I. Methods for breeding high-protein cultivars of soybeans; II. Transfer of Phytophthora resistance in soybean [Glycine max (L.) Merr] by backcrossing

The need to find an effective breeding method to develop soybean cultivars with high yield and high protein percentage from crosses of adapted cultivars is important. The objective of this study was to determine which kind of method (single cross vs backcross) would offer the best opportunity to increase yield of Vinton 81 while maintaining its current level of protein percentage. Three crosses were made using a moderately high protein cultivar (Vinton 81) with three high-yielding cultivars of different maturity group. The F(,4)-derived and BC(,1)F(,3)-derived lines were evaluated and compared with Vinton 81 for seed yield, maturity, lodging, height, seed weight, and protein and oil percentage;Significant differences were observed among lines derived from the F(,4) and BC(,1)F(,3) generations for the seven strains. In both generations, most of the lines were not significantly different from Vinton 81 for yield and protein percentage. Overall, only two lines were found that had greater yield and equal protein percentage to Vinton 81. Because the two superior lines identified came from the F(,4) generation, the single-cross method was favored over the backcross method in the development of productive soybean cultivars with high protein percentage;The efficiency of backcrossing in the transfer of Phytophthora resistance into susceptible cultivars was evaluated. A78-123018 and Cumberland were crossed to a resistant cultivar, Williams 82 and four backcrosses were made. The objectives of this study were to determine the number of backcross generations required to obtain Phytophthora resistant lines with the yield potential of the recurrent parent, and to determine in what backcross generation a composite of phenotypically similar lines could be made that would yield as much as the recurrent parent. Lines comprising the different generations were evaluated for yield and maturity in 1984;Significant variation among generations were observed for yield and maturity. Mean yields of the BC(,0) and BC(,1) generations were significantly lower than the mean yields of the BC(,2) and succeeding generations. Almost 100% of the lines from the BC(,2) and succeeding generations had yields equal to the recurrent parent. Comparable mean yield and maturity to the recurrent parent can be obtained from a composite of visually similar lines in the second backcross generation when a cultivar with acceptable yield is used as the donor parent

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

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

INHERITANCE PATTERN OF YELLOW FOLIAGE COLOUR AND ACTIVITIES OF TRANSPOSABLE ELEMENT IN COWPEA Vigna unguiculata (L.) Walp

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

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

Hybrid Decay: A Transgenerational Epigenetic Decline in Vigor and Viability Triggered in Backcross Populations of Teosinte with Maize.

In the course of generating populations of maize with teosinte chromosomal introgressions, an unusual sickly plant phenotype was noted in individuals from crosses with two teosinte accessions collected near Valle de Bravo, Mexico. The plants of these Bravo teosinte accessions appear phenotypically normal themselves and the F1 plants appear similar to typical maize × teosinte F1s. However, upon backcrossing to maize, the BC1 and subsequent generations display a number of detrimental characteristics including shorter stature, reduced seed set, and abnormal floral structures. This phenomenon is observed in all BC individuals and there is no chromosomal segment linked to the sickly plant phenotype in advanced backcross generations. Once the sickly phenotype appears in a lineage, normal plants are never again recovered by continued backcrossing to the normal maize parent. Whole-genome shotgun sequencing reveals a small number of genomic sequences, some with homology to transposable elements, that have increased in copy number in the backcross populations. Transcriptome analysis of seedlings, which do not have striking phenotypic abnormalities, identified segments of 18 maize genes that exhibit increased expression in sickly plants. A de novo assembly of transcripts present in plants exhibiting the sickly phenotype identified a set of 59 upregulated novel transcripts. These transcripts include some examples with sequence similarity to transposable elements and other sequences present in the recurrent maize parent (W22) genome as well as novel sequences not present in the W22 genome. Genome-wide profiles of gene expression, DNA methylation, and small RNAs are similar between sickly plants and normal controls, although a few upregulated transcripts and transposable elements are associated with altered small RNA or methylation profiles. This study documents hybrid incompatibility and genome instability triggered by the backcrossing of Bravo teosinte with maize. We name this phenomenon "hybrid decay" and present ideas on the mechanism that may underlie it

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

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