P1 Generations Research Articles

Grain Appearance Quality of Parental and \(F_2\) Segregating Populations of Aus Rice (Oryza sativa L.)

Longer grain length with smaller grain breadth, length-breadth ratio and 1000-grain weight is considered desirable character for the development of fine grain premium quality rice. In the present experiment, grain appearance quality of 15 F2 families and 10 parental genotypes were determined to select fine grain rice. The maximum mean value for thousand seed weight was found from the genotypes P2 (29.32g), P1 (28.89g), and F2 generations of P2 x P5 (32.77g), P2 x P1 (27.30g), P1 x P4 (26.04g) and were considered as high yielders in terms of grain weight. The highest mean values for grain length were found from the genotypes P6 (9.95 mm; grain breadth 2.23 mm), P7 (9.36 mm; grain breadth 2.62 mm), and F2 generations of P6 x P7 (9.46 mm; grain breadth 2.44 mm), P3 x P6 (9.40 mm; grain breadth 2.18 mm), P7 x P6 (9.37 mm; grain breadth 2.29 mm), P7 x P3 (9.36 mm; grain breadth 2.33 mm). The F2 progenies of the cross P1 x P4 (7.79 to 11.61 mm) and P6 x P3 (7.69 to 11.11 mm) showed extremes performance for grain length indicating transgressive segregation for this trait. The superior genotypes with desirable grain characters could be selected from transgressive segregation of F2 families for the development of new varieties of fine grain rice.

Differences in endocrine and reproductive responses to substance exposure across generations: highlighting the importance of complementary findings

This article analyzes the results from 112 Extended One-Generation Reproductive Toxicity studies. The objective was to determine if test animals show consistent endocrine and reproductive effects within the same and across different generations and life stages. The analysis, grounded in a comprehensive Binary Matrix, included 530 observed effects and 193 unique, statistically significant associations. Associations’ strength was quantified using Jaccard (J) coefficients to measure effect co-occurrence in the same study. Associated effects co-occur infrequently across the whole dataset (median J = 0.231). However, specific patterns emerged: associations of same effects across generations exhibited a higher strength (median J = 0.400) compared to associations of different effects (median J = 0.222). Notably, associations with effects observed in both the parental animals of the adult first filial generation (P1) and developing second filial generations (dF2) demonstrated J coefficients (with medians ranging from 0.300 to 0.430) that were approximately twofold higher than those of other associations. Consistently, equivalent life stage associations across generations revealed statistically significant higher association strengths for the P1 and dF2 generations (medians of 0.375 and 0.333, respectively) compared to other generations (medians of 0.200 and 0.174), possibly due to longer exposure duration and altered cross-talk between pregnant P1 dam and its conceptus. Overall, it is concluded that co-occurrence of associated effects in the same study is rather infrequent and that associations with effects in P1 and dF2 are stronger than all other associations. In general, the findings underscore the importance of independently analyzing each effect per generation due to the generally low co-occurrence rates of associated effects, challenging traditional expectations of generational continuity in toxic effects.

Characterization and identification of primarily cultured astrocytes and microglia

