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Colegio de Postgraduados (COLPOS) Consejo Nacional de Ciencia y Tecnología (CONACYT) 2012

Rendimiento y contenido de prolina en maíz mejorado por selección masal para resistencia a sequía

Acevedo Cortés, María de los Angeles

Titre : Rendimiento y contenido de prolina en maíz mejorado por selección masal para resistencia a sequía

Auteur : Acevedo Cortés, María de los Angeles

Université de soutenance : Colegio de Postgraduados (COLPOS) Consejo Nacional de Ciencia y Tecnología (CONACYT)

Grade : Maestría en Ciencias, especialista en Genética 2012

Résumé partiel
The objectives of this work were to estimate the average genetic gain for yield per selection cycle in different composites of stratified visual mass selection (SVMS) carried out for drought resistance in two maize (Zea mays L.) varieties, where the grain yield was the selection criterion ; to estimate the indirect genetic gain for proline content (PC) in plants from the SVMS composites ; and to know if there is a relationship between yield and PC in order to know whether PC qualifies as a selection criterion for drought resistance in maize. Yield was evaluated in the field for the following genotypes : SVMS composites Z0, Z3, Z6, Z9, Z12, Z15, Z18 (Zacatecas 58 maize variety), C0, C3, C6, C9, C12, and C16 (Cafime variety), and the hybrids for rainfall conditions H-40 (commercial) and (T1 x T3) x T4 (an experimental one from the Colegio de Postgraduados, Mexico) as checks. The genotypes were evaluated in three environments : under irrigation (I), drought (D), and rainfall conditions (R) in Montecillo, Texcoco, Mexico, in a randomized complete block design with three replications. Experimental units were two-row plots of 4 m in length with inter-row spacing of 0.8 m. and had 44 plants. Yield (Y) in kg of ears per plant was recorded along with yield components and agronomic traits. Data were analyzed using an analysis of variance followed by pairwise multiple comparisons of means, a phenotypic correlation, and a simple linear regression of Y on the number of cycles of SVMS. To quantify the PC in plants and estímate the relationship between Y and PC, SVMS composites Z0, Z5, Z10, Z15, C0, C5, C10, and C16, and the hybrids H-40 and (T1 x T3) x T4, used as checks, were planted also in Montecillo in a greenhouse in I and D conditions. All genotypes were planted in D, and only Z0, Z15, C0, C16, and the checks were planted in I. Each genotype was planted in plastic pots that had 4.5 kg of loam soil. Four seeds per pot were sown and thinned to two plants, so that 20 plants were kept in each genotype. Sowing was done in dry soil and then the pots were irrigated constantly with a hose and a spray gun until plants had the third ligulated leaf. At this phenological stage, all the pots were saturated with water to allow the soil reached field capacity (FC), and starting from that point no more irrigation was provided to the pots in D. In the I treatment all the pots were irrigated and kept near FC all the time. When the plants in D treatment reached the permanent wilting point, 8 cm of tissue from the third ligulated leaf of all plants was cut with scissors, wrapped in foil, labeled, kept in liquid nitrogen, and liofilized to quantify the PC by a colorimetric determination. PC data were first analyzed using a graphic comparison and then by a comparison among the means of cycles of SVMS. It was also done two simple linear regression analyses, one of PC on the number of cycles of SVMS and the other of PC on the mean Y of each cycle. A phenotypic correlation was between Y and PC also calculated. Results showed that Y was greater in I, where no restricitions in humidity prevailed, than in D or R, and it was also greater in the advanced composites of SVMS, but these did not equate the Y of checks, from which the best was the experimental hybrid, formed with an inbred from Zacatecas 58 and two of Cafime. The observed genetic gain for Y was different in each variety, and this depended on the different genetic background between them. Thus, the genetic gain was 7.4% for Zacatecas 58 and 2.6% for Cafime.



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