Complementary Genes Research Articles

The bHLH transcription factor VfTT8 underlies zt2, the locus determining zero tannin content in faba bean (Vicia faba L.)

Faba bean (Vicia faba L.) is an important protein-rich fodder crop, which is widely cultivated in temperate areas. However, antinutritional compounds such as condensed tannins, limit the use of this protein source in monogastric feed formulations. Previous studies demonstrated that two recessive and complementary genes, zt1 and zt2, control absence of tannin and white flower colour in faba bean. An ortholog of the Medicago WD40 transcription factor TTG1 was reported to encode the zt1 phenotype, but the responsible gene for zt2 is still unknown. Here we used a candidate gene approach combined with linkage mapping, comparative genomics and gene expression to fine map the zt2 genomic region and to identify the regulatory gene controlling both traits. Seventy-two genes, including 23 MYB and bHLH regulatory genes predicted to be associated with anthocyanin expression together with WRKY proteins, were screened and genotyped in three mapping populations. The linkage groups constructed identified the regulatory gene, TRANSPARENT TESTA8 (TT8), encoding a basic helix-loop-helix (bHLH) transcription factor, as the candidate for zt2. This finding was supported by qPCR analysis and further validated in different genetic backgrounds. Accordingly, VfTT8 was downregulated in white flowered types while showing high levels of expression in wild genotypes. Our results provide new insights on the regulatory mechanisms of tannin biosynthesis in faba bean and will facilitate the development of an ultimate zt2 diagnostic marker for the fast generation of new value-added cultivars free of tannins and with improved nutritional value.

High temperature stress response is not sexually dimorphic at the whole-body level and is dependent on androgens to induce sex reversal

The understanding of the molecular and endocrine mechanisms behind environmentally-induced sex reversal in fish is of great importance in the context of predicting the potential effects of climate change, especially increasing temperature. Here, we demonstrate the global effects of high temperature on genome-wide transcription in medaka (Oryzias latipes) during early development. Interestingly, data analysis did not show sexual dimorphic changes, demonstrating that thermal stress is not dependent on genotypic sex. Additionally, our results revealed significant changes in several pathways under high temperature, such as stress response from brain, steroid biosynthesis, epigenetic mechanisms, and thyroid hormone biosynthesis, among others. These microarray data raised the question of what the exact molecular and hormonal mechanisms of action are for female-to-male sex reversal under high temperatures in fish. Complementary gene expression analysis revealed that androgen-related genes increase in females (XX) experiencing high water temperature. To test the involvement of androgens in thermal-induced sex reversal, an androgen antagonist was used to treat XX medaka under a high-temperature setup. Data clearly demonstrated failure of female-to-male sex reversal when androgen action is inhibited, corroborating the importance of androgens in environmentally-induced sex reversal.

Identification of Fusarium solani f. sp. pisi (Fsp) Responsive Genes in Pisum sativum.

Pisum sativum (pea) is rapidly emerging as an inexpensive and significant contributor to the plant-derived protein market. Due to its nitrogen-fixation capability, short life cycle, and low water usage, pea is a useful cover-and-break crop that requires minimal external inputs. It is critical for sustainable agriculture and indispensable for future food security. Root rot in pea, caused by the fungal pathogen Fusarium solani f. sp. pisi (Fsp), can result in a 15–60% reduction in yield. It is urgent to understand the molecular basis of Fsp interaction in pea to develop root rot tolerant cultivars. A complementary genetics and gene expression approach was undertaken in this study to identify Fsp-responsive genes in four tolerant and four susceptible pea genotypes. Time course RNAseq was performed on both sets of genotypes after the Fsp challenge. Analysis of the transcriptome data resulted in the identification of 42,905 differentially expressed contigs (DECs). Interestingly, the vast majority of DECs were overexpressed in the susceptible genotypes at all sampling time points, rather than in the tolerant genotypes. Gene expression and GO enrichment analyses revealed genes coding for receptor-mediated endocytosis, sugar transporters, salicylic acid synthesis, and signaling, and cell death were overexpressed in the susceptible genotypes. In the tolerant genotypes, genes involved in exocytosis, and secretion by cell, the anthocyanin synthesis pathway, as well as the DRR230 gene, a pathogenesis-related (PR) gene, were overexpressed. The complementary genetic and RNAseq approach has yielded a set of potential genes that could be targeted for improved tolerance against root rot in P. sativum. Fsp challenge produced a futile transcriptomic response in the susceptible genotypes. This type of response is hypothesized to be related to the speed at which the pathogen infestation advances in the susceptible genotypes and the preexisting level of disease-preparedness in the tolerant genotypes.

