Enhance Yield Stability Research Articles

Yield stability of hybrids versus lines in wheat, barley, and triticale

We present experimental data for wheat, barley, and triticale suggesting that hybrids manifest on average higher yield stability than inbred lines. Yield stability is assumed to be higher for hybrids than for inbred lines, but experimental data proving this hypothesis is scarce for autogamous cereals. We used multi-location grain yield trials and compared the yield stability of hybrids versus lines for wheat (Triticum aestivum L.), barley (Hordeum vulgare L.), and triticale (×Triticosecale Wittmack). Our study comprised three phenotypic data sets of 1,749 wheat, 96 barley, and 130 triticale genotypes, which were evaluated for grain yield in up to five contrasting locations. Yield stability of the group of hybrids was compared with that of the group of inbred lines estimating the stability variance. For all three crops we observed a significantly (P < 0.05) higher yield stability of hybrids compared to lines. The enhanced yield stability of hybrids as compared to lines represents a major step forward, facilitating coping with the increasing abiotic stress expected from the predicted climate change.

Stabilization of yield in plant genotype mixtures through compensation rather than complementation.

Background and AimsPlant genotypic mixtures have the potential to increase yield stability in variable, often unpredictable environments, yet knowledge of the specific mechanisms underlying enhanced yield stability remains limited. Field studies are constrained by environmental conditions which cannot be fully controlled and thus reproduced. A suitable model system would allow reproducible experiments on processes operating within crop genetic mixtures.MethodsPhenotypically dissimilar genotypes of Arabidopsis thaliana were grown in monocultures and mixtures under high levels of competition for abiotic resources. Seed production, flowering time and rosette size were recorded.Key ResultsMixtures achieved high yield stability across environments through compensatory interactions. Compensation was greatest when plants were under high levels of heat and nutrient stress. Competitive ability and mixture performance were predictable from above-ground phenotypic traits even though below-ground competition appeared to be more intense.ConclusionsThis study indicates that the mixing ability of plant genotypes can be predicted from their phenotypes expressed in a range of relevant environments, and implies that a phenotypic screen of genotypes could improve the selection of suitable components of genotypic mixtures in agriculture intended to be resilient to environmental stress.

Simulating Seed Number in Grain Sorghum from Increases in Plant Dry Weight

Simulation of seed number for crop models is important in identifying cultural practices, which enhance yield stability. Field and crop simulation studies examined the relationship between dry weight accumulation and seed number per plant to potentially improve the capability of the grain sorghum [Sorghum bicolor (L.) Moench] model, SORKAM, to simulate seed number. The best estimates of seed numbers were obtained from plant dry weight accumulated during the 360 growing degree day intervals encompassing panicle branch–spikelet formation (PBSI) and panicle elongation through anthesis (EAI). Comparison of observed vs. simulated seed numbers using SORKAM’s original equations accounted for 57% of the variation in seed number, but it underestimated high seed numbers. Accumulated plant dry weight for the PBSI and EAI intervals accounted for 49 and 64% of the variation in seed number, respectively. Simulation of seed numbers improved when the more sensitive water stress coefficient (for leaf area, WATCOle) was applied to the interval (PBSI or EAI) experiencing the highest water stress while the less sensitive water stress coefficient (for dry weight, WATCOdw) was applied to the interval experiencing the lowest water stress. The slope from the regression of observed on simulated seed numbers was 0.80 (r2 = 0.57) for SORKAM with the WATCOle switch compared with 0.59 (r2 = 0.57) in the original SORKAM model. Hence, the timing and recovery of water stress during the panicle development period was important in estimating seed number of sorghum.

