Agronomy2015, 5(3), 341-362; doi:10.3390/agronomy5030341 (registering DOI) - published 31 July 2015 Show/Hide Abstract
Abstract: Sugarcane (Saccharum spp.) brown rust (caused by Puccinia melanocephala Syd. & P. Syd.) was first reported in the United States in 1978 and is still one of the great challenges for sugarcane production. A better understanding of sugarcane genotypic variation in response to brown rust will help optimize breeding and selection strategies for disease resistance. Brown rust ratings were scaled from non-infection (0) to severe infection (4) with intervals of 0.5 and routinely recorded for genotypes in the first clonal selection stage of the Canal Point sugarcane breeding program in Florida. Data were collected from 14,272 and 12,661 genotypes and replicated check cultivars in 2012 and 2013, respectively. Mean rust rating, % infection, and severity in each family and progeny of female parent were determined, and their coefficients of variation (CV) within and among families (females) were estimated. Considerable variation exists in rust ratings among families or females. The families and female parents with high susceptibility or resistance to brown rust were identified and ranked. The findings of this study can help scientists to evaluate sugarcane crosses and parents for brown rust disease, to use desirable parents for crossing, and to improve genetic resistance to brown rust in breeding programs.
Abstract: Biochars are complex heterogeneous materials that consist of mineral phases, amorphous C, graphitic C, and labile organic molecules, many of which can be either electron donors or acceptors when placed in soil. Biochar is a reductant, but its electrical and electrochemical properties are a function of both the temperature of production and the concentration and composition of the various redox active mineral and organic phases present. When biochars are added to soils, they interact with plant roots and root hairs, micro-organisms, soil organic matter, proteins and the nutrient-rich water to form complex organo-mineral-biochar complexes Redox reactions can play an important role in the development of these complexes, and can also result in significant changes in the original C matrix. This paper reviews the redox processes that take place in soil and how they may be affected by the addition of biochar. It reviews the available literature on the redox properties of different biochars. It also reviews how biochar redox properties have been measured and presents new methods and data for determining redox properties of fresh biochars and for biochar/soil systems.
Abstract: Minichromosome technology has the potential to offer a number of possibilities for expanding current biofortification strategies. While conventional genome manipulations rely on random integration of one or a few genes, engineered minichromosomes would enable researchers to concatenate several gene aggregates into a single independent chromosome. These engineered minichromosomes can be rapidly transferred as a unit to other lines through the utilization of doubled haploid breeding. If used in conjunction with other biofortification methods, it may be possible to significantly increase the nutritional value of crops.
Abstract: High yield in snap bean (Phaseolus vulgaris L.) production requires relatively high nitrogen (N) inputs. However, little information is available on whether the use of rhizobial inoculants for enhanced biological dinitrogen fixation can provide adequate N to support green pod yield. The objectives of this study were to test the use of rhizobia inoculation as an alternative N source for snap bean production under rain fed conditions, and to identify suitable cultivars and appropriate agro-ecology for high pod yield and N2 fixation in Ethiopia. The study was conducted in 2011 and 2012 during the main rainy season at three locations. The treatments were factorial combinations of three N treatments (0 and 100 kg·N·ha−1, and Rhizobium etli (HB 429)) and eight snap bean cultivars. Rhizobial inoculation and applied N increased the total yield of snap bean pod by 18% and 42%, respectively. Cultivar Melkassa 1 was the most suitable for a reduced input production system due to its greatest N2 fixation and high pod yield. The greatest amount of fixed N was found at Debre Zeit location. We concluded that N2 fixation achieved through rhizobial inoculation can support the production of snap bean under rain fed conditions in Ethiopia.
Abstract: Finger millet (Eleusine coracana (L.) Gaertn) is a staple food crop grown by subsistence farmers in the semi-arid tropics of South Asia and Africa. It remains highly valued by traditional farmers as it is nutritious, drought tolerant, short duration, and requires low inputs. Its continued propagation may help vulnerable farmers mitigate climate change. Unfortunately, the land area cultivated with this crop has decreased, displaced by maize and rice. Reversing this trend will involve achieving higher yields, including through improvements in crop nutrition. The objective of this paper is to comprehensively review the literature concerning yield responses of finger millet to inorganic fertilizers (macronutrients and micronutrients), farmyard manure (FYM), green manures, organic by-products, and biofertilizers. The review also describes the impact of these inputs on soils, as well as the impact of diverse cropping systems and finger millet varieties, on nutrient responses. The review critically evaluates the benefits and challenges associated with integrated nutrient management, appreciating that most finger millet farmers are economically poor and primarily use farmyard manure. We conclude by identifying research gaps related to nutrient management in finger millet, and provide recommendations to increase the yield and sustainability of this crop as a guide for subsistence farmers.
Abstract: Sugarcane has been widely used as a biofuel crop due to its high biological productivity, ease of conversion to ethanol, and its relatively high potential for greenhouse gas reduction and lower environmental impacts relative to other derived biofuels from traditional agronomic crops. In this investigation, we studied four sugarcane cultivars (H-65-7052, H-78-3567, H-86-3792 and H-87-4319) grown on a Hawaiian commercial sugarcane plantation to determine their ability to store and accumulate soil carbon (C) and nitrogen (N) across a 24-month growth cycle on contrasting soil types. The main study objective establish baseline parameters for biofuel production life cycle analyses; sub-objectives included (1) determining which of four main sugarcane cultivars sequestered the most soil C and (2) assessing how soil C sequestration varies among two common Hawaiian soil series (Pulehu-sandy clay loam and Molokai-clay). Soil samples were collected at 20 cm increments to depths of up to 120 cm using hand augers at the three main growth stages (tillering, grand growth, and maturity) from two experimental plots at to observe total carbon (TC), total nitrogen (TN), dissolved organic carbon (DOC) and nitrates (NO−3) using laboratory flash combustion for TC and TN and solution filtering and analysis for DOC and NO−3. Aboveground plant biomass was collected and subsampled to determine lignin and C and N content. This study determined that there was an increase of TC with the advancement of growing stages in the studied four sugarcane cultivars at both soil types (increase in TC of 15–35 kg·m2). Nitrogen accumulation was more variable, and NO−3 (<5 ppm) were insignificant. The C and N accumulation varies in the whole profile based on the ability of the sugarcane cultivar’s roots to explore and grow in the different soil types. For the purpose of storing C in the soil, cultivar H-65-7052 (TC accumulation of ~30 kg·m−2) and H-86-3792 (25 kg·m−2) rather H-78-3567 (15 kg·m−2) and H-87-4319 (20 kg·m−2) appeared to produce more accumulated carbon in both soil types.