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Vasal, S.K.

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Vasal
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S.K.
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Vasal, S.K.

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Region: Global × AGROVOC: GERMPLASM ×

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Now showing 1 - 4 of 4
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    Programa de manejo, mejoramiento y utilización de germoplasma de maíz en el CIMMYT
    (CIMMYT, 1983) Vasal, S.K.; Ortega Corona, A.; Pandey, S.
    El tema de esta publicacion es el mejoramiento de la planta de maiz. Para empezar describe varios esquemas para el mejoramiento de poblaciones y luego explica el enfoque que el Centro ha adoptado en su programa de maiz. Ademas trata sobre la estructura y las actividades de las diversas unidades que componen el programa (por ejemplo, la unidad "de apoyo" que maneja el banco de germoplasma y 29 complejos germoplasmicos del Centro, asi como la unidad "avanzada que trabaja en poblaciones). La publicacion tambien describe los esfuerzos del programa por mejorar maiz para que tenga atributos especiales como la precocidad y la resistencia a enfermedades. Por
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    CIMMYT's maize germplasm management, improvement, and utilization program
    (CIMMYT, 1982) Vasal, S.K.; Ortega Corona, A.; Pandey, S.
    This paper discusses alternatives for improving the maize plant. While maize hybrids dominate in the developed world, open-pollinated varieties mostly are grown in the developing countries. The importance of population improvement in maize has been emphasized. Population improvement procedures not only improve the population for developing superior varieties but also increase the chances of extracting superior lines that will result in better hybrid combinations. The accomplishments in the development of population improvement methods in maize are discussed. Some of the important population improvement schemes, such as mass selection, modified ear-to-row selection, and several recurrent selection schemes, are briefly discussed. In addition, mating design-1 and some family selection schemes such as full-sib, half-sib, and S1 have been mentioned. CIMMYT's maize improvement program, including the research activities of the Advanced Unit, Back-Up Unit, Quality Protein, and Special Projects, is discussed. The structure and function of these units are presented. The Back-Up Unit handles the germplasm bank and the gene pools. A total of 29 gene pools are being improved continuously by the half-sib selection procedure. The handling of gene pools is discussed along with information on population size, selection in male and female rows before and after flowering, among- and within-family selection intensity, stresses to diseases and insects, adaptation, and introgression of new germplasm in the pools. The various operations in the Advanced Unit are described both with normal and quality protein maize (OPM) populations. The full-sib system of family improvement is used in each population. Various stages in population improvement, such as progeny regeneration, progeny evaluation, and within-family improvement during the intervening cycles, are discussed. In addition to population improvement, site-specific and across-site experimental varieties are developed using approximately 10 top-performing families. The experimental varieties are evaluated in experimental variety trials (EVTs). The top performing EVs are designated as elites for further testing in elite experimental variety trials (EL VTs). The breeding effort concentrating on special attributes such as earliness and resistance to downy mildew, stunt, and streak is described. Breeding for resistance to fall armyworm, borers, and earworm also is being practiced in the gene pools and populations. The technique utilizing larvae instead of egg masses has been presented and the field execution of insect resistance work is briefly described. The problems encountered in OPM and the breeding strategy used in the accumulation and exploitation of genetic modifiers are discussed. The germplasm development effort and the breeding methodology used in breeding OPM has been presented. The salient features of the conversion process are given. The objective of OPM pools and their formation and handling have been discussed. The experimental evidence showing progress in pools and the performance of OPM materials in the international tests has been presented.
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    Incorporation of elite subtropical and tropical maize germplasm into elite temperate germplasm
    (Consiglio per la Ricerca e la sperimentazione in Agricoltura, Unità di Ricerca per la Maiscoltura, 2006) Whitehead, F.C.; Caton, H.G.; Hallauer, A.R.; Vasal, S.K.; Cordova, H.S.
    Elite germplasm and adequate genetic variation are essential in successful plant breeding programs.Maize (Zea mays L.) breeding programs in the U.S. Corn Belt have realized significant genetic advance with a limited sample of the available maize germplasm. The objective of our study was the incorporation of elite subtropical and tropical germplasm into elite U.S. Corn Belt germplasm. Crosses, backcrosses, and testcrosses were evaluated to identify superior progenies that were intermated to form germplasm sources that include 75% temperate germplasm and either 25% subtropical or 25% tropical germplasm. Backcrosses (25%) and testcrosses (12.5%) with 25% exotic germplasm had maturities and agronomic traits similar to the elite temperate germplasm sources. The populations formed by intermating the superior backcross progenies, based on backcross and testcross data, will provide additional germplasm resources for future use in temperate maize breeding programs.
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    Heterotic patterns of eighty-eight white subtropical CIMMYT maize lines
    (Consiglio per la Ricerca e la sperimentazione in Agricoltura, Unità di Ricerca per la Maiscoltura, 1992) Vasal, S.K.; Srinivasan, G.; Han, G.C.; Gonzalez Ceniceros, F.
    Hybrid-oriented source germplasm with established heterotic pattern is essential for initiating hybrid development. The objective of this study to identify and from heterotic groups of maize (Zea mays L.) with subtropical adaptation. Eighty-eight inbred maize lines derived from six CIMMYT subtropical maize populations and pools were crossed to four tester lines, one each from Pool 32 and Populations 34, 42 and 44. The 352 line x tester hybrid combinations were divided into four sets, each set comprising of crossed of 22 lines with the four testers, and evaluated during two seasons at Tlaltizapan, Mexico during 1989 and 1990. Mean grain yields for the four sets ranged from 9.0 t/ha (set 1) to 8.2 t/ha (set 4). General combining ability (GCA) and specific combining ability (SCA) for grain yield were calculated by line x testers analysis. Of the 88 lines tested, 14 from Population 44, 11 from Population 42, nine from Pool 32 and one from Population 34 had positive GCA effects for grain yield. Among testers, Tester 2 (Pop. 44) showed positive GCA effects for yield, and Tester 1 (Pool 32) had negative GCA effects for yield. Significant differences were observed for SCA effects for yield in the different line x tester crosses. Several combinations were identified having yields of 10 t/ha or more and possessing high SCA effects. Interpopulation crosses generally outyielded and had greater SCA effects as compared with intrapopulation crosses. Superior intrapopulation combinations, however, were observed among crosses involving lines from Populations 44. Two heterotic groups STHG "B" are being formed from these materials using the testcross data. Several of the lines included in this study were announced as CIMMYT maize lines (CML) during 1991 and are made available to our cooperators worldwide. Twelve of the 20 top-yielding single crosses (fice from each set) were between CML lines. The material and information generated from this study may be useful for future hybrid development work at CIMMYT and in other public and private breeding programs, particularly in the developing world.
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