The unique disarticulation layer formed in the rachis of Aegilops longissima probably results from the spatial co-expression of Btr1 and Btr2.

The brittle rachis trait is a feature of many wild grasses, particularly within the tribe Triticeae. Wild Hordeum and Triticum species form a disarticulation layer above the rachis node, resulting in the production of wedge-type dispersal units. In Aegilops longissima, only one or two of the nodes in the central portion of its rachis are brittle. In Triticeae species, the formation of a disarticulation layer above the rachis node requires the co-transcription of the two dominant and complementary genes Btr1 and Btr2. This study aims to establish whether homologues of Btr1 and/or Btr2 underlie the unusual brittle rachis phenotype observed in Ae. longissima. Scanning electron microscopy was used to examine the disarticulation surfaces. Quantitative RT-PCR and RNA in situ hybridization experiments were used to identify gene expression in the immature inflorescence. Analysis based on scanning electron microscopy was able to demonstrate that the disarticulation surfaces formed in the Ae. longissima rachis are morphologically indistinguishable from those formed in the rachises of wild Hordeum and Triticum species. RNA in situ hybridization showed that in the immature Ae. longissima inflorescence, the intensity of Btr1 transcription varied from high at the rachis base to low at its apex, while that of Btr2 was limited to the nodes in the central to distal portion of the rachis. The disarticulation pattern shown by Ae. longissima results from the limitation of Btr1 and Btr2 co-expression to nodes lying in the centre of the rachis.

Gene effect and heritability of yield and its components in eggplant

Eggplant (Solanum melongena L.) is one of the most important fruit vegetables in the world, with several nutritional and medicinal benefits. However, little is known about the genetic divergence of yield and its related traits. The objective of this study was to explore gene action and heritability of traits to help direct and strengthen breeding programmes, geared towards improving yield of the crop. Six generations (P1, P2, F1, F2, BC1 and BC2) derived from two crosses (SM001-07 x ST004-03 and SM001 x San005-01) of eggplant accessions, were grown in pots in an open field, using Randomised Complete block Design (RCBD). Estimated data indicated that, the additive-dominance model was adequate to demonstrate the genetic variation and its significance in the inheritance of fruit weight, days to flowering and fruit yield traits. Although non-allelic interactions were found in plant height and number of seeds, additive effect was more pronounced in the genetic control of days to flowering and fruit weight; while dominance effect was more important in the control of plant branching and fruit length. Plant height and fruit yield were influenced by complementary gene action. Furthermore, the study revealed low magnitudes of dominance and environmental variances for most traits showing higher heritability values. In view of the diverse gene actions, with additive, dominant and epistasis, playing significant roles in the control of different traits, backcross, recurrent selection or bi parental could be appropriate for advancing the segregating populations to meet the need of yield improvement in both crosses.
 Key words: Additive, dominance, Epistasis, gene action

Candidate genes for monitoring hydrogen peroxide resistance in the salmon louse, Lepeophtheirus salmonis

BackgroundHydrogen peroxide (H2O2) is one of the delousing agents used to control sea lice infestations in salmonid aquaculture. However, some Lepeophtheirus salmonis populations have developed resistance towards H2O2. An increased gene expression and activity of catalase, an enzyme that breaks down H2O2, have been detected in resistant lice, being therefore introduced as a resistance marker in the salmon industry. In the present study the aim was to validate the use of catalase expression as a marker and to identify new candidate genes as additional markers to catalase, related to H2O2 resistance in L. salmonis.MethodsA sensitive and an H2O2 resistant laboratory strain (P0 generation, not exposed to H2O2 for several years) were batch crossed to generate a cohort with a wide range of H2O2 sensitivities (F2 generation). F2 adult females were then exposed to H2O2 to separate sensitive and resistant individuals. Those F2 lice, the P0 lice and field-collected resistant lice (exposed to H2O2 in the field) were used in an RNA sequencing study.ResultsCatalase was upregulated in resistant lice exposed to H2O2 compared to sensitive lice. This was, however, not the case for unexposed resistant P0 lice. Several other genes were found differentially expressed between sensitive and resistant lice, but most of them seemed to be related to H2O2 exposure. However, five genes were consistently up- or downregulated in the resistant lice independent of exposure history. The upregulated genes were: one gene in the DNA polymerase family, one gene encoding a Nesprin-like protein and an unannotated gene encoding a small protein. The downregulated genes encoded endoplasmic reticulum resident protein 29 and an aquaporin (Glp1_v2).ConclusionsCatalase expression seems to be induced by H2O2 exposure, since it was not upregulated in unexposed resistant lice. This may pose a challenge for its use as a resistance marker. The five new genes associated with resistance are put forward as complementary candidate genes. The most promising was Glp1_v2, an aquaglyceroporin that may serve as a passing channel for H2O2. Lower channel number can reduce the influx or distribution of H2O2 in the salmon louse, being directly involved in the resistance mechanism.

