Posts Tagged ‘Zea mays’

Antibiosis Mechanism of Resistance to Larger Grain Borer, Prostephanus truncatus (Horn)(Coleoptera: Bostrichidae) in Maize

Posted by Carelia Juarez on , in Journal Articles

Published in Journal of Entomology  11 (5) : 248-260, 2014

Nhamucho, E.;  Mugo, S.N.;  Kinyua, M.;  Gohole, L.;  Tadele Tefera;  Mulima, E.

Host plant resistance is a valuable component of integrated pest management in maize. Maize stored on-farm without controlled moisture content and insecticide treatment is highly susceptible to damage by Larger Grain Borer (LGB),Prostephanus truncatus (Horn) (Coleoptera: Bostrichidae). The aim of this study was to determine the resistance of Mozambican maize genotypes against P. truncatus. Seventeen maize genotypes composed of seven experimental hybrids, one released hybrid, two improved open pollinated varieties (OPV), three landraces from Mozambique and four checks (two resistant and two susceptible) from Kenya were screened for their resistance to LGB. The F1 and F2 hybrids were evaluated at Kiboko, Kenya in a completely randomized design trial, replicated four times in a post-harvest laboratory. A selection index computed from the number of LGB, grain weight loss (%), seed damage (%) and flour weight were used to categorize the materials as either resistance or susceptible. Fifty percent of the F1 hybrids tested were resistant, 25% moderately resistant and 25% susceptible. Twenty five percent of F2 hybrids evaluated were resistant and 75% susceptible. EV8430DMRSR, an OPV and Kandjerendjere, a landrace were the most resistant genotypes with less than 10% weight loss and less than 25% seed damage. This study showed that high protein content contributed towards resistance while high starch contributed to susceptibility. It was concluded that antibiosis mechanism could contribute to LGB resistance in maize. The identified resistant genotypes could be used as cultivar or as source of resistance in maize breeding programs for resistance to LGB.

Combined small RNA and degradome sequencing reveals novel miRNAs and their targets in response to low nitrate availability in maize

Posted by Carelia Juarez on , in Journal Articles

Published in Annals of Botany 112 : 633-642, 2013

Yongping Zhao; Zhenhua Xu; Qiaocheng Mo; Cheng Zou; Wenxue Li; Yunbi Xu; Chuanxiao Xie

Background and Aims MicroRNAs (miRNAs) play an important role in the responses and adaptation of plants to many stresses including low nitrogen (LN). Characterizing relevant miRNAs will improve our understanding of nitrogen (N) use efficiency and LN tolerance and thus contribute to sustainable maize production. The objective of this study was to identify novel and known miRNAs and their targets involved in the response and adaptation of maize (Zea mays) to LN stress.

Methods MiRNAs and their targets were identified by combined analysis of deep sequencing of small RNA and degradome libraries. The identity of target genes was confirmed by gene-specific RNA ligase-mediated rapid amplification of 5′ cDNA ends (RLM-RACE) and by quantitative expression analysis.

Key Results Over 150 million raw reads of small RNA and degradome sequence data were generated. A total of 46 unique mature miRNA sequences belonging to 23 maize miRNA families were sequenced. Eighty-five potentially new miRNAs were identified, with corresponding miRNA* also identified for 65 of them. Twenty-five new miRNAs showed >2-fold relative change in response to LN. In addition to known miR169 species, two novel putative miR169 species were identified. Deep sequencing of miRNAs and the degradome, and RLM-RACE and quantitative polymerase chain reaction (PCR) analyses of their targets showed that miRC10- and miRC68-mediated target cleavage may play a major role among miR169 families in the adaptation to LN by maize seedlings.

Conclusions Small RNA and degradome sequencing combined with quantitative reverse transcription–PCR and RLM-RACE verification enabled the efficient identification of miRNAs and their target genes. The generated data sets and the two novel miR169 species that were identified will contribute to our understanding of the physiological basis of adaptation to LN stress in maize plants.

La importancia de los nichos de mercado. Un estudio de caso del maiz azul y del maiz para pozole en Mexico. The importance of niche markets. A case study of blue and pozole-making maize in Mexico

Posted by Carelia Juarez on , in Journal Articles

Published in Revista Fitotecnia Mexicana 36 (Supl. 3-A) : 315-328, 2013

Hellin, J.; Keleman, A.;Lopez, D.; Donnet, L.; Flores, D.

