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Grain Crop (grain + crop)
Selected AbstractsPests and Diseases of Prehistoric Crops: A Yield ,Honeymoon' for Early Grain Crops in Europe?OXFORD JOURNAL OF ARCHAEOLOGY, Issue 1 2001Petra Dark Before the agricultural improvements of recent centuries, grain yields in medieval Europe appear to have been extremely low: well below the full potential of the crops. If yields were similarly low in prehistory, the adoption of cereal cultivation could have conveyed few benefits in terms of productivity. Consideration of the key constraints on cereal yield highlights the previous neglect of the role of pests and diseases. It is suggested that these may have been particularly damaging in the medieval period, but much less so during the early stages of the adoption of agriculture. Textual and archaeological evidence for the past occurrence of pests and diseases is discussed and, combined with consideration of the development of pest and pathogen problems of recent crop introductions, used to provide a possible outline of the early development of the pest/disease burden. It is suggested that when grain crops were first introduced into temperate Europe there may have been a ,honeymoon period' with high yields: pests and diseases which had been endemic on cereals in semi-arid, continental, or Mediterranean climates did not thrive in the temperature climate, while species native to north-west Europe may not have been adapted to attack cereals. Subsequently, however, some pests and diseases evolved to attack cereals in this environment. These may have prompted changes in grain production methods to reduce the risk of damage. Pests and diseases must have been a driving force in agrarian change for several millennia, and cannot be ignored in attempts to understand the history of agriculture. [source] Soil Temperature and Planting Depth Effects on Tef EmergenceJOURNAL OF AGRONOMY AND CROP SCIENCE, Issue 3 2009S. Evert Abstract Tef [Eragrostis tef (Zucc.) Trotter] is an annual C4 grass crop that originated in Ethiopia. It has potential as a grain crop in the Great Plains because of its tolerance to drought and high temperatures. In Ethiopia, tef seed is typically broadcast on the soil surface and lightly incorporated. Shallow planting depths are used because the seed is very small and emergence can be limited by soil crusting. If planting equipment is to be used, planting depth may be important for successful tef production. The objective of this study was to identify optimal depths and soil temperatures to aid in developing tef planting recommendations for the central Plains. Tef was planted at five depths (0, 0.6, 1.3, 2.5 and 5.0 cm) in pots filled with a silt loam soil, and pots were placed in growth chambers at four temperature regimes (day/night: 15/19 °C; 19/23 °C; 23/27 °C and 27/31 °C). No plants emerged from the 5.0-cm depth, so this depth was not included in the analysis. Emergence was greatest for planting depths of 0.6 and 1.3 cm and lower at 0 and 2.5 cm depths. Temperature did not affect final emergence, measured 21 days after planting (DAP), but did influence emergence rates during the first 9 DAP. Plant dry matter production increased as planting depth increased, but plant dry matter per pot was not different among planting depths greater than 0.9 cm, suggesting that compensation between plants across different plant densities began early in the plants' life cycles. Our results show that tef seed can emerge from depths between 0.6 and 1.3 cm and that soil temperatures below 19 °C can slow emergence but should not affect final stands. [source] Can improvement in photosynthesis increase crop yields?PLANT CELL & ENVIRONMENT, Issue 3 2006STEPHEN P. LONG ABSTRACT The yield potential (Yp) of a grain crop is the seed mass per unit ground area obtained under optimum growing conditions without weeds, pests and diseases. It is determined by the product of the available light energy and by the genetically determined properties: efficiency of light capture (,i), the efficiency of conversion of the intercepted light into biomass (,c) and the proportion of biomass partitioned into grain (,). Plant breeding brings , and ,i close to their theoretical maxima, leaving ,c, primarily determined by photosynthesis, as the only remaining major prospect for improving Yp. Leaf photosynthetic rate, however, is poorly correlated with yield when different genotypes of a crop species are compared. This led to the viewpoint that improvement of leaf photosynthesis has little value for improving Yp. By contrast, the many recent experiments that compare the growth of a genotype in current and future projected elevated [CO2] environments show that increase in leaf photosynthesis is closely associated with similar increases in yield. Are there opportunities to achieve similar increases by genetic manipulation? Six potential routes of increasing ,c by improving photosynthetic efficiency were explored, ranging from altered canopy architecture to improved regeneration of the acceptor molecule for CO2. Collectively, these changes could improve ,c and, therefore, Yp by c. 50%. Because some changes could be achieved by transgenic technology, the time of the development of commercial cultivars could be considerably less than by conventional breeding and potentially, within 10,15 years. [source] Seed transmission of maize downy mildew (Peronosclerospora sorghi) in NigeriaPLANT PATHOLOGY, Issue 5 2000V. O. Adenle In an area of Nigeria where downy mildew of maize is present, histological assessment of maize seed revealed the presence of mycelium and oospores of Peronosclerospora sorghi in the kernels. Seed transmission of downy mildew of maize was demonstrated when grain purchased at local markets gave mean seedling infection rates of 12·3% (untreated seeds) and 10·0% (in metalaxyl-treated seeds) within 7 days of emergence, after storage in a desiccator for 30 days. When untreated seeds taken from nubbin ears of systemically infected plants from four states in southern Nigeria were planted at 9 days (17,22% moisture content) and 27 days (9,22% moisture content) after harvest, 20·0% infected seedlings resulted in both trials. Seeds from Borno state in northern Nigeria had 26·6% systemic seedling infection