Broad-sense Heritability Estimates Research Articles

Selection Efficiency and Environmental Sensitivity for Agronomic Traits in A Bread Wheat Population under Normal and Late Sowing Dates Conditions کفاءة الإنتخاب والحساسیة للبیئة للصفات المحصولیة فی عشیرة من قمح الخبز تحت ظروف میعادی الزراعة العادی والمتأخر

The present study was carried out during seasons, i.e. 2017/18 to 2019/20 at Shandaweel Agric. Res. Stat., Sohag Governorate, Egypt. Two cycles of pedigree selection for grain yield plant-1 and number of spikes plant-1 from F2 to F4 generations were practiced under normal and late sowing dates. The genotypic variance was slightly less than the phenotypic variance under both environments and generally decreased from (F2) to F4 generation. After two cycles of pedigree selection, broad sense heritability estimates were 90.27% and 73.83% for grain yield plant-1 and 88.21% and 82.47% for no. of spikes plant-1 under normal and late sowing dates, respectively. Evaluation of the selected families for high grain yield plant-1 under normal sowing date showed significant differences 18.33% and 9.31% when selection was practiced under normal sowing date, and 20.60% and 11.83% when selection was under late sowing date from the bulk sample and the better parent, respectively. The average observed gains of the selected families for high no. of pikes plant-1 under normal sowing date and evaluated under both conditions were 13.53% and 17.74% from the bulk sample and 9.67% and 11.51% from the better parent under normal and late sowing dates, respectively. While when selection was under late sowing date were 12.68% and 17.80% from the bulk sample and 8.78% and 11.57% from the better parent under normal and late sowing dates, respectively. The antagonistic and the synergistic selection nearly have the same effect on the sensitivity to heat stress under the two selection criteria.

Genotypic Variability in Some Morpho-Physiological Traits in Different Environments and Their Relationship with Cassava (Manihot esculentaCrantz) Root Yield

Cassava root yield under diverse environments is influenced by morpho-physiological traits that are in turn influenced by genotype, environment, and genotype × environment interaction (GEI). Most GEI analyses in cassava have been limited to root yield with less emphasis on stability of other yield-related traits. This study was carried out to assess the effect of GEI on some morpho-physiological traits in cassava and key traits that are useful for selection in different environments. The study utilized 20 cassava genotypes evaluated in six environments, namely, Fumesua 2013 and 2014, Nyankpala 2013 and 2014 (irrigation), and Nyankpala 2013 and 2014 (no irrigation). The genotypes were arranged in a randomized complete block design (RCBD) with three replications and assessed for a number of morpho-physiological traits, root yield and yield components. The data were subjected to analysis of variance using SAS statistical package. Subsequently, the GGE biplot was used to carry out genotype × environment, genotype × trait, and environment × trait interaction analyses to determine the specificity of genotypic performance and traits linked to particular environments. The results indicated significant (P<0.05) GEI effect on all traits except leaf temperature. The genotype × trait biplot analysis revealed closely related traits and those associated with root yield and genotypes that show weakness in these traits. Both environment × trait biplot and principal component analyses identified traits with higher discriminatory power among genotypes in various environments particularly in the dry environments. These can be used as secondary traits to select drought-tolerant genotypes. From this study, the GGE biplot was useful in identifying traits associated with specific genotypes in different environments to aid in selection. Moderate broad-sense heritability estimates werefound for storage root yield, harvest index, plant height, ratio of storage rootlength to girth, and cassava mosaic disease score indicating that progresscan be made through selection for these traits.

Culture selected somaclonal variants showing low-ODAP and high protein content in nineteen grass pea (Lathyrus sativus L.) genotypes

