Person: Crossa, J.
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Crossa
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Crossa, J.
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0000-0001-9429-5855 23 results
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- Genomic regions associated with resistance to tan spot of wheat(American Phytopathological Society, 2009) Singh, P.K.; Singh, R.P.; Crossa, J.; Herrera-Foessel, S.A.; Bhavani, S.; Huerta-Espino, J.; Duveiller, E.
Publication - Diversidad fenotípica y variantes distintivas de la raza Jala de maíz(Instituto Nacional de Investigaciones Forestales, Agrícolas y Pecuarias, 2006) Aguilar-Castillo, J.A.; Carballo-Carballo, A.; Castillo Gonzalez, F.; Santacruz-Varela, A.; Mejia-Contreras, J.A.; Crossa, J.; Baca-Castillo, G.
Publication - Resistance to barley scald (Rhynchosporium secalis)in the ethiopian donor lines 'Steudelli' and 'Jet', analyzed by partial least squares regression and interval mapping(Mendelian Society of Lund, 2004) Bjornstad, A.; Gronnerod, S.; Key, J.M.; Tekauz, A.; Crossa, J.; Martens, H.
Publication - Results of the 2008 regional and on-farm maize trials in West Africa(IITA, 2009) Badu-Apraku, B.; Menkir, A.; Onyibe, J.E.; Buah, S.; Chabi, Y.; Coulibaly, N.; Crossa, J.The DTMA project employs multi-location trials as vehicles for identification of drought tolerant varieties and hybrids with broad adaptation to a particular agro-ecological zone. Promising varieties selected based on trial results are included in farmer participatory on-farm trials and demonstrations which serve as important vehicles to showcase the effectiveness of new technology to farmers and thus are instrumental in the identification and release of drought tolerant maize varieties and hybrids in the participating countries. The mother-baby on-farm testing approach has been widely adopted by the DTMA project as the strategy for testing and promoting the release and adoption of maize varieties and hybrids. In 2008, three regional trials consisting of 20 early- (M0827) and 16 late-maturing (M0825) drought tolerant (DT) open-pollinated maize varieties as well as 20 three-way and top-cross DT hybrids (M0826) were dispatched to our DTMA project collaborators in 2008. Most of the DT varieties and hybrids included in these trials originated from IITA. However, Premier Seeds and Crops Research Institute of Ghana each contributed two hybrids while the Institute for Agricultural Research-Nigeria and INERA- Burkina Faso contributed three and two openpollinated varieties, respectively, to these trials. A total of 21, 21, 9, and 92 sets of the three regional trials were dispatched to Benin Republic, Ghana, Mali and Nigeria, respectively, in 2008. The numbers of data field books received for the regional trials evaluated in 2008 were 15 from Benin Republic, 16 from Ghana, 7 from Mali and 71 from Nigeria. Field data recorded from these regional trials received from collaborators was 71% for Benin, 76% for Ghana, 78% for Mali and 77% for Nigeria. Means of the late maturing DT varieties averaged over five sites in Benin Republic are presented in Table 1. Only four DT varieties (Entry #9, 10, 11 and 12) produced 10% to 21% more grain-yields than the local check variety. These DT varieties did not differ significantly from the local check in days to anthesis and silking as well as in plant height. Only one variety (Entry# 11) was high yielding and stable in Benin Republic. Mean of the late maturing DT varieties averaged over five sites in Ghana are presented in Table 2. Nine DT varieties out yielded the local check by 13% to 31%. Days to anthesis and silking as well as plant height of these varieties did not differ significantly from that of the local check. Five varieties (Entry# 3,4,8,9 and 10) were found to be high and stable-yielding across locations in Ghana. Means of the DT varieties tested in Mali were obtained from two sites only (Table 3). All varieties, except Entry#6, produced 15% to 58% more grain yields than the local check in Mali. Days to anthesis and silking as well as plant height of these varieties did not differ significantly from that of the local check. Mean grain yields averaged over 24 sites in Nigeria are presented in Table 4. All the DT varieties, except Entry# 5 and 7, out-yielded the local check by 14% to 36%. These varieties had days to anthesis and silking as well as plant height that did not differ significantly from the local check. Variety and variety x site biplot analysis explained 60% of the variation in grain yield (Figure not presented). Five varieties (Entry 8, 9, 10, 11 and 12) were high yielding and stable across locations in Nigeria.
