Selección entre y dentro de familias de hermanos completos de maíz en Chiapas, México

ABSTRACT Entre 2002 y 2005 se hicieron tres ciclos de selección recurrente de familias de hermanos completos en tres variedades de maíz (Zea mays L.) que se cultivan comercialmente en Chiapas: ¿V-424¿ (de ciclo precoz), ¿V-534¿ (de ciclo intermedio) y ¿V-526¿ (de ciclo tardío). El objetivo fue incrementar sus rendimientos de grano, y a la vez mantener el fenotipo y madurez de cada población. Durante los ciclos agrícolas de temporal o secano de 2005 y de riego de 2006 se evaluaron en Ocozocoautla y Villaflores, Chiapas, México, a 14 variedades experimentales formadas de los ciclos uno, dos y tres de cada población, más su población original. Se encontraron diferencias significativas entre localidades y entre variedades para las tres poblaciones en el rendimiento de grano, y la interacción localidades x variedades sólo fue significativa para la población ¿V-534¿; las variedades experimentales ¿V-424 Coita C3¿, ¿V-534 Coita C3¿ y ¿V-526 Villaflores C3¿ superaron en rendimiento a las respectivas variedades originales, sin cambiar su fenotipo y madurez, con respuestas de 3.0 %, 5.2 % y 4.2 % por ciclo de selección, respectivamente.

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    ABSTRACT: The objectives of this study were to evaluate direct and correlated responsestorecurrentselectionfordroughttoleranceintwoCIMMYT maize (Zea mays L.) source germplasm populations, 'DTP1' and 'DTP2', adapted to the lowland and mid-altitude tropics. Selection was primar- ily based on grain yield, ears per plant, anthesis-silking interval, and leaf senescence under drought. Cycles C0 ,C 3, and C6 of DTP1 and C0 ,C 3 ,C 5 and C9 of DTP2 were evaluated under drought, low N, and optimal conditions. In both populations, significant yield gains were observed under drought conditions, associated with a significant increase in numbers of ears per plant and grains per ear, and significant reductions in anthesis-silking interval, ovule number and abortion rate during grain filling. Abortion rate was positively correlated with the number of ovules at silking and with anthesis-silking interval. In DTP1, recurrent selection under drought was associated with a de- rease of tassel and stem dry weight and with an increase of ear dry weight and harvest index. This study confirms the effectiveness of recurrent selection under drought as a means of improving tropical maize source populations for performance under water deficits and to a lesser extent under low N. The primary mechanism underlying these changes appears to be improved partitioning of assimilates to the ear at flowering, at the expense of tassel and stem growth.
    Crop Science - CROP SCI. 01/2006; 46(1).
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    ABSTRACT: Maize (Zea mays L.) improvement involves formation, evaluation, selection, and recombination of genetically variable families or inbred lines, and because cultivars must combine many desirable traits, the process can be complicated and lengthy. This study compared 12 experimental open-pollinated varieties (OPVs) developed from maize population Pool 9A by two approaches, full-sib (FS) selection alone and FS selection combined with inbreeding with selection for Maize streakvirus (MSV) resistance. The experimental OPVs were evalu- ated in 13 environments in Africa, including three sites with artificial MSV inoculation. Full-sib selection combined with inbreeding and selection for MSV resistance (with mild selection for gray leaf spot resistance (GLS, caused by Cercospora zeae maydis Tehon & Daniels)), reduced ear height and reduced days to flowering) resulted in OPVs with similar grain yield but superior MSV resistance (P , 0.01), fewer days to anthesis (P , 0.01), and lower ear height (P , 0.05) than OPVs developed by FS selection alone. Each generation (from S0 to S3) of inbreeding with selection resulted in OPVs that were 16, 8, 2, and 1% improved for MSV and GLS resistance, ear height, and days to anthesis, respectively. Our results demonstrate improve- ment of a maize population for MSV resistance and other traits by selection during inbreeding (from S0 to S3), without negative impact on gains for grain yield achieved by evaluation and selection among the progenitor FS families.
    Crop Science - CROP SCI. 01/2006; 46(3).
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    ABSTRACT: methods include these three phases, they vary in types of progenies evaluated (i.e., inbred, full-sib, half-sib, Recurrent selection methods have been effectively used by maize etc.); number of progenies evaluated; number of se- (Zea mays L.) breeders to improve the performance of maize popula- tions for quantitatively inherited traits. Although theoretical compari- lected families (i.e., 5, 10, 20, 30, etc.); parental control; sons of such methods can be easily made, direct comparisons of the and the type of progenies intermated. It is this flexibility efficiencies of methods are time consuming and laborious. Because in the different types of methods and different parame- of these limitations, empirical data comparing multiple recurrent se- ters that has led to the utilization of a wide range of lection methods in the same base population are lacking for maize. recurrent selection methods for population improve- Our study was designed to compare the response to selection for ment with an equally wide range of responses. Even seven different methods (six intra- and one inter-population) in the with the diversity of recurrent selection methods, two BS11 maize population. A minimum of four cycles of selection were goals remain common throughout, increasing the mean conducted for each of the following methods: mass, modified ear-to- performance of the population and maintaining the ge- row, half-sib with inbred tester, full-sib, S1-progeny, S2-progeny, and netic variability in the population to facilitate long-term reciprocal full-sib selection. Selections for all programs except mass and reciprocal full-sib were based on an index composed of grain selection. The focus of our study was to improve the yield, grain moisture, stalk lodging, and root lodging. Each trait in mean performance of a single population with respect the selection index was weighted according to its heritability. The to four important agronomic traits via seven different populations per se, populations selfed, and testcrosses of the popula- recurrent selection methods. tions to the Cycle 0 population and to inbred B79 were evaluated in Grain yield has historically been the most important our study. Response to selection was measured for grain yield, grain trait and the trait most frequently used for selection moisture, stalk lodging, and root lodging along with other agronomic in maize population improvement. Recurrent selection traits. All selection methods were successful in significantly improving methods have not been widely adopted by maize breed- the population per se performance for grain yield. S2-progeny selection ers, although they have been effective for increasing
    Crop Science - CROP SCI. 01/1998; 38(2).

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