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1.
Aflatoxin accumulation in maize (Zea mays L.) kernels is a serious economic and health problem that reduces grain quality and nutritional values and causes death to livestock and humans. Understanding the genetic parameters and heterotic responses of exotic maize inbred lines can facilitate their use for developing aflatoxin resistant parents of hybrids in Africa. This study was designed to (1) determine the heterotic affinities of aflatoxin resistant exotic lines, (2) identify exotic inbreds with good combining ability, and (3) determine the mode of inheritance of resistance to aflatoxin contamination in these lines. A line?×?tester mating design was used to determine combining ability of 12 yellow and 13 white inbreds and classify them into heterotic groups. The inbreds were crossed to two adapted testers representing two African heterotic groups and the resulting testcrosses along with hybrid checks were evaluated in separate trials at two locations for 2 years in Nigeria. General combining ability (GCA) effects were more important than specific combining ability effects for aflatoxin and grain yield. Among 15 exotic inbred lines having negative GCA effects for aflatoxin and 13 with positive GCA effects for grain yield, six combined the two desired traits. Five white and six yellow endosperm testcrosses were found to be good specific combiners for the two desired traits. The exotic lines with negative GCA effects for aflatoxin accumulation will be used as donor parents to develop backcross populations for generating new inbred lines with much higher levels of resistance to aflatoxin accumulation.  相似文献   

2.
Modifier loci in QPM play a vital role in achieving acceptable degree of kernel hardness and accumulation of lysine and tryptophan. This study was undertaken to characterize a set of diverse QPM inbreds using SSRs linked to endosperm and amino acids modifier loci for their effective utilization in the breeding programme. Significant variation was observed for endosperm modification (25–100% opaqueness), tryptophan (0.056–0.111%) and lysine (0.223–0.444%). Generally, inbreds with soft endosperm possessed more tryptophan and lysine than inbreds with higher vitreousness. SSRs generated 341 alleles with two to seven alleles per locus. The frequency of unique and rare alleles was more for amino acid modifications, compared to endosperm modifications. Phylogenetic analyses grouped the inbreds into three major clusters, and the study identified suitable crosses for accumulation of endosperm and amino acids modifiers. QPM inbreds with desirable modifications identified here would serve as suitable donor for both opaque2 and modifier loci in the marker‐assisted backcross breeding. Further, contrasting inbreds can be used for generating mapping populations to identify new modifier loci underlying both endosperm and amino acids modifications.  相似文献   

3.
A kernel screening assay (KSA) was used to assess the genetic and environmental effects on the vulnerability of maize to aflatoxin accumulation. Kernels of 26 inbred lines that had been grown in seven environments, and 190 lines of the Intermated B73xMo17 (IBM) population grown in one location in the United States, were inoculated with a toxigenic strain of A. flavus and incubated in the dark at 30°C for 6 days. Percent kernel colonization (PKC), sporulation and aflatoxin were influenced by the maize genotypes (G), the location (“ear environment” or E) and the GxE interactions. Overall, low broad‐sense heritabilities were observed for PKC, sporulation and aflatoxin. PKC was significantly correlated with sporulation in all environments. Aflatoxin was positively correlated with colonization for two and with sporulation for all ear environments. Higher grain sulphur or magnesium in IBM was associated with less colonization or aflatoxin. Postharvest susceptibility of maize to aflatoxin is thus influenced by factors that are modulated by the ear environment. In a KSA, sporulation could be a proxy test for aflatoxin accumulation.  相似文献   