The aim of this study was to investigate the growth characteristics of primarily cultured astrocytes and microglia of different generations and then optimize the method for obtaining primary astrocytes and microglia effectively. Primarily cultured microglia were isolated and purified from the cortices of neonatal mice. The proliferation curve of mixed glia cells was measured by Cell Counting Kit-8 (CCK-8) assay, the proportion of astrocytes and microglia was detected by flow cytometry, and the polarization of the two types of glia cells was identified by immunofluorescence staining. Cell growth results showed that the mixed glia cells of P0 and P1 generation had the best proliferative activity; 97.3% of the high purity microglia could be obtained by mechanical shaking at 170 r/min for 30 min, and there was no significant difference in the morphology of ionized calcium-binding adapter molecule 1 (Iba-1) positive microglia and the proportion of M1 and M2 phenotype among the P0, P1 and P2 generations of microglia isolated by the above methods. Moreover, 95.7 % of the high purity astrocytes could be obtained by astrocyte cell surface antigen-2 (ACSA-2) magnetic beads separation, and there was no significant difference in the morphology of glial fibrillary acidic protein (GFAP) positive astrocyte and the proportion of A1 and A2 phenotype among the P0, P1 and P2 generations of astrocyte isolated by the above methods. Taken together, this study observed the growth characteristics of primarily cultured microglia and astrocyte in vitro, and then proved the best generations for purifying microglia and astrocytes. Finally, we optimized the methods of obtaining microglia and astrocyte, and verified that continuous culture within 2 generations will not affect the functional phenotypes of glia cells. These results provide technical support for studying the molecular mechanism of inflammation-associated diseases in nervous system.

A Study of External Ear Morphological Variation in Central Indian Population for Genealogical Purposes

The study aims to determine the inheritance pattern of different morphological features of the external ear in three generations from five states of India to assess the similarities between P1, F1, and F2 generations. The research involved 62 families, each with 124 grandparents P1 (62 males and 62 females), 124 parents F1 (62 males and 62 females), and 82 F2 generations (53 males and 29 females), a total of 330 samples, ranging in age from 1 to 75 years. All the samples were collected from five different states of India: Uttar Pradesh, Madhya Pradesh, Rajasthan, Bihar and Maharashtra. The external ear is distinct in terms of shape, size, and orientation. Its morphological variation aids in the determination of genetic inheritance. Fisher exact test was performed to assess the inter-generation association of morphological characteristics of the ear. Similar to other body characteristics, it is established that the auricle shape, lobule shape, and ear lobule attachment are also inherited. The associations of ear traits in three generations were studied, and the results might be used in forensic identification.

STUDIES ON INHERITANCE OF BACTERIAL WILT RESISTANCE IN TOMATO CROP CAUSED BY Ralstonia solanacearum (E.F. SMITH)

The study aimed at the inheritance of bacterial wilt resistance in tomato with six different generations (P1, P2, F1, F2, BC1 and BC2) obtained by 4 crosses (Susceptible X Resistant). Two susceptible cultivars (Arka Meghali and Arka Vikas) and two resistant lines (H-7996 and H-7997) of tomato were crossed during kharif , 2020 in four possible combinations to generate the experimental material. The P1, P2, F1, F2 BC1 and BC2 generations of 4 crosses were screened for bacterial wilt caused by Ralstonia solanacearum (E.F. Smith) in tomato research fields of Monsanto Holdings Private Ltd., Kallinayakana Halli village, Gauribidanuru Taluka, Chikkaballapura District, Karnataka to understand the mode of inheritance. Single dominant gene controlling the resistance to bacterial wilt was observed in two crosses between Arka Meghali x H-7996 and Arka Vikas x H- 7997. Chi-square test for goodness of fit indicated that the F2 is segregating in the ratio 3 resistant to 1 susceptible in the single gene model. Resistant to susceptible ratio in BC2 was 1:1. While, in the crosses between Arka Vikas x H-7996 and Arka Meghali x H-7997 the complimentary gene interaction was observed with the F2 expected ratio of 9:7 indicating duplicate recessive epistasis.

Evaluation of P1, P2, F1, F2, B1 and B2 generations of LM 95 × EC 362096 cross of mung bean for yield and yield attributes along with water use efficiency and heat stress tolerance related traits using generation mean analysis

