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Meiotic disturbances in F1 hybrids and their progenies are still major problems in wide hybridization.To investigate the genome affinity reflected in chromosome pairing and segregation,we studied chromosome behaviors during meiosis in two interspecific F1 hybrids[O.minuta×O.australiensis(Om×Oa,BCE genome)and Oa×O.ridleyi(Or,EHJ genome)]by using both traditional staining methods and genomic in situ hybridization(GISH).GISH analysis has been successfully performed on mitotic chromosomes to distinguish different Oryza genomes,but relatively fewer systematic analyses of meiotic chromosomes of interspecific hybrids have been reported.In the hybrids,highly irregular chromosome behaviors through meiosis resulted in producing microspores with unbalanced genome.At diakinesis of these two hybrids,most chromosomes present as univalent,with low frequency as bivalents and occasionally as trivalents.In a pollen mother cell,2 to 8 bivalents and 0 to 4 trivalents were observed in the hybrid Oa×Or,and 1 to 8 bivalents and 0 to 5 trivalents were observed in the hybrid Om×Oa.GISH results indicated that 51.52%bivalents in Oa×Or and 79.65%bivalents in Om×Oa involved allosyndetic association,which indicates that recombination and introgression should be possible if viable backcrosses can be recovered even from triploid hybrids.In this study,we revealed that the meiotic disturbance due to low affinities between parental genomes is the major reason for the sterility of these two triploid interspecific hybrids.The two hybrids showing vigor in reproductive growth are potential genetic resources in future breeding programs.A better understanding of genomic affinities between these distant Oryza species can facilitate planning an effective breeding program by using wide hybridization,and efficient and routine GISH analysis is helpful to monitor alien introgression in the process. 相似文献
3.
《Field Crops Research》1999,61(3):211-222
Grain-filling rate and duration influence grain yield in maize (Zea mays L.), but very little information on their inheritance exists. To devise effective breeding strategies, the genetic nature of these traits must be understood. The objectives of this study were to (1) examine general combining ability (GCA) and specific combining ability (SCA) for grain-filling rate, grain-filling duration, and related agronomic traits via North Carolina Design II, (2) determine the inter-relationships among these traits and their influence on yield via correlation and path coefficient analyses, and (3) identify an indirect selection criterion for yield. Design II crosses among four inbred lines used as males and a set of four inbred lines as female parents were grown in 1996. Combining ability analyses indicated that both GCA (Vg) and SCA mean squares (Vs) were significant for grain-filling rate (on a kernel or an ear basis) and effective filling duration. General combining ability was more important than SCA for both kernel-filling rate and effective filling duration, whereas SCA effect was more important for ear-filling rate. The ratio 2Vg/(2Vg + Vs) was 0.85, 0.88, and 0.45 for kernel-filling rate, effective filling duration, and ear-filling rate, respectively. Kernel-filling rate had a positive phenotypic correlation with kernel weight and was negatively correlated with midsilk date and effective filling duration. Kernel number per ear was more important than kernel-filling rate in influencing grain yield. These relationships were confirmed by results from a 1997 experiment using nine commercial hybrids. Chlorophyll readings taken with SPAD chlorophyll meter at a late developmental stage gave a positive genetic correlation with single-plant yield (r = 0.73). A path coefficient analysis revealed that chlorophyll concentration had a small direct effect on grain yield, whereas it had a large indirect effect on grain yield via kernel number per ear and grain-filling duration. Kernel weight and midsilk date could serve as indirect selection criteria for effective grain-filling duration and kernel-filling rate. Chlorophyll concentration at a late developmental stage could also be an indirect selection criterion for final grain yield. 相似文献
4.