4.
Summary A better understanding of the relationships between kernel characteristics associated with eating quality and stand establishment could be helpful in selection of superior genotypes by the sweet corn industry. A set of sweet corn (Zea mays L.) inbred lines with different endosperm mutations (su1, su1 se1 and sh2) were evaluated for field emergence and seedling growth rate at two locations over two years. Kernel characteristics associated with eating quality (kernel moisture concentration, kernel tenderness, sugars, phytoglycogen and dimethyl sulfide (DMS) concentrations were determined for the same inbreds by laboratory analysis from ears harvested at 18 and 22 days after pollination (DAP). Amounts of sugars, phytoglycogen and starch were also measured in mature dry kernel samples of the same inbreds. Extensive genetic variability was found among endosperm mutations and among genetic backgrounds within the different endosperm groups for most of the characteristics under study. Most of the kernel attributes associated with eating quality were uncorrelated indicating that selection to improve specific eating quality characteristics can be conducted simultaneously. A negative correlation between field emergence and sugar concentrations in immature kernels suggests that in breeding programs designed to develop germplasm with improved germination and stand establishment, concurrent attention must be given to the fresh quality of the harvested product. This information is of value to breeders and commercial growers for selection of sh2 and su1 se1 lines with superior field emergence and eating quality.Abbreviations (DAP) days after pollination - (DMS) dimethyl sulfide  相似文献   

5.
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6.
Water stress during silking or early kernel development decreases the number of kernels set by corn (Zea mays L.) plants. Previous work has suggested that lack of assimilate supply due to water stress at silking was a major factor in the resulting reproductive failure. A greenhouse experiment was conducted to test the hypothesis that sucrose supplementation of water stressed corn plants can prevent decreased kernel set. Sucrose was injected into corn stems at three concentrations [0 (distilled water), 150 and 300 g L?1] for 30 days starting at silking. Water availability was controlled by either maintaining a water table at 50 cm from the soil surface (well watered) or by withholding water starting one week before silking (water stress) until the fifth day after silking. The photosynthesis rate of water stressed plants was 25% that of well-water plants on the first day of silking. On average, the daily injection rate for distilled water was 1 mL higher than that of the sucrose treatments over a 30 day injection period. No difference in daily uptake rate was observed between the 150 and 300 g sucrose L?1 treatments. Over water availability treatments approximately 17 g sucrose were injected into corn plants during the 30 day injection period. Corn plants receiving sufficient water supply produced bigger ears, with more seeds and greater 100-seed weight values, leading to higher total plant dry matter accumulation than water stressed plants. Injection of 300 g sucrose L?1 increased the weight of the injected internodes by 28%, compared with distilled water injection. The highest grain yield was for the plants injected with 150 g sucrose L?1, but only under sufficient water supply. The plants injected with 300 g sucrose L?1 produced the least grain regardless of moisture availability. Thus, the exogenous sucrose supplementation influenced kernel set only under conditions of sufficient soil water supply. These results indicate that plant reproductive development after silking was limited more by water availability than assimilate supply, suggesting that some overall plant response to water stress, perhaps mediated by hormonal signalling, was more important than carbohydrate supply. These results indicated that plant desiccation occurred during floral development or pollination; irreversible loss of florets on unsuccessful pollination could result, thus, grain yield would be limited more by sink size than by availability of photosynthate.  相似文献   

7.
The European com borer (ECB) Ostrinia nubilalis H. is a major pest in World maize Zea mays L. production. Objectives of this study were to (1) investigate the genotypic variance and covariance in testcrosses of European flint and dent inbreds for ECB resistance and agronomic traits, and (2) estimate the correlation between line per se and testcross performance for ECB resistance traits. A total of 16 flint and 24 dent inbreds and their testcrosses with two testers from the opposite germplasm pool were evaluated in four and three German environments, respectively. Using artificial infestation with ECB larvae, resistance was assessed by damage rating of stalks, tunnel length in dissected stalks, and relative yield of infested plots compared with protected plots. Yield losses due to ECB damage in testcross hybrids amounted to 40%. Significant genotypic variances between flint and dent lines and high heritabilities were found for damage rating of stalks for both line per se and testcross performance. Heritabilities were low or intermediate for tunnel length and relative grain yield. Correlations between line per se and testcross performance were tight for the damage rating of stalks and moderate for tunnel length and relative yield in both flint and dent germplasm. For damage rating of stalks, per se performance of lines tested in a few environments can be used to predict their testcross performance. In contrast, assessment of testcross performance for tunnel length and relative yield requires evaluating testcrosses with several testers in multi-environment trials.  相似文献   

