Person: 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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- 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
Publication - 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.
Publication - Stability in performance of quality protein maize under abiotic stress(Consiglio per la Ricerca e la sperimentazione in Agricoltura, Unità di Ricerca per la Maiscoltura, 2008) Zaidi, P.; Vasal, S.K.; Maniselvan, P.; Jha, G.C.; Mehrajjudin; Singh, R.P.Quality protein maize (QPM) has emerged an affordable and viable option to alleviate protein malnutrition and reduce animal feed costs, given that its grain protein contains more than double the lysine and tryptophan concentrations of normal endosperm maize. For commercial success, QPM cultivars must be competitive with normal maize in productivity and should show stable performance across environments, especially with respect to yield and protein quality traits. In the tropics, drought and low-nitrogen (N) fertility are major constraints to maize productivity. In this study, we analyze the stability of performance of CIMMYT tropical and subtropical elite QPM hybrids across stressed (drought and low N) and unstressed environments. In general, stress significantly affected all agronomic traits except male flowering. The effect was comparatively large under drought stress. Among the quality traits, grain protein, tryptophan, and lysine contents showed significant variation across environments. There was an increase in grain protein (12.7%) and in lysine (10.3%) and tryptophan contents (8.1%) under drought stress, while levels of these grain quality traits were reduced under low N by 17.0, 12.5, and 15.6%, respectively. However, the effect of stressed environments was comparatively small on protein quality traits, including tryptophan and lysine content in protein. The variation in protein quality across environments was statistically significant but largely due to genotypic variability. Variation due to environment and genotype by environment (G x E) interaction was statistically non-significant for protein quality traits, except in the case of lysine content in protein, where G x E was significant. Our results suggest that grain yield and grain protein content are the most unstable traits, whereas tryptophan followed by lysine content are the most stable, across stressed and unstressed environments.
Publication - 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.
Publication - 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.
Publication - Inbred line evaluation nurseries and their role in maize breeding at CIMMYT(Consiglio per la Ricerca e la sperimentazione in Agricoltura, Unità di Ricerca per la Maiscoltura, 1999) Vasal, S.K.; Srinivasan, G.; Cordova, H.S.; Pandey, S.; Jeffers, D.P.; Bergvinson, D.J.; Beck, D.L.CIMMYT initiated its hybrid maize (Zea mays) research programme in 1985 in response to the growing needs of the national programmes for hybrid-oriented source germplasm. Since 1991 CIMMYT has released a total of 424 inbreds that are widely distributed and used by public and private sector researchers around the world. Inbred line evaluation nurseries are an important component of a hybrid research programme. At CIMMYT, inbreds are routinely evaluated for various biotic and abiotic stresses, their yield potential and other agronomic attributes. Several promising lines have been identified for specific stresses, although they were not selected during the development process which can be attributed to the genetic diversity of CIMMYT's source germplasm. Resistant/tolerant lines have been identified for abiotic stresses (drought, low-N use efficiency and acid soils). In addition, resistant lines have been identified for biotic stresses, including fusarium ear/stalk rot (Fusarium spp.), banded leaf and sheath blight (Rhizoctonia spp.), tar spot (Phyllachora maydis), grey leaf spot (Cercospora zeae-maydis), rust (Puccinia polysora), maize streak virus (MSV), fall armyworm (Spodoptera frugiperda), sugarcane borer (Diatraea saccharalis) and Striga. Lines with above average general combining ability and yield stability were identified. These lines are available for public use
Publication - Heterotic patterns of ninety-two white tropical CIMMYT maize lines(Consiglio per la Ricerca e la sperimentazione in Agricoltura, Unità di Ricerca per la Maiscoltura, 1992) Vasal, S.K.; Srinivasan, G.; Pandey, S.; Cordova, H.S.; Han, G.C.; Gonzalez Ceniceros, F.Development of inbread-based populations which are heterotic to each other was considered one of the primary goals when CIMMYT started of this study were to determine the combining ability and heterotica patters of tropical maize(Zea mays L.) inbred lines developed at CIMMYT and to identify and form beterotic grous for the topics. 92 tropical late white inbred lines at S3-S6 levels of inbreeding derived from nine CIMMYT populations and pools were crossed to four tester lines(two dent and two flint).
