Author: Chaba Jampatong Publisher: ISBN: Category : Corn Languages : en Pages : 160
Book Description
European corn borer (ECB), Ostrinia nubilalis Hübner, family Crambidae, order Lepidoptera, is a serious insect pest of maize (Zea mays L.) in the United States. Losses to farmers resulting from ECB damage and control costs exceed $1 billion each year. An understanding of the genetic basis for ECB resistance should increase the efficiency of breeding for insect resistant varieties. The objectives of this study were to determine the number, genomic positions, and genetic effects of quantitative trait loci (QTL) conferring resistance to the first- and second-generation of European corn borer (1ECB, 2ECB), and to observe QTL × environment interactions. The study included 244 F 2-3 families derived from the cross of B73 (susceptible) × Mo47 (resistant). Evaluating resistance against 1ECB, plants were manually infested at the eight- to ten-leaf stage of plant development. Leaf feeding damage was assessed three weeks after infestation with a visual rating scale. Evaluation for resistance to 2ECB involved manually infesting at anthesis stage of plant development. Approximately seven weeks later, stalks were split lengthwise and number and the length of tunnels visually estimated in inches. Plant height and rind penetrometer resistance were measured two weeks after flowering. Quantitative trait loci analyses for individual environments and combined across three environments were performed by composite interval mapping using QTL Cartographer. For 1ECB leaf feeding, nine QTLs were identified on chromosomes 1(three QTLs), 2, 4 (two QTLs), 5, 6, and 8. Seven QTLs for resistance to 2ECB tunnel length were found on chromosomes 2, 5 (two QTLS), 6 (two QTLs), 8, and 9. Twelve QTLs for resistance to 2ECB tunnel length adjusted for plant height were identified on chromosomes 1 (two QTLs), 2, 3 (two QTLs), 5, 6 (three QTLs), 8, 9, and 10. In addition, QTLs were identified for tunnel number (16 QTLS), plant height (11 QTLs) and rind penetrometer resistance (nine QTLs). In this experiment, a total of 47 QTLs for all traits were mapped in three individual environments and combined over environments. Nine (19%) QTLs were expressed in all three environments and combined, 17 (36%) were expressed in two environments and combined, and 21 (45%) were expressed only in single environment and combined. Inconsistency of QTLs across environments suggested need for breeders awareness when selecting markers linked to QTLs for marker-assisted selection (MAS). Further study on consistency of QTLs across populations is needed before applied breeding programs can fully utilized QTL information.
Author: Daniel Pablo Donadio Publisher: ISBN: Category : Languages : en Pages : 258
Book Description
The European corn borer (ECB) significantly affects the production of maize in temperate regions. Second-generation ECB larvae tunnel into the stalks leading to reduced plant growth and grain yield. Several inbreds such as B52, DE811, and B86 have been identified as resistant to tunneling. However, selection for native resistance is difficult because the genetic mechanisms controlling the trait are unknown. Backcross (BC) lines are derived from B73/B52 and B73/DE811 populations were developed and selected for reduced tunneling by ECB. Phenotypic analysis of the BC lines was performed to assess their degree of resistance with respect to the parental lines. Genotypic analysis of the BC lines was accomplished by use of simple sequence repeat (SSR) primer pairs. This analysis included the investigation of the origin of chromosomal segments, estimation of parental contribution, construction of graphical genotypes, detection of loci associated with resistance and their comparison with quantitative trait loci (QTL) reported by other researchers. For the B73/B52 population, 19 of the 34 BC lines were as resistant as B52 and 1 BC line was as susceptible as B73. No correlation was found between stalk tunneling and either plant height or anthesis date. The proportion of B52 alleles in the genome of the BC lines was 2.9 to 5.2 times greater than expected assuming absence of selection and linkage. Nineteen loci could be associated with resistance. However, only 5 of them coincided with QTLs reported in other studies. For B73/DE811 population, 1 of the 6 BC lines was as resistant as DE811. Percentage of damage caused by ECB and anthesis were significantly correlated ( -0.74). The proportion of DE811 alleles was 2.3 to 8.8 times greater than expected under the cited assumptions.
Author: Matthew David Krakowsky Publisher: ISBN: Category : Languages : en Pages : 338
Book Description
Composite interval mapping (CIM) was used to detect QTL for each trait, and the relationships between the QTL detected for the same traits in different generations and among different traits in the same generation were examined. Seven and fourteen QTL for stalk tunneling were observed in the mean environments for the F3 and RI lines of B73 x De811, four and twelve of which, respectively, are linked to QTL for CWCs. The previously reported genetic correlations for ECB stalk tunneling with CWCs in the F3 lines (r[Subscript g] = -0.11 to -0.33) indicate that a genetic association may exist between the two traits. However, the genetic correlations for the RIL were -0.03 to 0.08, raising the possibility that the correlations observed in the F3 lines were either due to environmental factors or the result of linkage disequilibrium. Factors other than concentrations of CWCs appear to be associated with the expression of resistance to stalk tunneling in this population.
Author: Publisher: CIMMYT ISBN: 9789686923797 Category : Corn Languages : en Pages : 316
Book Description
Mechanisms and bases of resistance; The genetics of resistance; Biotechnological manipulation of resistance; Advances in techniques, rearing, rating bioassays, mechanism detection; Resistance verification and utilization; Country reports.
Author: Chaba Jampatong
Author: Daniel Pablo Donadio
Author: Matthew David Krakowsky
Author: Khamis Ibrahim Khalifa
Author: Fidelis Ashimole Onukogu
Author: Mark Joseph Brinkman
Author: Chareinsuk Rojanaridpiched
Author: Kris Alan Nyhus
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