To develop low-ODAP grass pea genotypes with high protein content, in vitro tissue culture techniques were used for inducing somaclonal variation through internode explants that was cultured on B5 medium containing 2 mg L− l α-naphthaleneacetic acid and 1 mg L− l 6-benzylaminopurine of 19 grass pea genotypes. The selected somaclones (R3 and R4 generations) were evaluated for variation in ODAP, protein, and quantitative agronomic traits. The results showed statistically significant (P < 0.001) genotypic differences for ODAP %, Protein %, 100-seed weight (HSW) and pod width (PODW) in the R4 somaclones under field conditions. The somaclones showed broad-sense heritability estimate of 0.14 ± 0.064 for ODAP%, 0.87 ± 0.015 for protein, 0.78 ± 0.025 for HSW and 0.13 ± 0.062 for PODW. Among the 270 somaclones, Sel462-5 was significantly superior to the parent and other somaclones in terms of ODAP content (0.13%), protein content (28.47%) and pod width (1.43 cm). The correlation coefficients between parents and somaclones for pod width with 100-seed weight, ODAP-clones and protein-clones were positive and significant. The superiority of somaclones for ODAP, protein, 100-seed weight and pod width in R4 generation opened the possibility for grass pea improvement through somaclonal variation. Induction of somaclonal variation in grass pea is an alternate approach to introduce new and desirable genetic variability in the cultivated gene pool.

Assessing genetic variation for Fusarium wilt race 4 resistance in tetraploid cotton by screening over three thousand germplasm lines under greenhouse or controlled conditions

Cotton (Gossypium spp.) is the most widely-grown natural fiber crop used by the textile industry. Fusarium wilt, caused by Fusarium oxysporum f. sp. vasinfectum (FOV) comprised of eight nominal pathogenic races, is one of the most destructive diseases in cotton. FOV race 4 (FOV4) is an emerging threat to cotton production in the US. In this study, a total of 3258 lines including 3080 Upland (G. hirsutum) and 178 Pima (G. barbadense) germplasm lines were evaluated in 21 tests under greenhouse or temperature-controlled conditions for resistance to FOV4. A total of 2224 lines from 13 tests were screened in a commercial potting soil in the greenhouse under higher temperature (HT) conditions (24–32 °C), while 1204 lines from 8 tests were screened in a naturally FOV4-infected farm soil at a lower temperature (LT) setting (20–21 °C), both with artificial inoculations. The 170 Pima lines were evaluated in both temperature regimes. The results showed that, at 30 days post inoculation, both temperature regimes produced similar disease incidence (81.2% for HT vs. 86.8% for LT), but LT caused significantly higher disease severity ratings (DSR, 3.86 vs. 1.94) and plant mortality (81.7% vs. 7.5%) than did HT. DSR and morality rate were highly significantly correlated (r = 0.849–0.941) at LT. Significant genotypic variations in DSR were detected in all studies except two, and the broad-sense heritability estimates for DSR were 0.59–0.83 with an average of 0.70 at HT and 0.61–0.72 with an average of 0.69 at LT, indicating that 70% the phenotypic variation in FOV4 resistance was determined by genetic variation. Using the naturally FOV4-infected farm soil and LT to screen 1034 Upland and 170 Pima germplasm lines (with 20–40 plants for each line) with artificial inoculations, 48% showed 100% mortality; 22% had a mortality rate between 70 and 99%; 5% had mortality below 30%; and 0.5% (6 lines) did not display any apparent FOV4 symptoms. The results indicated that many existing available germplasm lines may be heterogeneous for FOV4 resistance and pedigree selection within germplasm may increase frequencies of resistant plants. This study represents one of the first publicly reported large-scale screenings of cotton for FOV4 resistance in the US and provides useful information for breeding cotton with resistance to FOV4.

A multiethnic genome-wide analysis of 44,039 individuals identifies 41 new loci associated with central corneal thickness

Central corneal thickness (CCT) is one of the most heritable human traits, with broad-sense heritability estimates ranging between 0.68 to 0.95. Despite the high heritability and numerous previous association studies, only 8.5% of CCT variance is currently explained. Here, we report the results of a multiethnic meta-analysis of available genome-wide association studies in which we find association between CCT and 98 genomic loci, of which 41 are novel. Among these loci, 20 were significantly associated with keratoconus, and one (RAPSN rs3740685) was significantly associated with glaucoma after Bonferroni correction. Two-sample Mendelian randomization analysis suggests that thinner CCT does not causally increase the risk of primary open-angle glaucoma. This large CCT study explains up to 14.2% of CCT variance and increases substantially our understanding of the etiology of CCT variation. This may open new avenues of investigation into human ocular traits and their relationship to the risk of vision disorders.

