Genetic Variation among Robusta Coffee Genotypes for Growth and Yield Traits in Ghana

Quantifying the level of variation and estimates of genetic parameters are important to make informed decisions regarding the improvement of agronomic traits in Coffea canephora. The objectives of the present study were to assess the growth and yield performance of 54 C. canephora clones derived through ortet selection, based on yield from a previous hybrid trial; estimate genetic parameters of growth traits (stem diameter, height, span, number of laterals, length of laterals and diameter of laterals), and yield; and determine the relationship between yield and the growth traits. The clones were planted in the field in 2009 using a randomized complete-block design with three replications. Significant (p < 0.01) clone effects for all traits and broadsense heritability range of 0.15 (mean yield of last 3 productive years)-0.43 (diameter of laterals) were observed. Stem diameter was moderately and positively correlated with early years’ yield (2012/13 mean yield, r = 0.49; p < 0.001), late years’ yield (2014 to 2016 mean yield, r = 0.44; p < 0.001), and mean yield across five years (r = 0.42; p = 0.001). Relatively high genotypic coefficient of variation and expected genetic advance values were obtained for the evaluated traits, which indicated a high probability of success of selection for these traits.

VARIASI GENETIK, HERITABILITAS, TINDAK GEN DAN KEMAJUAN GENETIK KEDELAI (Glycine max Merrill) PADA ULTISOL

Information on genetic variation, heritability, gene action and genetic advance were important in the development of soybean varieties adapted on Ultisol. The objective of this experiment was to estimate genetic variation, hertability, gene action and genetic advance from the populaton used in breeding program. Six genotypes, i.e Dempo, Cikuray, Davros, Orba, Sindoro and Wilis were intercrossed using diallel Griffings’ Method 2 Model 1 (1956). These six genotypes and 15 F1 hybrids were planted on Ultisol using randomized complete block design with three replications located in Medan Baru village, Bengkulu city in 1999. The results of this experiment revealed that all traits showed low to high genetic variation, high broadsense heritability, low to high narrowsense heritability and genetic advance. Date of flowering and root length were fully controlled by additive gene action, however harvest index was fully controlled by negative dominant gene action and epistasis. Other traits were controlled by positive and negative partially dominant, and positive overdominant genes.

Heritability for Yield and Glycoalkaloid Content in Potato Breeding under Warm Environments

High temperatures affect potato production in the tropics, putting tuber yield and quality at risk and leading to increased glycoalkaloid concentration the cause of the bitter taste in potatoes and a cause for concern for human health. The International Potato Center (CIP), has developed new heat tolerant clones which are heat tolerant and also resistant to late blight. These clones offer an opportunity to evaluate yield and glycoalkaloid levels after growth under high temperature environments. We evaluated four sets of 16 full-sib families and 20 clones for tuber yield and glycoalkaloid content in order to estimate narrow-sense and broad-sense heritability respectively. We used a randomized complete block design replicated in three locations in Peru; San Ramon, La Molina and Majes At harvest, the number and weight of marketable and nonmarketable tubers were recorded. We analyzed samples of tubers from each clone for glycoalkaloid content using spectrophotometry. Narrow-sense heritability for tuber yield, tuber number and average tuber weight were 0.41, 0.50 and 0.83, respectively, indicating that further gains in breeding for heat tolerance will be possible. Broadsense heritability for glycoalkaloid content was 0.63 and correlation with tuber yield was weak, r=0.33 and R²=0.11 (P<0.01). High heritability and weak correlation will allow us to select clones with high tuber yield and low glycoalkaloid content, to serve as candidate varieties and parents in breeding programs.

Evaluasi Toleransi Plasma Nutfah Padi terhadap P Rendah di Tanah Sawah

<p>A field experiment was conducted to assess<br />genotypic variability of tolerance and to identify tolerant<br />genotypes to low phosphorus (P) among rice germplasm on<br />lowland (paddy) rice field with low available and potential P<br />using strip plot design with three replications. P fertilization<br />(with and without added P) was assigned as horizontal factor<br />and 120 rice plant genotypes as vertical factor. Data on plant<br />height, tiller number, and shoot dryweight were collected. Low<br />P tolerance was judged by relative value i.e. observation value<br />at the plot without P treatment devided by the value at the plot<br />with P treatment. The judgement was determined based on<br />IRRI standard. Shoot P uptake of five tolerant and five<br />sensitive genotypes on no added P treatment was also<br />observed. The results showed that the germplasm exhibited<br />phenotypic and genotypic variability of low P tolerance. The<br />highest genotypic variability of tolerance was shown by the<br />value based on relative tillering number (28.7%), followed by<br />that of relative shoot dryweight (22,6%) and relative plant<br />height (7,6%). The highest broadsense heritability of tolerance<br />was shown by the value based on relative tiller number<br />(24.1%), followed by that of relative plant height (16.6%) and<br />relative shoot dry weight (15.0%) Fourteen genotypes were<br />identified as highly tolerant based on relative tiller number and<br />28 genotypes based on relative shoot dryweight. The tolerance<br />of genotype was attained by higher P uptake and higher<br />internal use efficiency.</p>

Parameters in the estimation of the most suitable F2 population size in conventional maize (Zea mays L.) breeding programs

The objective of the present study was to observe differences among four sizes of the F2 populations (100, 200, 300 and 500 plants) on the basis of test-crosses for grain yield according to the average values of the populations, genetic and phenotypic variances, genotypic and phenotypic coefficients of variations and broad-sense heritability. The values of genetic variance did not significantly differ over population sizes according to all possible comparisons, including the comparison of values obtained for the phenotypic variance. Furthermore, the values of broadsense heritability (67.8%-69%) did not significantly vary over different F2 population sizes. Genetic variability of the observed progenies, as a principal prerequisite of successful selection, was at the satisfactory level in all population sizes.