In mung bean, limited work has been done on yield attributes along with water use efficiency (WUE) and heat stress tolerance related traits. Realizing the significance of drought and heat stress on yield components, there is need to enhance the genetic potential of mung bean genotypes with high yield and drought and heat stress tolerance. The experimental material comprising six populations viz P1, P2, F1, F2, B1 and B2 of the cross LM 95 × EC 362096 was grown at the dryland farm of SV Agricultural College, Tirupati, Andhra Pradesh during rabi 2017 in compact family block design with two replications. The mean data obtained from six generations (P1, P2, F1, F2, B1 and B2) of selected superior cross LM 95 × EC 362096 for yield, yield components, WUE and heat stress tolerance related traits were subjected to generation mean analysis. Partitioning of generation means into six components revealed that the component mean [m] was positive and highly significant for all the traits. The results of scaling tests revealed that additive-dominance model was not sufficient to explain the inheritance of the characters studied. The inadequacy of additive-dominance model suggested the possible involvement of di-genic or higher order epistatic gene action in the expression of all the traits. It also indicated the presence of positively significant proportion of epistatic {[i], [j] and [l]} effects besides main {[d] and [h]} effects for yield, yield attributes, WUE and heat stress tolerance related traits. The findings divulged that both additive and the dominance components were important in the inheritance of yield, WUE and heat stress tolerance related components.

Glypican 4 Regulates Aβ Internalization in Neural Stem Cells Partly via Low-Density Lipoprotein Receptor-Related Protein 1.

Neural stem cell (NSC) damage has been reported in patients with Alzheimer’s disease. Intracellular Aβ plays a vital role in NSC damage. Heparan sulfate proteoglycans are potent mediators of Aβ enrichment in the brain. We hypothesized the heparan sulfate proteoglycan glypican 4 (Gpc4) regulates Aβ internalization by NSCs. We evaluated Gpc4 expression in NSCs from P0–P2 generations using immunofluorescence. Adenovirus and lentivirus were used to regulate Gpc4 expression in NSCs and APP/PS1 mice, respectively. Co-immunoprecipitation was used to determine the relationship between Gpc4, Aβ, and low-density lipoprotein receptor-related protein 1 (LRP1). Intracellular Aβ concentrations were detected using enzyme-linked immunosorbent assay and immunofluorescence. The role of Gpc4/LRP1 on toxic/physical Aβ-induced effects was evaluated using the JC-1 kit, terminal deoxynucleotidyl transferase dUPT nick end labeling, and western blotting. Gpc4 was stably expressed in NSCs, neurons, and astrocytes. Gpc4 was upregulated by Aβ in NSCs and regulated Aβ internalization. Gpc4 attenuation reduced Aβ uptake; Gpc4 overexpression increased Aβ uptake. Gpc4 regulated Aβ internalization through LRP1 and contributed to Aβ internalization and toxic/physical concentrations of Aβ-induced mitochondrial membrane potential and cell apoptosis, partly via LRP1. Therefore, Gpc4 is a key regulator of Aβ enrichment in NSCs. Inhibiting Gpc4 rescued the Aβ-induced toxic effect and attenuated the nontoxic Aβ enrichment into intracellular toxic concentrations. Gpc4 contributed to Aβ internalization and toxic/physical concentrations of Aβ-induced mitochondrial membrane potential damage and cell apoptosis, partly via LRP1. These findings suggest a potential role of Gpc4 in treating Alzheimer’s disease at an early stage, by targeting NSCs.

Generation Mean Analysis for Seed Yield and Wilt Resistance in Castor (Ricinus communis L.)