8.
A two season study was conducted to compare the onion cultivars TG1015Y and IPA-3 for resistance to thrips in South Texas. Narrow and broad sense heritabilities were estimated from populations developed from the cross, ‘IPA-3’ × ‘TG1015Y’. Parents, F1, F2, and the respective backcross populations were evaluated for thrips numbers at the Texas Agricultural Experiment Station, Weslaco, TX. ‘IPA-3’ had significantly fewer thrips than ‘TG1015Y’ in both seasons. Yield was significantly different only in the 1996–97 season. The heritability of thrips resistance in this study was very low. Depending on the methods of estimation h 2 was 5.3% and 4.0%, and H 2 was 4.1% and 8.0%. These results suggest that greater genetic gains for thrips resistance in onion can be achieved by selection on a family basis rather than using single plant selection. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

9.
The presence of high levels of sinigrin in the seeds represents a serious constraint for the commercial utilisation of Ethiopian mustard (Brassica carinata A. Braun) meal. The objective of this research was the introgression of genes for low glucosinolate content from B. juncea into B. carinata. BC1F1 seed from crosses between double zero B. juncea line Heera and B. carinata line N2-142 was produced. Simultaneous selection for B. carinata phenotype and low glucosinolate content was conducted from BC1F2 to BC1F4 plant generations. Forty-three BC1F4 derived lines were selected and subject to a detailed phenotypic and molecular evaluation to identify lines with low glucosinolate content and genetic proximity to B. carinata. Sixteen phenotypic traits and 80 SSR markers were used. Eight BC1F4 derived lines were very close to N2-142 both at the phenotypic and molecular level. Three of them, with average glucosinolate contents from 52 to 61 micromoles g−1, compared to 35 micromoles g−1 for Heera and 86 micromoles g−1 for N2-142, were selected and evaluated in two additional environments, resulting in average glucosinolate contents from 43 to 56 micromoles g−1, compared to 29 micromoles g−1 for Heera and 84 micromoles g−1 for N2-142. The best line (BCH-1773), with a glucosinolate profile made up of sinigrin (>95%) and a chromosome number of 2n = 34, was further evaluated in two environments (field and pots in open-air conditions). Average glucosinolate contents over the four environments included in this research were 42, 31 and 74 micromoles g−1 for BCH-1773, Heera and N2-142, respectively. These are the lowest stable levels of glucosinolates reported so far in B. carinata.  相似文献   

10.
Glucosinolate levels in leaves were determined in a collection of 36 varieties of nabicol (Brassica napus pabularia group) from northwestern Spain grown at two locations. Crude protein, acid detergent fibre, and sensory traits were also assessed by a consumer panel. The objectives were to determine the diversity among varieties in total glucosinolate content and glucosinolate profile and to evaluate their sensory attributes in relation to glucosinolate content for breeding purposes. Eight glucosinolates were identified, being the aliphatic glucosinolates, glucobrassicanapin, progoitrin, and gluconapin the most abundant. Glucosinolate composition varied between locations although the glucosinolate pattern was not significantly influenced. Differences in total glucosinolate content, glucosinolate profile, protein, acid detergent fibre, and flavour were found among varieties. The total glucosinolate content ranged from 1.4 μmol g−1 to 41.0 μmol g−1 dw at one location and from 1.2 μmol g−1 to 7.6 μmol g−1 dw at the other location. Sensory analysis comparing bitterness and flavour with variation in glucosinolate, gluconapin, progoitrin, and glucobrassicanapin concentrations suggested that other phytochemicals are probably involved on the characteristic flavour. The variety MBG-BRS0035 had high total glucosinolate, glucobrassicanapin, and gluconapin contents at both locations and could be included in breeding programs to improve the nutritional value of this vegetable crop.  相似文献   

