compared two selection strategies: a conventional method where individuals were chosen randomly from the phenotypically top-ranked HS families (HSP); and another where GEBVs were used to select the best individual from the top-ranked HS families (APWFGS). The mean predicted DMY GEBVs of the selected plants, as well as the predicted response to selection, were compared with those of the base population. This study showed that, compared with conventional selection (HSP), incorporating genomic selection (APWGSHS) is predicted to double the increase in DMY and response to selection relative to the base population. Synthetic populations based on these selections have been generated and will be tested in a field trial to determine empirically the impact of genomic selection for a complex trait.

Polycross Genetic Analysis of Forage Yield and Related Traits in Dactylis glomerata

ABSTRACTOrchardgrass (Dactylis glomerata L.) is a long‐lived perennial forage grass and one of the main perennial grasses that naturally grow in temperate pasture and rangelands in northern and western Iran. This study was conducted to increase knowledge about the genetic basis of agro‐morphological traits in orchardgrass, which may help further improvement of this species. Half‐sib families derived from a polycross of 25 parental genotypes were evaluated during 2 yr, and 11 agro‐morphological traits together with two quality traits were measured. Families were significantly different for all the traits measured. Significant differences were also observed between the 2 yr of evaluation for all the traits except for mean percent of dry matter and panicle length. Narrow‐sense heritability ranged from 0.12 (number of fertile shoot) to 0.79 (mean percent of dry matter). The estimate of narrow‐sense heritability for the most economically important trait (total dry matter yield) was relatively low (0.17 to 0.30), showing that both additive and non‐additive gene effects played a role in the genetic control of this trait. In addition to a weak phenotypic correlation, total dry matter yield had a high genetic correlation with plant height and number of fertile shoots. No significant phenotypic correlation was observed between forage yield and crude protein, though a negative genetic correlation was evident. According to the results of heritability estimations and correlation between the traits, indirect selection for dry matter yield would be possible through selection for plant height.

Analysis of variability, heritability, and genetic advance in seed yield and related traits of orchardgrass (Dactylis glomerata L.) populations

Orchardgrass (Dactylis glomerata L.) genotypes from different natural sources in the Eastern Anatolian Region of Turkey were clonally evaluated to study genetic variation and the relationships between seed yield and its components using a randomized complete block design. Results showed very significant genotypic variances among genotypes for all traits, including agronomic (seed, dry matter, and biological yields), morphological (plant height; panicle length; crown diameter; numbers of fertile, sterile, and total stems; and stem intensity), physiological (percent fertile stems, harvest and fertility indexes), and phenological (heading and anthesis dates) traits, as well as genotype × year interaction variances. Genotypic components were the main contributor to phenotypic variation of all traits (except physiologic traits, stem intensity, and number of sterile stems), resulting in high broad-sense heritability (>50%). Agromorphological and physiological traits had greater phenotypic (PCV), genotypic (GCV), and environmental coefficients of variation, while these were lower for phenological traits. After the phenological traits, plant height, crown diameter, and panicle length were the least variable traits, while stem intensity and fertility index were highly variable. Heritability estimates increased as GCV values approached PCV values. Expected genetic gain greatly increased as heritability estimates and PCV both increased, rather than heritability values alone. The first 5 principle components accounted for 84.90% of total variance. All agromorphological traits (except number of sterile stems) and fertile stem percentage were primary sources of variation of the PC1 axis, while harvest and fertility indexes were for PC2. Out of the 4 clusters, genotypes in cluster 4 of higher seed yield were faster in aboveground biomass accumulation. They also had the best agromorphological traits coupled with early maturity. Seed yield greatly increased as aerial biomass increased without any change in harvest index, but there was a significant decrease in fertility index. It was concluded that selection for dry matter yield could result in a simultaneous increase in seed yield.

Genetic variation, heritability and correlations of agro-morphological traits in tall fescue (Festuca arundinacea Schreb.)

