The use of a rising plate meter to evaluate lucerne (Medicago sativa L.) height as an important agronomic trait enabling yield estimation

A rising plate meter (RPM) is an instrument used for the measurement of compressed sward height and estimation of yield on grasslands. The aim of this study was to investigate the use of an RPM to evaluate lucerne height as an agronomic trait enabling yield estimation. Compressed height (CH), stem length, plant and stem density and yield measurements were recorded from the late‐vegetative stage to flowering in the first cut and from the late‐bud stage to flowering in the second and third cuts, during three successive years. For lucerne maximal stem‐length prediction, CH could be used successfully (with R ² over 0·90) in developmental stages before flowering and for stem lengths up to 80 cm, irrespective of stand density or order of cut. The dry‐matter yield of lucerne was better predicted using CH (R ² = 0·72) than maximal stem length (MSL) (R ² = 0·53). The recommended number of observations was 7–9 per treatment in the first cut and twice this in subsequent cuts because of higher variability in stand structure. The use of RPM to measure CH of lucerne is not recommended when MSL exceeds 80 cm, or in the case of lodging. RPM may also be suitable for similar forage crops with erect or semi‐erect stems, subject to consideration of disc weight and diameter. Heavy discs are unsuitable for lucerne height prediction but could be more suitable for yield prediction.     

Influence of cultivar and environment on quality of Latin American wheats

Wheat consumption is growing, with processors asking for wheat-based products showing better and more consistent quality. Genotype, environment and their interaction (G × E) play an important role in the final expression of quality attributes. An international research consortium was developed in order to evaluate the magnitude of genotype, environment and G × E effects on wheat quality of cultivars developed for different agro-ecological zones in Latin America. Genotypes released in Argentina, Brazil, Chile, Mexico, Paraguay and Uruguay, were cultivated in twenty different environments within the participating countries. Each environment was characterized for cultural practices, soil type and climatic conditions. Grain yield and analyses of test weight, protein, ash, gluten, Alveograph, Farinograph, Falling Number, SDS sedimentation and flour color were determined. Allelic variations of puroindolines and glutenins were determined in all the genotypes evaluated. Both puroindoline and gluten protein alleles corresponded to genotypes possessing medium to very good bread making quality. Large variability for most quality attributes evaluated was observed, with wider ranges in quality parameters across environments than among genotypes; even for parameters known to be largely determined by genotype. The importance of growing environment on grain quality was proved, suggesting that breeders’ quality objectives should be adapted to the targeted environments.     

Differences in the crude protein fractions of lucerne leaves and stems under different stand structures

Protein degradability in forage legumes is of global importance because utilization efficiency of forage has economic and environmental consequences. However, there are no published studies on the effect of legume stand structure on differences in crude protein (CP) fractions. The main objective of the present research was therefore to investigate differences in CP fractions in leaves and stems of lucerne (Medicago sativa L.) during the growing season. Stand traits were measured over 2 years, and forage was sampled at the early bud and early flower stages in the first, second and third cuts. Stems had significantly higher concentrations (in g kg^?1 CP) of non‐protein (fraction A: 430 g kg^?1 CP) and indigestible nitrogen (fraction C: 92 g kg^?1 CP) than leaves and had lower relative content of true protein (fraction B: 478 g kg^?1 CP). In the total forage (stems and leaves combined), about 80% of the variation in CP fractions was explained by year, cut and maturity. Year was the most important factor, particularly for the B fractions. Cut was the second‐most important factor; its main effect was that the relative abundance of fraction A declined from 394 g kg^?1 CP in the first cut to 293 in g kg^?1 CP the third cut. Maturity increased the amounts of indigestible fraction C and protein fractions B₁ and B₃. This was associated with the leaf weight ratio, which had an inverse relationship with maximal stem length and dry matter yield. Variation partitioning showed that 75% of CP fraction variability associated with cut, maturity and year could be explained by the evaluated stand traits. This research has highlighted the need to consider plant morphological traits when legume CP fractions are evaluated.     