Background: Castor is an important non-edible oil seeds crop of Gujarat state. Yield potentiality of this crop has been considerably improved through several breeding techniques. Now days, a wilt (Fusarium oxysporum f. sp. ricini) of castor has become a serious problem. The present study therefore, was under taken to use populations of P1, P2, F1, F2, BC1 and BC2 generations in each of six crosses of castor. The six crosses were selected in such a way that two crosses in each group of resistance × resistance, resistance × susceptible and susceptible × susceptible made available for detail study of gene effects for wilt resistance.Methods: The experiment was laid out in a compact family block design with three replications during kharif, 2017. The experimental materials consisted of four pistillate lines viz., VP-1, Geeta, SKP-84 and SKP-106 and six inbred lines viz., VI-9, JI-35, 48-1, SH-72, SKI-215 and PCS-124 selected from the germplasm maintained at the Castor and Mustard Research Station, S.D. Agricultural University, Sardarkrushinagar. Each entry was planted in a single row of 10 dibbles maintaining 120 cm row to row and 60 cm plant to plant distances.Result: The analysis of variance revealed significant difference among different generations for wilt incidence and seed yield indicating considerable variability in the material tested. The estimation of the gene effects revealed that additive as well as non-additive gene effects were observed for wilt incidence and seed yield in all the six cross. In the cross, VP - 1 × JI- 35 the wilt incidence estimation of scaling test and gene effect was observed non-significant indicating non-allelic interaction was absent for this character, while for seed yield, all the crosses have significant scaling test indicating the presence of non-allelic interactions for this trait.

Heterosis and inbreeding studies for seed cotton yield and its component traits in desi cotton

A study was conducted to assess the extent of the heterosis for sixteen yield and yield-attributing traits in four cotton hybrids (each having P1, P2, F1, F2, BC1 and BC2 generations) obtained by crossing four interspecific lines of desi cotton in a compact family block design with three replications during kharif 2017-18. Highly significant and positive relative heterosis, heterobeltiosis and inbreeding depression were recorded in most of the crosses. For seed cotton yield per plant, positive and highly significant relative heterosis, heterobeltiosis and inbreeding depression were recorded in all the four crosses indicated major role of non-additive gene actions in the inheritance of seed cotton yield per plant and its attributes, while cross III (GShv 362/12 x PA 812) recorded the highest heterotic effect among all crosses which also performed well for monopodia per plant, average boll weight, lint yield per plant, ginning percentage, lint index, fibre fineness and fibre strength.

A study of heritability and genetic advance in pigeon pea. (Cajanus cajan (L.) Mill spp.)

The present investigation was conducted at Pulses and Castor Research Station, Navsari Agricultural University, Navsari during Kharif 2017-20 with a view to study heterosis of four crosses (each having P1, P2, F1, F2, BC1 and BC2 generations) in a Compact Family Block Design with three replications. Out of four crosses studied, high heritability coupled with high to moderate genetic advance for trait grain yield per plant in cross I and IV; days to flowering in cross I and II; days to maturity in cross II and IV; reproductive phase duration in cross I, III and IV; Plant height in cross II, III and IV; primary branches per plant in cross IV and pods per plant in cross II and IV. Simple selection method would be fruitful for improvement of various characters because they are predominantly inherited by genetic effect. Involvement of environment effect is very less in inheritance of above-mentioned traits.

Genetics of white rust resistance in Indian mustard (Brassica juncea L.) and its validation on using molecular markers

White rust resistance loci (AcB1-A4.1 and AcB1-A5.1) associated with intron polymorphic (IP) markers i.e. At5g41560 and At2g36360, respectively, were used for validation of P1, P2, F1, F2, BC1F1 and BC2F1 generations. The donor parents namely, Bio-YSR and BEC-144 produced desired banding pattern of 430 and 750 bp while recipients viz., NRCHB 101 and DRMR-150-35 exhibited different pattern from donors confirming white rust resistance loci 4.1 and 5.1 with marker At5g41560 and At2g36360, respectively. Confirmation of these set of two IP markers in the parents and F1s lead us to further screening of selected F2, BC1F1 and BC2F1 populations. Available data on white rust reaction in different generations under study revealed that single dominant gene is responsible for white rust resistance. Potential of molecular markers in developing white rust resistant genotypes is proved under present study.