To study the genetic variation, heritability and genetic correlations of some agro-morphological traits in tall fescue, 25 parents from a genetically broad-base germplasm were polycrossed and their respective half-sib families were generated. Clonally propagated parents and their half-sib families were grown as spaced single plants using a randomized complete-block design with three replications, and observed for seven traits in 2006 and 2007. The estimates of broad-sense heritability \( \left( {h^{2}_{\text{n}} } \right) \) were moderate to high \( \left( {h^{2}_{\text{b}} \, = \, 0.43\, - \,0.80} \right) \) for the traits studied. Narrow-sense heritability \( \left( {h^{2}_{\text{n}} } \right) \) estimates from analyses of progenies and from regression of half-sib (HS) progenies on parents \( \left( {h^{2}_{\text{op}} } \right) \) suggested that genetic variation for these traits was largely controlled by additive gene action. Association of dry matter yield (DMY) with plant height, number of fertile shoot, curbs width and spring growth was positive and significant. With the exception of number of days to pollination, correlation coefficients of the traits between the parents and offspring were not significant. Based on parent-offspring regression, genetic gain from selection for DMY was high, demonstrating genetic potential for improving this trait. Overall, there was high genetic variation and moderate heritability for most traits in the tall fescue populations evaluated. In conclusion, to improve herbage yield, selection would be more effective based on forage yield components.

Efficiency of Indirect Selection for Dry Matter Yield Based on Fresh Matter Yield in Perennial Ryegrass Sward Plots

Forage dry matter yield (DMY) is a high‐priority trait in breeding perennial ryegrass (Lolium perenne L.). However, determining dry matter concentration is highly labor intensive. For a similar level of resources, indirect selection based on fresh matter yield (FMY) would allow a greater number of replicates, genotypes, or both to be evaluated. Our objective was to estimate the efficiency of indirect selection for DMY based on FMY of pure perennial ryegrass sward plots. Over a 14‐yr period, replicated trials, containing perennial ryegrass genotypes of similar ploidy and maturity category, were sown in Ireland and assessed for DMY and FMY at each harvest over two consecutive years. Forage was generally surface dry when harvested. The estimated efficiency of indirect selection based on two replicates and comparable selection intensity was high (≥0.80). Simulation models indicated that resources would be used more efficiently by evaluating more genotypes than by increasing the number of replicates. For example, doubling the number of plots to increase the number of replicates from two to four indicated an increase in the efficiency of indirect selection from a mean 0.88 to 0.94. However, doubling the number of plots and including more genotypes, facilitating greater selection intensity, indicated an increase in the efficiency of indirect selection from a mean 0.88 to 1.04. This study indicates that FMY can be used successfully as an indirect selection method of increasing DMY in perennial ryegrass swards.

Prediction of indirect selection for seed and forage yield of lucerne based on evaluation under spaced planting

AbstractPhenotypic selection under spaced planting is frequently used in forage species. This study aimed to compare the predicted efficiency of direct selection for lucerne seed or forage yield under dense planting with indirect selection based on the same traits or seed yield components evaluated under spaced planting. Sixteen genotypes randomly chosen from a representative sample of locally adapted germplasm were grown for two years as individual clones spaced at 75 cm (density =1.78 plants/m2) and in dense plots formed by one row of four clones spaced at 10 cm (density = 50 plants/m2) using a randomized complete block design with three replications. Indirect selection based on seed yield under spaced planting was just 19% less efficient than direct selection, owing to moderate genetic correlation between plant densities (rg = 0.66) and somewhat higher broad‐sense heritability under spaced planting than under dense planting. The relative efficiency of indirect selection for seed yield in density based on individual seed yield components under spaced planting ranged from modest to very low and was always below 45%. The efficiency of indirect selection for dry matter yield based on yield response under spaced planting was moderate for total yield (64%) and very low for second‐year yield (32%) relative to direct selection.