Genotype-by-environment interactions for grain yield associated with water availability at flowering in rainfed lowland rice

While a large genotype-by-environment (G × E) interaction component of variance for grain yield (GY) has been widely reported for rainfed lowland rice, the reasons for such large interactions are not well known. A random reference population of 34 genotypes taken from the Cambodian rice improvement program was used to examine the magnitude and nature of G × E interactions for GY in Cambodia. These genotypes were evaluated in a multi-environment trial (MET) conducted across 3 years (2000–2002) and eight locations in the rainfed lowlands. The G × E interaction was partitioned into components attributed to genotype-by-location (G × L), genotype-by-year (G × Y) and genotype-by-location-by-year (G × L × Y) interactions. The G × L × Y interaction was the largest component of variance for GY. The G × L interaction was also significant and comparable in size to the genotypic component (G). The significant G component was partly explained by a group of four genotypes that were broadly adapted to different environmental conditions represented by three environmental groups. The three environmental groups were identified from a pattern analysis, and the grouping was partly related to the time of sowing, and hence water availability at flowering. A major factor contributing to the large G × L × Y interactions for GY was late maturing genotypes being affected greatly when soil water availability at flowering was reduced greatly, compared to earlier maturing genotype groups. While the differential genotypic responses to the water availability environment explained part of a large G × E interaction for GY, other non-water related environmental conditions also appeared to have contributed to the interaction. Three target environments were identified for focusing efforts of the breeding programs in Cambodia, and four putative genotypes were selected for their high yield and wide adaptation in the rainfed lowlands.     

Does the “high sugar” trait of perennial ryegrass cultivars express under temperate climate conditions?

The objective was to evaluate water‐soluble carbohydrate (WSC) and crude protein (CP) concentration of perennial ryegrass (PRG) cultivars with different genetic potential for producing WSC under two contrasting agronomic managements in temperate climate (southern Chile). A 4 × 2 factorial design was randomly allocated to 24 plots (31 m² each, three blocks): four PRG cultivars (diploid standard cultivar, “2nSt”; tetraploid standard cultivar, “4nSt”; diploid high sugar cultivar developed in New Zealand, “2nHSNZ”; and tetraploid high sugar cultivar developed in Europe, “4nHSEU”) and two agronomic managements (“favourable,” defoliations at three leaves per tiller and nitrogen (N) fertilization rate of 83.3 kg N ha^?1 year^?1; “unfavourable,” defoliations at two leaves per tiller and N fertilization rate of 250 kg N ha^?1 year^?1). Herbage samples were collected in early spring, spring, summer and autumn. Concentration of WSC did not differ among cultivars in spring and summer, averaging 194 and 251 g/kg DM, respectively. The cultivar 4nHSEU had the greatest WSC concentration in early spring and autumn (187 and 266 g/kg DM, respectively) and the greatest CP concentration across samplings (average 230 g/kg DM). Favourable management improved WSC concentrations in early spring and summer and decreased CP in spring, summer and autumn. Annual DM yield did not vary with cultivar or management, averaging 8.43 t/ha. Within a 12‐month study at one site in a temperate environment in southern Chile, PRG cultivars have not shown a consistent expression of the “high sugar” trait, where a genetic × environment interaction might be operating.     

An economically based evaluation index for perennial and short‐term ryegrasses in New Zealand dairy farm systems

Grazed pastures based on ryegrass species provide most of the feed for dairy cattle in New Zealand. There are many cultivars of perennial (Lolium perenne), annual and Italian (L. multiflorum), and hybrid (L. boucheanum) ryegrasses available for dairy farmers to use in pasture renewal. This study describes an index which ranks ryegrass cultivars relative to a genetic base according to the estimated economic value (EV) of seasonal dry matter (DM) traits. A farm system model was used to derive EVs (Grazed pastures based on ryegrass species provide most of the feed for dairy cattle in New Zealand. There are many cultivars of perennial (Lolium perenne), annual and Italian (L. multiflorum), and hybrid (L. boucheanum) ryegrasses available for dairy farmers to use in pasture renewal. This study describes an index which ranks ryegrass cultivars relative to a genetic base according to the estimated economic value (EV) of seasonal dry matter (DM) traits. A farm system model was used to derive EVs ($ ha^?1 calculated as change in operating profit divided by unit change of the trait) for additional DM produced in different seasons of the year in four regions. The EV of early spring DM was consistently high across all regions, whereas EV for late spring DM was moderate to low. Genotype × environment analysis revealed significant reranking of DM yield among ryegrass cultivars across regions. Hence, separate performance values (PVs) were calculated for two mega‐environments and then combined with the corresponding season and region EV to calculate the overall EV for twenty‐three perennial ryegrass and fifteen short‐term ryegrass cultivars. The difference in operating profit between the highest ranked and lowest ranked perennial ryegrass cultivar ranged from $556 ha^?1 to $863 ha^?1 year^?1 depending on region. For short‐term ryegrasses used for winter feed, the corresponding range was $394 to $478 ha^?1 year^?1. Using PV for DM yield, it was estimated that plant improvement in perennial ryegrass has added $12–$18 ha^?1 year^?1 (depending on region) operating profit on dairy farms since the mid‐1960s.     

