CREA Journals (Consiglio per la ricerca in agricoltura e l’analisi dell’economia agraria)
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Genetic variation for cell wall degradability in maize inbred lines without and after alkaline pretreatments
Get PDFAlkali pretreatments were applied at two temperatures on a set of eight maize lines exhibiting a large range of cell wall degradability, which was comprised between 49.4 and 24.9%. The effect of NaOH concentration on cell wall degradation was shown strongly preponderant over the effect of temperature, with significant interactions be- tween alkali concentrations and temperatures. Interactions between lines and NaOH concentration or temperature were weak or non significant. With mild-alkaline 0.02 N pretreatment, cell wall degradation was similarly increased by 36% for all considered lines, without any difference between 22°C or 50°C temperature conditions. With more severe 0.2 N alkaline pretreatment, average cell wall degradation was increased by 114% and 140% at 22°C and
50°C, respectively, leading also to a reduced range of variation between lines, especially at the highest tempera- ture. However, whatever pretreatment conditions, the line effect stayed highly significant, even when it was greatly reduced. With a solution of 0.2 N NaOH at 22°C, nearly 80% and 70% of cell walls were solubilized in more and less degradable lines, respectively. Such pretreatment conditions limit both energy costs and amounts of effluents to be recycled. Breeding maize lines and hybrids for higher degradability of their cell walls is thus a relevant goal for both animal feeding and environmentally friendly production of bioenergy
The bacterial diversity in Zea mays L: A critical review
Get PDFMaize is a plant of great value to humanity, so the bacterial diversity in association with the cultivation is equally important. Various protocols have been developed for studied bacterial diversity associated with maize from the cultivable bacterial diversity to nonculturable bacterial diversity. In this article the importance of maize, microbial diversity associated with the plant and bacterial diversity associated with the rhizosphere and inside of the plant is review. The methods that have been used for information in the past 20 years and a reflection on the prospects of the current knowledge of the diversity of bacteria associated in Zea mays
Genetic variability for drought tolerance in early-maturing maize inbreds under contrasting environments
Get PDFDrought severely constrains maize (Zea mays L) production in the savannas of West and Central Africa (WCA). Understanding the levels of drought tolerance in early-maturing maize inbreds is crucial for the development of drought-tolerant maize hybrids for the sub-region. A total of 156 inbred lines were evaluated under drought and well-watered conditions at Ikenne and Bagauda in Nigeria for 2 yr. The objectives were to (i) determine the levels of drought tolerance in early-maturing inbreds, (ii) assess the performance of the inbreds and relationship among traits under the contrasting environments, and (iii) identify the most stable inbreds across environments. Inbreds differed significantly (p < 0.01) in grain yield and other measured traits under drought and well-watered conditions. Grain yield of inbreds was significantly (p < 0.01) correlated with ears per plant (r = 0.50), anthesis-silking interval (r = -0.55), plant aspect (r = -0.57), ear aspect (r = -0.35) and stay-green characteristic (r = -0.28) under drought. Forty-eight percent of the lines were identified as drought tolerant with tolerance indices ranging from 0.17 to
15.31. Broad-sense heritability estimate was 43% for grain yield under drought and 47% under well-watered con- ditions. Drought reduced grain yield of the inbreds by 3-88%, averaging 52%. Biplot analysis identified inbreds TZEI 18, TZEI 56, TZEI 1, and TZEI 19 as the most stable across environments. The inbreds with high levels of drought tolerance could be utilised for the development of drought-tolerant hybrids and synthetic varieties as well as for introgression of tolerance genes into tropical maize breeding populations
Waxy maize yield and components as influenced by environment, water regime, and hybrid
Get PDFLimited research on environment and production practices on grain yield and yield components of waxy maize (Zea mays L) has been conducted. Research was conducted in 2012 and 2013 at Mead and North Platte, NE under irrigated and rainfed water regimes with the objective to determine the influence of environment, water regime and hybrid on waxy maize yield and yield components. The waxy maize hybrids P0461EXR, P35F36, P1162EXR, and P1395EXR were grown. Grain yield, ears m-2, kernels ear-1, kernels row-1, rows ear-1, ear length, and circumfer- ence and kernel weight were determined. Average grain yield was 9.5 Mg ha-1 across environments and irrigation increased grain yield by 3.1 to 3.3 Mg ha-1 at Mead and 8.1 to 12.7 Mg ha-1 at North Platte. The highest irrigated grain yields of 14.2 Mg ha-1 were produced at North Platte in 2013 while the highest rainfed grain yields of 10.1
Mg ha-1 were produced in Mead in 2013. Kernel weight in Mead and North Platte irrigated environments had the highest correlation with grain yield (R = 0.67), while kernels ear-1 had the highest correlation (R = 0.78) with grain yield in the North Platte rainfed environment. Hybrid influenced yield and yield components, however the influ- ence on yield was much less than for environment and water regime. Waxy maize had similar grain yield and yield components to previous studies with dent maize. Irrigated and higher rainfall environments produced high waxy maize yields, thus waxy maize should be a viable specialty crop option if minimal market incentives are available
Higher emergency vigor seed traits of sweet maize (Zea mays L) inbred lines in China by factor analysis and cluster analysis
Get PDFFactor analysis and cluster analysis is broadly applied to define seed nutrient components that mostly determine the seed vigor in the field that can be used as breeding and selection criteria. By using factor analysis and clus- ter analysis, relationship of seed emergence percentage and seed traits of 122 sweet maize inbred lines were investigate in the experiment. Reserves compositions variability of the sweet maize kernels which processed by drying milling were determined. The results showed that the reserves compositions and emergency percentage were significantly different among the sweet maize inbred lines. The emergency percentage of sweet maize inbred lines was concerned with five principal components from factor analysis and the contribution rate of single kernel weight was the most important, which could account for 26.97%. Sweet maize inbred lines with emergency per- centage higher than the 3rd quartile of the index could be classified into four groups by cluster analysis