《Field Crops Research》2001,70(1):43-53
In a series of legume-based cropping systems experiments, the economic optimum N fertiliser rate for cotton ranged from 0 to 186 kg N ha−1 depending on the cropping system and soil N fertility. The economic optimum N fertiliser rate was closely correlated with pre-sowing soil nitrate-N (0–30 cm) and petiole nitrate-N (at early flowering). Pre-sowing soil nitrate-N and petiole nitrate-N were also strongly correlated with cotton N uptake at late boll-filling and lint yield of unfertilised cotton.These analyses allow for the estimation of the N fertiliser requirement, providing revised calibrations that more precisely estimate the N-fertiliser requirement of irrigated cotton crops where legume cropping has substantially improved soil N fertility. Such management tools are essential to avoid the problems associated with over- or under-fertilizing cotton crops.The importance of optimising N fertiliser application was demonstrated by examining the effects of crop N nutrition on cotton maturity and fibre quality. Crop maturity (rate of boll opening) was delayed by 1 day for each 83, 16 or 24 kg fertiliser N applied per hectare in the three experiments. Increasing N fertiliser rates generally increased fibre length, and tended to increase fibre strength, whereas micronaire tended to decline. 相似文献
5.
Wang Yingheng Cai Qiuhua Xie Hongguang Wu Fangxi Lian Ling He Wei Chen Liping Xie Hua’an Zhang Jianfu 《水稻科学》2018,25(5):261-269
To compare the heterosis levels among various groups of parental lines used extensively in China, identify foundational heterotic groups in parental pools and understand the relationship between genetic distance and heterosis performance, 16 parental lines with extensive genetic variation were selected from various sub-groups, and 39 hybrid combinations were generated and evaluated in Fujian and Hainan Provinces of China. The main results were as follows:(1) The 16 parental lines can be grouped into 7 sub-groups consisting of 1 maintainer sub-group and 6 restorer sub-groups;(2) Mean grain yield of the restorer lines was higher than that of the maintainer lines, and mean yield of parental lines was higher than that of the hybrid combinations;(3) The two best heterotic patterns were II-32A × G5 and II-32A × G6, moreover, the order of restorer sub-groups according to grain yield, from the highest to lowest, was G7, G6, G5, G4, G3 and G2; High specific combining ability values were observed for combinations of II-32A × G5, II-32A × G6 and Tianfeng A × G7;(4) Hybrid combinations derived from II-32A crossed with 13 restorer lines had higher yield trait values(mid-parent heterosis, better-parent heterosis, standard heterosis over check and specific combining ability) than any other combinations;(5) Genetic distance was positively correlated with panicle number, grain length and length-to-width ratio(P 0.05) and negatively correlated with grain width, grain yield, seed-setting rate, as well as mid-parent heterosis, standard heterosis over check, and specific combining ability for grain yield(P 0.01). These heterotic groups and patterns and their argonomic traits will provide useful information for future hybrid rice breeding programs. 相似文献
6.
《Field Crops Research》2001,70(1):27-41
Many Australian cotton growers now include legumes in their cropping system. Three experiments were conducted between 1994 and 1997 to evaluate the rotational effects of winter or summer legume crops grown either for grain or green manuring on following cotton (Gossypium hirsutum L.). Non-legume rotation crops, wheat (Triticum aestivum) and cotton, were included for comparison. Net nitrogen (N) balances, which included estimates of N associated with the nodulated roots, were calculated for the legume phase of each cropping sequence. Faba bean (Vicia faba — winter) fixed 135–244 kg N ha−1 and soybean (Glycine max — summer) fixed 453–488 kg N ha−1 and contributed up to 155 and 280 kg fixed N ha−1, respectively, to the soil after seed harvest. Green-manured field pea (Pisum sativum — winter) and lablab (Lablab purpureus — summer) fixed 123–209 and 181–240 kg N ha−1, respectively, before the crops were slashed and incorporated into the topsoil.In a separate experiment, the loss of N from 15N-labelled legume residues during the fallow between legume cropping and cotton sowing (5–6 months following summer crops and 9 months after winter crops) was between 9 and 40% of 15N added; in comparison, the loss of 15N fertilizer (urea) applied to the non-legume plots averaged 85% of 15N added. Little legume-derived 15N was lost from the system during the growth of the subsequent cotton crop.The improved N fertility of the legume-based systems was demonstrated by enhanced N uptake and lint yield of cotton. The economic optimum N fertilizer application rate was determined from the fitted N response curve observed following the application of N fertilizer at rates between 0 and 200 kg N ha−1 (as anhydrous ammonia). Averaged over the three experiments, cotton following non-legume rotation crops required the application of 179 kg N ha−1, whilst following the grain- and green-manured legume systems required only 90 and 52 kg N ha−1, respectively.In addition to improvements in N availability, soil strength was generally lower following most legume crops than non-legume rotation crops. Penetrometer resistance during the growth of the subsequent cotton crop increased in the order faba bean, lablab, field pea, wheat, cotton, and soybean. It is speculated that reduced soil strength contributed to improvement in lint yields of the following cotton crops by facilitating the development of better root systems. 相似文献
7.