Pod yield performance and stability of peanut genotypes under differing soil water and regional conditions

Genetic gains of cultivated peanut (Arachis hypogaea L.) have increased harvest index and disease tolerance, resulting in improved yield potential and broad-range adaptability of peanut cultivars to United States (U.S.) peanut production regions. Although this strategy has been successful, future yield increases may require peanut cultivars specifically adapted to environmental and management systems of a particular production region. Irrigation is one major management factor that varies across U.S. production regions and influences yield stability. Therefore, peanut germplasm selection for developing specifically adapted cultivars depends on knowledge of genotypic (G) pod yield responses to irrigation (M) across contrasting environmental (E) conditions (G × E × M interaction). The objectives of this 2-year study were to characterize germplasm by: (i) examining genotypic pod yield response to irrigation at locations in Florida and Texas; and (ii) estimating the genotypic pod yield performance and stability using genotype plus genotype-by-environment interaction (GGE) biplots. At the Florida location, genotypes New Mexico Valencia C (NMVC), COC 041, and Chico responded positively to increasing water application, whereas FloRun? ‘107?, C76 16, and FlavorRunner 458 responded negatively. Genotypes C76 16, ICGS 76, Chico, and ICGV 86015 had pod yields greater than the population mean. The genotype ICGS 76 had both high pod yields and stability. Pod yields of Chico were greater at the southwest locations, whereas ICGV 86015 had greater pod yields at the southeast locations. These results demonstrate a range in adaptability of distinct peanut genotypes that can be used in breeding programs for developing improved cultivars.

Abbreviations: G × E: genotype-by-environment interaction; G × E × M: genotype-by-environment-by-management interaction; G × M: genotype-by-management interaction; NMVC: New Mexico Valencia C; TWRPET: total water received as a percentage of ET_o     

Agronomic value and adaptation across climatically contrasting environments of Italian red clover landraces and natural populations

This study aimed to support red clover (Trifolium pratense L.) breeding programmes by investigating germplasm adaptive variation. Four landraces representative of the former commercial ecotypes from northern and central Italy, thirteen natural populations collected in Italy across a wide latitudinal and altitudinal range in exploited or abandoned old natural grasslands, natural pastures or in the wild, and the varieties Perseo and Divin were evaluated for 2‐year forage yield, for plant survival and for some morphophysiological traits. Evaluations were made at two sites, one with a subcontinental climate (Lodi) and the other with a Mediterranean climate (Viterbo). Specific adaptation was particularly large in natural populations, whose interaction with location implied a widespread inversion of population ranks across sites for forage yield depending on their geographical origin. Forage yield and persistence of the populations were not correlated, owing to the trend of landrace and variety germplasm towards high yield but poor persistence. At Lodi, forage yield was associated with winter hardiness and was maximized by landrace germplasm, whereas persistence depended on various factors and was high only in a set of natural populations collected from pastures. At Viterbo, natural populations that evolved under severe summer drought stress tended towards high yield and persistence, showing no yield disadvantage relative to the best‐performing landrace or variety germplasm.     

Growth, yield and mineral content of Miscanthus × giganteus grown as a biofuel for 14 successive harvests

Miscanthus × giganteus, a perennial rhizomatous grass commercially used as a biofuel crop was grown in a field experiment on a silty clay loam soil for 14 years. There were 3 rates of fertilizer nitrogen (N), none (control), 60 kg N ha⁻¹ yr⁻¹ and 120 kg N ha⁻¹ yr⁻¹ as cumulative applications. The crop was harvested in winter and dry matter yield measured. N did not influence yield. Yield, which increased for the first 6 years, decreased in years 7 and 8, but then increased again and was highest in the 10th year averaging 17.7 t ha⁻¹ across all treatments. Differences in total production over the14 years were only 5% between the highest and lowest yielding treatments and averaged 178.9 t ha⁻¹ equivalent to 12.8 t ha⁻¹ yr⁻¹. In the first 10 harvests, 92% of dry matter was stem. Although the study showed N fertilizer was not required, it is considered that an application of 7 kg P ha⁻¹ yr⁻¹ and 100 kg K ha⁻¹ yr⁻¹ would avoid soil reserve depletion. Pesticides were not required every year and the crop can be considered as low input with a high level of sustainability for at least 14 years.     