Effects of drought on agronomic and fiber quality in an introgressed backcross inbred line population of Upland cotton under field conditions

Upland cotton (Gossypium hirsutum) is the most important fiber crop and an important oilseed crop in the world. Developing drought tolerant cultivars is important to sustainable cotton production in arid and semi-arid regions. However, there is a lack of information on genetic variation for drought tolerance in breeding populations. In this study, a backcross inbred line (BIL) Upland population with germplasm introgression from a more drought-tolerant American Pima cotton (G. barbadense) parent was evaluated in multiple field environments under well-watered (WW) and water-limited (WL) conditions at the flowering stage. Drought at the flowering stage reduced seedcotton yield (SCY), lint yield (LY), boll weight (BW), fiber length (FL), and fiber strength (STR) but increased lint percentage (LP), micronaire (MIC), neps per size, nep per gram, seedcoat nep size, and seed coat fragment count by gram. Significant genetic differences in the BIL population were detected for most agronomic and fiber quality traits and drought susceptibility index (DSI) for these traits. DSI of SCY and LY ranged from 0.01 to 1.5 and 0.1–1.45, respectively, reflecting the tolerance level of the BILs under WL conditions. The broad-sense heritability estimates were moderate for most agronomic traits and moderate to high for most fiber quality traits. Results indicated that highly positive correlation was detected for agronomic and fiber quality traits between WW and WL conditions, with the highest correlations for SCY, LY, UHM, SCY, and MIC. Promising BILs with drought tolerance were identified. This study has provided a line of evidence that field drought tolerance was transferred from the more drought tolerant Pima line to Upland cotton.

SELECTION AMONG SOME MELON STRAINS FOR TOLERANCE TO THE TWO-SPOTTED SPIDER MITE, Tetranych usurticae koch

This study was conducted during the period from 2016 to 2018. Seven different strains of melon (Cucumis melo L.) were tested for their response to Tetranychus urticae. Data revealed that, all plant growth parameters were affected significantly with infestation of T. urticae; leaf area which considered the main source of mite feeding was the most affected one. However, (L5) had the lowest leaf area (24.98 cm2 ) while (L7) recorded the highest leaf area (41.26 cm). Also, accumulated moving stages in (L2) showed the lowest population density with an average of 1.70 individual /in2 during 4 weeks, of season 2016. During season 2017, the highest leaf area was in hybrids (L4×L1) and (L4×L2) with an average 62.93 and 61.86 cm2 . All hybrids explained three levels of infestation; high level was observed in hybrids (L6×L2), (L5×L2) and (L7×L1) and accumulated the population density of moving stages with an average of 80.70, 70.60 and 61.40 individual /in2 . While medium level was recorded in hybrids (L5×L1 and L7×L2) and the third, low level of infestation was recorded in hybrids (L6×L1, L4×L1, L3×L2, L3×L1 and L4×L2) and moving stages average were 2.70, 3.30, 3.70, 3.90 and 5.30 individual /in2 so these hybrids were resistant to infestation of T .urticae . Regarding horticultural characters obtained data on total yield ranged from 4015.0 to 2185.0 g/plant; (L4) gave the highest value of total yield. Estimates of broad sense heritability were high for all studied traits indicating minor role of the environment. The results showed significant and highly significant mean squares for both general combining ability and specific combining ability in all studied traits, indicating the important role of both additive and non-additive gene effects in the expression of these traits. Highly significant SCA effects in all studied traits were recorded for the crosses (L3×L2), (L5×L2), (L6×L2) and (L3×L1).

Combining Ability Analysis of Dry Matter Content, Reducing Sugars and Yield of Potato (Solanum tuberosum L.) Genotypes in Uganda