Inheritance of Resistance to Sclerotinia minor in Selected Spanish Peanut Crosses1

TxAG-5, a sclerotinia resistant Spanish germplasm line released jointly by the Texas Agricultural Experiment Station, USDA, and the Oklahoma Agricultural Experiment Station, was crossed in reciprocal to two Spanish lines, Tx851856 and Sn73–30. Parent, F1, F2, BC1F1, and F3 populations were evaluated under high natural inoculum for resistance to Sclerotinia minor using a disease rating scale of 1 (no disease) to 5 (severely diseased), and the number of days from first appearance of the fungus until plant death was recorded. F2:3 families were compared for disease the following year for genotypic assessment of the F2 parents. F1 generation plants of the Sn73–30 cross were susceptible, but F1 plants from Tx851856 were intermediate. Some TxAG-5 succumbed to the disease. F2 distributions were continuous. F2 genotypic frequency distributions based on F3 and BC1F3 families were near continuous. Broadsense heritability estimates for disease ratings for TxAG5/Tx851856 and TxAG-5/Sn73–30 were 14 and 23%, respectively. Narrowsense heritabilities based on parent offspring regression of F3 families on F2 plants were 11% for Tx851856/TxAG-5 and 1% for Sn73–30/TxAG-5. Selection for resistance among the F2 plants to increase the frequency of resistant F3 families would have been ineffective.

Roasted Peanut Flavor Variation Across Germplasm Sources1

Roasted flavor is a critical factor in the acceptance of a peanut cultivar. A three-year study was made on the variation in roasted peanut flavor intensity of U.S. peanut cultivars and advanced breeding lines. An initial set of 83 entries was reduced to 71 by removing samples that showed evidence of extraneous environmental conditions, immaturity, and handling or improper sample preparation effects. All entries for the cv. New Mexico Valenicia C, representing the Valencia market type, were lost because of improper roasting or intense fruity flavor. Florigiant, Florunner, and Pronto were used as comparison standards for roasted peanut attribute values in evaluating the Virginia, runner, and Spanish market types, respectively. The positive estimated difference between control and test germplasm sources was largest within the Virginia type, with a least-square mean difference of +1.4 for roasted peanut attribute intensity. Spanish types were next with a positive estimated difference of +1.3, and runner types were lowest with a positive estimated difference of +0.5. Broadsense heritability for the roasted peanut attribute among germplasm sources was determined to be 24%, suggesting a potential for improving the roasted peanut attribute level through proper breeding stratagems.

Inheritance of Late Leafspot Resistance and Agronomic Traits in Peanut1

Twenty peanut (Arachis hypogaea L.) populations in F2 generation from an M x N mating design involving five late leafspot (Cercosporidium personatum)-resistant female parents and four adapted male parents were evaluated for late leafspot resistance with a detached leaf culture technique. Agronomic traits were evaluated in the field. Objectives were 1) to identify the best parent for agronomic traits and the best source of resistance to late leafspot, 2) determine the correlations among components of resistance, 3) determine the correlations of resistance and agronomic traits, and 4) estimate heritability of late leafspot resistance. General combining ability was highly significant for agronomic traits and for most measurements of late leafspot resistance. Specific combining ability was significant for pod length and seed size. Of the male parents, NC 6 and NC 7 produced the best progenies for both agronomic traits and late leafspot resistance. Components of resistance to late leafspot among resistant female parents were not significantly different. NC 17090 produced the best progenies for pod yield and seed yield. NC 17135 produced progenies with good agronomic traits. Correlations among components of resistance to late leafspot indicated that lines with increased latent period, decreased lesion number, lesion size and defoliation, and reduced spore production can be selected. However, high yielding plants tended to be susceptible to late leafspot. Broadsense heritability for components of resistance was low to moderate (0.13–0.68). Narrow-sense heritability for parameters of resistance was consistently low (0.0–0.128). Selection for late leafspot resistance in the F2 populations was not effective.

Variability for Seedling Vigour in Maize

SUMMARYConsiderable variation in seedling vigour was observed among 36 maize populations; genotypic variances were generally high for emergence percentage (E%), emergence index (EI), dry-matter accumulation and relative growth rate (RGR). Broadsense heritability values and environmental variances indicated that E% and EI would be more reliable indices for seedling vigour than emergence rate index (ERI). The expression of growth rate (GR) was influenced more by the environment than the genetic constitution of seedlings; GR was not therefore an effective indicator for seedling vigour, and RGR would be preferred because it was more heritable and less influenced by the environment.

Inheritance of Cowpea Yields under Different Soil Conditions in Papua New Guinea

SUMMARYBroadsense heritability, and correlations of grain yield and related characters, were estimated in three crosses under two levels of soil fertility, which profoundly affected heritability of height and seed weight. Grain yield exhibited heritability of 51–81%, and in one cross significant heterosis in F2. Amongst yield-related characters only pods/plant and seeds/pod were both correlated to yield, and also lacked negative genotypic correlations with other economic characters. However, direct selection for grain yield was considered more efficient than indirect selection using yield-related characters.