11.
The endosperm structure of the wheat kernel determines its end-use quality. The known diversity in endosperm structure is related to the Pina-D1 and Pinb-D1 genes comprising the Ha locus on chromosome 5DS. We studied the effect of a gene introduced into bread wheat from the diploid relative, Aegilops speltoides, a putative donor of the B genome. Grain hardness and vitreousness were investigated in lines with homoeologous introgressions into chromosome 5A of spring wheat cultivar ‘Rodina’. One introgression changed the endosperm texture from hard to soft and had the same effect when transferred to other wheat genotypes. This indicated that its action was analogous to the dominant allele at the Ha locus. The temporary symbol Ha–Sp is given to the gene. Segregation for vitreousness in F3 offspring from monosomic hybrids was also investigated. Genetic variability for endosperm structure in wheat may be extended by manipulating both hardness and vitreousness. Wheat germplasm with introgressions from wild relatives can increase the genetic variability of milling characteristics.  相似文献   

12.
Firmness is an indicator of fruit freshness and a main component of tomato (Solanum lycopersicum) fruit texture. In this work, the genetic variability in fruit firmness and stiffness was analyzed in pre- and postharvest periods and underlying anatomical and biochemical traits were identified. Three tomato contrasted parental lines and six derived quantitative trait loci (QTL)-NILs harboring texture QTL on chromosome 4 (QTL4) and 9 (QTL9) were analyzed; the seasonal variability was assessed on two distant trusses. Firmness and stiffness were measured by compression and puncture tests at harvest and after 7-day storage at 20 °C. QTL4 poorly influenced the textural variables, on the contrary to QTL9 which increased firmness measured by puncture test and had similar effects in the two genetic backgrounds. According to this test, firmness increased along the season, but ranks among genotypes and QTL effects were hardly affected. Only some of the QTL effects were still significant after storage and firmness losses were not predicted by firmness at harvest. Fruit firmness and stiffness measured by puncture tests correlated with both morphological (locular number, R = −0.89), histological (cell size, R < −0.80) and biochemical (dry matter (R > 0.82) and soluble sugar content (R < −0.74)) fruit traits. In contrast, compression test values hardly correlated with any of the measured traits. This work provided an original comprehensive approach to analyse fleshy fruit firmness and paves the way for a future predictive model.  相似文献   

13.
Pearl millet (Pennisetum glaucum) is the most important cereal in crop-livestock production systems in arid and drier semi-arid environments valued for its grain and dry stover. The conventional approach of improving grain yield through greater partitioning of biomass to the grain and decreased stover yield is not a viable strategy for arid regions where biomass also needs to be improved. The current research tested the hypothesis whether biomass can be improved without extending the crop duration. The 232 F5 lines derived from a cross (J28 × RIB 335/18) were evaluated in their testcross form along with three commercial hybrids under arid zone conditions. Biomass, grain and stover yields, panicle number, grain size and grain number panicle−1 varied 1.8 to 2.7 fold in progeny testcrosses. Variation in duration of flowering time accounted for only 2% of variation in biomass, indicating that considerable scope existed for selection of testcrosses, and by implication, of F5 progenies with high biomass independent of crop duration. Stover yield accounted for 72% of differences in total biomass with remaining accounted for by grain yield. From among 92 and 132 testcrosses that had flowering time comparable to two early checks, most had significantly higher biomass, grain and stover yields than these early checks but none of the testcrosses had earliness on par with extra-early maturing hybrid HHB 67. Mean superiority of best 5% testcrosses over early checks was 58% for biomass, 68% for stover yield and 53% for grain yield. The results indicated that there are good prospects of improving biomass in arid zone pearl millet without significantly compromising crop duration.  相似文献   

