Backcross Research Articles

Identification of Ceruloplasmin as a Gene that Affects Susceptibility to Glomerulonephritis Through Macrophage Function.

Crescentic glomerulonephritis (Crgn) is a complex disorder where macrophage activity and infiltration are significant effector causes. In previous linkage studies using the uniquely susceptible Wistar Kyoto (WKY) rat strain, we have identified multiple crescentic glomerulonephritis QTL (Crgn) and positionally cloned genes underlying Crgn1 and Crgn2, which accounted for 40% of total variance in glomerular inflammation. Here, we have generated a backcross (BC) population (n = 166) where Crgn1 and Crgn2 were genetically fixed and found significant linkage to glomerular crescents on chromosome 2 (Crgn8, LOD = 3.8). Fine mapping analysis by integration with genome-wide expression QTLs (eQTLs) from the same BC population identified ceruloplasmin (Cp) as a positional eQTL in macrophages but not in serum. Liquid chromatography-tandem mass spectrometry confirmed Cp as a protein QTL in rat macrophages. WKY macrophages overexpress Cp and its downregulation by RNA interference decreases markers of glomerular proinflammatory macrophage activation. Similarly, short incubation with Cp results in a strain-dependent macrophage polarization in the rat. These results suggest that genetically determined Cp levels can alter susceptibility to Crgn through macrophage function and propose a new role for Cp in early macrophage activation.

Zinc biofortification of wheat through preceding crop residue incorporation into the soil

Abstract We conducted a two-year field experiment to investigate the potential benefit of preceding crop residue incorporation into the soil as a strategy to enhance the density of bioavailable grain zinc (Zn) in a subsequent wheat ( Triticum aestivum L.) crop. Sunflower ( Heilianthus annuus L. cv. Allstar), sorghum ( Sorghum bicolor L. cv. Speed Feed), clover ( Trifolium pratense L.) and safflower ( Carthamus tinctorius L. cv. Koseh-e-Isfahan) were grown as preceding crop (precrop) on a Zn-deficient calcareous soil in central Iran, followed by a culture of two wheat cultivars i.e., Kavir and Back Cross Rushan. The harvested aboveground plant matter was air-dried, crushed into pieces of 0.5–2 cm size, mixed, and after taking a sample for analysis, incorporated manually into the upper 15 cm of the soil of one half of the same plot from which it had been harvested, while the other half received no residues. The aboveground residues of precrops were incorporated into soil or removed. A treatment with no preceding crop (fallow) and no residue incorporation, but with the same management otherwise, was implemented as control treatment. For both wheat cultivars studied, higher grain yield was obtained after clover (between 14 and 25.6%) and sunflower (between 11.3 and 19.5%) than that after safflower, sorghum and the fallow. All precrop treatments significantly increased the accumulation of grain Zn and N and decreased the phytic-acid-to-Zn (PA:Zn) molar ratio (by 5–41% in Kavir and by 11–48% in Back Cross), most effectively the clover treatment. The treatment effects on grain Zn were closely correlated with soil pH and dissolved soil organic carbon (DOC). The results show that the cultivation of appropriate precrops, especially legumes, can be an effective strategy to biofortify wheat grains with Zn without compromising yields.

Transposable Element Misregulation Is Linked to the Divergence between Parental piRNA Pathways in Drosophila Hybrids.

Interspecific hybridization is a genomic stress condition that leads to the activation of transposable elements (TEs) in both animals and plants. In hybrids between Drosophila buzzatii and Drosophila koepferae, mobilization of at least 28 TEs has been described. However, the molecular mechanisms underlying this TE release remain poorly understood. To give insight on the causes of this TE activation, we performed a TE transcriptomic analysis in ovaries (notorious for playing a major role in TE silencing) of parental species and their F1 and backcrossed (BC) hybrids. We find that 15.2% and 10.6% of the expressed TEs are deregulated in F1 and BC1 ovaries, respectively, with a bias toward overexpression in both cases. Although differences between parental piRNA (Piwi-interacting RNA) populations explain only partially these results, we demonstrate that piRNA pathway proteins have divergent sequences and are differentially expressed between parental species. Thus, a functional divergence of the piRNA pathway between parental species, together with some differences between their piRNA pools, might be at the origin of hybrid instabilities and ultimately cause TE misregulation in ovaries. These analyses were complemented with the study of F1 testes, where TEs tend to be less expressed than in D. buzzatii. This can be explained by an increase in piRNA production, which probably acts as a defence mechanism against TE instability in the male germline. Hence, we describe a differential impact of interspecific hybridization in testes and ovaries, which reveals that TE expression and regulation are sex-biased.

