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.

Identification of Saline Soils with Multiyear Remote Sensing of Crop Yields

Abstract: Soil salinity is an important constraint to agricultural sustainability, but accurate information on its variation across agricultural regions and its impact on regional crop productivity are difficult to obtain. We evaluated the relationships between remotely sensed wheat (Triticum aestivum L.) yields and salinity in an irrigation district in the Colorado River Delta region. The goals of this study were to: (i) document the relative importance of salinity as a constraint to regional wheat production; and (ii) develop techniques to accurately identify saline fields. Estimates of wheat yield from 6 yr of Landsat data agreed well with ground-based records on individual fields (R 2 = 0.65). Salinity measurements on 122 randomly selected fields revealed that average 0- to 60-cm salinity levels >4 dS m -1 reduced wheat yields, but the relative scarcity of such fields resulted in <1% regional yield loss attributable to salinity. Moreover, low yield was not a reliable indicator of high salinity, because many other factors contributed to yield variability in individual years; however, temporal analysis of yield images derived from remote sensing data showed that a significant fraction of fields exhibited consistently low yields during the 6-yr period. A subsequent survey of 60 additional fields, half of which were consistently low yielding, revealed that this targeted subset had significantly higher salinity at 30- to 60-cm depth than the control group (P = 0.02). These results suggest that consistently low yields are an indicator of high subsurface salinity, and that multiyear yield maps derived from remote sensing therefore hold promise for mapping salinity across agricultural regions.

Gains in Maize Genetic Improvement in Eastern and Southern Africa: I. CIMMYT Hybrid Breeding Pipeline

Abstract: Monitoring of genetic gain in crop genetic improvement programs is necessary to measure the efficiency of the program. periodic measurement of genetic gain also allows the efficiency of new technologies incorporated into a program to be quantified. Genetic gain within the International Maize and Wheat Improvement Centre (CIMMYT) breeding program for eastern and southern Africa were estimated using time series of maize (Zea mays L.) hybrids. A total of 67 of the best-performing hybrids from regional trials from 2000 to 2010 were selected to form an era panel and evaluated in 32 trials in eight locations across six countries in eastern and southern Africa. Treatments included optimal management, managed and random drought stress, low-nitrogen (N) stress and maize streak virus (MSV) infestation. Genetic gain was estimated as the slope of the regression of grain yield on the year of hybrid release. Genetic gain under optimal conditions, managed drought, random drought, low N, and MSV were estimated to have increased by 109.4, 32.5, 22.7, 20.9 and 141.3 kg ha−1 yr−1, respectively. These results are comparable with genetic gain in maize yields in other regions of the world. New technologies to further increase the rate of genetic gain in maize breeding for eastern and southern Africa are also discussed. J.E. Cairns, B. Masuka, J. Macrobert, C. Magorokosho, A. Tarekegne, and M. Zaman-Allah, International Maize and Wheat Improvement Centre (CIMMYT), PO Box MP163, Harare, Zimbabwe; G. Alvarado, J. Crossa, M. Bänziger, and K.V. Pixley, CIMMYT, Km. 35 Carr. Mexico-Veracruz, Texcoco, Edo de Mexico, DF, Mexico; G.N. Atlin, Bill & Melinda Gates Foundation, PO Box 23350, Seattle, WA 98102; B.M. Prasanna, B. Das, M. Olsen, and D. Makumbi, CIMMYT, United Nations Avenue, Gigiri PO Box 1041, Village Market 00621, Nairobi, Kenya; M. Labushchangne and A. von Biljong, Dep. of Plant Sciences, Univ. of Free State, South Africa; B.S. Vivek, CIMMYT, Patancheru 502 324, India. Received 16 May 2016. Accepted 8 Sept. 2016. *Corresponding author ( j.cairns@cgiar.org). Assigned to Associate Editor Jode Edwards. Abbreviations: ASI, anthesis–silking interval; CIMMYT, International Maize and Wheat Improvement Center; DH, doubled haploid; ESA, eastern and southern Africa; GCA, general combining ability; MSV, maize streak virus; OPV, open-pollinated variety; QTLs, quantitative trait loci; SNP, single-nucleotide polymorphism; SSA, sub-Saharan Africa. Published in Crop Sci. 57:168–179 (2017). doi: 10.2135/cropsci2016.05.0343 © Crop Science Society of America | 5585 Guilford Rd., Madison, WI 53711 USA This is an open access article distributed under the CC BY license (https:// creativecommons.org/licenses/by/4.0/). Published January 19, 2017