A focus of agricultural research efforts in México is on breeding higher-yielding improved maize (Zea mays L.) varieties and enhancing farmer adoption of these varieties despite the fact that maize landraces continue to play a key role in the livelihoods of farmers. There are a number of reasons, not least the economic ones, behind the decision of farmers to grow landraces. Grain from landraces can be more profitable when farmers access specialty maize markets. Furthermore, many landraces produce multiple products, besides grain, for which there is a market, such as husks (“totomoxtle”) for wrapping tamales (a traditional dish). We explore in more detail the rationale behind the decision of farmers to grow landraces. For illustrative purposes, we look at maize markets for blue and pozole-making in the Mexican central highlands. Using a value chain approach, we explore the challenges and opportunities farmers face in accessing these markets. The pozole (a traditional dish) value chain relies on localized production and infrastructure investment that contributes to value-adding activities such as producing pre-cooked pozole. Blue maize, meanwhile, is more widely cultivated, and although there are fewer opportunities for farmers to add value, this grain feeds into small-scale, largely female-run businesses. Both markets contribute to local livelihood improvements and in situ conservation, but careful policy design is necessary to scale-up these markets without diminishing their benefits. This research helps explain the persistence of maize landraces in Mexican agriculture. Thus, it has implications for the direction of agricultural research. It provides plant breeders and nutritional experts with information on the agronomic characteristics required by producers and quality traits demanded by the market. It suggests that plant breeders should focus more attention on improving farmer-identified quality characteristics of their landraces along with higher and more stable yields. The desired impact would be a segmented maize seed sector characterized by both improved landraces and improved maize varieties.

Diversidad genetica en maices nativos mexicanos tropicales. Genetic diversity in tropical Mexican landraces of maize

Posted by Carelia Juarez on , in Journal Articles

Published in Revista Fitotecnia Mexicana 36 (Supl. 3-A) : 329-338, 2013

Gonzalez Castro, M.E.; Palacios Rojas, N.; Espinoza Banda, A.; Bedoya Salaza, C.A.

Mexico is considered the center of origin and domestication of maize (Zea mays L.), and it is recognized as one of the most important centers of diversity. Evaluation of native maize diversity is specially important for conservation strategies design, germplasm characterization and its use in breeding; native maize is potentially a source of new, favorable and exotic features. In this study, 30 microsatellite molecular markers were tested to characterize intraracial and between population genetic diversity present in 196 tropical populations representing 20 corn races. Results indicated that these accessions can be grouped into three ecological areas: Gulf of México, South Pacific and Yucatán Peninsula (A), the Northwestern and Western (B), and Intermediate Lowland Oaxaca and Chiapas (C). Average number of alleles per locus within the populations was 9. Average genetic diversity of 20 tropical Mexican maize races was 0.57 across all accessions. There was greater variability among races (23.18) than within each race (0.99 to 8.72). Genetic erosion due to limited geographical distribution for Zapalote and Jala races was evident, thus indicating the need for preservation efforts. Genetic diversity indices of 0.53 found for Tuxpeño germplasm confirm that although they have been widely used in breeding programs, there is untapped diversity in this race.

Preferences and constraints of maize farmers in the development and adoption of improved varieties in the mid-altitude, sub-humid agro-ecology of Western Ethiopia

Posted by Carelia Juarez on , in Journal Articles

Published in African Journal of Agricultural Research 8 (14) : 1245-1254, 2013

W. Abera, S. Hussein, J. Derera, M. Worku and M. D. Laing

Understanding farmers’ production constraints and preferences is important in maize breeding, especially underlying successful adoption of improved varieties and their production packages. This study was conducted to assess the present importance, and productivity constraints of maize in the mid-altitude, sub-humid agro-ecology of Western Ethiopia. Data was collected through a semi-structured questionnaire and focus group discussions, using 240 randomly selected respondent farmers, in 12 sub-districts, within three administrative zones. Maize was ranked number one as both food and cash crop by 82.9% of respondents. Most farmers (59%) use hybrids, while 24% grow landrace varieties. Unavailability of improved seed and lack of production inputs were the two major constraints reducing maize productivity, as reported by 62 and 60% of respondents, respectively. A high proportion of respondents (80%) indicated that, unpredictable grain prices are the major market constraint as 97% of the respondents sell their maize crop in the local market. Northern corn leaf blight (NCLB) was reported to be important by 46% of respondents. Breeding for improved disease resistance and grain yield, enhancing the availability of crop input and stabilizing market price during harvest time are the most important strategies to increase maize production by small-scale farmers in Western Ethiopia.