RAPD assisted selection of black gram (Vigna mungo L. Hepper) towards the development of multiple disease resistant germplasm

Black gram (Vigna mungo L. Hepper), is an extensively studied food crop which is affected by many abiotic and biotic factors, especially diseases. The yield potential of Black gram is shallow due to lack of genetic variability and biotic stress susceptibility. Core biotic stress factors include mung bean yellow mosaic virus (MYMV), urdbean leaf crinkle virus (UCLV), wilt (Fusarium oxysporum) and powdery mildew (Erysiphe polygoni DC). Although many studies determine resistant varieties to a particular disease, however, it is often complimented by low yield and susceptibility to other diseases. Hence, this study focuses on investigating the genetic relationships among three varieties and nine accessions of black gram having disease resistance to previously described diseases and susceptibility using random amplified polymorphic deoxyribonucleic acid (RAPD) markers. A total of 33 RAPD primers were used for diversity analysis and yielded 206 fragments. Number of amplified fragments ranged from two (OPN-1) to 13 (OPF-1). The highest similarity coefficient was observed between IC-145202 and IC-164118 (0.921), while lowest similarity was between PU-31 and IC-145202 (0.572). The genetic diversity obtained in this study along with disease analysis suggests PU31as a useful variety for the development of markers linked to MYMV, UCLV, wilt and powdery mildew resistance by marker-assisted back cross breeding and facilitates the production of crosses with multiple disease resistance.

Dissection of genetic architecture for oil content in soybean seed using two backcross populations

AbstractSoybean seed oil was valued in foods, animal feed and some industrial applications. Molecular marker‐assisted selection (MAS) for high‐oil‐content cultivars was an important method for soybean breeders. The objective of this study was to identify quantitative trait loci (QTL) and epistatic QTL underlying the seed oil content of soybeans across two backcross (BC) populations (with one common male parent ‘Dongnong47’) and two different environments. Two molecular genetic maps were constructed. They encompassed 1046.8 cM [with an average distance of 6.75 cM in the ‘Dongnong47’ × ‘Jiyu89’ (DJ) population] and 846.10 cM [with an average distance of 5.76 cM in the ‘Dongnong47’ × ‘Zaoshu18’ (DZ) population]. Nine and seven QTL were identified to be associated with oil content in the DJ and DZ populations, respectively. The phenotypic variation explained by most of the QTL was usually less than 10%. Among the identified QTL, those stable ones across multiple environments and populations often had stronger additive effects. In addition, three stable QTL in the DZ populations were identified in the similar genomic region of the three QTL in the DJ population [qDJE and qDZE‐1 were located near Satt151 of Chromosome 15 (Chr15), qDJA1 and qDZA1 were located near Satt200 of Chr15 (LG A1), and qDJD2‐1 and qDZD2‐1 were located near Sat365 of Chr17]. In conclusion, MAS will be able more effectively to combine beneficial alleles of the different donors to design new genotypes with higher soybean seed oil content using the BC populations.

Rapid Introgression of the Fusarium Wilt Resistance Gene into an Elite Cabbage Line through the Combined Application of a Microspore Culture, Genome Background Analysis, and Disease Resistance-Specific Marker Assisted Foreground Selection.