Potato (Solanum tuberosum L.) in Uganda is a major food and cash crop mainly grown in the highland regions by small-scale farmers. The increasing importance of potato as a processed product requires new varieties possessing quality processing attributes with acceptable yield. The objectives of this study were to estimate the combining ability effects for dry matter content, reducing sugars, and yield related traits in potato. Nineteen F1 families generated from eight parents using a half diallel mating design were evaluated for dry matter content, reducing sugars, average weight per tuber and total tuber yield at Kachwekano research station. Additive genetic effects were predominant for dry matter content while non-additive effects for the other traits. The GCA/SCA ratios were 0.58, 0.28, 0.17 and 0.44 for dry matter content, reducing sugars, average weight per tuber and total tuber yield respectively. Broad sense heritability estimates were 50.6% for dry matter content, 77.8% for reducing sugars, 90.3% for average weight per tuber and 29.5% for total tuber yield. Parents NAROPOT 3 and 395096.2 had desirable GCA effects for both dry matter content and reducing sugars. Families of nkrk19.17 x Rutuku had desirable SCA effects for dry matter content while Rutuku x 393077.54 and nkrk19.17 x 392657.8 had desirable SCA effects for reducing sugars. Additive genetic effects for dry matter content imply that, genetic gains can be achieved through different selection methods and trait transferred to the respective progenies. The selected parents and families will be subjected to further clonal evaluation and selection.

Mixed models and multivariate approach applied to maize breeding: A useful tool for biofortification

Biofortification and bioactive compounds enrichment of maize genotypes is a great alternative for mitigating micronutrients deficiency in human and animal diet, and also for improving the benefits of maize for human health. This work aimed to estimate variance components and genetic parameters of bioactive compounds and micronutrients to predict superior maize hybrids from different genetic bases, and to apply the RELM/BLUP methodology to multivariate techniques. The inbreed lines were crossed and the F1 hybrids were grown for evaluations in 2014/2015 and 2015/2016 growing seasons, respectively. Then, micronutrients and bioactive compounds related traits were evaluated. The variance components and genetic parameters were estimated by REML methodology. The BLUP methodology was employed to predict genetic values and to verify the percentages of genetic gain with selection. The predicted genetic values were applied to estimate genetic distances by the Mean Euclidean Distance. The relative contribution of each trait to genetic divergence was evaluated and the principal components analysis determined, proposing the genotypes that are potentially capable to increase a given trait. The presence of genetic variability was evidenced among genotypes, while some of them presented potential for increasing specific traits. The top cross hybrid L64XAS1590 showed the highest estimates for increasing antioxidant-responsible traits, and micronutrients contents such as manganese, cooper, iron and zinc. In general, there was the possibility of achieving genetic gains with selection under application of biofortified and bioactive compounds to enhance maize hybrids through conventional breeding. However, it does not applicable for iron content due to its low estimate of broad sense heritability.

Genetic Variability, Heritability and Genetic Advance Among Bread Wheat Genotypes at Southeastern Ethiopia

The knowledge of nature and magnitude of variation existing in available breeding materials is great importance for successful selection of varieties. This study was conducted to generate information on the extent of genetic variability in advanced bread wheat lines. Thirty bread wheat genotypes were tested at Sinana and Agarfa, Southeastern Ethiopia, in alpha lattice design with three replications. Combined over locations ANOVA was carried out for yield and yield related traits. There were highly significant differences among genotypes for all traits. Highly significant location effects at P < 0.01 were observed for yield and yield related except for harvest index which showed significant effect at P < 0.05 and grain yield non-significant location effect. This indicates the presence of variability for these characters among the tested genotypes. In combined analysis, grain yield had high PCV (27.1%) and moderate GCV was observed for biomass weight, grain yield and harvest index. Phenotypic coefficient of variance (PCV) moderate for biomass weight and harvest index. Heritability estimates in broad sense (H2) was very high for most of the characters except for grain yield (52.3%) and number of kernel per spike (73.2%). However, low GAM was observed for most of the characters except moderate GAM was observed for harvest index (15.9%). Finally, the presence of variability among the genotypes, performance of heritability and GAM in the tested traits of the genotypes confirmed possibility to increase wheat productivity. Hence, selection and hybridization on those genotypes can be recommended for farther yield improvement of bread wheat.

