International Maize and Wheat Improvement Center

About: International Maize and Wheat Improvement Center is a nonprofit organization based out in Texcoco, Mexico. It is known for research contribution in the topics: Population & Agriculture. The organization has 1976 authors who have published 4799 publications receiving 218390 citations.

Is heterosis in maize mediated through better water use

Abstract: Summary • Heterosis increases yield potential and improves adaptation to stress in maize (Zea mays); however, the underlying mechanisms remain elusive. • A set of tropical inbred lines and their hybrids were grown in the field for 2 yr under three different water regimes. First-year plant water use was evaluated by measuring instantaneous traits (stomatal conductance (gs) and steady-state chlorophyll fluorescence (Fs)) in individual leaves together with time-integrative traits, which included mineral accumulation in the whole leaves of plants and oxygen isotope enrichment above source water (D 18 O) and carbon isotope discrimination (D 13 C) in the same pooled leaves and in mature kernels. Second-year water use was evaluated by measuring leaf temperature, gs and relative water content (RWC). • Within each growing condition, hybrids showed higher Fs, mineral accumulation, RWC, and lower leaf temperature, D 18 O and D 13 C than inbred lines. Therefore, hybrids had a better water status than inbred lines, regardless of the water conditions. Differences in grain yield across growing conditions were explained by differences in water-use traits, with hybrids and inbred lines following a common pattern. Within each growing condition, most variations in grain yield, between hybrids and inbred lines, were also explained by differences in plant water-use traits. • Heterosis in tropical maize seems to be mediated by improved water use, irrespective of the water conditions during growth.

Water and nitrogen conditions affect the relationships of Δ13C and Δ18O to gas exchange and growth in durum wheat

Abstract: Whereas the effects of water and nitrogen (N) on plant D 13 C have been reported previously, these factors have scarcely been studied for D 18 O. Here the combined effect of different water and N regimes on D 13 C, D 18 O, gas exchange, water-use efficiency (WUE), and growth of four genotypes of durum wheat [Triticum turgidum L. ssp. durum (Desf.) Husn.] cultured in pots was studied. Water and N supply significantly increased plant growth. However, a reduction in water supply did not lead to a significant decrease in gas exchange parameters, and consequently D 13 C was only slightly modified by water input. Conversely, N fertilizer significantly decreased D 13 C. On the other hand, water supply decreased D 18 O values, whereas N did not affect this parameter. D 18 O variation was mainly determined by the amount of transpired water throughout plant growth (Tcum), whereas D 13 C variation was explained in part by a combination of leaf N and stomatal conductance (gs). Even though the four genotypes showed significant differences in cumulative transpiration rates and biomass, this was not translated into significant differences in D 18 Os. However, genotypic differences in D 13 C were observed. Moreover, ;80% of the variation in biomass across growing conditions and genotypes was explained by a combination of both isotopes, with D 18 O alone accounting for ;50%. This illustrates the usefulness of combining D 18 O and D 13 C in order to assess differences in plant growth and total transpiration, and also to provide a time-integrated record of the photosynthetic and evaporative performance of the plant during the course of crop growth.

Genetic Yield Gains In CIMMYT's International Elite Spring Wheat Yield Trials By Modeling The Genotype × Environment Interaction.

Abstract: We calculated the annual genetic gains for grain yield (GY) of wheat (Triticum aestivum L.) achieved over 8 yr of international Elite Spring Wheat Yield Trials (ESWYT), from 2006-2007 (27th ESWYT) to 2014-2015 (34th ESWYT). In total, 426 locations were classified within three main megaenvironments (MEs): ME1 (optimally irrigated environments), ME4 (drought-stressed environments), and ME5 (heat-stressed environments). By fitting a factor analytical structure for modeling the genotype × environment (G × E) interaction, we measured GY gains relative to the widely grown cultivar Attila (GYA) and to the local checks (GYLC). Genetic gains for GYA and GYLC across locations were 1.67 and 0.53% (90.1 and 28.7 kg ha-1 yr-1), respectively. In ME1, genetic gains were 1.63 and 0.72% (102.7 and 46.65 kg ha-1 yr-1) for GYA and GYLC, respectively. In ME4, genetic gains were 2.7 and 0.41% (88 and 15.45 kg ha-1 yr-1) for GYA and GYLC, respectively. In ME5, genetic gains were 0.31 and 1.0% (11.28 and 36.6 kg ha-1 yr-1) for GYA and GYLC, respectively. The high GYA in ME1 and ME4 can be partially attributed to yellow rust races that affect Attila. When G × E interactions were not modeled, genetic gains were lower. Analyses showed that CIMMYT's location at Ciudad Obregon, Mexico, is highly correlated with locations in other countries in ME1. Lines that were top performers in more than one ME and more than one country were identified. CIMMYT's breeding program continues to deliver improved and widely adapted germplasm for target environments.