1991. Molecular-marker-mediated dissection of quantitative inheritance in maize (Zea mays L)

1991. Molecular-marker-mediated dissection of quantitative inheritance in maize (Zea mays L)

DOWNLOAD: PDF
SÐT: 0981800855 (A. LONG)
PRICE: 100.000 VND
EMAIL: FOODCROPS@GMAIL.COM

Abstract

 
RAGOT, MICHEL. Molecular-Marker-Mediated Dissection of Quantitative Inheritance in Maize (Zea mays L.): Characterization of Favorable Exotic Factors and Comparisons of Statistical Methodologies and Marker Technologies. (Under the direction of Charles W. Stuber and Paul H. Sisco.)

Exotic maize germplasm, shown to be useful for developing improved temperate cultivars, has remained little used partly because of many inherent shortcomings. Molecular markers allow the identification of genetic factors underlying the expression of agronomic traits and can also facilitate their introgression from donor (exotic) into recipient (US) germplasm. However, cost and time involved in molecular marker analyses are still limiting factors for most breeding applications.

Five F2 populations, developed from South American and US germplasm, were used to detect favorable factors of exotic origin at agronomic trait loci, using isozymes and RFLPs. A number of traits of agronomic importance, including grain yield, were measured on F2 individuals and / or F3 families grown in several environments, and analyzed using several statistical methodologies, whose relative merits were evaluated. Many QTLs were identified, mostly with small effects. Major QTLs for grain yield and number of ears per plant were located on chromosomes 3 and 6. Favorable exotic factors were found for both traits on these chromosomes. Single-factor analyses and interval mapping yielded very similar results in terms of QTL detection. However, interval mapping allowed more precise location of QTLs than single-factor analyses. Selective genotyping failed to detect QTLs with minor effects but allowed the identification of QTLs possibly epistatic to major QTLs. Stability of QTLs across environments was high. Differences among locations often could be attributed to the chosen significance thresholds.

Three molecular marker technologies, RFLPs based on chemiluminescence, RFLPs based on radioactivity, and RAPDs, were compared in terms of cost and time efficiencies using simulations of maize genotyping projects. RAPDs were the most cost-efficient strategy when small sample sizes were to be analyzed. RFLPs were the least expensive methods for large numbers of individuals. Relative time efficiencies were comparable to cost efficiencies, except that RFLPs based on radioactivity always required more time than RFLPs based on chemiluminescence. The choice of a molecular marker strategy should be determined by the type and amount of information sought, the availability of markers or previous information for the species, and the ability to integrate the generated information into a general database .