QTL Mapping and Inheritance of Clubroot Resistance Genes Derived From Brassica rapa subsp. rapifera (ECD 02) Reveals Resistance Loci and Distorted Segregation Ratios in Two F2 Populations of Different Crosses

In this study, Brassica rapa subsp. rapifera (ECD 02) which exhibits broad-spectrum resistance to many Canadian Plasmodiophora brassicae isolates was crossed with two clubroot-susceptible B. rapa accessions to produce two F2 populations. The F2 plants were screened against P. brassicae pathotypes 3H, 5X, and 5G. The Chi-square goodness of fit test showed that the vast majority (≈75%) of the crosses that produced the F2 populations showed segregation ratios of 9R:7S, 7R:9S, 13R:3S, 3R:13S, 5R:11S, 11R:5S, and 1R:15S. These were modifications of the 15R:1S ratio expected for the inheritance of two dominant major clubroot resistance (CR) genes from ECD 02. The distorted segregation ratios suggest that the two resistance genes are on different chromosomes and that two genes interact in an epistatic manner to confer resistance. Genotyping was conducted with 144 PCR-based markers in the two F2 populations. Linkage and QTL analysis with the polymorphic markers identified two QTLs on chromosome A03 to be associated with resistance to P. brassicae pathotypes 5X and 5G in Popl#1 while only the second QTL on chromosome A03 was associated with resistance to pathotypes 5X and 5G in Popl#2. The QTLs clustered in genomic regions on the A03 chromosome of B. rapa where the CRa/CRbKato gene(s) are mapped. In addition, the Crr1 gene on the A08 chromosome of B. rapa was detected in the two F2 populations. Therefore, the phenotypic and molecular data confirm the existence of two CR genes in ECD 02. This is the first study that shows that major dominant genes in Brassica interact in a non-additive manner to confer resistance to different P. brassicae pathotypes.Key Message: This study provides knowledge on the inheritance and type of gene action for clubroot resistance derived from Brassica rapa subsp. rapifera (ECD 02). The results indicated that duplicate recessive and recessive suppression epistatic interactions, digenic additivity and complementary gene action between the CRa/CRbKato gene(s) on the A03 and the Crr1 gene on the A08 chromosome of B. rapa controlled clubroot resistance to P. brassicae pathotypes 3H, 5X and 5G.

Sources, Spectrum, Genetics, and Inheritance of Phaseolus vulgaris Resistance Against Xanthomonas citri pv. fuscans.

Common bean (Phaseolus vulgaris) is one of the most consumed agricultural products in the world. Its production is affected by common bacterial blight (CBB) caused by Xanthomonas citri pv. fuscans and X. phaseoli pv. phaseoli. In this work, we investigated the spectrum, genetics, and inheritance of common bean resistance to X. citri pv. fuscans. Inoculation of nine selected cultivars with an X. citri pv. fuscans strain showed that BRS Radiante and IAPAR 16 were resistant. These two cultivars were also resistant to six X. phaseoli pv. phaseoli strains of different geographic origins, demonstrating their broad-spectrum resistances. BRS Radiante sustained smaller X. citri pv. fuscans populations than two susceptible cultivars. Stomatal densities of IAPAR 16 and BRS Radiante were significantly higher than or not different from susceptible cultivars. BRS Radiante showed the lowest general combining ability values and the combination BRS Radiante × Carioca MG the lowest specific combining ability (SCA) values, revealing the capacity of BRS Radiante to increase resistance to X. citri pv. fuscans. Positive and negative parental SCA values indicated dominant and recessive genes involved in X. citri pv. fuscans resistance. Resistance of the BRS Radiante × Carioca MG cross segregated in a 9:7 ratio in the F2 population, indicating that it is governed by two complementary dominant genes. Maximum likelihood analysis showed that the resistance of BRS Radiante to X. citri pv. fuscans is conferred by a gene of major effect with contribution of additional polygenes. This study contributes with important knowledge on the resistance against CBB in Brazilian common bean cultivars as well as with molecular tools for confirmation of common bean hybrids.