14.
以玉米品种登海11为材料, 分别进行大田和温室试验, 观察灌浆期果穗不同部位籽粒玉米素(Z)+玉米素核苷(ZR)、吲哚-3-乙酸(IAA)、脱落酸(ABA)和赤霉素(GA3)含量变化及其与胚乳发育和籽粒灌浆的关系。结果显示, 籽粒最大胚乳细胞数目、最大胚乳细胞增殖速率及平均速率、最大灌浆速率、平均灌浆速率和百粒重表现为果穗下部籽粒>中部籽粒>上部籽粒。在胚乳细胞活跃增殖期或活跃灌浆期, 籽粒Z+ZR、IAA和ABA含量以果穗下部籽粒最高, 中部籽粒其次, 上部籽粒最低。GA3含量则为果穗上部籽粒>中部籽粒>下部籽粒。两个试验的结果趋势一致。胚乳细胞增殖速率和籽粒灌浆速率与籽粒Z+ZR、IAA和ABA含量呈极显著正相关, 与籽粒GA3含量呈显著负相关。说明玉米果穗上部籽粒轻主要是由于这些籽粒的胚乳细胞增殖速率小, 导致其胚乳细胞数少, 这与其灌浆期较低的Z+ZR、IAA和ABA含量及较高的GA3含量有密切关系。  相似文献   

15.
The ability of grape cultivars to produce resveratrol in response to UV radiation is associated with their resistance to fungal pathogens. In this study, we evaluated the UV-induced resveratrol production potential of grape flowers and green berries of 72 grape genotypes. Their ability to produce resveratrol in response to UV radiation was used to establish a selection criterion for screening genotypes for resistance to gray mold and powdery mildew. We quantified resveratrol in grape flower extracts from pre-bloom and early bloom flowers after exposure to UV radiation. There was a strong negative correlation between UV-induced resveratrol production and susceptibility to Botrytis infection. The grape genotype was considered to be susceptible to gray mold when the resveratrol content of whole flower clusters was less than 10 μg g−1 FW after the UV treatment. We determined resveratrol production in response to UV radiation in whole grape berries from 0 to 30 days after full bloom. The ability to produce resveratrol in response to UV increased by 8- to 20-times during this period, depending on the genotype. At 30 days after full bloom, Vitis vinifera genotypes generally had low levels of resveratrol (<50 μg g−1 FW), while interspecific hybrids, especially the North American cultivars, had high levels (>50 μg g−1 FW). There were clear varietal differences in resistance to Erysiphe (powdery mildew) infection. Susceptibility to Erysiphe infection was strongly negatively correlated with UV-induced resveratrol production.  相似文献   

16.
Protein digestibility in grain sorghum (Sorghum bicolor (L.) Moench) is affected by the structure of endosperm protein bodies that limits access of digestive enzymes to storage protein. In this experiment, we studied the effect of endosperm dosage of high digestible alleles (hd+) on protein digestibility in sorghum hybrids carefully constituted for such a study. We also examined the effect that these alleles may have on endosperm protein body structure and agronomic performance of the hybrids. The results showed that protein digestibility, endosperm texture and protein body morphology were highly influenced by dosage of mutant alleles. Genotypes carrying two or more hd+ alleles had significantly higher protein digestibility than those with one or no mutant allele. Similarly, higher doses of these alleles resulted in opaque endosperm phenotype while the wild type alleles produced normal vitreous texture. Moreover, hybrids carrying variable proportions of mutant alleles had uniquely irregular but variable protein body structure that was distinct from spherical protein bodies found in normal genotypes. Agronomic performance was not affected by dosage of digestibility alleles.  相似文献   

17.
磷肥对甜玉米籽粒植酸和锌有效性的影响   总被引：1，自引：0，他引：1  
为明确磷肥对甜玉米籽粒营养特性的影响,利用不同品种的磷肥定位试验以及磷肥梯度水平试验,探讨甜玉米籽粒植酸、磷(P)、锌(Zn)含量及Zn有效性的时间(不同灌浆期)和空间(果穗上、中、下部;籽粒果皮、胚乳和胚)变化及其对外源磷肥的响应特性。试验结果表明,甜玉米籽粒的P和植酸含量随磷肥用量的增加而增加,Zn含量及其有效性则呈现下降趋势。磷肥投入对吐丝后16～24 d籽粒的植酸、P和Zn的积累(mg plant–1)的影响最为显著,而对不同灌浆时期Zn有效性均表现出抑制效应。在中磷水平下,果穗不同穗位籽粒植酸(g kg–1)和Zn有效性的差异并不显著。高磷水平显著提高了中、下部果穗植酸的含量,但对不同穗位籽粒Zn含量和Zn有效性均存在抑制效应。对籽粒内不同部位(果皮、胚乳和胚)进行比较,植酸、P以及Zn含量均以胚中含量最高,积累量占比则以胚乳中最高;而Zn有效性以胚中最高。高磷处理可显著提高籽粒内不同部位植酸和磷含量,降低Zn含量及其有效性。综上,合理磷肥施用可促进籽粒Zn积累,而过量磷肥投入会显著增加不同灌浆时期,以及胚乳和胚中的植酸含量和积累量...  相似文献   