Genetic control of traits related to maturity in cowpea

Abstract The aim of this study was to investigate genetic control of the traits number of days to flowering (NDF) and number of days to maturity (NDM) in a cowpea cross. Genetic parameters were estimated in segregating and non-segregating generations of a cross between two contrasting cowpea genotypes (MNC05-828C-1-9-1 × MNC04-792F-146). No evidence for maternal effect was found for either trait. Broad and narrow sense heritability estimates were above 50%, allowing genetic gains from selection of plants in the F2 generation. High significance of additive gene effects and low contribution of dominance and epistatic effects were detected for both traits. The estimated number of genes controlling the traits was around 4 for NDF and 5 for NDM. The results suggest that early-maturing cowpea self-fertilized cultivars can be developed through standard breeding approaches, meeting the demands of modern agricultural systems for more crop seasons per year and mechanized harvesting.

Optimising the number of test sites, crop-years and replications to maximize post-release testing efficiencies

The South African sugar industry develops commercial sugarcane cultivars across multiple testing sites, crop-years and replications. The extent of such parameters has not been well quantified for optimum breeding and resource allocation. The objective of this study was to identify the optimum number of testing sites, crop-years and replications needed to maximize efficiency of post-release cultivar evaluations in South Africa. Ten commercial sugarcane varieties were evaluated in randomized block designs across five regions tested over five crop cycles. The study was conducted from the main plant to third ratoon crops across the locations. The general linear model was used to estimate variance components. Genotype × location (G×L) interactions were significant (p ≤ 0.01) for cane yield (TCANE), estimated recoverable crystal content (ERC), sugar yield (TERC) and fibre (F). Tonnes of estimated recoverable crystal were highly influenced by G×L interaction, suggesting that evaluating cultivars across locations is essential. High broad sense heritability estimates were observed for TCANE (71.17%), ERC (97.11%) and F % (93.11%), implying that these traits were genetically controlled. The G×L and G×L×C variances were the largest source of variation, suggesting that the evaluation of sugarcane cultivars across locations as opposed to crop cycles would be essential.

LINE X TESTER ANALYSIS FOR YIELD COMPONENTS AND FIBER PROPERTIES IN SOME COTTON CROSSES OF (Gossypium barbadense L.)

The present study was carried out at Sakha Agricultural Research Station, Cotton Research Institute, Agricultural Research Center, Egypt, during 2017 and 2018 seasons. This investigation was carried out to estimate heterosis, combining ability, proportional contributions, genetic components and heritability estimates of some characters for six Egyptian cotton varieties as lines i.e, Giza 90, Giza 95, Giza 86, Giza 94, Giza 92 and Giza 96, while, the other five genotypes used as testers were Karshenky, Suvin, Australy 13, Pima S7 and Pima S6, using line x tester analysis. In 2018 season a randomized complete blocks design with three replications was carried to evaluate all genotype (eleven parents and their 30 F1s crosses) for some genetic parameters.The results indicated that mean squares due to the genotypes, parents, crosses and parents vs. crosses were significant and highly significant for all traits studied, except No. of bolls/plant in the parents, lint percentage in the crosses and fiber strength in the crosses and parents vs. crosses. The mean squares due to lines were significant for all studied traits. Mean square for testers and Line x Tester were significant for most traits studied. The following crosses demonstrated the best heterosis relative to mid- and better-parent, i.e, Giza 95 x Karshenky, Giza 95 x Australy 13 and Giza 95 x Pima S7 for most traits studied, while the following crosses demonstrated the best heterosis relative to mid- and better-parent for most studied yield traits, i.e. Giza 90 x Australy 13 and Giza 86 x Karshenky. The crosses Giza 92 x Karshenky, Giza 92 x Australy 13, Giza 92 x Pima S7, Giza 96 x Suvin and Giza 96 x Pima S7 were the best heterosis relative to mid-parent for most studied fiber traits. The results revealed that the line Giza 95 was significant and positive desirable GCA effects for all yield traits. Giza 92 had significant and positive desirable GCA effects for seed index and fiber strength and negative desirable for micronaire reading Giza 96 had significant and positive desirable GCA effects for fiber strength and negative desirable for micronaire reading. In this respect, the results of testers showed that Australy13 had significant and positive desirable for No. of bolls/plant, seed cotton yield/plant and lint cotton yield/plant. However, estimates of specific combining ability (SCA) effects for the crosses Giza 90 x Karshenky, Giza 95 x Pima S7, Giza 92 x Karshenky and Giza 96 x Suvin were significant desirable SCA effects for some yield traits. Proportion contribution of testers contribution was higher than lines contribution for all traits studied except No. of bolls/plant. However proportion contribution of lines x testers interaction was higher than of lines and testers for most traits studied. The non-additive of genetic parameters were larger than additive genetic variance with respect to all studied traits. Broad sense heritability (h2b%) estimates were larger than the corresponding values of narrow sense heritability (h2n%) for all traits studied. The highest broad sense heritability estimates was observed in case of lint percentage with values of 71.70% and the lowest was for uniformity index with value of 27.55%, while for narrow sense heritability, it ranged from zero to 4.37% for boll weight and lint index, respectively. Generally, Giza 95 and Australy13 could be used in breeding programs for improving high yielding varieties, while Giza 92 and Giza 96 could be considered as excellent parents for breeding programs to produce new varieties characterized with best fiber properties.