Carbon Isotope Discrimination and Yield in 14 Cool-Season Grasses

Selection for carbon isotope discrimination (delta) has potential for improving water-use efficiency in cool-season grasses. An understanding of how delta is affected by differential water application and its association with dry mater yield may be helpful in identifying the best cool-season grass species for breeding and improvement, and may assist in designing selection and breeding procedures for improving cool-season grasses. We designed a study to evaluate the response of delta and dry matter yield to a gradient of water application in 14 cool-season, perennial grasses. The grasses were established in a rainout shelter facility equipped with a line-source irrigation system to study the: i) trends in dry matter yield across 6 water levels (WL-1 through 6, ranging from 981 to 64 mm water applied) and delta across 3 water levels (WL-1, 3, and 5), ii) grass x water level interactions for these traits, and iii) relationship between dry matter yield and delta in these grasses across a 2-year period. When averaged across years, the grasses differed significantly for delta at the highest (WL-1) and lowest (WL-5) water levels, but not at WL-3. Reductions in delta were strongly linear from WL-1 to WL-5, and although some inconsistencies were evident, the trend was similar for all grasses. Grasses differed significantly for dry matter yield at each of the water levels. Although the change in dry matter yield was mostly linear across water levels, the trend was not consistent among the grasses. In general, delta was not closely associated with dry matter yield; however, some exceptions with high dry matter yield and high delta were evident. This lack of close association between dry matter yield and delta in these 14 grasses suggests that breeding efforts to improve these grasses should involve simultaneous selection for dry matter yield and delta. DOI:10.2458/azu_jrm_v56i6_johnson

Carbon isotope discrimination and yield in 14 cool-season grasses

Selection for carbon isotope discrimination (delta) has potential for improving water-use efficiency in cool-season grasses. An understanding of how delta is affected by differential water application and its association with dry mater yield may be helpful in identifying the best cool-season grass species for breeding and improvement, and may assist in designing selection and breeding procedures for improving cool-season grasses. We designed a study to evaluate the response of delta and dry matter yield to a gradient of water application in 14 cool-season, perennial grasses. The grasses were established in a rainout shelter facility equipped with a line-source irrigation system to study the: i) trends in dry matter yield across 6 water levels (WL-1 through 6, ranging from 981 to 64 mm water applied) and delta across 3 water levels (WL-1, 3, and 5), ii) grass x water level interactions for these traits, and iii) relationship between dry matter yield and delta in these grasses across a 2-year period. When averaged across years, the grasses differed significantly for delta at the highest (WL-1) and lowest (WL-5) water levels, but not at WL-3. Reductions in delta were strongly linear from WL-1 to WL-5, and although some inconsistencies were evident, the trend was similar for all grasses. Grasses differed significantly for dry matter yield at each of the water levels. Although the change in dry matter yield was mostly linear across water levels, the trend was not consistent among the grasses. In general, delta was not closely associated with dry matter yield; however, some exceptions with high dry matter yield and high delta were evident. This lack of close association between dry matter yield and delta in these 14 grasses suggests that breeding efforts to improve these grasses should involve simultaneous selection for dry matter yield and delta.

Within‐Row Spacing Influences on Diverse Sorghum Genotypes: II. Dry Matter Yield and Foratge Quality

AbstractResearch was conducted to determine changes in dry matter yield, cell wall composition, and digestibility of four diverse sorghum [Sorghum bicolor (L.) Moench.] genotypes as influenced by withinrow spacing. Genotypes (IS‐0469, IS‐0865, P‐954063, and IS‐2952) were selected to represent a range in morphology and cell wall composition, and were sown at five within‐row spacings of 5,10, 15, 30, and 60 cm at two field locations in 1986 and 1987. Harvested herbage was separated into stem, leaf sheath, and leaf blade components for main‐shoot and tillers. Forage dry matter yield declined linearly from 10.9 to 8.1 Mg ha−1 as within‐row spacing increased from 5 to 60 cm. Total forage neutral detergent fiber and permanganate lignin concentrations declined linearly from 717 to 700 g kg−1 and 79.5 to 71.5 g kg−1, respectively, as within‐row spacing increased from 5 to 60 cm. Main‐shoot permanganate lignin concentration in the stem component declined 15.3%, while leaf sheath and leaf blade components were relatively unchanged in lignin concentration with increased within‐row spacing. Total forage in vitro dry matter digestibility and N content increased 8.7 and 16.1%, respectively, as within‐row spacing increased. Reduced plant populations, through increased within‐row spacing, improved forage quality and increased digestibility and protein content, however, dry matter yield was significantly reduced. Within‐row spacing may significantly influence genotype selection for dry matter yield. Genotypic selection for improved forage quality in a breeding nursery should not be greatly affected by within‐row plant spacings of 15 cm or less.