Cabbage is an economically important vegetable worldwide. Cabbage Fusarium Wilt (CFW) is a destructive disease that results in considerable yield and quality losses in cole crops. The use of CFW-resistant varieties is the most effective strategy to mitigate the effects of CFW. 01-20 is an elite cabbage line with desirable traits and a high combining ability, but it is highly susceptible to CFW. To rapidly transfer a CFW resistance gene into 01-20 plants, we used microspore cultures to develop 230 doubled haploid (DH) lines from a cross between 01-20 (highly susceptible) and 96-100 (highly resistant). One of the generated DH lines (i.e., D134) was highly resistant to CFW and exhibited a phenotypic performance that was similar to that of line 01-20. Therefore, D134 was applied as the resistance donor parent. We generated 24 insertion–deletion markers using whole genome resequencing data for lines 01-20 and 96-100 to analyze the genomic backgrounds of backcross (BC) progenies. Based on the CFW resistance gene FOC1, a simple sequence repeat (SSR) marker (i.e., Frg13) was developed for foreground selections. We screened 240 BC1 individuals and 280 BC2 individuals with these markers and assessed their phenotypic performance. The proportion of recurrent parent genome (PRPG) of the best individuals in BC1 and BC2 were 95.8 and 99.1%. Finally, a best individual designated as YR01-20 was identified from 80 BC2F1 individuals, with homozygous FOC1 allele and genomic background and phenotype almost the same as those of 01-20. Our results may provide a rapid and efficient way of improving elite lines through the combined application of microspore culture, whole-genome background analysis, and disease resistance-specific marker selection. Additionally, the cabbage lines developed in this study represent elite materials useful for the breeding of new CFW-resistant cabbage varieties.

Development of opaque-2 introgression line in maize using marker assisted backcross breeding

Two elite normal maize inbreds that produced heterotic experimental hybrid (OML 17-3×OML 42-9) with 45% yield advantage over the standard check Vivek QPM 9, were used for conversion to QPM status using opaque-2 donors (CML 176 and CML 186) using marker assisted back cross breeding. Each of the normal maize parental inbreds was used as female parent in separate conversion programme using cross combination OML 17-3×CML 176 and OML 42-9×CML 186. Foreground selection (using opaque-2 specific marker phi 057) combined with phenotypic selection for recipient parent at early back cross generations (BC1 to BC3) was carried out for rapid recovery of recurrent parent genotype. The BC3F1 plants showing heterozygous status (O2o2) were selfed and advanced to BC3F2 to enable for identification of homozygous recessive opaque-2 segregants at seedling stage. The most promising BC3F3 introgression lines from either cross combinations were finally selected based on higher tryptophan and lysine content. The newly developed introgression lines (OQL 176-17-3 and OQL 186-42-9) were at par with the QPM donors (CML 176 and CML 186) and nearly double the lysine and tryptophan content as compared to respective normal inbreds (OML 17-3 and OML 42-9). These may serve as valuable breeding materials for development of QPM hybrids.

Study on Backcross Population with Their Parents for Different Agro-Morphological Traits of Wild and Cultivated Rice ( Oryza sativa L.) Species

Wild rice is a potential source of many biotic and abiotic stress tolerant genes that could be incorporated to improve cultivated rice. The present rice varieties have narrow genetic base, thus wild rice could serve to extend the genetic base of the cultivated cultivars. To study the inheritance and ancillitary characters of different back cross populations and landraces available among us, we performed line X tester cross followed by backcrossing with recurrent parents. We used both local landraces and cultivated inbreds as parents to fulfill our crossing demand. The crossing of cultivated rice with wild rice and their backcross behavior showed that wild rice consists some desirable traits which can be introgressed to cultivated rice if there is no linkage drag. Some most desirable traits such as flag leaf angle, leaf width, panicle length which are responsible for higher photosynthesis were found higher in backcross progeny which indicates that these genotypes can be utilized further in generation nursery.

Combining ability of recombinant lines of papaya from backcrossing for sexual conversion