Genetic variability, heritability and genetic advance in cucumber (Cucumis sativus L.)

Genetic variability in a crop population is important for successful plant breeding. Eight cucumber (Cucumis sativus L.) genotypes namely Green Long, Simran, Bhaktapur Local, Saihni-2, Ninja-179, Garima, Farmer’s variety and wild genotype were evaluated at Lamahi Municipality, Dang district of Nepal to estimate the magnitude of their genetic variability and heritability. Analysis of variance revealed significant differences among genotypes for growth and yield traits. The estimates of genotypic coefficient of variation (GCV) and phenotypic coefficient of variation (PCV) were highest for weight of fruit whereas traits namely fruit length, fruit diameter and days to maturity had medium value for both GCV and PCV. Broad sense heritability estimates ranged from 0.74 for fruit diameter to 0.98 for days to germination. Fruit yield showed high significant positive correlation with fruit diameter (r= 0.649) and negative significant correlation (r= -0.538) with days to flowering. Traits namely weight per fruit, days of germination, no. of flower and days to flowering can be used effectively in selection process of crop improvement program as they had high GCV, PCV and heritability along with high genetic advance as percentage of mean.

Genetics of Inheritance and Interrelationship of Various Agronomic Traits of F2 Population in Cotton (Gossypium hirsutum L.)

Background: Cotton (Gossypium hirsutum L.) is grown in more than sixty countries worldwide. It is an important fiber crop in the world. It plays a vital role in our national economy being the source of earning of foreign exchange, therefore, it is considered to be the backbone of the economy of Pakistan. In Pakistan, millions of families are associated with cotton and textile industry for their livelihood.&#x0D; Results: In this experiment F2 population of the cross L. A. Frego Bract x CIM-600 and their parents was sown in randomized complete block design with three replications during normal growing season of the year 2014 to sort out best performing genotypes for yield related traits. Analysis of variance (ANOVA) revealed that parental and their F2 population showed significant differences for all the observed agronomic traits (plant height, number of monopodia branches, number of sympodial branches, number of bolls per plant, boll weight, ginning out turn, bract type, boll shape, beak size, seed cotton yield, staple length, fiber strength and fiber fineness). Estimation of correlation revealed that seed cotton yield was found positively correlated sympodial branches, fiber fineness and boll weight while ginning out turn, bract type, beak size, staple length and fiber strength were negatively associated with seed cotton yield. Epistasis was not found to be involved in any of the traits.&#x0D; Conclusion: The correlation and genetics study of various yield related traits provides us useful information for effective selection and sustainable breeding programs. Estimation of broad sense heritability ( ) in F2 populations for different traits vary as following order; ginning out turn&gt;plant height&gt;seed cotton yield&gt;sympodia branches&gt;fiber length&gt;fiber strength&gt;bolls per plant&gt;monopodia branches&gt;boll weight&gt;fiber fineness with heritability 0.90, 0.79, 0.78, 0.75, 0.73, 0.71 0.67, 0.64, 0.63 and 0.50 respectively. Results suggested form heritability and correlation that these traits can be improved either through appropriate selection method or hybrid breeding programme.

Genetic Variability of Agronomic Traits as Potential Indicators of Drought Tolerance in Common Beans (Phaseolus vulgaris L.)