Genetic control of yellow vein mosaic virus resistance in okra (Abelmoschus esculentus)

Yellow vein mosaic virus is the most serious disease of okra which causes severe losses in okra production mainly in the tropics. An experiment was carried out in kharif 2017–18 to understand the inheritance pattern and gene action involved in resistance to yellow vein mosaic virus disease on okra. Based on screening of genotypes, two resistant (DOV-12 and DOV-66) and two susceptible (DOV-1 and Pusa Sawani) parents were identified for this study. The inheritance pattern of okra was studied in six generations (P1, P2, F1, F2, BC1P1 and BC1P2) of four selected crosses (resistant × resistant, two susceptible × resistant and susceptible × susceptible). The Qualitative genetic analysis was done in segregating generations for all the four crosses under study. It revealed that a complementary dominant gene governing the disease resistance in resistant × resistant cross while a single dominant gene was responsible for inheriting resistance in susceptible × resistant cross. The significance of scaling test and joint scaling test also revealed the presence of digenic gene interaction for days to first appearance of YVMV which involved both additive and non-additive gene action. Thus, the present study confirmed the role of genetic architecture of the parents for resistance reaction

Ciliate mitoribosome illuminates evolutionary steps of mitochondrial translation.

To understand the steps involved in the evolution of translation, we used Tetrahymena thermophila, a ciliate with high coding capacity of the mitochondrial genome, as the model organism and characterized its mitochondrial ribosome (mitoribosome) using cryo-EM. The structure of the mitoribosome reveals an assembly of 94-ribosomal proteins and four-rRNAs with an additional protein mass of ~700 kDa on the small subunit, while the large subunit lacks 5S rRNA. The structure also shows that the small subunit head is constrained, tRNA binding sites are formed by mitochondria-specific protein elements, conserved protein bS1 is excluded, and bacterial RNA polymerase binding site is blocked. We provide evidence for anintrinsic protein targeting system through visualization of mitochondria-specific mL105 by the exit tunnel that would facilitate the recruitment of a nascent polypeptide. Functional protein uS3m is encoded by three complementary genes from the nucleus and mitochondrion, establishing a link between genetic drift and mitochondrial translation. Finally, we reannotated nine open reading frames in the mitochondrial genome that code for mitoribosomal proteins.

Analysis of Generation Means for Yield and Its Components in Tomato Crosses

Generation mean analysis was studied among hybridization of local cultivated tomato(P1) with wild type(Lycopersicon pimpinellifolium) (P2), the F1 plants was selfed for F2 seeds and backcrossed to get 6 tomato genotype plants P1, P2, F1, F2, BC1F1 and BC2F1 plants were planted in a randomized block design with three replications. The experiment was carried out at the Horticulture Department, University of Mosul. The results showed that The genetic parameters was additive for number of fruits/plant vit c, plant height, number of seeds / fruit,and fruit weight. Whereas the dominant effect was significant for: flower number/cluster fruit weight(g), plant height (cm) and total yield of fruits. The values of F1, BC1F1 and BC2F1 genotypes were exceeded their parents in the characters: of yield and number of fruits per cluster, Vit C, TSS%, and were under the control of duplicate epistasis while the number of locules per fruit was governed by complementary gene interaction.

Genetic analysis of resistance to Fusarium oxysporum f. sp. niveum race 2 in cultivated watermelon [Citrullus lanatus (Thunb.) Matsum & Nakai

The genetics and nature of gene action involved in resistance to Fusarium oxysporum f. sp. niveum race 2 causing wilt in watermelon was studied. Five resistant accessions were crossed with a common susceptible parent to develop six generations for each combination. The populations were screened in two consecutive assays during June to September 2019. Based on the segregation of F2, the resistance in IC0523048, EC794455 and EC759804 was found to be governed by two major complementary dominant genes. However, the deviation from the expected ratio in BC1 progeny suggested the involvement of modifying genetic factors. The F2 and backcross progenies of BIL-53 × IIHR-9 and BIL-53 × EC794421 did not follow any of the ratios tested. Allelism test revealed the absence of any allelic relationship between IIHR9 and IC0523048 for resistance. Generation mean analysis revealed presence of epistasis in BIL-53 × EC794455 and BIL-53 × EC759804 while in the other three crosses, simple additive-dominance interaction was observed. These resistant accessions and the inheritance information generated in this study would help in incorporation of resistance to Fusarium wilt race 2 into elite commercial backgrounds.