Os objetivos deste trabalho foram gerar estimativas de capacidade combinatoria de 22 linhagens de mamoeiro com testadores do grupo ‘Solo’ e ‘Formosa’ em esquema de top cross e identificar hibridos agronomicamente superiores. As linhagens foram selecionadas em geracoes de retrocruzamentos para conversao sexual, tendo como genitor recorrente, o genotipo dioico ‘Cariflora’ e como doador a linhagem elite ginoico-andromonoica, ‘SS 783’. As linhagens per se, os hibridos top crosses (hibridos T1 e hibridos T2) e duas testemunhas comercias foram avaliados em um delineamento em latice 8x8 quanto ao numero de nos sem fruto (NNSF-un), numero de frutos deformados (NFD-un), numero de frutos comerciais (NFC-un), peso medio de fruto (PMF-g), comprimento do fruto (CF-mm), diâmetro do fruto (DF-mm), espessura media da polpa (EP-cm), firmeza do fruto (FF-N), firmeza da polpa (FP-N), teor de solidos soluveis (TSS-°brix) e Produtividade (PROD-t ha-1). Obtiveram-se as estimativas de capacidade especifica de combinacao pela diferenca entre a media de cada hibrido obtido de um testador, com a media geral dos cruzamentos com o mesmo testador. A analise de variância realizada com as medias ajustadas revelou variabilidade genetica entre grupos de tratamentos para todas as caracteristicas avaliadas, bem como dentro de cada grupo de tratamento. Considerando os hibridos T1, as combinacoes que melhor conciliaram as estimativas de CEC para as caracteristicas produtivas e de qualidade de frutos foram: L3xT1, L8xT1, L10xT1, L11xT1, L16xT1, L17xT1 e L20xT1. Para os hibridos T2 foram: L12xT2, L13xT2, L17xT2, L21xT2 e L22xT2.

In-ovulo embryo culture in interspecific crosses of Gossypium

The immature hybrid embryos of five back crosses viz., (MCU 5 x G. armourianum ) MCU 5, (MCU 5 x G. raimondii ) MCU 5, (MCU 12 x G. raimondii ) MCU 12, (TCH 1569 x G. armourianum ) TCH 1569,(TCH 1609 x G. raimondii ) TCH 1609 were excised 8 days after pollination and were cultured in various concentrations of auxin and cytokinin. To prevent boll shedding in all the crosses, growth hormones NAA 100 mg/l and GA 3 50 mg/l was applied at the base of the pedicel for 8 days and then the ovules were excised and cultured on media to form calli. Out of different media combinations tried, maximum callus induction was observed in the medium containing IAA 2.0 mg/l, Kn 1.0 mg/l, CH 250 mg/l, AS 40 mg/l in all the crosses. Maximum response of callus induction was observed in the cross (MCU 5 x G. raimondii ) MCU5.

Morphological characterization and genetic diversity analysis of interspecific hybrids of sugarcane

Interspecific hybrid derivatives involving Saccharum spontaneum, S. robustum and S. barberi were morphologically characterized with twenty two qualitative and six agronomic traits. Principal component analysis (PCA) of qualitative traits revealed that first nine principal components with eigen value > 1 accounted for a cumulative variance of 62.40%. The traits viz., ligule shape, auricle type, internode shape and its alignment, cane thickness, dewlap color, leaf blade width and curvature, leaf sheath hairiness, bud cushion and bud groove were identified as principal discriminatory characters which will be useful in preliminary screening and identification of interspecific hybrids. Cluster analysis of qualitative traits grouped hybrids into seven clusters. Maximum inter cluster distance was between cluster IV and VI followed by cluster I and III, III and VII and between VI and VII. Metroglyph analysis of agronomic traits categorized hybrids into ten groups. Groups III, IV, V, VIII and X with highest mean index scores were identified as genetically most distant. Thirty eight superior interspecific hybrids with high index score for agronomic traits (from metroglyph analysis) and wider inter cluster distance were identified as prebreeding stocks and utilized in further backcross programmes. BC1 progenies of SBH 12–45 x Co 0303 and SRH 12–275 x Co 0240 were significantly superior for single cane weight and brix %. Elite recombinants from back crosses SSH 12–158 x Co 0209, SSH 12–409 x Co 09014 and SRH 12–119 x Co 94008 surpassed commercial check for cane yield and were on par for quality.