《Industrial Crops and Products》2006,23(2):194-200
The genetic control determining the days to flowering, defined as the number of days from emergence to the beginning of flowering is considered an important characteristic for breeding purpose. We investigated this factor in kenaf (Hibiscus cannabinus L.), as part of an agroindustrial project in northwest Argentina. A diallelic cross approach was considered in this study. Six highly inbred photosensitive cultivars were used in the cross, namely, Endora, Pandora, Tainung 1, Line 42, Line 21, and Line 29. Significant differences among F1 family means as well as among general combining ability (GCA) and specific combining ability (SCA) components were found based on the Griffing genetic-statistical method IV, Model 1. A predominant additive effect was detected for the days to flowering, giving high heritability estimates (H = DGD = 0.96; h2 = 0.69), and suggests the possibility of effective selection for earliness in these cultivars. Early flowering in Line 29 was highly heritable, and therefore, is important for breeding purposes. Line 42, despite being the earliest, did not transmit this characteristic to its progenies, possibly because of epistatic genetic effects. The regression of the covariances of F1 families on the non-recurrent parent (Wr) and the variance of the “n” families (Vr) revealed that some dominance effects also occurred in the form of a partial dominance for early flowering. These results support the evidences revealed by the analysis of means of combinations between early and late flowering lines. 相似文献
8.
《Field Crops Research》2001,71(3):159-171
The burgeoning poultry industry in the southeastern US is presenting a major environmental problem of safe disposal of poultry litter (PL). In a comprehensive study, we explored ways of PL use in conservation tillage-based cotton (Gossypium hirsutum L.) production systems on a Decatur silt loam soil in north Alabama, from 1996 to 1999. The study reported here-in presents the residual effects of PL applied to cotton in mulch-till (MT) and no-till (NT) conservation tillage systems in 1997 and 1998 cropping seasons on N uptake, growth, and yield of rye (Secale cereale, L.) cover crop and rotational corn (Zea mays L.) in 1999. Rye was grown without additional N, whereas corn was grown at three inorganic N levels (0, 100, and 200 kg N ha−1). Poultry litter was applied to cotton in 1997 and 1998 at 0, 100, and 200 kg N ha−1. Residual N from PL applied to cotton in 1997 and 1998 produced up to 2.0 and 17.3 Mg ha−1, respectively, of rye cover crop and corn biomass (includes 7.1 Mg ha−1 of corn grain yield) without additional fertilizer. Therefore, in addition to supplying crop residues which reduce soil erosion, increase soil organic matter, and conserve soil moisture, the rye cover crop was able to scavenge residual N left by the cotton crop, which would otherwise, be at risk of being leached and pollute groundwater resources. Poultry litter applied to cotton also increased corn grain quality as shown by up to 100% increase in grain N content compared to the 0N treatment. Using PL with a slower rate of N release compared to inorganic fertilizer to meet some of the N requirements of corn, will not only reduce N fertilizer costs for corn, but will also reduce the risk of nitrate N leaching into groundwater. The maximum amount of crop residues added to the cotton based cropping system by residual N from PL and inorganic N was 21.3 Mg ha−1. This will lead to an increase in soil organic carbon and soil structure in the long term and a reduction in soil erosion, thereby further improving soil productivity, while at the same time, protecting the environment from nitrate pollution and soil degradation. Our study demonstrates that cotton under conservation tillage system in combination with rye cover crop and rotational corn cropping could use large quantities of PL thereby avoiding serious potential environmental hazards. 相似文献
9.
