Heterosis in maize single crosses derived from a yellow Tuxpeño variety in Brazil.

Most maize (Zea mays L.) crosses in Tropical regions use the heterotic pattern of Tupeno dent and Caribbean flint. Corsses between related lines are not used for commercial production. Related inbred lines are used in either double or three-way hybrids with other unrelated lines to develop superior hybrids. This study was conducted to determine the combining ability among 11 related inbred lines from a Tuxpeno population. The 11 inbred lines were crossed in a diallel series and were evaluated at six locations. A combinig ability analysis was made for grain yeild. The average yield across environments for the 55 single (44.8 q/ha) was not comparable to that of the single-cross hybrid (56.5 q/ha), induced as check. General combining ability (GCA) effects and specific combining ability (SCA) effects were highly significant (P < 0.01). Variation due to GCA, however, accounted for 68% of the variation among crosses. Indicating that additive genetic effects were more important than nonadditive effects. Highly significantly positive GCA effects were observed for lines 6 (2.44 q/ha) and 7 (6.40 q/ha) and highly significantly negative GCA effects for lines 5 (1.63 q/ha), 10 (2.64 q/ha), and 11 (4,01 q/ha). Significantly positive SCA effects were observed with line 4 x line 11, line 5 x line 9, and line 5 x 11 crosses. Lines 6 and 7 may have potential use as parents for three-way or double-cross hybrids

Evolving Behavior Allocations in Robot Swarms

Behavioral diversity is known to benefit problem solving in biological social systems such as insect colonies and human societies, as well as in artificial distributed systems including large-scale software and swarm-robotics systems. We investigate methods of evolving robot swarms in which individuals have heterogeneous behaviours. Two approaches are investigated to create swarm of size n. The first encodes a repertoire of n behaviours on a single individual, and hence evolves the swarm directly. The second approach uses two phases. First, a large repertoire of diverse behaviours is evolved and then another evolutionary algorithm is used to search for an optimal allocation of behaviours to the swarm. Results indicate that the two phase approach of generate then allocate produces significantly more effective collective behaviors (in terms of task accomplishment) than the direct evolution of behaviorally heterogeneous swarms

Evolving Herding Behaviour Diversity in Robot Swarms

Behavioural diversity has been demonstrated as beneficial in biological social systems, such as insect colonies and human societies, as well as artificial systems such as large-scale software and swarm-robotics systems. Evolutionary swarm robotics is a popular experimental platform for demonstrating the emergence of various social phenomena and collective behaviour, including behavioural diversity and specialization. However, from an automated design perspective, the evolutionary conditions necessary to synthesize optimal collective behaviours (swarm-robotic controllers) that function across increasingly complex environments (difficult tasks), remains unclear. Thus, we introduce a comparative study of behavioural-diversity maintenance methods (swarm-controller extension of the MAP-Elites algorithm) versus those without behavioural diversity mechanisms (Steady-State Genetic Algorithm), as a means to evolve suitable degrees of behavioural diversity over increasingly difficult collective behaviour (sheep-dog herding) tasks. In support of previous work, experiment results demonstrate that behavioural diversity can be generated without specific speciation mechanisms or geographical isolation in the task environment, although the direct evolution of a functionally (behaviorally) diverse swarm does not yield high task performance

Capacidade combinatória entre 15 populações de milho de ciclo superprecoce no Brasil.

Suplemento. Edição dos resumos do 41º Congresso Nacional de Genética, Caxambu, MG, 1995

Evaluation of Iowa Stiff Stalk Synthetic for resistance to gray leaf spot

Gray leaf spot (GLS) of maize (Zeamays), caused by Cercospora zeae-maydis, has become an increasing disease problem in the United States. Resistance to this pathogen is generally higher in inbred lines of Lancaster origin compared to lines derived from Iowa Stiff Stalk Synthetic (BSSS). This study was conducted to determine whether recurrent selection for yield had altered the level of GLS resistance in BSSS and to identify BSSS(R)Cl 1 S1 lines that combine GLS resistance with high yield. The distribution of GLS ratings for S1 lines derived from BSSSCO and BSSS(R)CI I were very similar, indicating that selection for yield had not altered G LS resistance· levels. Although the mean rating for both cycles was a susceptible 7 (I= resistant, 9 =susceptible), S1 lines with intermediate levels of resistance (4-6) were identified. The 250 BSSS(R)Cl I S1 lines were crossed to LH51, and the testcrosses were evaluated for yield and agronomic performance. S1 lines were identified which combine intermediate levels of GLS resistance with above-average standability and yield. These S1 lines will be recombined to develop an Iowa Stiff Stalk Synthetic population adapted to eastern maize growing conditions

