Efficiency Of Selection For Yield Research Articles

Relative Efficiency of Selection for Yield and Some Related Characters in Some Populations of Grain Sorghum Sorghum bicolor L. Moench)

Relative Efficiency of Selection for Yield and Some Related Characters in Some Populations of Grain Sorghum Sorghum bicolor L. Moench)

Efficiency of early generation selections for yield and related characters in safflower (Carthamus tinctorius L.)

The efficiency of early generation selection for yield and related characters in safflower (Carthamus tinctorius L.) was studied in the F2, F3 and F4 generations. Twenty-five F2 progenies derived from various crosses were studied. In the F2 generation, number of capitula per plant (CNSP), number of seeds per capitulum (SPSP), test weight (SWSP), and seed yield (SYSP) were the criteria used for single plant selection. The analysis of variance showed significant differences for all of the characters in the F2, F3, and F4 generations. The analysis of variance in each of the selection classes showed highly significant genotypic differences. A large number of selections in the CNSP and SYSP classes showed greater yield than the check variety. In each class the mean for that particular character showed a positive shift. The observed F3 and F4 means for seed yield per plant was higher in SYSP, indicating the effectiveness of single plant selection for yield. Correlated response showed that selection for number of capitula per plant was effective for improvement of yield.

The impact of genotype x soil texture interaction on the efficiency of selection for yield in maize (Zea mays L.)

This study was undertaken to investigate the implications of genotype x soil texture interaction on response to selection in maize. Mass honeycomb selection for yield was applied for 11 cycles from the F2 of the single cross maize hybrid F68×NE2 in a field B with silty-clay-loam soil texture. Response to selection compared to the original single cross hybrid was estimated both in absence of competition and under solid stand in the selection field B and in a nearby field A differing in soil texture (clay-loam).

Genotype × environment interactions in sugarcane. II. Use of performance in plant cane as an indirect selection criterion for performance in ratoon crops

This study aimed to determine whether sugar yield of sugarcane genotypes in the plant crop could be used to predict relative yield in subsequent ratoon crops. Results from two series of trials, planted in 1985 and 1986, were examined. Within each series genotypes were planted at four locations and evaluated in plant, first ratoon and second ratoon crops. The genotypes used had not been selected previously in the test environments. Genetic correlations between sugar yield in plant and ratoon crop-years were moderate to high (greater than 0.65) for most locations. The relative efficiency of selection for yield in ratoon crop-years via indirect selection in the plant crop-year averaged 0.67. Realized gains from selection were compared for selection based on only plant crop results and selection based on average performance across all crop-years (the latter being the method routinely used in sugarcane breeding programs at present). In most cases the increases in realized gains in yield across independent environments brought about by considering results from more than the plant crop-year were small or non-existent. In the two series of trials, 11 and 12 of the top ranking 15 genotypes, respectively, based on mean performance across all crop-years, were also in the top 15 genotypes based on only the plant crop results. It is suggested that the testing of genotypes in only the plant crop may be appropriate in the early stages of selection in sugarcane breeding programs. Resources otherwise allocated to testing early stage material in ratoon crops may be more usefully employed elsewhere such as testing in more sites, with more replicates or more genotypes. It is emphasized, however, that this strategy may not be appropriate for highly selected populations, such as those in the final stages of selection, where genetic variance and genetic correlations between crop-years would be expected to be smaller than those obtained in this study.