The grain yield of normal oil maize (Zea mays L.) might increase when pollinated by high oil maize (HOM) hybrids because of heterosis. To testify that the grain yield increase might be a result of improved photosynthetic rate and related traits, the normal oil maize (NOM) hybrid, Nongda108, was cross-pollinated by three HOM hybrids, HOM202, HOM115 and HOM4515 (for short as ND108pHOM202, ND108pHOM115 and ND108pHOM4515). We found that the ND108pHOM202 and ND108pHOM115 exhibited higher net photosynthetic rate (Pn), accompanied by larger stomatal conductance (gs) and transpiration rate (E). Moreover, delayed leaf senescence was observed in their leaves, including larger leaf area index (LAI) and higher Chl content and Chl a/b ratio. Apart from higher phosphoenolpyruvate carboxylase (PEPCase) activity, the soluble proteins were also higher in the two cross-pollinations. The higher leaf photosynthesis could explain the grain increase in ND108pHOM202 and ND108pHOM115. However, ND108pHOM4515 exhibited a decreased photosynthetic characteristic and yield performance. Significantly positive relation between grain yield and biomass (r2 = 0.96, P < 0.05), Pn and biomass (r2 = 0.74, P < 0.05) also suggested that the yield increase in the two cross-pollination treatments was generally owing to the higher photosynthetic rate and related photosynthetic traits. 相似文献
10.
《Field Crops Research》2006,98(1):68-75
Direct seeding instead of transplanting for rice (Oryza sativa L.) has increasingly been used in northern and eastern China because of labor and cost saving. However, poor germinability is still one of the major problems faced in the adoption of direct seeding under low temperature (low temperature germinability: LTG) and anoxia (anoxia germinability: AG) condition. To gain an understanding of the genetic control of seed germinability under these unfavourable conditions, two rice lines, USSR5 (japonica type) and N22 (indica type) and F2 individuals derived from the cross USSR5 × N22 were tested for LTG and AG. USSR5 and N22 differ significantly for both LTG and AG. The LTG of the F2 individuals ranged from 0 to 100% after a 10 days incubation. AG ranged from 0.0 to 4.0 cm shoot length. Based on segregation in the F2 population, a linkage map was constructed using 121 SSR markers. The map covered 1821.5 cM, with a mean inter-marker distance of 16.7 cM. Eleven putative QTLs for LTG were detected, one on each of chromosomes 3–5, 7, 9–11, and four on chromosome 5. The USSR5 alleles in all these QTLs acted to increase LTG. Two QTLs for AG were located on chromosomes 5 and 11, respectively, at both of which the USSR5 alleles acted to increase AG. We propose that USSR5 could make a major contribution to improving LTG and AG in rice breeding programs. 相似文献
11.
The magnitude of relationships among different traits is important in plant breeding programs to identify the best selection criteria and improve the efficiency of selection. This study was conducted to determine relationships between seed yield and seed oil content with other important agronomic traits among 36 diverse accessions of Vernonia (Vernonia galamensis variety ethiopica), a potentially novel industrial oilseed crop. Field evaluations were conducted during 2005, 2006 and 2007 at the Limpopo Province in South Africa using a partially balanced lattice design. Simple correlation and path analysis were performed to identify the best selection criteria for increased seed yield and seed oil content. Simple correlation and path analyses revealed that the formation of productive primary heads strongly associated with increased seed yield (rg = 0.81, p < 0.001). Furthermore, path analysis indicated selection for increased number of primary heads would bring about simultaneous and favorable change towards reduced days to maturity and shorter plant height. Further associational study of traits with seed oil content showed a significant (p < 0.05) correlation between oil content with 1000 seed weight (rg = 0.4). The path analysis, however, exposed seed yield followed by 1000 seed weight with significant direct effect on seed oil content. The study demonstrated that selection for increased number of productive primary heads is the principal selection criterion to improve seed yield. Whereas selection for 1000 seed weight and increased seed yield serve as major selection criteria to achieve increased oil content in V. galemanesis. 相似文献
12.