FA

Climatic change emphasize the importance of biodiversity maintenance, Suggesting that germplasm adapted to organic, low input, or conventional conditions is needed to face future demands. This Study presents: I - The two steps genesis of the synthetic maize population Fandango, A) NUTICA creation: in 1975, Miguel Mota and Silas Pego, initiated a new type of polycross method involving 77 yellow elite inbred lines (dent and flint; 20% Portuguese and 80% North American germplasm) from the NUMI programme (NUcleo de melhoramento de Milho, Braga, Portugal). These inbreds were intermated in natural isolation and progenies submitted to intensive selection for both parents during continued cycles; B) From NUTICA to Fandango: Tandango was composed of all the crosses that resulted from a North Carolina Design I matting design (1 male crossed with 5 females) applied to NUTICA. II - The diversity evolution of Fandango under a Participatory Breeding project at the Portuguese Sousa Valley region (VASO) initiated in 1985 by Pego, with CIMMYT support. Morphological, fasciation expression, and yield trials were conducted in Portugal (3 locations, 3 years) and in the USA (4 locations, I year) using seeds obtained from five to seven cycles of mass selection (MS). The selection across cycles wits clone by the breeder (until cycle 5) and farmer (before cycle II in present). ANOVA and regression analysis on the rate of direct response to selection were performed when the assumption of normality was positively confirmed. Otherwise the non parametric Multivariate Adaptive Regression Splines (MARS) was performed. Response to mass selection in lowa showed significant decrease in yield, while in Portugal a significant increase for time of silking, plant and ear height, ear diameters 2, 37 4, kernel number, cot) diameters, and rachis was observed. At this location also a significant decrease was observed for thousand kernel weight and ear length. These results showed that mass selection were not effective for significant yield increase, except when considered Lousada with breeder selection (3.09% of gain per cycle per year). Some non-para metric methods (MARS, decision trees and random forests) were used to get insights on the causes that explain yield in Fandango. Kernel weight and ear weight were the most important traits, although row numbers, number of kernels per row, ear length, and ear diameter were also of some importance influencing Fandango yield

Bias in the prediction of genetic gain due to mass and half-sib selection in random mating populations

The prediction of gains from selection allows the comparison of breeding methods and selection strategies, although these estimates may be biased. The objective of this study was to investigate the extent of such bias in predicting genetic gain. For this, we simulated 10 cycles of a hypothetical breeding program that involved seven traits, three population classes, three experimental conditions and two breeding methods (mass and half-sib selection). Each combination of trait, population, heritability, method and cycle was repeated 10 times. The predicted gains were biased, even when the genetic parameters were estimated without error. Gain from selection in both genders is twice the gain from selection in a single gender only in the absence of dominance. The use of genotypic variance or broad sense heritability in the predictions represented an additional source of bias. Predictions based on additive variance and narrow sense heritability were equivalent, as were predictions based on genotypic variance and broad sense heritability. The predictions based on mass and family selection were suitable for comparing selection strategies, whereas those based on selection within progenies showed the largest bias and lower association with the realized gain

Maize Cultivar Performance under Diverse Organic Production Systems

Maize (Zea mays L.) performance can vary widely between different production systems. The need for high-performing hybrids for organic systems with wide adaptation to various macroenvironments is becoming increasingly important. The goal of this study was to characterize inbred lines developed by distinct breeding programs for their combining ability and hybrid yield performance across diverse organic environments. Parent lines were selected from five different breeding programs to give a sample of publically available germplasm with potential for use in organic production systems with expired plant variety protection (Ex-PVP) and current commercial inbreds as benchmarks. A North Carolina Design II mating design was used to produce all possible cross combinations between seven lines designated as males and seven lines designated as females. A significantly positive general combining ability for the female inbred UHF134 suggests that it performs well in hybrid combination. Significant general combining ability was not observed for any male inbred line in this study. Several significantly positive specific combining abilities suggest that nonadditive genetic effects play an important role in determining yield in this germplasm. Further analysis revealed that hybrids containing either an Ex-PVP line or a commercial inbred line were on average superior to hybrids containing only inbreds developed by the cooperators of this study. This demonstrates the utility of testing inbreds from diverse sources when developing hybrids for organic production systems

"Fandango": long term adaptation of exotic germplasm to a Portuguese on-farm-conservation and breeding project

Climatic change emphasize the importance of biodiversity maintenance, Suggesting that germplasm adapted to organic, low input, or conventional conditions is needed to face future demands. This Study presents: I - The two steps genesis of the synthetic maize population 'Fandango', A) 'NUTICA' creation: in 1975, Miguel Mota and Silas Pego, initiated a new type of polycross method involving 77 yellow elite inbred lines (dent and flint; 20% Portuguese and 80% North American germplasm) from the NUMI programme (NUcleo de melhoramento de Milho, Braga, Portugal). These inbreds were intermated in natural isolation and progenies submitted to intensive selection for both parents during continued cycles; B) From 'NUTICA' to 'Fandango': Tandango' was composed of all the crosses that resulted from a North Carolina Design I matting design (1 male crossed with 5 females) applied to 'NUTICA'. II - The diversity evolution of 'Fandango' under a Participatory Breeding project at the Portuguese Sousa Valley region (VASO) initiated in 1985 by Pego, with CIMMYT support. Morphological, fasciation expression, and yield trials were conducted in Portugal (3 locations, 3 years) and in the USA (4 locations, I year) using seeds obtained from five to seven cycles of mass selection (MS). The selection across cycles wits clone by the breeder (until cycle 5) and farmer (before cycle II in present). ANOVA and regression analysis on the rate of direct response to selection were performed when the assumption of normality was positively confirmed. Otherwise the non parametric Multivariate Adaptive Regression Splines (MARS) was performed. Response to mass selection in lowa showed significant decrease in yield, while in Portugal a significant increase for time of silking, plant and ear height, ear diameters 2, 37 4, kernel number, cot) diameters, and rachis was observed. At this location also a significant decrease was observed for thousand kernel weight and ear length. These results showed that mass selection were not effective for significant yield increase, except when considered Lousada with breeder selection (3.09% of gain per cycle per year). Some non-para metric methods (MARS, decision trees and random forests) were used to get insights on the causes that explain yield in Fandango. Kernel weight and ear weight were the most important traits, although row numbers, number of kernels per row, ear length, and ear diameter were also of some importance influencing 'Fandango' yield