Toward the identification of dwarfing gene d60 that complements gametic lethal gene gal by Next-Generation Sequencer oriented genome analysis

The author previously discovered dwarfing gene, d60, and it complements the gametic lethal gene, gal, to cause gametic lethality in rice. Namely, in the F1 hybrid (genotype D60d60Galgal) of Koshihikari (D60D60galgal) × Hokuriku 100 (d60d60GalGal), male and female gametes having both gal and d60 become gametic lethal and the pollen and seed fertility decrease to 75%. Therfore, F2 progeny shows a unique mode of inheritance that is segregated into a ratio of 6 fertile long-culm (4D60D60: 2D60d60GalGal) : 2 partially fertile long-culm (D60d60Galgal = F1 type) : 1 dwarf (d60d60GalGal).Prior to Next-Generation Sequencing analysis targeting d60, it is required to develop isogenic genome of reference except for target d60 gene. When, the F1 (D60d60Galgal) progenies of ‘Koshihikari’ × ‘Hokuriku 100’ were backcrossed to ‘Koshihikari’ (D60D60galgal), BC1 F1 individuals segregated in a ratio of 1 tall and 25% sterile (D60d60galGal):2 tall (1 D60D60Galgal:1 D60D60galgal). Here, D60d60Galgal-heterozygous plants, can be recognized by pollen sterility prior to anthesis. Then Tall and 25% sterile BC1F1 plants (D60d60galGal) were selected by 25% pollen sterility and backcrossed with ‘Koshihikari’ as female parent to produce BC2F1 seeds. Hereafter, D60d60Galgal-heterozygous plants were selected in the first generation of each backcross (BCnF1) and immediately backcrossed repeatedly with Koshihikari to obtain isogenic genome useful for next-generation sequencing. That is to say, the target d60 DNA region narrowed down with each back cross generation, enabling identification of the target DNA mutation point by whole genomic sequencing.

Root uptake and xylem transport of cadmium in wheat and triticale as affected by exogenous amino acids

Organic acids exuded from plant roots significantly modify uptake and long-distance translocation of metals. Little is known about the effect of amino acids on metal ion uptake by plant roots. The present study investigated the effects of exogenous amino acids (histidine and glycine) in a nutrient solution on root uptake and xylem sap transport of cadmium (Cd) in triticale (× Triticosecale cv. Elinor) and bread wheat (Triticum aestivum L. cv. Back Cross Rushan). Plant seedlings were grown in a Cd-free modified Hoagland nutrient solution to which 1 µm Cd was added with either 50 µm histidine or 50 µm glycine or without amino acids at 4 weeks after germination. A control treatment consisted of a nutrient solution free of Cd and amino acids. In bread wheat, addition of histidine to the Cd-containing nutrient solution resulted in a higher operationally defined symplastic Cd fraction but a lower apoplastic one in the roots. In triticale, addition of either amino acid decreased the symplastic Cd fraction but increased the apoplastic one. Addition of histidine to the nutrient solution increased Cd concentration in wheat xylem sap but had no significant effect on Cd concentration in triticale xylem sap. Compared with the Cd-only treatment, the glycine-containing treatment led to significantly reduced Cd concentrations in xylem sap of both plant species. Wheat plants supplied with histidine and Cd accumulated greater amounts of Cd in their shoots than those supplied with Cd alone. Glycine had no significant effects on the Cd content of wheat shoots but decreased it in triticale shoots. Results indicate that the effects of amino acids on plant root uptake and xylem sap translocation of Cd depend on the type of amino acid supplemented. This finding is of great importance for selecting and/or breeding cultivars with Cd-toxicity tolerance.

Plasma membrane ATPase and H+ transport activities of microsomal membranes from wheat roots under Ni deficiency conditions as affected by exogenous histidine

ATPase activity and ATP-dependent H+ transport have been analyzed in membrane vesicles isolated from a winter wheat cultivar (Triticum aestivum cv. Back Cross Rushan) which was exposed to different concentrations of nickel (Ni) and histidine (His). Seedlings were grown in a modified Johnson nutrient solution and then exposed to the uptake solution containing 10μM Ni to which either 100μM His or no amino acid was added. Control plants were transplanted to nutrient solutions free of Ni and His. According to our results, using Ni alone or together with His enhanced the activity of plasma membrane (PM) H+-ATPase and resulted in a higher pH gradient across the plasma membrane. The highest initial rate of H+-pumping by PM H+-ATPase also achieved in the Ni alone treatment which was roughly 2.2 times higher than the control treatment. His applied together with Ni to the nutrient solution resulted in higher Ni uptake but lower H+-ATPase activity. Our results suggest that the (PM) H+-ATPase in wheat roots plays an important role in Ni uptake but using His in combination with Ni can moderate the pump activity. Undissociated Ni-His may directely taken up via His transporters which seems to be less dependent on ATPase activity.