Publication - User's manual for the LCDMV software (calculation software of molecular distances between varieties): for fingerprinting and genetic diversity studies(CIMMYT, 2003) Dubreuil, P.; Dillmann, C.; Warburton, M.; Crossa, J.; Franco, J.; Baril, C.LCDMV (in English, known as the Calculation Software of Molecular Distances between Varieties) is a computer program developed in the SAS language (SAS Institute Inc., version 6.12), with the help of the modules SAS-STAT, and SAS-IML. It was written to analyze biochemical markers (isozymes) or molecular markers (RFLP, STS, SSR, RAPD, AFLP) obtained on homogenous or heterogeneous varieties. Its main function is to estimate genetic distances between varieties, and to analyze the structure of the genetic makeup of a given collection of OTU’s (Operational Taxonomic Units).
Publication - Data analysis in the CIMMYT applied biotechnology center: for fingerprinting and genetic diversity studies(CIMMYT, 2002) Warburton, M.; Crossa, J.The molecular genetic characterization of the diversity present in the CIMMYT maize and wheat germplasm collections is an ongoing process, to which many different persons have contributed. Furthermore, one of the mandates of CIMMYT is training of our national program partners, who have also expressed interest in learning the statistical techniques we use here at CIMMYT. It may even be possible one day to combine data from different labs into one analysis. In an effort to standardize the process and the results, and as a teaching tool for interested parties, this manual was prepared to act as a set of guidelines for future diversity analyses of maize and wheat germplasm. The analysis tools will also work in other species. Three main steps are involved in the statistical analysis of molecular data in diversity studies: (1) Data collection (scoring and entry of band information into the computer); (2) Data analysis using Univariate and Multivariate Statistical approaches; and (3) Interpretation of the data. Each tep in the process should follow a standardized format if the output of one diversity study is to be compared to other studies and inferences drawn in this manner. Likewise, laboratory procedures must be standardized between different workers; to achieve this end, all users should read the manual entitled “Laboratory Protocols: CIMMYT Applied Molecular Genetics Laboratory,” which should be followed when initiating diversity studies. This manual will provide both simple examples of all procedures in the main body of the text and real examples of data analyses in the appendices. Please refer to these examples when questions arise regarding any procedure mentioned in this manual.
Publication - SAS macro for analysing unreplicated designs(CIMMYT, 2000) Burgueño, J.; Crossa, J.Augmented or unreplicated experiment designs have two type of treatments, the replicated checks and the unreplicated new entries. The latter are usually considered to be random effects while the checks treatments are considered as fixed effects. Augmented designs have several advantages over the systematic check arrangement such as more than one check can be included and standard errors of differences between unreplicated entries and between unreplicated entries and checks are available. The SAS macro presented in this manual analyzes unreplicated design when the repeated checks are arranged in incomplete blocks. Usually 4-6 different checks are repeated several times throughout the experiment and 2-3 checks are arranged in each incomplete block. The incomplete block has plots for checks and plots for the unreplicated genotypes.