Genetic interrelationships among medium to late maturing tropical maize inbred lines using selected SSR markers

Posted by Carelia Juarez on , in Journal Articles

Published in Euphytica 191 (2) : 269-277, 2013

Abera Wende, Hussein Shimelis, John Derera, Worku Mosisa, Jedidah Danson and Mark D. Laing

Understanding the genetic relationships among breeding lines is fundamental in crop improvement programs. The objectives of this study were to apply selected polymorphic single sequence repeat (SSR) DNA markers and cluster medium to late maturing tropical elite maize inbred lines for effective hybrid breeding. Twenty elite inbred lines were genotyped with 20 SSR markers. The analysis detected a total of 108 alleles. The unweighted pair group method with arithmetic mean allocated the inbred lines into five clusters consistent with the known pedigrees. The tested inbred lines that were adapted to mid-altitude, sub-humid agro-ecologies were classified in different clusters, except for a few discrepancies. The greatest genetic distance was identified between the clusters of lines CML-202 and Gibe-1-91-1-1-1-1. The analysis determined the genetic grouping present in the source population, which will assist in effective utilization of the lines in tropical hybrid maize breeding  programs to exploit heterosis.

QTLs asociados al contenido de carotenos en hojas de maiz (Zea mays L.)

Posted by Carelia Juarez on , in Journal Articles

Published in Agrociencia 46 (4): 333-345, 2012

Viridiana Silva-Pérez, F. Carlos Gómez-Merino, J. Jesús García-Zavala, Juan Burgueño-Ferreira, Amalio Santacruz-Varela, Natalia Palacios-Rojas, Axel Tiessen

Los carotenos son pigmentos antioxidantes que captan fotones del espectro de luz visible y protegen a los tejidos de las plantas contra la foto-oxidación, lo cual está relacionado con la tasa fotosintética y rendimiento de los cultivos. La biosín-tesis de los carotenos ocurre dentro de los plástidos, donde se sintetizan a partir de la vía mevalónica independiente, con la participación de más de 10 enzimas y un número de factores aún no definidos. Con el objetivo de identificar regiones cromosómicas de maíz (Zea mays L.) asociadas al conteni¬do de carotenos, se midió el contenido de estos compuestos en hojas de 200 líneas endogámicas recombinantes de maíz, provenientes de la cruza B73×Mo17, sembradas en Irapuato, México, en el ciclo primavera-verano 2009. Los QTLs localizados se asociaron a los siguientes compuestos: luteína, a-ca-roteno, b-caroteno, b-criptoxantina y zeaxantina. El caroteno presente en mayor cantidad en las hojas fue b-caroteno (80 % del total) y el menor b-criptoxantina (0.2 %). En los cro¬mosomas 1, 2, 4, 5, 6 y 8, se detectaron 21 QTLs significativos. En el bin 1.07 se localizó un QTL altamente significativo (p£0.001) con valor aditivo alto para luteína (-89.16 mg g-1 PMS, r2=0.07), a-caroteno (-25.41 mg g-1 PMS, r2=0.07) y b-caroteno (-674.98 mg g-1 PMS, r2=0.09). Un QTL de b-criptoxantina en el cromosoma 8 fue detectado mediante el marcador psy2 que es parálogo de la enzima fitoeno sintasa, y otro QTL coincidió con un QTL evaluado para ácido abscísico, relacionado al gen caroteno dioxigenasa. Se infiere que en el genoma de maíz existen factores aún no identificados relacionados al contenido de carotenos en hojas verdes, y los QTLs identificados en este estudio podrían ayudar a encon trar nuevos genes o factores que determinan el contenido de carotenos en hojas de maíz.

 

Striga hermonthica parasitism in maize in response to N and P fertilisers

Posted by Carelia Juarez on , in Journal Articles

Published in Field Crops Research 134 (12): 1-10, 2012

M. Jamil, F.K. Kanampiu, H. Karaya, T. Charnikhova, H.J. Bouwmeester

Parasitism by the parasitic weed, Striga hermonthica (Striga), constitutes a major biological constraint to maize production in sub-Sahara Africa. Nutrient deficiency is known to aggravate Striga infestation and in a number of plant species it was recently shown that this may be due to increased secretion of Strigagermination stimulants into the soil. The present study was designed to observe the connection between soil fertility, secretion of germination stimulants and Striga infection in maize under greenhouse and field conditions. The experiments were conducted during two successive cropping seasons (2008 and 2009). The greenhouse study showed that maize secretes a number of so far unidentified strigolactones that induceStriga seed germination and the amount of these strigolactones increases upon N and P deficiency. The increased secretion of germination stimulants under N and P deficiency resulted in increased Striga infection in pot experiments. The on-station and on-farm field trials in Western Kenya also showed reduction in Strigainfestation with the application of mineral nutrients but the results were less consistent than in the greenhouse. Increasing levels of N showed a fair reduction of Striga in the field especially during the first year, whereas P application did not have much effect in contrast to the greenhouse study where both N and P clearly reduced Striga infection. The likely explanation for this discrepancy is that availability of mineral nutrients under field conditions is less predictable than under greenhouse conditions, due to a number of factors such as soil texture and structure, pH, salinity, drought, leaching and runoff. Hence, further studies are needed on the importance of these factors before a fertiliser application strategy can be formulated to improve control of Striga in maize in the field.