Comparison of Genetic Parameters in Non-segregating and Segregating Populations of Sugar Beet in Egypt

This work aimed mainly at comparison among non-segregating (P1, P2 and F1) and segregating (F2, BC1 and BC2) generations using genetic parameters for four traits in the cross Eg27 x Fc723 cmsduring 2015 to 2018 in Ras-Sudr station, Desert Research Center (DRC), South Sinai and Private Farm in Kafr El Sheikh Governorate. According to combined analysis of variance, highly significant environments (E) for all studied traits and significant or highly significant genotype (G) and GxE interactions for most traits were observed during six generations. In respect to mean performances, Kafr El-Shiekh location was higher than Ras-Sudr location for most studied traits at six generations. Significant differences among six generation means were found for all studied traits in the two locations. The F2 generation was lower than the P1, P2, F1, BC1 and BC2 generations for most studied traits at the two locations. The cross (Eg27 x Fc723 cms) recorded positive and highly significant heterosis, heterobeltiosis and inbreeding depression for most studied traits under two locations. A high broad sense heritability and genetic advance as percent of mean (GAM%) estimates were observed for root diameter/plant at BC1, root weight/plant at BC2 and T.S.S.% at BC1 and BC2. Generally, the values of the all studied genetic parameters for all studied traits during segregating generations were higher than non-segregating generations. The principal component analysis of the relationship between the six generations revealed that the most appropriate generations for selecting these traits were BC1 and BC2 under the two locations. Backcrossing may be done for 2–5 cycles (BC2 – BC5) at Eg27 parent for improving sugar beet yield in Egypt.

Estimates of genetic parameters of pigments and agronomic traits in green and purple lettuce

ABSTRACT Understanding genetics and the gene interactions involved in the expression of certain characteristics becomes a determining factor for better exploration of its use. The development of breeding programs that combine one or more desirable trait into a single cultivar is directly impacted by this lack of knowledge of the genetic bases involved. The objective of the present study was to estimate the genetic parameters involved in pigment expression and agronomic characteristics in lettuce. Parental evaluations of lettuce, P1 (green) and P2 (purple) parental generations, the segregating generations F1 and F2, and the backcrosses Bc1 and Bc2 originating from the UFU-Crespa199#1#1 x UFU-Albina#2 crossing were evaluated. The chlorophyll and anthocyanin contents, number of leaves and plant diameter were evaluated. The study was conducted by testing all generations and the estimates obtained by averages and variances. Indications of polygenic or oligogenic inheritance were verified by the characteristic number of leaves, plant diameter, and anthocyanin content. The complete and additive-dominant models satisfactorily explained the performance of the variables, except the anthocyanin content.

Cardiac Fibroblast-Specific Activating Transcription Factor 3 Promotes Myocardial Repair after Myocardial Infarction.