18.
The data presented herein reports a rapid and efficient method for direct plant regeneration at high frequency without intervening callus formation from shoot tip (93%) and nodal segment (60%) cultured on MS media supplemented with 0.5 mg l−1 KIN, 0.25 mg l−1 BAP, 0.1 mg l−1 IAA and 100 mg l−1 CH. Conversely, leaf and internodal explants were poorly responsive. Adventitious shoot buds arose not only from the cut ends but all along the surface of the explants leading to the formation of clusters with multiple shoots. Multiple shoots upon transfer to MS media supplemented with 2.0 mg l−1 IBA induced efficient rooting (80%). In vitro flowering was observed when tissue culture-raised plantlets were maintained for extended period in culture. Shikonin was induced in roots of regenerated plants which often exudates in the culture medium was quantified spectrophotometerically by recording absorbance at 620 nm and estimated to be 0.50 mg g−1 fresh weight of tissue at the end of the 50 days of culture. The regenerated plants were successfully acclimatized, hardened, and transferred to soil in green house for micropropagation. The protocol developed here will be very useful for the supply of Arnebia hispidissima all year as a raw product necessary for obtaining Shikonin for the cosmetic, dyeing, food, and pharmaceutical industries.  相似文献   

19.
Summary The genetic control of endosperm modification in 12 opaque-2 maize (Zea mays L.) inbred lines was investigated by means of a diallel cross experiment conducted across two environments. Kernel vitreousness and kernel hardness were determined by partially dominant genes. Additive gene action was largely responsible for kernel modification. A favourable general combining ability for kernel vitreousness and kernel hardness was positively correlated with an accumulation of dominant kernel modifying genes. South African sources of endosperm modifiers have been found to be similar to those used in other quality protein maize breeding programmes. Certain inbred lines displayed sufficient genetic potential for use in a quality protein maize hybrid breeding programme.  相似文献   

20.
Summary This study analyzes the components of phenotypic variation for abscisic acid (ABA) content in maize (Zea mays L.) leaves and the correlations with drought sensitivity index (DSI) and silk delay (SD), involved in the reaction to water deficit. Eight early- and seven medium-maturity inbreds were examined in field trials: in 1990 with low irrigation volume and in 1991 with low and high irrigation volumes. ABA concentration and DSI were investigated at growth stages (S) corresponding to stem elongation (S3), appearance of the first husks (S4), and mid-end of silking (S5). The ABA concentration was significantly higher in conditions of water deficit and in the later growth stage. The genetic component for ABA concentration attained higher relative values than those shown by DSI in the same growth stages and by SD; moreover, it increased from growth stage 3 to stage 5. The genotype × year and genotype × irrigation volume interactions were smaller for ABA concentration than for DSI and SD. The broad sense heritability on a plant basis, estimated in drought conditions, for ABA concentration ranged from 21.4 to 55.1% according to maturity group and growth stage. A wide variation was observed among lines for ABA concentration: the medium-maturity group showed a three-fold range (from 219 to 605 ng ABA g–1 dry weight). No clear relationships between ABA concentration, DSI and SD were found. These results indicate the feasibility of a selection for ABA concentration within segregating populations derived from crosses between the inbred lines herein tested.Abbreviations ABA - abscisic acid - DSI - drought sensitivity index - DW - dry weight - SD - silk delay  相似文献   

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