Estimating root mass in maize using a portable capacitance meter

Abstract: Time and expense are major constraints limiting the detection of genotypic differences in the length, structure, and growth rate of root systems in the soil. Recent development of a hand-held capacitance meter could enable the routine quantification of root mass. The objective of this study was to determine the accuracy with which a BK Precision 810A capacitance meter can estimate root fresh mass in maize (Zea mays L.) using a technique that allows a rapid and noninvasive capacitance reading. The capacitance meter measured root capacitance of maize grown under greenhouse (8 genotypes) and field (6 genotypes) conditions. After the capacitance readings, 14 plants per genotype were uprooted, roots were washed thoroughly, and root fresh mass was obtained. The statistical relationship between capacitance and root fresh mass in greenhouse experiments was significant early in the growth seasqn for all genotypes (r 2 = 0.73, P < 0.001), and significant only late in the growth season for inbreds (r 2 = 0.56, P < 0.001). Field studies showed that capacitance and root fresh mass were statistically correlated for all genotypes at flowering (r 2 = 0.69, P < 0.001). In conclusion, capacitance meters equipped with a clamp for rapid attachment to the plant may facilitate the nondestructive identification of genotypes with root characteristics that confer adaptation to various environments. Conditions for accurate capacitance measurements included a moist medium around the plant's root system and a consistent placement of the electrode at 6 cm above the crown.

Assessment of ICCV 2 × JG 62 chickpea progenies shows sensitivity of reproduction to salt stress and reveals QTL for seed yield and yield components

Abstract: Salinity is a complex abiotic stress and understanding the physiological and genetic basis of salinity tolerance is a prerequisite for improving existing crop cultivars. Experiments were undertaken using 126 recombinant inbred lines from a cross between JG 62 (tolerant) and ICCV 2 (sensitive) to characterize traits related to seed yield differences under saline conditions and to map quantitative trait loci (QTL). The population segregated for flowering time and entries were separated into ‘early’ and ‘late’ phenology groups to undertake the analysis. In both groups seed yield varied under salinity, with seed number being the most closely related trait to yield. In contrast, seed yield was not related to 100-seed weight or flowering time. Shoot dry weight was positively correlated with seed yield in the early entries only, but had no significant relationship with seed number. The higher sensitivity to salinity of the early entries was related both to a smaller biomass and lesser seed number under saline conditions. A QTL for seed yield under saline conditions was found in linkage group 3 in the late group, and a cluster of QTL for seed yield components in linkage group 6, including a QTL for seed number which explained 37% of the variation. In contrast, no QTL for seed yield was found in the early group, but a QTL for seed number under saline conditions was found. These data indicate that salinity tolerance traits are linked to the degree of earliness in chickpea. Tolerance is determined by the success of reproductive sites in both early and late entries, which relates in part to constitutive traits, and by the capacity of maintaining growth in early-flowering lines only. This is the first report of QTL for seed yield and seed number in chickpea exposed to salinity.

Developmental and growth controls of tillering and water-soluble carbohydrate accumulation in contrasting wheat (Triticum aestivum L.) genotypes: can we dissect them?

Abstract: In wheat, tillering and water-soluble carbohydrates (WSCs) in the stem are potential traits for adaptation to different environments and are of interest as targets for selective breeding. This study investigated the observation that a high stem WSC concentration (WSCc) is often related to low tillering. The proposition tested was that stem WSC accumulation is plant density dependent and could be an emergent property of tillering, whether driven by genotype or by environment. A small subset of recombinant inbred lines (RILs) contrasting for tillering was grown at different plant densities or on different sowing dates in multiple field experiments. Both tillering and WSCc were highly influenced by the environment, with a smaller, distinct genotypic component; the genotype × environment range covered 350-750 stems m(-2) and 25-210 mg g(-1) WSCc. Stem WSCc was inversely related to stem number m(-2), but genotypic rankings for stem WSCc persisted when RILs were compared at similar stem density. Low tillering-high WSCc RILs had similar leaf area index, larger individual leaves, and stems with larger internode cross-section and wall area when compared with high tillering-low WSCc RILs. The maximum number of stems per plant was positively associated with growth and relative growth rate per plant, tillering rate and duration, and also, in some treatments, with leaf appearance rate and final leaf number. A common threshold of the red:far red ratio (0.39-0.44; standard error of the difference=0.055) coincided with the maximum stem number per plant across genotypes and plant densities, and could be effectively used in crop simulation modelling as a 'cut-off' rule for tillering. The relationship between tillering, WSCc, and their component traits, as well as the possible implications for crop simulation and breeding, is discussed.