Publication - El análisis AMMI y la gráfica del biplot en SAS(CIMMYT, 2000) Vargas Hernández, M.; Crossa, J.En este documento se presentan tres ejemplos de casos en los que se emplearon programas creados en SAS para obtener Modelos AMMI, asi como la prueba de Gollob (Gollob, 1967) para determinar la significancia de cada termino AMMI. Con estos programas, se obtiene tambien de manera automatica el biplot derivado de los modelos AMMI. Las diferentes modalidades que aqui se presentan son: 1) Cuando se cuenta unicamente con las medias ajustadas. En este caso, las medias ajustadas son suficientes para obtener los modelos AMMI y para graficar el biplot. Sin embargo, para la prueba de Gollob se necesita tener un estimador del error del analisis combinado, los grados de libertad del error y el numero de repeticiones, los cuales se deben proporcionar al programa. 2) Cuando se cuenta con toda la informaci6n, por ejemplo los valores de la variable de interes medida en cada uno de los ambientes, los genotipos y las repeticiones, pero se utiliza un analisis combinado que se considera que proviene de experimentos individuales e los que se utiliz6 un diseno de bloques completos. Se asume que los modelos son de efectos fijos y se analizan utilizando PROC GLM. En este caso, se obtiene de forma automatica el estimador del error, los grados de libertad del error y el numero de repeticiones. 3) Similar al caso anterior, pero ahora se consideran experimentos individuales en los que se utiliz6 un diseno de latices (bloques incompletos), y se asume que los modelos son de efectos fijos y aleatorios simultaneamente (modelos mixtos). Se utiliza PROC MIXED para la obtenci6n de las medias ajustadas y un estimador del error ponderado decada uno de los analisis que se hicieron por separado. Asimismo, se emplean grados de libertad y numero de repeticiones tambien ponderados. En los tres casos anteriores se pretende lograr los mismos objetivos: i) Uniformizar los conceptos y resultados de los modelos AMMI, determinar la significancia de cada termino AMMI y obtener los biplots, ii) Que los investigadores puedan realizar lo anterior de forma simplifi ada y automatizada. En terminos generates, los tres casos presentan el mismo programa base, con ligeras adecuaciones en algunas secciones, dependiendo del caso que se este estudiando.
Publication - Modelos estadísticos multiplicativos para el análisis de la interacción genotipo x ambiente(CIMMYT, 2000) Crossa, J.; Cornelius, P.L.; Vargas Hernández, M.En los últimos 1O años se han logrado avances importantes en el uso de los modelos estadísticos multiplicativos para el análisis de ensayos de genotipos en ambientes múltiples y el estudio del complicado fenómeno de la interacción genotipo x ambiente (IGA
Publication - Heterosis and combining ability among CIMMYT's mid-altitude early to intermediate maturing maize (Zea mays L.) populations(Consiglio per la Ricerca e la sperimentazione in Agricoltura, Unità di Ricerca per la Maiscoltura, 2009) Vivek, B.; Crossa, J.; Alvarado Beltrán, G.Maize is an important food crop in sub-Saharan Africa. There is an increasing demand for early maturing maize cultivars even though long-season maize cultivars yield more than early maturing cultivars under favourable conditions. This is because vast areas of maize are routinely affected by drought and low N fertility and early maturing maize cultivars offer more flexibility than full season cultivars for a farmer with respect to cultivation and food security. CIMMYT?s early maturing maize program, which aims to supply seed to approximately 3 million hectares of maize area in east and southern Africa lacks adequate information on heterotic relationships of its germplasm. 190 crosses (generated from a diallel of eighteen populations and two within heterotic group single crosses) and their 20 parentals were evaluated for heterotic relationships at six locations in Zimbabwe (four optimal conditions of rainfall and fertilizers (but different agro-ecological regions / mega-environments), one managed low nitrogen environment and one managed drought environment). Three heterotic patterns were seen under stress while six heterotic patterns were seen under optimal conditions. P9 (CML312/CML442) expressed a consistent heterotic pattern across stress and non-stress environments thus justifying its continued use as a tester. Moving towards the use of multiple heterotic groups in the CIMMYT-Zimbabwe program may be worthwhile provided that the budgetary scenario still supports its core mandate of germplasm development, germplasm exchange and strengthening of national research systems.
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