Effects of nickel on zinc uptake and translocation in two wheat cultivars differing in zinc efficiency

Low availability of zinc (Zn) in soil can limit plant growth and yields. In soils with elevated nickel (Ni) concentrations, which can be due to anthropogenic and geogenic sources, Zn uptake by plants may be inhibited due to competition between the two elements. Here we used a hydroponic system to investigate short-term effects of a wide range of Ni concentrations on Zn uptake and translocation in two spring wheat cultivars at two different levels of Zn supply. Seedlings of the Zn efficient cultivar Back Cross Rushan and the Zn inefficient cultivar Kavir were grown for three weeks in Zn and Ni free nutrient solution and then exposed for two days to either 0, 1, 2, 10, 20, or 40μM Ni and either 400nM or 2μM Zn, before they were harvested. Increasing Ni had no influence on Zn uptake by Kavir at the low Zn level and even slightly enhanced it in Back Cross Rushan, which means that competition by Ni for uptake sites was irrelevant and suggests that Zn uptake was governed by a highly selective uptake system under these conditions. At the high Zn level, Ni had contrasting effects on the uptake of Zn in the two cultivars: Increasing Ni led to a strong increase in Zn uptake in Kavir as opposed to a slight decrease in Back Cross Rushan. The difference indicates that the two cultivars strongly differ in their low-affinity Zn uptake systems. Also the fraction of Zn translocated to the shoots differed between the two cultivars at high Zn supply, while they were very similar at the low Zn level. A strong decrease with increasing Ni solution concentration was observed in Kavir at the high Zn level, whereas there was little Ni dependence of root-to-shoot translocation in Back Cross Rushan. The findings suggest that differences in root Zn compartmentalization may be involved in the different Zn efficiencies of the cultivars.

Assessment of variability for yield, component traits and reaction to foliar fungal diseases in back cross population of groundnut (Arachis hypogaea L.)

Three BC1F1 populations viz., TMV (Gn) 13 × GPBD 4, CO 7 × GPBD 4 and TMV 2 × GPBD 4 along with their parental lines of groundnut were evaluated for variability, heritability and genetic advance. High magnitude of PCV and GCV coupled with broad sense heritability and genetic advance as per cent of mean for these characters studied such as number of pods per plant, shell weight per plant, rust disease score, late leaf spot (LLS) disease score, pod yield per plant and kernel yield per plant in all the populations. So, it could be concluded that these characters were under the control of additive type of gene action and hence selection may be effective for these traits in these populations.

Genetic Analysis and QTL Detection on Fiber Traits Using Two Recombinant Inbred Lines and Their Backcross Populations in Upland Cotton.

Cotton fiber, a raw natural fiber material, is widely used in the textile industry. Understanding the genetic mechanism of fiber traits is helpful for fiber quality improvement. In the present study, the genetic basis of fiber quality traits was explored using two recombinant inbred lines (RILs) and corresponding backcross (BC) populations under multiple environments in Upland cotton based on marker analysis. In backcross populations, no significant correlation was observed between marker heterozygosity and fiber quality performance and it suggested that heterozygosity was not always necessarily advantageous for the high fiber quality. In two hybrids, 111 quantitative trait loci (QTL) for fiber quality were detected using composite interval mapping, in which 62 new stable QTL were simultaneously identified in more than one environment or population. QTL detected at the single-locus level mainly showed additive effect. In addition, a total of 286 digenic interactions (E-QTL) and their environmental interactions [QTL × environment interactions (QEs)] were detected for fiber quality traits by inclusive composite interval mapping. QE effects should be considered in molecular marker-assisted selection breeding. On average, the E-QTL explained a larger proportion of the phenotypic variation than the main-effect QTL did. It is concluded that the additive effect of single-locus and epistasis with few detectable main effects play an important role in controlling fiber quality traits in Upland cotton.