Dynamic patterns of components of genotype × environment interaction for pod yield of peanut over multiple years: A simulation approach

The relative importance of the genotype × year (G × Y), genotype × location (G × L) and genotype × location × year (G × L × Y) interactions has significant implications on the testing strategy of crop breeding lines. The goal of this study was to examine the dynamic patterns of these three interactions for pod yield of peanut using a crop simulation model. Pod yields of 17 peanut lines in the early-rainy, mid-rainy and dry seasons at 112 locations covering all peanut production areas in Thailand were simulated for 30 years (1972–2002) with the Cropping System Model (CSM)-CROPGRO-Peanut. Combined analyses of variance were preformed for individual seasons and for overall seasons, with the number of year incrementally increasing from 2 to 30, and the relative contributions of the individual sources of variation were determined. This procedure was repeated four times with different starting years. The results showed that the environmental effects accounted for the major proportion of the total yield variation, followed by the genotype effects, while the genotype × environment (G × E) effects were rather small. The contributions of the individual sources changed as the number of years in the analysis changed. Increasing number of years in the analyses resulted in an increase in the magnitude of the G × Y and G × L × Y interactions, but a decline in the G × L contribution. The contributions of the G × Y and G × L interactions were greater and more fluctuated in the dry season, while those of the G × L × Y interactions were greater in the mid-rainy season. Notable increases in the G × Y interaction in the dry season were observed in certain years. The decline in the G × L interaction with increasing number of years was closely associated with the increase in the G × L × Y interaction, and both became stable when 6 or more years were included. Several cross-over in the ranks of peanut lines for mean pod yield in two contrasting years were also observed for the mid-rainy season. These results raise a question on the effectiveness of the strategy for using locations to replace years in varietal testing that is normally employed by breeders. The practical limit of multi-year evaluation of crop breeding lines could be overcome by the use of a crop simulation model.     

向日葵菌核病田间接种方法及品种抗病性研究

为建立有效的向日葵菌核病田间接种鉴定方法,本研究以菌核病菌菌丝体悬浮液和高粱粒菌丝体作为接种物,分别对不同抗感向日葵品种在始花期和盛花期进行人工接种,从而筛选出最佳接菌物类型、浓度及接种时期,并用此方法对52个品种进行抗性评价。试验结果表明：两种接种物均可使向日葵感病品种产生盘腐症状。用菌丝体悬浮液接种时,7.5~15.0 g/L浓度即可区分出向日葵品种间抗感性差异。始花期接种较盛花期可获得更高的发病率及病情指数。同时筛选出5个对盘腐型菌核病表现抗病的向日葵品种。本研究所建立的田间接种方法能够有效地对向日葵进行抗菌核病筛选和鉴定,可用于向日葵抗菌核病育种。      

A comparison, under controlled environmental conditions, of a Lolium multiflorum selection bred for high dry-matter content and non-structural carbohydrate concentration with a commercial cultivar

Abstract The nutritional value of Italian ryegrass (Lolium multiflorum) selection 121, bred for a high dry‐matter content and a high concentration of total non‐structural carbohydrate (TNC), was compared with that of Westerwolds ryegrass (L. multiflorum ssp. Westerwoldicum) cv. Midmar in a controlled environment. The concentration of neutral‐detergent fibre (NDF), acid‐detergent fibre (ADF), acid‐detergent lignin (ADL), nitrogenous compounds, minerals and in vitro digestibility were investigated as characteristics of nutritive value. The anatomical features of selection 121 and the Midmar cultivar were studied to determine possible structural differences. Thirty pots each of selection 121 and Midmar containing four plants per pot were arranged in a randomized block design in a controlled environment chamber. There were two temperature regimes during the study, the first being a warm regime (30 °C/20 °C) for 7 weeks followed by a cold regime(20 °C/7 °C) of a further 7 weeks. In the warm regime, the dry‐matter (DM) content and the TNC concentration of selection 121 were 0·17 and 0·16 higher, respectively, than Midmar. The NDF concentration was significantly (P < 0·01) higher in Midmar than in selection 121. When grown under warm conditions, Midmar had significantly (P < 0·001) higher concentrations of Mg, K, Na and Mn than selection 121. In the cold regime, the DM content and TNC concentration of selection 121 were 0·25 and 0·22 higher, respectively, than Midmar. No significant differences in the anti‐quality factors investigated were found between the two ryegrasses. In the cold regime, Midmar had significantly (P < 0·001 and P < 0·01) higher Ca, Mg, K, Na, Zn, Mn and P concentrations than selection 121. The results from this controlled environment study suggest that selection 121 is superior to Midmar in terms of the quality characteristics DM and TNC, and that these characteristics are not positively linked to anti‐quality factors associated with forage species.