Secondary traits related to kernel setting in transgenic maize hybrids at low and high plant densities and their potential use in breeding programs

Maize (Zea mays. L) traditional breeding presents limitations when selection is performed by adaptation to suboptimalconditions. One strategy to achieve greater efficiency in these environments is to include measurements ofsecondary traits related to the main grain yield component, i.e. kernel number per plant (KNP), which is associatedto other three secondary traits: plant growth rate during the critical period (PGRcp) for kernel setting, biomasspartitioning index to the ear during this period (PIcp) and the efficiency of the ear to set kernels or reproductiveefficiency (RE). Phenotypic variations in these KNP related traits were evaluated considering: i) plant densities,and ii) simple and staked transgenic maize hybrids. The objective of this study was to identify the contribution ofthese secondary traits to KNP in six modern single-cross transgenic hybrids: the simple and staked transgenic versionsof DK747 and DK190 (Bt: 747MG and 190MG; RR: 747RR and 190RR; and Bt-RR: 747MGRR and 190MGRR)cultivated at low and high plant densities. For this purpose, KNP and secondary traits were recorded at the individualplant level and the data set was analyzed using multivariate analysis techniques. At low plant density, PGRcpwas the critical trait for kernel setting in all hybrids but PIcp or RE also contributed to KNP of the DK747 groupand the D190 group, respectively. At high plant density, a differential contribution of secondary traits to KNP wasrecorded among hybrids. For DK747MG and DK190MG, RE mainly determined KNP, but for the DK747RR andDK747MGRR higher PIcp had a positive impact on KNP. These results highlight the importance of including secondarytraits associated to KNP in breeding programs

Desarrollo vegetativo y reproductivo de vástagos de diferente orden de tres híbridos comerciales de maíz en dos densidades de siembra

21-32La producción de macollos puede otorgar estabilidad al rendimiento del maíz en ambientes con oferta variable de recursos, o compensar fallas en el establecimiento de plántulas. El objetivo de este trabajo fue analizar la fenología de los estadios vegetativos y reproductivos de vástagos principales y macollos y su relación con el crecimiento en etapas tempranas del cultivo, en escenarios de alta oferta de recursos bajo densidades de siembra contrastantes. Se realizó un experimento a campo en la FA-UBA durante 2014-2015, con dos híbridos dentados (ARV2194HXRR y ARV2183MGRR) y un híbrido pisingallo (Argenpop 141) sembrados en dos densidades (3 y 6 plantas m-2) sin limitaciones hídrico-nutricionales. Desde etapas tempranas del ciclo, la proporción de plantas con macollos presentó diferencias (0,005 menor a P menor a 0.1) entre densidades (mayor en baja densidad). En ARV2194HXRR y Argenpop141, esta proporción respondió positiva y linealmente a la tasa de crecimiento del vástago principal durante los primeros 42 días desde emergencia. Para similares tasas, el ARV2183MGRR nunca presentó macollos. Debido a la mayor producción de macollos en baja densidad, ARV2194HXRR y Argenpop141 presentaron estabilidad en el número de vástagos m-2 (ca. 7,6 y 8,3 vástagos m-2 para ARV2194HXRR y Argenpop141; respectivamente) entre densidades. A pesar del menor número de hojas (ca. 13,8 vs 22 y 10,4 vs 18 hojas para macollos y vástagos principales de ARV2194HXRR y Argenpop141; respectivamente) y similar filocrono (ca. 44,6 y 56,5 °Cd hoja-1 para ARV2194HXRR y Argenpop141; respectivamente), los macollos florecieron más tardíamente (ca. 120 y 70 °Cd para ARV2194HXRR y Argenpop141; respectivamente) y presentaron una mayor asincronía floral (ca. -123 y -71°Cd para ARV2194HXRR y Argenpop141; respectivamente) que el vástago principal (ca. 18 y 7°Cd para ARV2194HXRR y Argenpop141; respectivamente), probablemente debido a la demora en el inicio del macollaje (aprox. en 8-9 hojas aparecidas del vástago principal) y en la iniciación floral de sus ápices

Genetic diversity among plants of non-transgenic and transgenic versions of a single cross maize hybrid

Previous studies have documented that transgene introduction may alter the phenotypic expression of several traits (e.g., biomass production, grain yield). We hypothesized that genetic diversity could influence the phenotypic variation among hybrids of a same genetic background and also among plants of a hybrid. The objectives of this preliminary study were: (i) to quantify the genetic diversity between the non-transgenic (DK747) and transgenic versions (DK747MG, DK747RR and DK747MGRR) of a single-cross maize hybrid and among plants of each version, (ii) to observe the distribution of genetic diversity along the genome and (iii) to explore relationships between phenotypic variability and genetic diversity. Hybrids were cultivated at field conditions during two growing seasons and plants of each hybrid with high, intermediate and low biomass at physiological maturity were selected to perform a study of single nucleotide polymorphisms (SNP). Genetic diversity among plants of each version was greater than among versions and both sources of variation were significant (ΦST = 0.45, P < 0.01). Genetic diversity of the non-transgenic DK747 was higher than those of the transgenic versions, probably reflecting the conventional breeding history of these iso-hybrids. Similarity coefficients indicate that the most homogeneous group was that composed by plants of DK747MGRR. A Fisher's exact test together with a principal component analysis identified certain SNPs related to the contrasting plant biomass of DK747, 747MG and DK747RR. Caution should be taken with these results, because of the small sample size for SNPs study and the narrow set of tested hybrids.Fil: Laserna, María Paula. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; ArgentinaFil: López, C. G.. Universidad Nacional de Lomas de Zamora; ArgentinaFil: Aulicino, Mónica Beatriz. Universidad Nacional de La Plata. Facultad de Ciencias Agrarias y Forestales. Instituto Fitotécnico de "Santa Catalina"; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Maddonni, Gustavo Angel. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; Argentin

IDENTIFICATION OF LISTERIA-MONOCYTOGENES IN FOOD AND ENVIRONMENT BY POLYMERASE CHAIN-REACTION

Samples of mozzarella cheese, lettuce leaves (in suspension 1:10), tap water and wastewaters were artificially contaminated with L. monocytogenes in a ten-fold decreasing number. DNA extracted directly from these samples was amplified by PCR technique utilizing two primers for target sequence. Amplified DNA fragment compared with one of known weight, was of 326 bp, characteristic of L. monocytogenes. Amplification was obtained up to a concentration of 3 cfu/ml in tap water, and in mozzarella cheese and lettuce leaves suspensions, corresponding to 30 cfu/g of this two products; up to 300 cfu/ml in wastewaters. in these last case probably some interference due to organic and inorganic compounds present inhibited PCR. The present procedure does not require an enrichment culture step and is capable of identification of this microorganism within 3 h and a half