Background:Myocardial ischemia injury is one of the leading causes of death and disability worldwide. Cardiac fibroblasts (CFs) have central roles in modulating cardiac function under pathophysiological conditions. Activating transcription factor 3 (ATF3) plays a self-protective role in counteracting CF dysfunction. However, the precise function of CF-specific ATF3 during myocardial infarction (MI) injury/repair remains incompletely understood. The aim of this study was to determine whether CF-specific ATF3 affected cardiac repair after MI.Methods:Fifteen male C57BL/6 wild-type mice were performed with MI operation to observe the expression of ATF3 at 0, 0.5, 1.0, 3.0, and 7.0 days postoperation. Model for MI was constructed in ATF3TGfl/flCol1a2-Cre+ (CF-specific ATF3 overexpression group, n = 5) and ATF3TGfl/flCol1a2-Cre− male mice (without CF-specific ATF3 overexpression group, n = 5). In addition, five mice of ATF3TGfl/flCol1a2-Cre+ and ATF3TGfl/flCol1a2-Cre− were subjected to sham MI operation. Heart function was detected by ultrasound and left ventricular remodeling was observed by Masson staining (myocardial fibrosis area was detected by blue collagen deposition area) at the 28th day after MI surgery in ATF3TGfl/flCol1a2-Cre+ and ATF3TGfl/flCol1a2-Cre− mice received sham or MI operation. Quantitative real-time polymerase chain reaction (qRT-PCR) was used to detect cell proliferation/cell cycle-related gene expression in cardiac tissue. BrdU staining was used to detect fibroblast proliferation.Results:After establishment of an MI model, we found that ATF3 proteins were increased in the heart of mice after MI surgery and dominantly expressed in CFs. Genetic overexpression of ATF3 in CFs (ATF3TGfl/flCol1a2-Cre+ group) resulted in an improvement in the heart function as indicated by increased cardiac ejection fraction (41.0% vs. 30.5%, t = 8.610, P = 0.001) and increased fractional shortening (26.8% vs. 18.1%, t = 7.173, P = 0.002), which was accompanied by a decrease in cardiac scar area (23.1% vs. 11.0%, t = 8.610, P = 0.001). qRT-PCR analysis of CFs isolated from ATF3TGfl/flCol1a2-Cre+ and ATF3TGfl/flCol1a2-Cre− ischemic hearts revealed a distinct transcriptional profile in ATF3-overexpressing CFs, displaying pro-proliferation properties. BrdU-positive cells significantly increased in ATF3-overexpressing CFs than control CFs under angiotensin II stimuli (11.5% vs. 6.8%, t = 31.599, P = 0.001) or serum stimuli (31.6% vs. 20.1%, t = 31.599, P = 0.001). The 5(6)-carboxyfluorescein N-hydroxysuccinimidyl ester assay showed that the cell numbers of the P2 and P3 generations were higher in the ATF3-overexpressing CFs at 24 h (P2: 91.6% vs. 71.8%, t = 8.465, P = 0.015) and 48 h (P3: 81.6% vs. 51.1%, t = 9.029, P = 0.012) after serum stimulation. Notably, ATF3 overexpression-induced CF proliferation was clearly increased in the heart after MI injury.Conclusions:We identify that CF-specific ATF3 might contribute to be MI repair through upregulating the expression of cell cycle/proliferation-related genes and enhancing cell proliferation.

Comparative study on biological characteristics between different generations of rabbit nucleus pulposus cells

To research the biological characteristics of different generations of rabbit nucleus pulposus cells (NPCs) that were cultured with natural culture and subculture method. The thoracolumbar segments of New Zealand white rabbits (6-8 weeks old and weighing 1.5-2.5 kg) were obtained and nucleus pulposus were isolated from disc regions. And NPCs were harvested by enzymatic digestion from nucleus pulposus. Primary NPCs were counted as P0 generation. Then, NPCs were passaged by trypsin and counted as P1, P2, P3 with a totle of 4 generations. P0 to P3 generations NPCs were separately examined by observation of cell morphology and proliferation time, detection of apoptosis rates of cells by flow cytometry, and detection of hypoxia-inducible factor 1α (HIF-1α), matrix metalloproteinases 2 (MMP-2), Aggrecan, and collagen type Ⅱ proteins by immunofluorescence and Western blot. The morphology of NPCs transformed from triangular or polygonal in P0 generation to spindle in P3 generation; the characteristic vacuolated cells gradually disappeared; and the cell volume and cell proliferation time increased. The cell apoptosis rates were 5.47%±0.91%, 13.77%±2.42%, 33.46%±1.82%, and 38.76%±1.50% from P0 to P3 generations, with the increase of culture time, and there were significant differences between 4 generations ( P<0.05). Immunofluorescence staining showed that with the increase of cells generation, the fluorescence intensity of HIF-1α, collagen type Ⅱ, and Aggrecan decreased, and the fluorescence intensity of MMP-2 increased. Western blot results showed that the relative expression of HIF-1α protein was high in P0 generation, the P1 generation has a rising trend, and then gradually decreased; the differences between generations were significant ( P<0.05). The relative expression of collagen type Ⅱ protein decreased from P0 to P3 generations and there were significant differences between generations ( P<0.05). The relative expression of Aggrecan protein decreased from P0 to P2 generations and there were significant differences between generations ( P<0.05); but no significant difference was found between P2 and P3 generations ( P>0.05). The relative expression of MMP-2 protein increased significantly in P3 generation; except that the difference between P0 and P2 generations was not significant ( P>0.05), the significant differences were found between the other generations ( P<0.05). Rabbit NPCs degeneration model was successfully established by the natural culture and subculture method. Transforming of NPCs morphology, increasing of cell apoptosis rates, decreasing of anabolism, and increasing of catabolism were presented in NPCs degeneration model.