Earthworm activity and soil structural changes under conservation agriculture in central Mexico

Posted by Carelia Juarez on , in Journal Articles

Published in Soil and Tillage Research 123: 61-70, 2012

A. Castellanos-Navarretea, C. Rodríguez-Aragonés, R.G.M. de Goede, M.J. Kooistra, K.D. Sayre, L. Brussaard, M.M. Pullema

Crop residue mulching combined with zero tillage and crop rotation, known as conservation agriculture (CA), is being promoted as an alternative system to revert soil degradation in maize-based farming in the central highlands of Mexico. The goal of this paper was to determine the effects of CA vs. conventional tillage systems on soil quality, with a special focus on the role of earthworms in affecting the soil structure morphology, and on crop yield. For the conventional tillage system, the effect of crop residue retention (CONV + RES) was also compared to the conventional farmers’ practice (residues removed; CONV). CA resulted in four times higher earthworm abundance when compared to CONV. Residue retention per se (CONV + RES) did not favor earthworm abundance. In all cases the earthworm community was dominated by exotic species. CA increased total N and soil organic C concentrations relative to CONV, but only at 0–5 cm soil depth. Nevertheless, the more pronounced vertical stratification of soil organic carbon content under CA favored soil surface aggregation and aggregate stability as expressed by the aggregate mean weight diameter after dry sieving (MWDds = 2.6 mm for CA and 1.6 mm for CONV) and wet sieving (MWDws = 0.9 mm and 0.6 mm, respectively). Also, CA improved topsoil water stable macroaggregation (WSA = 415 mg g−1) when compared to CONV (251 mg g−1). Residue retention within conventional tillage (CONV + RES) led to small increases in topsoil aggregate stability (i.e. MWDds and WSA). Soil structural improvements were accompanied by a higher direct surface water infiltration. Micromorphological analysis of thin sections indicated a loose and highly biogenic soil microstructure in CA, whereas CONV was characterized by a physicogenic microstructure, despite similar soil bulk densities (SBD). SBD is thus a poor indicator of soil physical quality when comparing different tillage systems. Redundancy analysis illustrated that CA resulted in improvement in most parameters related to soil quality, especially at the soil surface, but significant yield increases were recorded only in 2004. CONV + RES lead to marginal improvements in soil quality with no yield increases.

Near-Infrared Reflectance Spectroscopy (NIRS) for Protein, Tryptophan, and Lysine Evaluation in Quality Protein Maize (QPM) Breeding Programs

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Published in Journal of Agricultural and Food Chemistry 59(20): 10781-10786, 2011

Near-Infrared Reflectance Spectroscopy (NIRS) for Protein, Tryptophan, and Lysine Evaluation in Quality Protein Maize (QPM) Breeding Programs

Aldo Rosales, Luis Galicia, Ezequiel Oviedo, Catalina Islas and Natalia Palacios-Rojas

Quality protein maize (QPM) has approximately twice the tryptophan (Trp) and lysine (Lys) concentrations in protein compared to normal maize. Because several genetic systems control the protein quality of QPM, it is essential to regularly monitor Trp and/or Lys in breeding programs. Our objective was to examine the potential of near-infrared reflectance spectroscopy (NIRS) to enhance the efficiency of QPM research efforts by partially replacing more expensive and time-consuming wet chemistry analysis. More than 276 maize samples were used to develop NIRS models for protein content (PC), Trp, and Lys. The standard error of prediction (SEP) for the calibration and the coefficient of determination for validation (R2v) were 0.26 and 0.96 for PC, 0.005 and 0.85 for Trp, and 0.02 and 0.75 for Lys. When the NIRS models were used to evaluate 266 S2 lines from five QPM breeding populations, the coefficients of determination between NIRS and the chemical data were 0.94, 0.76, and 0.80 for PC, Trp, and Lys, respectively. Therefore, the NIRS models can be used to support the QPM breeding efforts.