Sixteen progeny lines of common beans obtained from single crosses made between two parents, GLP2 and KAT B1, were grown in randomized complete block design in a rainout shelter at the Agricultural and Mechanization Research Institute, Machakos, Kenya. The experiment was conducted to study inheritance of traits associated with drought stress adaptation and to establish if significant variation for those traits was existing in order to carry out selection for drought tolerance. The calculated mean values were used to estimate heritability, genetic advance, and correlation study for each trait. Water stress had a significant (p≤0.01) effect on the number of pods per plant, grains per plant, 100-seed weight, and yield per plant. The highest values for genotypic coefficient of variation (36.11%) and phenotypic coefficient of variation (36.70%) were recorded for pods plant-1 under stress condition. Highest broad-sense heritability estimates (96.54%, 94.97%, and 93.16%) coupled with high genetic advance as percent of the mean (22.32%, 34.97%, and 26.32%) were obtained for the number of pods plant−1, days to maturity, and yield plant−1, respectively, showing that selection of these traits together could lead to yield improvement under stressed conditions. Harvest index showed a significant and positive relationship with biomass aboveground (r=0.86) and the number of pods plant−1 (r=0.86) indicating the possibility of identifying high performing lines of common beans for drought stress environment for further studies on these traits.

GENETIC ANALYSIS OF SOME ECONOMIC CHARACTERS IN PEA

These experiments were carried out at Kaha Vegetable Research Farm, Qalubia Governorate, Horticulture Research Institute during the period from 2013 to 2016 to study the inheritance of some garden pea ( Pisum sativum L.) economic characters, viz ., plant length, number of days to flowering, green pod yield/plant, number of pods/plant, number of seeds/pod and shelling percentage. Four garden pea crosses, viz., Master × PS 210713, Master × Sugar gem, Victory freezer × Sugar gem and Victory freezer × 6-Lebanon and their reciprocals were produced. Then, parents, F1, F1r, and F2 populations of each of the four crosses were cultivated on mid October, 2015 in a randomized complete block design (RCBD). The aim of this study was to determine genetic analysis of some economic traits in garden pea. Knowledge about genetics of particular traits is helpful to plant breeder before planning a successful breeding program. Obtained results show that maternal effect was not observed in any cross for all studied traits. Over-dominance or complete dominance was detected for high shelling percentage trait in all studied crosses. High plant length, earliness, high yielding, high no. of pods/plant and high no. of seeds/pod were dominant in some studied populations and contrary were found in others. Positive heterosis over better parent (based on early flowering parent) was noted in all studied populations for earliness and shelling percentage traits, however, negative heterosis was found in all studied populations for other traits. Minimum number of genes (MNG) was 1-5 for plant length, 1-3 for number of days to flowering, 3-4 for green pod yield/plant, 4-10 for number of pods/plant, 1-4 for number of seeds/pod and one gene for shelling percentage. Broad sense heritability (BSH) estimates were 45.52-82.47% for plant length, 65.18-90.11% for number of days to flowering, 77.12-96.10% for green pod yield/plant, 60.60-88.86% for number of pods/plant, 68.20-80.95% for number of seeds/pod and 72.21-74.91% for shelling percentage. The previous results indicate that all studied traits except no. of pods/plant are controlled by one to few numbers of genes and had moderate to high heritability, so the selection for these traits can be preferred in the early generations.

Morphological traits based genetic diversity assessment of Ethiopian potato [Plectranthus edulis (Vatke) Agnew] populations from Ethiopia