Stanisław Jeżowski 《Industrial Crops and Products》2008,27(1):65-68
Miscanthus species are highly productive with low inputs and are excellent candidates for bioenergy feedstock production. A field experiment was conducted to characterize phenotypic differences in selected clones generated from interspecific hybrids of Miscanthus sinensis × Miscanthus sacchariflorus and intraspecific hybrids within M. sinensis. The field experiment was planted in plots of 20 m2 at a density of 1 plant m−2 in three randomized blocks. The trial was monitored for 3 years for traits important to biomass production including plant height, tiller density, tuft diameter and shoot diameter. ANOVA showed significant genotypic variation in these traits once the stand was 2 years old. This study shows that tillering and tuft diameter in years 1 and 2 are the most important traits influencing biomass yield, but over 3 years when the highest yielding potential is reached, tillering and tuft diameter have the highest correlation with biomass yield. These results identifying high-yielding Miscanthus clones will be utilized in our plant improvement program. 相似文献
13.
《Plant Production Science》2013,16(4):233-239
SummaryPhotosynthetic ability in terms of CO2 exchange rate and leaf area, dry matter accumulation (dry weight) and other important growth components along with yield and yield contributing characters in two F1 hybrids of Akebono × Chiyonishiki (A × C) and Zenith × Akebono (Z × A) were studied. The photosynthetic rate at the flowering stage was lower than that at the panicle initiation stage in all the inbred parent cultivars and F1 hybrids. Heterosis in photosynthetic rate was higher at the panicle initiation stage than that at the flowering stage. Pre-anthesis leaf area in the F1 hybrid was significantly larger than that in the parent cultivars. However, the post- anthesis decline in leaf area was more rapid in the F1 hybrids than in the parent cultivars and its magnitude was the highest in the F1 hybrid of Z × A which was tall having long and curved panicles. Pre-anthesis dry matter accumulation in both hybrids was significantly higher in the F1 plants than the parental cultivars, but post-anthesis dry matter accumulation in the F1 hybrid was lower than the mid-parental value in Z × A. The degree of heterosis in grain yield varied with the hybrid combination, an average heterosis being 1.03. Heterosis in grain yield was closely associated with heterosis in harvest index. 相似文献
14.
《Field Crops Research》2006,95(2-3):383-397
Genetic gains in grain yield and related phenotypic attributes have been extensively documented in maize (Zea mays L.), but the effect of breeding on the physiological determinants of grain yield is yet poorly understood. We determined genetic gains in grain yield and related physiological traits for seven maize hybrids developed for the central region of Argentina between 1965 and 1997. Gains were expressed as a function of the year of release (YOR). Hybrids were cropped in the field at five stand densities (from almost isolated plants to supra-optimal levels) during two contrasting growing seasons (E1 and E2). Water and nutrient stress were prevented and pests controlled. Genetic gains in grain yield (≥13.2 g m−2 YOR−1) were mainly associated with improved kernel number, enhanced postsilking biomass production, and enhanced biomass allocation to reproductive sinks, but computed gains were affected by the environment. Differences among hybrids arose at the start of the critical period, and were evident as improved mean radiation use efficiency (≥0.026 g MJ−1 YOR−1), enhanced plant growth rate at near optimum stand density (≥0.04 g pl−1 YOR−1), and improved biomass partitioning to the ear around silking (0.0034 YOR−1, only for E1). Improved biomass production after silking was related to an increased light interception (≥4.7 MJ m−2 YOR−1), and allowed for an almost constant source–sink ratio during grain filling. This trend determined no trade-off between kernel number and kernel weight. In contrast to previous studies, genetic gains were detected for potential productivity (e.g., maximum grain yield) on a per plant basis (i.e., under no resource competition), a promising aspect for the improvement of crop grain yield potential. 相似文献
15.