Grazing studies on the Guadalcanal Plains, Solomon Islands. 2. Effects of pasture mixtures and stocking rate on animal production and pasture components

SummaryAnimal production was compared on three pastures, Brachiaria mutica (para), B. decumbens (signal) and Panicum maximum cv. Hamil (hamil) each sown with a common legume mixture of Centrosemapubescens (centro), Macroptilium atropurpureum cv. Siratro, and Stylosanthes guianensis cv. Endeavour (stylo), at four stocking rates, 1·8, 21·87, 31·86, and 41·85 animals/ha, over 4 years on the GuadalcanalPlains, Solomon Islands.Mean live-weight gain per head over the four stocking rates and 4 years on para pastures was 01·847, on signal pastures 01·838, and on hamil pastures 01·828 kg/head/day. Mean production per hectare at the optimum stocking rates were: para at 3.6 animals/ha, 607 kg; signal at 31·86 animals/ha, 442 kg; hamil at 21·87 animals/ha, 362 kg/ha/year.The high stocking rates of 31·86 and 41·85 animals/ha caused the hamil pastures to decline to the stage where they were destocked in the 4th year of grazing.Superior production on para pastures was not simply related to green dry matter (GDM) on offer. In the 1st year of grazing, GDM was highest in hamil pastures, but in the 2nd year highest in para, and in the 3rd year mean yields were similar in all pastures, but were very low at the 31·86 and 41·85 animals/ha stocking rate in the hamil pastures.Para pastures maintained highest legume contents. The quadratic relationship between live-weight gain/head and legume content was significant over all pastures and stocking rates. Live-weight gain (LWG) per head increased up to 15% legume content, after which there was little change. Yield of green leaf, percentage green leaf, and sward bulk density did not appear to be related to LWG/head. Para pastures had lower values for all these components than the other pastures.Chemical factors contributed to the higher animal production from para pastures. Para leaf maintained consistently higher in vitro dry-matter digestibility values. Na content of para averaged 01·812%, whereas other species were 01·801 to 01·802%, and below the critical level (01·805%) for animal intake. N and S in leaf material, and Cu in total tops were also consistently higher in para grass.Results of this grazing trial suggest that selection of grass species on the basis of quality including dry-matter digestibility and mineral content, on ability to persist with increasing stocking rate, on compatibility with legumes, and on growth habit are more important than selection for dry-matter yield.

SELECTION FOR DRY MATTER YIELD IN LOLIUM PERENNE L. II. CORRELATED RESPONSES UNDER TWO CUTTING REGIMES

The correlated responses to divergent selection for dry matter yield within an ecotype of Lolium perenne L. were evaluated in two experiments under different cutting regimes. Both experiments showed that selection for dry matter yield did not affect leaf size and caused asymmetrical correlated responses on the rate of tiller production and the rate of leaf appearance. Selection for high dry matter yield resulted in an increased rate of tiller production without change in the rate of leaf appearance. Selection for low dry matter yield did reduce both the rate of leaf appearance and the rate of tiller production.

The phosphorus content and yield of grain of different wheat varieties in relation to phosphorus deficiency

Several varieties of Australian and two American bread wheats were grown in the glass-house under conditions of controlled phosphorus deficiency. A wide range of final phosphorus concentrations occurred in the grain of all varieties in response to variations in phosphorus supply. Suffcient phosphorus at sowing raised the value for Australian grain to 0.4% P. Under deficiency conditions, the concentration in all varieties fell below 0.25% P, a typical value for grain from southern Australia. Yields of two Australian varieties, Bencubbin and Charter, were further examined. Variety Bencubbin was shown to give larger grain yields than Charter under conditions of phosphorus deficiency, and its grain had lower concentrations of phosphorus. The higher yields were not associated with higher uptakes of phosphorus. Bencubbin showed a marked luxury uptake in the straw at moderate rates of phosphorus application. It is suggested that the lower phosphorus concentrations in the higher-yielding variety are necessarily associated with success in selection for dry matter yield, where the uptake of the nutrient is limited.