Inheritance of bacterial wilt resistance and performance of horticultural traits in bell pepper (Capsicum annuum var. grossum)

The genetic nature of bacterial wilt resistance was studied in bell pepper (Capsicum annuum L. var. grossum Sendt.) plants using the P1, P2, F1, F2 and backcross generations obtained from four crosses between four parental lines, viz, EC 464107, EC 464115, Kandaghat Selection and Sweet Happy I considered as standards for resistance and/or susceptibility. The evaluation trial was conducted in bacterial wilt sick plots along with two susceptible checks, namely Indira (Hybrid) and California Wonder (Open-pollinated variety) that were included after every 15th row to ensure uniform distribution of inoculum in the experimental fields. Simultaneously, in a separate block, the parents and their F1’s were also evaluated for twelve different horticultural traits. The findings revealed that bacterial wilt resistance was governed by a single dominant gene in the cross EC 464107 × Sweet Happy I, whereas two genes with dominant and recessive epistasis dictated resistance in the crosses EC 464107 × Kandaghat Selection and EC 464115 × Kandaghat Selection, respectively. Based upon the mean performance, the hybrid EC 464107 × Kandaghat Selection was the best in terms of total and marketable fruit yield, fruits per plant and fruit length, which underscores its importance to be exploited, especially during wet season. In addition, the resistant parents EC 464107 and EC 464115 can be used to develop bacterial wilt resistant F1 hybrids as they expressed complete or near complete dominance for resistance in combination with the moderately resistant and susceptible varieties Kandaghat Selection and Sweet Happy I. Backcrossing with commercial cultivars and recombinant breeding accompanied by selection would also help to evolve bacterial wilt disease resistant, high yielding and horticulturally desirable pure line varieties.

Generation Means Analysis for Estimation of Genetic Parameters for Striga hermonthica Resistance in Maize (Zea mays L.)

Striga hermonthica is a parasitic weed species that causes considerable yield loss in susceptible maize cultivars in western Kenya. A generation means analysis was conducted to estimate gene effects influencing resistance/tolerance to Striga hermonthica in maize cultivars adapted to western Kenya. A resistant inbred line developed by Maseno University, MSMP1/P2 was crossed to Striga susceptible inbred line 5057. Experimental units comprised of resistant parent P1, susceptible parent P2, their F1 and F2 generations, and BC1P1 and BC1P2 generations. The six generations were evaluated under Striga sick plots at Nyahera during the short rains of 2012 and long rains of 2013. Field evaluation for entries were grown in a randomized complete block design with three replicates. The results showed significant differences among generations for emerged Striga, Striga damage rating and maize growth including Plant and Ear height. Most of the additive, dominance, additive x additive, additive x dominance and dominance x dominance effects were significant indicating the importance of the additive, dominance and epistatic modes of gene actions in controlling emerged Striga, Striga damage rating, plant and ear height. Most components conferring Striga tolerance behaved in a qualitative manner. Dominance effects had higher mean values over additive effects. Significant dominant genetic effects (d) for Striga emergence and Striga damage rating suggested preponderance of non-additive genetic effects in the inheritance of Striga tolerance. The results also reveal the involvement of duplicate epistasis where the dominance estimate and dominance x dominance interaction had opposite signs. The presence of duplicate type of gene interaction confirms the importance of dominance gene effects.