Genetic analysis of grain yield performance and weevil [Sitophilus zeamais (Motschulsky)] resistance in southern African maize hybrids
Get PDFMaize (Zea mays L) grain losses due to grain weevils threaten food security in poor rural communities where grain is stored on farm without any chemical treatment in developing countries. Progress in developing high-yielding and weevil-resistant maize varieties is scarcely reported in the literature. Knowledge of the mode of inheritance for both grain yield and weevil resistance in elite maize germplasm would be crucial in designing viable breeding strategies. Therefore hybrids that were generated in a North Carolina design II mating scheme were evaluated for grain yield over three environments. Hybrids were also evaluated for maize weevil (Sitophilus zeamais Motsch) resistance under controlled temperature and relative humidity in the laboratory. Results revealed that only a few hybrids combined high grain yield potential and maize weevil-resistance reflecting the challenges which may be encountered in developing productive hybrids. However, highly significant differences between hybrids for both grain yield and weevil resistance indicated opportunities for selection. Furthermore, weevil resistance was found in at least four major heterotic groups suggesting that development of weevil-resistant hybrids could be created by crossing complementary lines from these heterotic groups. Significance of GCA and SCA effects suggested that genes with both additive and non-additive effects, respectively, were important for grain yield. The SCA effects were not significant (P > 0.05) for grain weevil resistance parameters, suggesting that genes with additive effects played a predominant role in governing the resistance in hybrids. Generally the baseline resistance to maize weevil could be improved through selection, while procedures that emphasize both GCA and SCA would be exploited to enhance grain yield in this set of maize germplasm
Quantifying Zea mays L tassel development and correlation with anther developmental stages as a guide for experimental studies
Get PDFIn the study of Zea mays L early anther development, anther length is tightly correlated with developmental stage over the initial eight days of ontogeny. The developing tassel is enveloped inside the whorl of developing leaves, and the pace of its growth is environmentally sensitive. Determining the size of a young tassel without sacrific- ing the plant remains difficult. This obstacle can present problems when trying to study pre-meiotic and meiotic stages of anther development in planta or when conducting sequential sampling from the same tassel. In this study a range of exterior characteristics (leaf number, stem circumference, and tassel height above the soil line) were measured and correlated with tassel length. Anther lengths at seven tassel locations were also measured to correlate tassel length with anther development at these locations. Results indicate that tassel length can occupy a wide-range for a given exterior measurement, but also that anther development at specific tassel locations is highly reproducible for a tassel of known length. This information provides a useful guide for the study of anther development in the context of the maize tassel
Metarhizium anisopliae biopesticides and fungus isolates: control efficacy against Rhynchophorus ferrugineus (Olivier) (Coleoptera Dryophthoridae) on different contamination substrata.
Get PDFThe lack of biological insecticides based on Metarhizium anisopliae (Metsch.) Sorokin registered in Italy for the control of the Red Palm Weevil (RPW), Rhynchophorus ferrugineus (Olivier), prompted studies to evaluate the efficacy of two commercial products, Met52® and BioStormTM and of their fungal isolates, M. anisopliae (Man52) and (ManBS) respectively, against the adults. The virulence of the M. anisopliae strains (Man52) and (ManBS) was compared with that of an indigenous M. anisopliae (Man08/I05) strain obtained from R. ferrugineus specimens collected in the wild and that showed to be very virulent against the RPW in previous studies. In both tests the sublethal effects of the treatments on female reproductive potential were examined in relation to the infective substratum. Laboratory results indicated that the commercial formulations mixed directly into the soil were not active in transmitting the infection to RPW adults and in reducing female fecundity and fertility. Diversely the fungal M. anisopliae (ManBS), (Man52) and (Man08/I05) strains inoculated on a rice substratum caused over 80% mortality of the phytophagous. In particular, M. anisopliae (ManBS) and the M. anisopliae (Man08/I05) produced the highest mortality (100%), with LT50 e LT90 reached in 3 and 6 days respectively. M. anisopliae (Met52) strain instead led to 85% mortality of RPW specimens in 28-days but it took longer to reach LT50 (6 days) and LT90 (12 days). The reproductive potential of females infected with the fungal strains was also significantly reduced with respect to the control. This study indicates the possibility of using also M. anisopliae strains in use against other insects of agricultural importance, for the control of R. ferrugineus although their effectiveness is conditioned by the formulations and/or methods employed against the RPW
The effects of short-term cold storage on the survival of the endoparasitoid Ooencyrtus pityocampae Mercet (Hymenoptera Encyrtidae).
Get PDFIn the Mediterranean basin the Pine Processionary Moth (PPM), Thaumetopoea pityocampa is often responsible for damaging coniferous stands. The parthenogenetic thelytochous Ooencyrtus pityocampae because of its host location strategy and capacity to develop on alternative hosts plays a key role in the control of PPM. In the context of biological control, storage at low temperatures of parasitoids proved to be effective in improving their mass rearing for field release. Unfortunately, cold storage is often associated with high mortality even above the freezing temperature. Therefore, the present work focused on O. pityocampae juvenile stages submitted to 10-days storage at 15°C and then transferred to 26°C and 30°C until adult hatching. Two different hatching temperatures were used to test the hypothesis whether the speeding of O. pityocampae development could affect its survival and synchronization of emergencies. After the treatment, adult emergence percentage, adult emergence time and synchronization of emergencies were evaluated. Results showed that all life stages successfully survived the thermal regime.Nonetheless, pupae because of their high emergence rates and synchronization of adult hatching appeared to be the best stage for short time storage