Aluminum tolerance mechanisms in Kenyan maize germplasm are independent from the citrate transporter ZmMATE1

Aluminum (Al) toxicity on acid soils adversely affects maize yields, which can be overcome by combining soil amendments with genetic tolerance. In maize, ZmMATE1 confers Al tolerance via Al-activated citrate release, whereby citrate forms non-toxic complexes with Al3+ in the rhizosphere. Here, we investigated Al tolerance mechanisms in maize germplasm originated from Kenya based on quantitative trait loci (QTL) mapping. Five QTLs and four epistatic interactions explained ~51% of the phenotypic variation for Al tolerance. The lack of Al tolerance QTL on chromosome 6 and the much lower expression of ZmMATE1 in both Kenyan lines than in Cateto Al237, which donates the superior allele of ZmMATE1, strongly indicate that this gene does not play a significant role in Al tolerance in neither parent. In turn, maize homologs to genes previously implicated in Al tolerance in other species, ZmNrat1, ZmMATE3, ZmWRKY and ZmART1, co-localized with Al tolerance QTL and were more highly expressed in the parent that donate favorable QTL alleles. However, these candidate genes will require further studies for functional validation on maize Al tolerance. The existence of Al tolerance mechanisms independent from ZmMATE1 suggests it is possible to develop highly Al tolerant cultivars by pyramiding complementary Al tolerance genes in maize.

Selection for Yield, Rust Resistance and Quality Traits in Early Generations of Giza 171 X Sids 12 Cross of Bread Wheat

The F2 and F3 populations resulting from Giza171 × Sids12 hybrid were used from 2015/2016 to 2018/2019 seasons at Sakha Agricultural Research Station to study the inheritance of some agronomic characters and resistance to rusts diseases and select new bread wheat families with high yield potential and good grain quality. Giza171 was preferable for yield and its components, while Sids12 was desirable for earliness characters. The ranges of the F2 and F3 populations went out the means of its parents for the studied characters. All characters showed moderate to high values of broad sense heritability in F2 and F3 generations. The best responsive characters to selection in F2 were No. spikes plant-1 and grain yield plant-1, while days to maturity was the least responsive character. F3 families hadhighly significant variations for all studied characters. Correlation coefficients referred that grain filling rate, followed by No. spikes m-2, then kernels weight spike-1, later the No. kernels spike-1 had the most impact on grain yield in F3 families. The resistance of yellow and leaf rusts was controlled by two dominant genes and stem rust was controlled by two complementary dominant genes. Thirteen promising families were high yielding, resistant to the three rusts and have appropriate height were selected to promote to the next advanced of segregating generations and five of them were preferable for grain quality of wheat.

Study of Inheritance and Linkage of Virulence Genes in a Selfing Population of a Pakistani Dominant Race of Puccinia striiformis f. sp. tritici.

Wheat stripe rust is a severe threat of almost all wheat-growing regions in the world. Being an obligate biotrophic fungus, Puccinia striiformis f. sp. tritici (PST) produces new virulent races that break the resistance of wheat varieties. In this study, 115 progeny isolates were generated through sexual reproduction on susceptible Himalayan Berberis pseudumbellata using a dominant Pakistani race (574232) of PST. The parental isolate and progeny isolates were characterized using 24 wheat Yr single-gene lines and ten simple sequence repeat (SSR) markers. From the one-hundred-and-fifteen progeny isolates, 25 virulence phenotypes (VPs) and 60 multilocus genotypes were identified. The parental and all progeny isolates were avirulent to Yr5, Yr10, Yr15, Yr24, Yr32, Yr43, YrSp, YrTr1, YrExp2, Yr26, and YrTye and virulent to Yr1, Yr2, Yr6, Yr7, Yr8, Yr9, Yr17, Yr25, Yr27, Yr28, YrA, Yr44, and Yr3. Based on the avirulence/virulence phenotypes, we found that VPs virulent to Yr1, Yr2, Yr9, Yr17, Yr47, and YrA were controlled by one dominant gene; those to YrSp, YrTr1, and Yr10 by two dominant genes; and those to YrExp2 by two complementary dominant genes. The results are useful in breeding stripe rust-resistant wheat varieties and understanding virulence diversity.