Yield Stability of Hybrid vs. Pureline Hard Winter Wheats in Regional Performance Trials

Hybrid hard winter wheats (Triticum aestivum L.) have shown superior grain yield potential in regional performance trials during the last decade. Evidence for enhanced yield stability, combined with enhanced yield potential, would facilitate wider acceptance of hybrid wheat by growers. Hybrid and pureline yield stability and environmental responsiveness were compared with the use of data from the Southern Regional Performance Nursery (SRPN), 1990 through 1995, and Agripro Standard Variety Trial (SVT), 1993 and 1994. Hybrid and pureline yields were regressed on an environmental index based on location mean yields for purelines, and response slope and deviations were calculated. Analyses were conducted separately for each nursery, as hybrid and pureline entries varied. Hybrids showed significantly higher mean yields compared with purelines and the yield advantage generally increased with increasing environmental yield potential. Average regression slope for hybrids was significantly higher (1.09–1.12) than for purelines (1.0) in the 1994 and 1995 SRPN and 1993 and 1994 SVT. Hybrid slopes were not significantly different from those for purelines in the 1990 through 1993 SRPN, where they ranged from 1.0 to 1.07. There was no crossover in yield response between hybrids and purelines at lower yield levels. Deviations from regression were of similar magnitude for hybrids and purelines. Confidence intervals for hybrid and pureline regressions generally overlapped throughout the observed yield ranges in the SRPN. In the 1993 and 1994 SVT, hybrid and pureline confidence intervals diverged as environmental yield potential increased. Compared with pureline cultivars, hybrid wheats have potential for enhanced mean yield and greater yield response to favorable environmental conditions with similar deviations from expected response.

Interrelationships among Three Major Loci Controlling Heading Date of Spring Barley when Grown under Short Daylengths1

Early maturing cultivars of barley (Hordeum vulgare L.) would enhance yield stability in lowland, low rainfall areas of Morocco. The objective of this work was to study the inheritance of heading date in crosses involving six spring barleys developed in the Sacramento Valley of California, USA and the Yaqui Valley of Sonora, Mexico. Data were gathered under short daylengths at 32° 15′ N Lat with December sowing in Morocco. Frequency distributions of parental, F1, F2, and backcross generations indicated a three‐locus model with recessive and duplicate dominant epistasis accounting for most of the phenotypic variability. Recessive gene interaction resulted in plants that were about 19 to 35 days earlier than later counterparts with the dominant allele present. Among the later genotypes, the presence of a dominant allele at either of the duplicate loci in the genotypes not homozygous for extreme earliness resulted in increased earliness of 5 to 14 days over the duplicate double recessive depending upon modifiers. A genotype for each parent was suggested; however, the three‐locus model did not account for the 4‐ to 6‐day differences between two pairs of parents. Apparently, modifying loci or different alleles were present in some parents.

Yield stability and population diversity in oats (Avena sp.)

The relationship between yield stability and populations containing various numbers and combinations of diverse homozygous and homogeneous lines was examined in an environment in which considerable variability occurs among and within growing seasons. Two groups (1,2), each containing 15 populations (4 pure lines grown singly and 11 multilines consisting of mechanical mixtures of all possible 2,3 and 4 way combinations of these 4 pure lines) were tested in each of 5 consecutive years. The pure lines in group 1 and 2 were selected on the basis of previous yield and yield variability respectively. In group 1, no significant differences were found among the 5 year means or the deviation mean squares of the 15 populations but highly significant differences among regression coefficients were present. The regression coefficients of the 4 pure lines differed considerably, indicating that this stability parameter was genetically influenced. The regression coefficients of the multilines tended towards unity regardless of the regression coefficients of the pure lines involved. In group 2, highly significant differences were found among the 5 year means, regression coefficients and deviation mean squares of the 15 populations. No consistent, predictable pattern was apparent between the mean and stability values of the pure lines and the multilines in which they were included. Differences between the 2 groups suggest that higher yield and greater stability result in the multilines if relatively high yielding pure lines are selected for inclusion. In general, the results indicated that multilines containing a number of diverse homozygous and homogeneous pure lines have satisfactory yields and enhanced yield stability. However, adequate testing of the pure lines and potential multilines over a broad range of environments is essential to determine desirable combinations.