Biometrical analysis of alternative plot types for selection in rye

Maximizing the efficiency of selection for yield and baking quality of winter rye (Secale cereale L.) requires reliable knowledge on the pertinent population parameters. This study reports estimates of variances, heritabilities and genetic correlations from a) large (≈5 m2) drilled (LD) plots, b) micro drilled (MD) plots, and c) one-row plots of 4 spaced plants (SP). Thirty eight single crosses of rye were grown at two locations for two years in LD, MD and SP plots replicated 2, 4, and 6 times, respectively. Genotypic differences were significant in all plot types for all agronomic and quality traits, although estimates of genetic variances were smaller in LD than MD or SP plots for grain yield, 32-spike weight, and kernels per spike. Heritabilities on an entry mean basis (0.62 to 0.95) were similar among plot types, but on a single plot basis estimates were lower for SP than for MD or LD plots. Genetic correlations were high between all three plot types, with correlations between LD and SP plots being approximately 1.0 for falling number, thousand-kernel weight, and bloom date, 0.90 for grain yield, kernels per spike, test weight and height, and 0.70 for tiller number. Based on the high heritabilities achieved in small plots and the close agreement between MD- or SP- with LD-plot performance we conclude that greater use should be made of small plot types when selecting for yield and quality in winter rye.

Genetic parameters and selection efficiency using part-records for production traits in strawberries

The efficiency of selection for yield and fruit size using parts of the complete-season record was evaluated using data collected for individual strawberry seedlings (Fragaria x annanasa) in four genetic tests. Part-records were generated for each trait using cumulative weekly sums, and these were compared with complete records to assess the value of extended data collection. In addition, part-records were generated using data from alternate weeks of harvest. Scoring separate sets of seedlings in alternate weeks was assumed to allow a doubling of the unselected population size, halving the selection proportion and increasing selection intensity. Heritabilities estimated for part-records were often larger for mid-season cumulative part-records than for the complete-season records. Seasonal patterns for broad-sense and narrow-sense heritabilities differed, suggesting temporal expression of genes that condition yield and fruit size. Predicted genetic gains were largest using cumulative part-records between 4 and 12 weeks of the 15-week season, depending on trait and breeding objective (breeding value versus clonal value), with 8-9 weeks as a reasonable compromise. Selection using alternate-weeks records was identified as an efficient alternative to selection using total complete-season records. Superiority of the alternate-weeks option depends on the balance between increased selection intensity and decreased individual genetic information, and will differ for specific traits and program designs.

The effect of the weight of the seedling‐derived tuber on subsequent clonal generations in a potato breeding programme

SUMMARYTwo experiments are reported. In the first, the weight of seed tuber planted in the first clonal year was examined in relation to clonal performance in the first three clonal generations. The weight of seed tuber planted in first clonal year influenced breeders' preference scores and yield characteristics in the first, second and third clonal generations thus suggesting that size of tuber produced by seedlings is in part genetically controlled. The relationship between weight of seed tuber produced by seedlings and clonal performance was, however, reduced with increasing generations from true seed. In the second experiment, the size of seed tubers produced was manipulated by growing seedlings in different sized pots. When seedlings were grown in small pots (2.5 cm) first‐clonal‐year plants produced low yields of small tubers. In contrast, when larger pots were used to raise seedlings, first‐clonal‐year genotypes gave higher yields and were given greater preference scores. Hence, performance of genotypes in the first clonal year was dependent on the size of pot used to raise seedlings. After the first clonal generation however, clonal performance was not influenced by the size of pot used at the seedling stage. The overall conclusion was that, although the size of tuber produced by seedlings had a genetic component, the largest effect of seed tuber size used in the first clonal year was non‐genetic and would adversely influence efficiency of selection for yield, yield components and breeders' preference in the early generations of a potato breeding programme.

Accelerated pedigree selection: An alternative to individual plant selection in the normal pedigree breeding method in the self-pollinated cereals

Accelerated pedigree selection (APS) involves initial selection based on the assessment of lines rather than individual plants. These lines can be derived by accelerated generation procedures. Unlike single seed descent (SSD), line selection can begin in an early generation. This minimises the risk of differential mortality or sterility. Brief outlines of APS for spring and winter cereals are given. The length of the APS breeding cycle is shorter than that of either pedigree selection (PS) or SSD. In addition to higher efficiency of selection for yield, which must be offset against the need for greater resources, it is expected that APS should result in valuable genotypes being retained and better selection for desirable combinations of characters.