Combining ability and gene action analysis in a half-diallel cross of Brassica rapa L.

Fifteen hybrids along with six parents were tested to identify good combiners through analyzing combining ability and gene action for yield and its attributes. The experiment was conducted in randomized complete block design with three replications during 2010/11 at research farm of Sher-e-Bangla Agricultural University (SAU), Dhaka. Data for days to 50% flowering and 80% maturity, plant height, number of primary and secondary branches, number of pods per plant, number of seeds per pod, pod length, seed yield and 1000-seed weight was recorded for analysis.The results showed that mean squares for parents, hybrids, parent vs hybrid were significantly different (p<0.01 or p<0.05) for most of the traits. Highly significant mean squares due to general combining ability (GCA) were found for all the traits except for length of pod, whereas highly significant mean squares due to specific combining ability (SCA) were also found for days to 50% flowering, number of secondary branches per plant, number of pods per plant, length of pod and seed yield per plant. This indicated that both additive and non-additive gene effects were important but additive gene effects were predominant for the expression of most of the measured traits. Estimates of GCA and SCA effects for yield and its attributes suggested that parent BARI Sarisha-6, BARI Sarisha-15 and Tori-7 was good combiners for different traits. Hayman’s graphical analysis indicated both over- and partial-dominance for growth and yield attributes. As dominant (non-fixable) variation was high for most of the attributes, substantial improvements of these traits may be possible by transferring complementary gene into non-epistatic high-dominance crosses or eliminating duplicate genes from high-dominance crosses. Considering GCA, SCA and per se performance BARI Sarisha-6, BARI Sarisha-15 and Tori-7 might be good parents towards an effective breeding programme.

Synthesizing Fluorescently Labeled dsRNAs and sRNAs to Visualize Fungal RNA Uptake.

Fungal pathogens are responsible for severe crop losses worldwide. Defending crops against fungal disease is critical for global food security; however, most current disease management approaches rely on chemical fungicides that can leave dangerous residues in the environment. RNA interference (RNAi) is an important process through which RNA molecules target and silence complementary genes, regulating gene expression during both transcription and translation. Recently, it has been discovered that some species of fungi can efficiently take up RNAs originating from their host plant and the environment. If these RNAs are complementary to fungal genes, this can lead to the targeting and silencing of fungal genes, termed "cross-kingdom RNAi," if the RNA originated from a plant host, or "environmental RNAi," if the RNA originated from the environment. These discoveries have inspired the development of spray-induced gene silencing (SIGS), an innovative crop protection strategy involving the foliar application of RNAs which target and silence fungal virulence genes for plant protection against fungal pathogens. The effectiveness of SIGS is largely dependent on the ability of fungi to take up environmental RNAs. Here, we describe the protocols used to label and visualize RNAs which are taken up by Botrytis cinerea. This protocol could easily be adapted for use across various fungal species. Determining the efficiency of RNA uptake by a specific fungal species is a critical first step to determining if SIGS approaches could be an effective control strategy for that fungus.

Body Conformation, Morphometry Indices and Inheritance Pattern of Indigenous Dwarf Chickens of Bangladesh

The study was conducted to investigate the body dimension, morphometric features and inheritance pattern of indigenous dwarf chicken (IDC) of Bangladesh under intensive management condition. The experiment was conducted at Bangladesh Agricultural University (BAU) poultry farm for a period of 28 months from March 2013 to June 2015 including a total of 979 birds. Body weight, shank length and circumference, chest girth, length of trunk, wing, keel and body, and body conformation indices were recorded at 8, 24 and 52 weeks of age. The average shank length, shank circumference and live weight at 24th week in adult dwarf males and females were 7.38 and 4.37 cm, 6.20 and 3.63 cm, and 1650 and 1067 g, respectively. The reduction of live weight for dwarf male and female chickens relative to their normal shank counterpart (NSC) at same age was 14.06 and 16.05%, respectively. Length of body, trunk, wing, shank and keel of IDC were also significantly shorter than NSC at all ages. The indices of shape, massiveness and long leggedness of NSC were significantly greater than IDC almost all ages. Shank lengths of day old chicks were measured within 1.4-1.6 cm. The ratio of non-dwarf and dwarf in indigenous chicken populations was found 9:7 for 1st generation where significant deviation observed in subsequent generations. Among the dwarf progeny, the male and female ratio was close to 1:1. Current hypothesis is in favor of autosomal dwarfism control by at least 2 pairs of genes where duplicate recessive gene interaction also known as complementary gene effect has probably been exerted between two pairs of genes. In conclusion, the present estimates give some insight information on morphometry and body conformational aspects between normal shanked and dwarf chickens which relate with lowered motoric activity, reduced metabolic rate and their body surface-mass makes the dwarf birds suitable for hot-humid climate like Bangladesh.