after 9 months of storage at 11% moisture content. When seeds harvested from maize plants inoculated with P. sorghi through silks were examined histologically, hyphae of P. sorghi were observed mostly in the scutellum of the embryo. Transmission of disease to seedlings was observed when the silk-inoculated seeds (9% moisture content) were planted in pots in a greenhouse; however, no disease transmission was observed when such seeds were planted in the field. The epidemiological significance of seed transmission is discussed with particular reference to survival of inoculum and development of epidemics. Also noteworthy is the overall significance of seed transmission in Nigeria, where the major source of seed is that saved by farmers from their grain crop, occasionally supplemented by seed bought from the local market. [source] Pests and Diseases of Prehistoric Crops: A Yield ,Honeymoon' for Early Grain Crops in Europe?OXFORD JOURNAL OF ARCHAEOLOGY, Issue 1 2001Petra Dark Before the agricultural improvements of recent centuries, grain yields in medieval Europe appear to have been extremely low: well below the full potential of the crops. If yields were similarly low in prehistory, the adoption of cereal cultivation could have conveyed few benefits in terms of productivity. Consideration of the key constraints on cereal yield highlights the previous neglect of the role of pests and diseases. It is suggested that these may have been particularly damaging in the medieval period, but much less so during the early stages of the adoption of agriculture. Textual and archaeological evidence for the past occurrence of pests and diseases is discussed and, combined with consideration of the development of pest and pathogen problems of recent crop introductions, used to provide a possible outline of the early development of the pest/disease burden. It is suggested that when grain crops were first introduced into temperate Europe there may have been a ,honeymoon period' with high yields: pests and diseases which had been endemic on cereals in semi-arid, continental, or Mediterranean climates did not thrive in the temperature climate, while species native to north-west Europe may not have been adapted to attack cereals. Subsequently, however, some pests and diseases evolved to attack cereals in this environment. These may have prompted changes in grain production methods to reduce the risk of damage. Pests and diseases must have been a driving force in agrarian change for several millennia, and cannot be ignored in attempts to understand the history of agriculture. [source] Transgenic rice hybrids that carry the Rf-1 gene at multiple loci show improved fertility at low temperaturePLANT CELL & ENVIRONMENT, Issue 4 2005TOSHIYUKI KOMORI ABSTRACT By using a genomic fragment that carries the rice (Oryza sativa L.) fertility restorer gene, Rf-1, rice restorer lines harbouring multiple Rf-1 genes on different chromosomes were developed by genetic engineering and crossing. Hybrid lines that were obtained by crossing the restorer lines having two and three Rf-1 genes with a cytoplasmic male sterile (CMS) line had nearly 75 and 87.5% pollen fertility rates under a normal condition, respectively, whereas a conventional hybrid line showed a 50% pollen fertility rate. Furthermore, the seed set percentage under low temperature conditions was much higher in the hybrid lines with multiple Rf-1 genes than the conventional hybrid line. These results indicate that multiplication of the Rf-1 gene conferred cold tolerance at the booting stage to hybrid rice through increasing the potentially fertile pollen grains. This strategy to improve fertility at low temperature of hybrids could be applied to any grain crops that are developed based on CMS and its gametophytic restorer gene, let alone rice. [source] Resource distribution and the trade-off between seed number and seed weight: a comparison across crop speciesANNALS OF APPLIED BIOLOGY, Issue 1 2010B.L. Gambín In grain crops, total sink capacity is usually analysed in terms of two components, seed number and individual seed weight. Seed number and potential individual seed weight are established at a similar timing, around the flowering period, and seed weight at maturity is highly correlated with the potential established earlier. It is known that, within a species, available resources during the seed set period are distributed between both yield components, resulting in a trade-off between seed number and seed weight. Here we tested if this concept could apply for interspecific comparisons, where combinations of numbers and size across species could be related to the total available resources being either allocated to more seed or larger potential individual seed weight during the seed set period. Based on this, species differences in seed weight should be related to resource availability per seed around the period when seed number is determined. Resource availability per seed was estimated as the rate of increase in aboveground biomass per seed around the period of seed set. Data from 15 crop species differing in plant growth, seed number, seed weight and seed composition were analysed from available literature. Because species differed in seed composition, seed weight was analysed following an energy requirement approach. There was an interspecific trade-off relationship between seed number per unit of land area and seed weight (r = 0.92; F(1, 13) = 32.9; n = 15; P < 0.001). Seed weight of different species was positively correlated (r = 0.90; F(1, 13) = 52.9; n = 15; P < 0.001) with resource availability per seed around the seed set period. This correlation included contrasting species like quinoa (Chenopodium quinoa; ,100000 seeds m,2, ,4 mg equivalent-glucose seed,1) or peanut (Arachis hypogaea; ,800 seeds m,2, ,1000 mg equivalent-glucose seed,1). Seed number and individual seed weight combinations across species were related and could be explained considering resource availability when plants are adjusting their seed number to the growth environment and seeds are establishing their storage capacity. Available resources around the seed set period are proportionally allocated to produce either many small seeds or few larger seeds depending on the particular species. [source] | ||||||||||