Generation mean analysis of spring wheat (Triticum aestivum L.) seedlings tolerant to high levels of manganese

Effective utilisation of wheat (Triticum aestivum L.) germplasm tolerant to high manganese (Mn) in a breeding program requires an understanding of the genetics of Mn tolerance. Five wheat cultivars differing in their response to high Mn were crossed in a half diallel design with no reciprocals. Seedlings of parents and progeny generations were phenotyped in high Mn nutrient solutions. Total chlorophyll concentration, which was positively correlated with leaf elongation rate during recovery from Mn stress, was used for phenotyping Mn tolerance. Means of chlorophyll concentration of P1, P2, F1, F2, BC1, and BC2 generations, in all crosses which showed significant variation among generations, were subjected to line crosses analysis to estimate gene effects. The continuous frequency distribution of seedlings with differential Mn tolerance, the similarity of the F1 and F2 means, and the high and significant levels of additive gene action indicated quantitative inheritance for Mn tolerance at seedling stage. A preponderance of additive effects indicated that selection for Mn tolerance in early generations should be effective.

Inheritance of waterlogging tolerance in cucumber (Cucumis sativus L.)

Flooding of vegetable crop fields along the Yangtze River basin in China has been an annual occurrence; therefore the cultivation of tolerant varieties has become one of the most promising control strategies. Our objective was to investigate the inheritance of waterlogging tolerance of cucumber at the early stage of growth with two cucumber parents consisting of PW0832 (tolerant) and PW0801 (susceptible). In 2006, 4-weeks-old potted plants of P1, P2, F1, F2, B1 and B2 generations were subjected to one week waterlogged stress, control plants were not flooded. The simple additive model explained the variations of tolerance score (TOL) adventitious root formation (ARF) and waterlogged root dry weight (RDW) while the additive-dominance model explained the control treatment of RDW. Non-allelic interactions were detected for waterlogged vine length (VLH) and root length (RLH). Complementary epistasis occurred in waterlogged VLH while additive × additive, additive × dominance and dominance × dominance epistastic effects were significant for waterlogged RLH. Transgressive segregation was also observed in most of the traits in the F2 generation indicating some alleles are dispersed in the parents used in this study. The estimates of narrow-sense heritabilities for TOL and ARF were moderately high. Backcross of F1 to both parents in ARF, waterlogged SDW and waterlogged RDW showed good convergence of genes in the B2. These results suggest that it should be possible to develop varieties with high levels of tolerance by selecting transgressive segregants in this cross.

Inheritance of Tomato yellow leaf curl virus Resistance Derived from Solanum pimpinellifolium UPV16991.

Resistance to tomato yellow leaf curl disease (TYLCD) in accession UPV16991 Solanum pimpinellifolium has been previously reported by our group. A breeding program was developed from an initial S. lycopersicum × S. pimpinellifolium UPV16991 cross. This first cross was followed by several selfing generations. Selection for resistance to Tomato yellow leaf curl virus (TYLCV) and Tomato yellow leaf curl Sardinia virus (TYLCSV) was carried out for plants of each generation. One partially resistant F6 plant (L102) was chosen to form the family to study the genetic control of resistance to TYLCV. Crosses between four breeding lines susceptible to TYLCD and L102 were also performed to study the dominance of the resistance in S. lycopersicum genetic backgrounds. Response to TYLCV infection of P1, P2, F1, F2, BC1, and BC2 generations fitted, for this line, a monogenic control with partial recessiveness and incomplete penetrance. The percentage of homozygotic plants with partial resistance was 72.75. Among the four hybrids developed, the highest levels of resistance were found in the hybrid formed from the most vigorous S. lycopersicum line. These results must be considered for breeding purposes. Partial resistance derived from UPV16991 will be useful in homozygosis or combined with resistance genes from other sources.