Publication - Heterosis and combining ability of CIMMYT's tropical late white maize germplasm(Consiglio per la Ricerca e la sperimentazione in Agricoltura, Unità di Ricerca per la Maiscoltura, 1992) Vasal, S.K.; Srinivasan, G.; Beck, D.L.; Crossa, J.; Pandey, S.; De Leon, C.Seven tropically adepted, late maturity maize gene pools and populations (Populations 21, 22, 25, 29, 32 and 43, and Pool 24) developed and improved at CIMMYT were crossed in a 7 x 7 diallel mating system. The parent and 21 crosses were evaluated for graind yiedl, days to silk and plant height at five locations in México, and one each in Colombia and Thailand. The objectives of the study were to determine the heterosis and combining ability among these materials and to identify appropriate germplasm suitable for hybrid development work. The combined analysis of variance for all three traits measured showed no significant genotype x environment (G xE) interaction. Genotypes themselves showed significant differences for all three traits, as did their partitions into partents and crosses. General combining ability (GCA) was significant for all traits whereas specific combining ability (SCA) was not significant for any of the traits. Mean grain yeild for the trial was 6.98 t/ha. the highest yielding combination was Population 21 x Population 43 (7.83 t/ha) followed by crosses of Population 22 with Population 32 (dent x flint) yielded 7.36 t/ha while exhibiting the maximun high-parent heterosis (12.7%) for yield. Population 43 (La Posta) was the tallest and latest parent and produced high yields in crosses whit other populations. All crosses to Population 43 per se. Population 21 (0.24 t/ha), Population 22 (0.13 t/ha) and Population 43 (0.23 t/ha) possessed significant positive GCA for yield. Populations 21 and 43 also showed significant positive GCA for days to silk while only Population 43 showed positive GCA for plant height. Aignificant (P <0.05) positive SCA effects for yield were observed in two crosses involving Population 32 whit Population 22 and 29 (flint x dent). Based on our study the best choices for initianting hybrid work are Populations 21, 22, 29 and 43. Many of the Tuxpeño based populations are ideal candidates forinterpopulation improvement using Population 32 (ETO Blanco) as heterotic partner.
Publication - A comparative study of protein changes in normal and quality protein maize during tortilla making(American Association of Cereal Chemists, 1986) Ortega Martinez, E.I.; Villegas, E.; Vasal, S.K.Protein changes were evaluated in two different maize genotypes of contrasting protein quality made into tortillas. In both types of maize, albumins, globulins, zeins, and glutelinlike components became insoluble after interacting with other biochemical entities catalyzed by the alkaline pH and the heat produced in tortilla-making. Increased nitrogen recovery with solvents having alkaline pH, a reducing agent, and sodium dodecyl sulfate indicate that hydrophobic interactions may have been involved in this change in solubility of proteins that are more easily solubilized in the unprocessed maize grain. In vitro protein digestibility with pepsin declined as nitrogen content increased in the glutelin fraction and in the residue after fractionation. Tortillas made from quality protein maize (QPM) had a superior amino acid score mainly because of their very high lysine and tryptophan content, which was not significantly affected during tortilla preparation. The superiority of the product obtained with the QPM sample was demonstrated by its high content of available lysine. Although the in sulfate indicate that hydrophobic interactions may have been involved in vitro digestibility of protein with pepsin and the amount of available lysine this change in solubility of proteins that are more easily solubilized in the changed during tortilla-making, no evidence was found of a specific unprocessed maize grain. In vitro protein digestibility with pepsin declined detrimental effect on the protein quality of the original QPM grain.
Publication - Heterosis and combining ability of CIMMYT's tropical early and intermediate maturity maize (Zea mays L.) germplasm(Consiglio per la Ricerca e la sperimentazione in Agricoltura, Unità di Ricerca per la Maiscoltura, 1990) Beck, D.L.; Vasal, S.K.; Crossa, J.A 10 parent diallel was formed to determine combining ability and heterotic patterns among CIMMYT'S tropically adapted, early and intermediate maturity maize (Zea mays L.) gene pools and populations. The parents and their crosses were avaluated for yeild (t/ha), plant and ear height (cm), and days to silk at five locations in México, and one each in Colombia, Ecuador, India and Thailand. The test for average heterosis, parents vs. crosses, was significant for graind yield, and plant and ear height in the combined analysis of variance. General combining ability (GCA) was significant for all traits. Specific combining anility (SCA) was significant anly for ear height. Although yield heterosis over the better parent was low in most crosses, moderate levels were observed in the Population 49 x Population 26 cross (9.6%). Population 26 also combined over the better parent. Pool 22 had the highest GCA effect for yield (0.37 t/ha), and was a parent in three of the five top yielding crosses. High yielding combinations included Pool 22 with Pool 20 (6.33 t/ha), Population 23 (6.24 t/ha), and Population 26 (6.23 t/ha). However, maximun heterosis over the better parent was only 3.2% in these crosses. The only cross wiht a significant positive SCA effect for yield was Population 23 x Pool 20 yielding 6.13 t/ha with 6.7% heterosis. Heterosis for plant and ear height, and days to silk were generally low. Based on our study, the best choices for initiating hybrid work among white grain materials are Population 23 and Pool 20, and among yellow grain materials Populations 26, Pool 21, and Pool 22.
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