Estimation of mean performance in sorghum downy mildew resistant back cross progenies (BC3F1) of maize

The present investigation was carried out at Department of Millets, Centre for Plant Breeding and Genetics, Tamil Nadu Agricultural University, Coimbatore, Tamil Nadu, India to identify the best performing sorghum downy mildew resistant progeny for agronomical traits. The objective of this study was to identify the better per se performance of the resistant progeny. Twelve biometrical characters of sixteen SDM resistant progenies viz., UMI 79/936-C1-3-2, UMI 79/936-C1-3-4, UMI 79/936-C1-7-2, UMI 79/936-C1-7-7, UMI 79/936-C1-29-8, UMI 79/936-C1-29-9, UMI 79/936-C1-29-13, UMI 79/936-C1-29-23, UMI 79/936-C1-29-35, UMI 79/936-C1-29-36, UMI 79/936-C1-67-3, UMI 79/936-C1-67-12, UMI 79/936-C1-67-25, UMI 79/936-C1-101-12, UMI 79/936-C1-101-13 and UMI 79/936-C1-101-14 were used for mean performance. Studies revealed that among the progenies, UMI 79/936-C1-7-7 and UMI 79/936-C1-7-2 showed better per se performance for yield contributing characters. These two progenies showed highest mean values than the other progenies. It exhibited more mean values than the parents for the characters viz., cob length, cob diameter, number of rows per cob, number of. kernels per row, cob weight, yield per plant, 100 grain weight. Based on the mean values progenies UMI 79/936-C1-7-7 and UMI 79/936-C1-7-2 confirmed as the best progenies.

Evaluation of BC3F1 progenies against sorghum downy mildew in maize (Peronosclerospora sorghi)

An experiment was carried out during Rabi, 2013 at Eastern Block of the Central Farm Unit, Department of Agronomy, Tamil Nadu Agricultural University, Coimbatore, Tamil Nadu, India to identify resistant progenies in BC 3 F 1 population against sorghum downy mildew (SDM) incited by Peronosclerospora sorghi . Sorghum downy mildewis one of the most serious diseases in maize producing areas throughout the world. P. sorghi (SDM) is a factor that limits maize production in several countries of Asia (Rifin, 1983). Therefore, there is a need to develop the new maize cultivars with resistance to SDM in order to enhance the yield. In this present study, experiments were undertaken under vigorous artificial infection conditions in spreader row technique during Rabi, 2013 for characterization of responses of 22 back cross progenies to the SDM; in which 16 progenies were confirmed as phenotypically resistant to sorghum downy mildewviz., UMI 79/936- C1-3-2, UMI 79/936-C1-3-4, UMI 79/936-C1-7-2, UMI 79/936-C1-7-7, UMI 79/936-C1-29-8, UMI 79/936-C1-29-9, UMI 79/ 936-C1-29-13, UMI 79/936-C1-29-23, UMI 79/936-C1-29-35, UMI 79/936-C1-29-36, UMI 79/936-C1-67-3, UMI 79/936-C1-67-12, UMI 79/936-C1-67-25, UMI 79/936-C1-101-12, UMI 79/936-C1-101-13 and UMI 79/936-C1-101-14. Resistant lines will serve as basis material for developing single cross and double cross hybrids for resistance against sorghum downy mildew in maize.

Genetic Analysis of a Dwarf Vine and Small Fruit Watermelon Mutant

The dwarf vine and small fruit watermelon, referred to as ‘dsh’ in this study, is a natural mutant of the ordinary watermelon, ‘Hanxuan Lvyuan’. Morphological assessment indicated that its main vine length, internode length, and single-fruit weight were significantly lower than those of the ordinary watermelon (P < 0.05). After crossing the mutant with two ordinary watermelons, following by inbreeding the F1 and backcrossing (BC) F1 to ‘dsh’, the F1, F2, and BC generations were obtained. Genetic analysis of vine type and single-fruit weight showed that the F1 generation consisted of long-vine plants, with single-fruit weight significantly higher than that of the ordinary parent watermelon (P < 0.05). The long and short vine plant ratios of the F2 and BC populations conform to the Mendel's segregation ratios of 3:1 and 1:1 (P > 0.05), respectively. It was suggested that this dwarf and small fruit mutation was a single recessive gene trait that followed a Mendel's inheritance.