Molecular Genetic Mapping of Two Complementary Genes Underpinning Fruit Bitterness in the Bottle Gourd (Lagenaria siceraria [Mol.] Standl.).

Fruit bitterness is a serious problem threatening the bottle gourd (Lagenaria siceraria [Mol.] Standl.) industry worldwide. Previous genetic studies indicated that fruit bitterness in the bottle gourd was controlled by a pair of complementary genes. In this study, based on two non-bitter landraces “Hangzhou Gourd” and “Puxian Gourd,” each of which carries a single bitterness gene, and their derived segregation populations, we mapped the complementary genes causing fruit bitterness. Quantitative trait locus (QTL) scanning based on an F2 population detected two QTLs, which was QBt.1 locating in a 17.62-cM interval on linkage group (LG)2 corresponding to a 1.6-Mb region on chromosome 6, and QBt.2 mapped to a 8.44-cM interval on LG9 corresponding to a 1.9-Mb region on chromosome 7. An advanced bulked segregant analysis (A-BSA) well validated the QTL mapping results. Sequence-based comparative analysis showed no syntenic relationship between QBt.1/QBt.2 and the known bitterness genes in cucumber, melon, and watermelon, suggesting that causal genes underlying QBt.1 and QBt.2 were not direct orthologs of the reported cucurbit bitterness genes. Our results shed light on the molecular genetic mechanisms underlying fruit bitterness in the bottle gourd and is useful to guide breeders to properly select parental lines to avoid the occurrence of bitter fruits in breeding programs.

The Gametic Non-Lethal Gene Gal on Chromosome 5 Is Indispensable for the Transmission of the Co-Induced Semidwarfing Gene d60 in Rice.

The gametic lethal gene gal in combination with the semidwarfing gene d60 causes complementary lethality in rice. Here, we attempted to ascertain the existence of gal and clarify male gamete abortion caused by d60 and gal. Through the F2 to F4 generations derived from the cross between D60gal-homozygous and d60Gal-homozygous, progenies of the partial sterile plants (D60d60Galgal) were segregated in a ratio of 1 semidwarf (1 d60d60GalGal):2 tall and quarter sterile (2 D60d60Galgal):6 tall (2 D60d60GalGal:1 D60D60GalGal:2 D60D60Galgal:1 D60D60galgal), which is skewed from the Mendelian ratio of 1 semidwarf:3 tall. However, the F4 generation was derived from fertile and tall heterozygous F2 plants (D60d60GalGal), which were segregated in the Mendelian ratio of 1[semidwarf (d60d60GalGal)]:2[1 semidwarf:3 tall (D60d60GalGal)]:1[tall (D60D60GalGal)]. The backcrossing of D60Gal-homozygous tall F4 plants with Hokuriku 100 resulted in fertile BCF1 and BCF2 segregated in a ratio of 1 semidwarf:3 tall, proving that d60 is inherited as a single recessive gene in the D60d60GalGal genetic background (i.e., in the absence of gal). Further, gal was localized on chromosome 5, which is evident from the deviated segregation of d1 as 1:8 and linkage with simple sequence repeat (SSR) markers. Next-generation sequencing identified the candidate SNP responsible for Gal. In F1 and sterile F2, at the binucleate stage, partial pollen discontinued development. Degraded pollen lost vegetative nuclei, but second pollen mitosis raising two generative nuclei was observed. Thus, our study describes a novel genetic model for a reproductive barrier. This is the first report on such a complementary lethal gene, whose mutation allows the transmission of a co-induced valuable semidwarfing gene d60.