122,869 research outputs found

    Genetic parameters and selection strategies for soybean genotypes resistant to the stink bug-complex

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    Soybean genotypes resistant to stink bugs are derived from complex breeding processes obtained through indirect selection. The aim of the present work was to estimate genetic parameters for guiding selection strategies towards resistant genotypes, based on those traits associated with responses to pod-attacking stink bugs, such as the grain filling period (GFP), leaf retention (LR), percentage index of pod damage (PIPD) and percentage of spotted seeds (PSS). We assessed the parental lines IAC-100 (resistant) and FT-Estrela (susceptible), the progenies F2 and F 4 , 30 progenies F 2:3 , 30 progenies BC 1 F 2:3 and 30 progenies BC 2 F 2:3 , besides the cultivars BRS Celeste and MGBR-46 (Conquista). Three field experiments, using randomized complete block design with three replications, were installed in Goiânia-GO, in the 2002/03 season. Each experiment consisted of 36 treatments (6 common and 30 regular). Heritability estimates were: 74.6 and 36.1 (GFP); 51.9 and 19.9 (LR); 49.6 and 49.6 (PIPD) and 55.8 and 20.3 (PSS), in both the broad and narrow senses, respectively. Based on these results, we concluded that the best strategy for obtaining stink bug-resistant genotypes consists of selecting the PIPD trait in early generations (F 3 or F 4 ), followed by selection for the GFP, LR and PSS traits in generations with higher endogamy levels


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    Foliage colour may affect the photosynthetic activities of a plant and consequently yield.  Differences in the green foliage colour of plants often reflect differences in chlorophyll concentration of the leaves. This study investigated the inheritance pattern of a yellow foliage mutant in cowpea. Seeds of a nuclear yellow foliage mutant and three green foliage cowpea lines were planted in plastic buckets filled with garden soil on the roof top garden of Department of crop Protection and Environmental Biology, University of Ibadan, Nigeria and crossed to produce six generations per cross comprising parents, F1, F2 and BC. The various generations were and on the field at the Teaching and Research Farm of the University of Ibadan, Nigeria and data were collected on phenotypic traits. The nuclear yellow foliage mutant segregated in the ratio 3green:1yellow, thus indicating that the trait was controlled by monogenic recessive gene. Some F2 and BC plants of the yellow foliage mutant exhibited variegation for leaf colour indicating gene instability resulting from the action of transposable element. The frequencies of reversion from the yellow to green of F3 progenies vary widely within and between progeny rows. Of a total of 309 individual plants that were scored, 55% were variegated, 23% were green while 22% exhibited the yellow phenotype. The gene symbol yfc-3 was assigned to the recessive condition, while yfc-3un was assigned to the unstable allele of yellow foliage

    Band Codes for Energy-Efficient Network Coding with Application to P2P Mobile Streaming

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    A key problem in random network coding (NC) lies in the complexity and energy consumption associated with the packet decoding processes, which hinder its application in mobile environments. Controlling and hence limiting such factors has always been an important but elusive research goal, since the packet degree distribution, which is the main factor driving the complexity, is altered in a non-deterministic way by the random recombinations at the network nodes. In this paper we tackle this problem proposing Band Codes (BC), a novel class of network codes specifically designed to preserve the packet degree distribution during packet encoding, ecombination and decoding. BC are random codes over GF(2) that exhibit low decoding complexity, feature limited and controlled degree distribution by construction, and hence allow to effectively apply NC even in energy-constrained scenarios. In particular, in this paper we motivate and describe our new design and provide a thorough analysis of its performance. We provide numerical simulations of the performance of BC in order to validate the analysis and assess the overhead of BC with respect to a onventional NC scheme. Moreover, peer-to-peer media streaming experiments with a random-push protocol show that BC reduce the decoding complexity by a factor of two, to a point where NC-based mobile streaming to mobile devices becomes practically feasible.Comment: To be published in IEEE Transacions on Multimedi

    Evolved polygenic herbicide resistance in Lolium rigidum by low-dose herbicide selection within standing genetic variation

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    The interaction between environment and genetic traits under selection is the basis of evolution. In this study, we have investigated the genetic basis of herbicide resistance in a highly characterized initially herbicide-susceptible Lolium rigidum population recurrently selected with low (below recommended label) doses of the herbicide diclofop-methyl. We report the variability in herbicide resistance levels observed in F1 families and the segregation of resistance observed in F2 and back-cross (BC) families. The selected herbicide resistance phenotypic trait(s) appear to be under complex polygenic control. The estimation of the effective minimum number of genes (NE), depending on the herbicide dose used, reveals at least three resistance genes had been enriched. A joint scaling test indicates that an additive-dominance model best explains gene interactions in parental, F1, F2 and BC families. The Mendelian study of six F2 and two BC segregating families confirmed involvement of more than one resistance gene. Cross-pollinated L. rigidum under selection at low herbicide dose can rapidly evolve polygenic broad-spectrum herbicide resistance by quantitative accumulation of additive genes of small effect. This can be minimized by using herbicides at the recommended dose which causes high mortality acting outside the normal range of phenotypic variation for herbicide susceptibility
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