Ethiopian potato syno Ethiopian dinich [Plectranthus edulis (Vatke) Agnew], is one of the ‘orphans’ and ‘neglected’ indigenous edible tuber crops in the country. Nowadays, the crop, both the cultivated and wild forms, are close to total extinction partly because of climate change, habitat instability, and very little research intervention targeting its improvement and conservation. Hence, in the present study, we intended to generate baseline information through morphological traits based genetic diversity estimation that is useful for improvement and conservation actions. We tested 174 populations at three experimental locations using alpha lattice design with two replications/location and three blocks/replication/location following appropriate management practises. Data were recorded for 12 qualitative and 16 quantitative traits and analysed using Statistical analysis software 9.0, MINITAB® 14.13 and FigTree v1.4.3 packages. A wide range of variations and mean performance values have been recorded for the phenetic traits, suggesting the existence of considerable variations for use in breeding and conservation. Analysis of variance revealed a highly significant (p < 0.001) variation among the populations and non-significant environment-population interaction for most of the quantitative traits, implying the minimal environment effect on their expression. High genotypic coefficients of variation, coupled with a high estimate of broad sense heritability and high genetic advance as a percent of population mean, were observed in tuber weight per hill, number of primary branches per plant, tuber number per hill and number of plants per hill with eventually large magnitude of positive phenotypic and genotypic correlation with tuber yield per hectare. This result suggests importance of the traits in selection program that targets tuber yield improvement. Principal components analysis revealed about 77% of the total variation for the first six principal axes with high factor loadings again from the same traits. The populations were grouped into four clusters but weak region (zone) of origin-based pattern implying the historical or contemporary gene flow, specially germplasm (tubers) exchange among the regions (ethnicities). In general, there is high genetic-based variability for Ethiopian potato improvement and conservation. However, more collections and evaluation over multiple locations and seasons are recommended for well-refined genetic diversity estimation.

Whitefly resistance in African cassava genotypes

Whitefly ( Bemisia tabaci ), a major pest and vector of viruses in cassava, is the greatest current threat to cassava production in sub-Saharan Africa (SSA). Research efforts have focused on management of the two viral diseases: cassava mosaic disease (CMD) and cassava brown streak disease (CBSD), and have ignored the whitefly vector that is driving the spread of the viruses, causing CMD and CBSD in SSA. The objective of this study was to evaluate cassava genotypes for resistance to B. tabaci based on field infestation and damage in Uganda. The study was carried out in four sites with diverse agro-ecologies including: Namulonge, Kasese, Ngetta and Serere during 2015 and 2016.Whitefly nymph abundance and feeding damage were assessed on each test genotype from 3 to 6 months after planting (MAP). In 2015, the highest broad sense heritability estimates were 39% (4 MAP) and 53% (5 MAP) for whitefly nymph abundance and feeding damage, respectively. In 2016, broad sense heritability estimates were 23% (3 MAP) and 41% (4 MAP) for whitefly nymph abundance and feeding damage, respectively.Analysis of variance of whitefly nymph abundance showed a significant (P< 0.05) location × genotype × season interactions at 3, 4, 5 and 6 MAP. There were also significant (P< 0.05) location × genotype × season interactions at 3 and 4 MAP for whitefly feeding damage. Ten genotypes showed good levels of resistance to whitefly infestation and feeding damage including: UG120202, UG120174, NASE13, UG120160, UG120286, UG120293, UG130075, CSI-142, CS1-144 and UG130085. These genotypes may serve as parental materials for breeding programmes for whitefly and viral disease control. Key words: Bemisia tabac i, cassava brown streak disease, cassava mosaic disease

Estimates for heritability and consumer-validation of a penetrometer method for phenotyping softness of cooked cassava roots

Although breeders have made significant progress in the genetic improvement of cassava (Manihot esculenta Crantz) for agronomic traits, lack of information on heritability and limited testing of highthroughput phenotyping methods are major limitations to improving root quality traits, such as softness after cooking, which rank high among Ugandan consumers. The objectives of this study were to determine heritability for softness of cooked cassava roots, and quantify the relationship between penetrometer and consumer testing methods for phenotyping softness of cassava roots. Softness defined as the maximum force (N) needed to penetrate cooked root samples using a penetrometer, was evaluated at four cooking time intervals: 15, 30, 45, and 60 min on 268 cassava genotypes. Estimates of broad-sense heritability (repeatability) ranged from 0.17 to 0.37, with the highest value observed at 45 min of cooking time interval. In the second study involving 135 cassava consumers from Kibaale district in Uganda, penetrometer measurements of cooked roots from six cassava varieties were found to be in strong agreement (r2 = 0.91; P-value = 0.003) with ordinal scores of root softness from consumer testing. These results suggest that: (a) softness of cooked cassava roots is a trait amenable for evaluation and selection; and (b) a penetrometer can readily be used for assessment of cooked root softness. These findings form the basis for operationalising the routine assessment of root softness in cassava breeding trials, an output that will enhance ongoing efforts to breed for desired end-user root quality traits.