《Industrial Crops and Products》2003,17(1):9-14
Kenaf (Hibiscus cannabinus L.) is a potential alternative crop being developed for fiber production. Because planting area varies dramatically from year to year, seed supplies may greatly exceed use so that the excess seed must be stored for one to several years. The objectives of this study were to determine the effect of seed storage duration at 10 °C on germination, vigor, emergence, and yield. Replicated trials were established at Starkville, MS in 1999 and 2000 to evaluate field emergence and biomass yield of kenaf seed from five ‘Everglades 41’ (‘E41’) harvest year seed lots stored at 10 °C in ambient relative humidity for up to 4 years. Germination of these same seed lots under standard (20–30 °C) and cool (20 °C) temperatures, and seed vigor was evaluated over time. Field emergence was the same for the different seed storage durations up to 4 years, but was directly affected by drought conditions for each planted year. Biomass yields ranged from 12.39 to 14.57 Mg ha−1 in 1999 and 16.82 to 18.47 Mg ha−1 in 2000, but were not different between storage durations. Seed germination remained greater than 80% regardless of storage duration. Electrolyte leakage, based on conductivity, was 38–50% less with freshly harvested seed than seed stored for 4 years at 10 °C. However, neither the conductivity nor accelerated aging test were reliable predictors of field emergence. Kenaf seed stored up to 4 years at 10 °C retained germination rates acceptable for commercial use. Neither field emergence nor biomass yield was affected by seed storage duration. 相似文献
16.
《Industrial Crops and Products》2007,25(1):75-88
Miscanthus × giganteus is one of the most promising biomass crops for non-food utilisation. Taking into account its area of origin (Far East), its temperature and rainfall requirements are not well satisfied in Mediterranean climate. For this purpose, a research was carried out with the aim of studying the adaptation of the species to the Mediterranean environment, and at analysing its ecophysiological and productive response to different soil water and nitrogen conditions. A split plot experimental design with three levels of irrigation (I1, I2 and I3 at 25%, 50% and 100% of maximum evapotranspiration (ETm), respectively) and three levels of nitrogen fertilisation (0 kg ha−1: N0, 60 kg ha−1: N1 and 120 kg ha−1: N2 of nitrogen) were studied. The crop showed a high yield potential under well-watered conditions (up to 27 t ha−1 of dry matter). M. × giganteus, in Mediterranean environment showed a high yield potential even in very limited water availability conditions (more than 14 t ha−1 with a 25% ETm restoration). A responsiveness to nitrogen supply, with great yield increases when water was not limiting, was exhibited. Water use efficiency (WUE) achieved the highest values in limited soil water availability (between 4.51 and 4.83 g l−1), whilst in non-limiting water conditions it decreased down to 2.56 and 3.49 g l−1 (in the second and third year of experiment, respectively). Nitrogen use efficiency (NUE) decreased with the increase of water distributed (from 190.5 g g−1 of I0 to 173.2 g g−1 of I2); in relation to N fertilisation it did not change between the N fertilised treatments (N1 and N2), being much higher in the unfertilised control (177.1 g g−1). Radiation use efficiency (NUE) progressively declined with the reduction of the N fertiliser level (1.05, 0.96 and 0.86 g d.m. MJ−1, in 1994, and 0.92, 0.91 and 0.69 g d.m. MJ−1, in 1995, for N2, N1 and N0, respectively). 相似文献
17.
Kenaf (Hibiscus cannabinus L.) is a nonwoody fiber source with many uses. To evaluate the dry matter yield potential of kenaf at two locations in the southern High Plains of the USA and the effects of late planting/late emergence as a possible replacement for hail damaged cotton, four varieties were grown in 2004 and 2005 at New Mexico State University's Agricultural Science Centers at Clovis, under limited irrigation, and Tucumcari, under rainfed conditions. Each study was a randomized complete block design having four replicates. A year × location interaction existed (P < 0.0469) for kenaf yield largely due to precipitation amount and distribution. Either late planting or late emergence due to low soil moisture at planting significantly reduced yields (3.62 vs. 0.63 Mg ha?1 for mid-May planting and emergence and early July emergence or planting, respectively, P < 0.0001). Consequently, kenaf would not be suitable for recovering input costs when planted after failure of cotton. The very late maturing variety Gregg had consistently lower numeric yields than Dowling, Everglades 41, and Tainung 2 in all comparisons, with the strongest trend within the emergence date comparison (P < 0.0912). Kenaf varieties should be selected for any location that finish blooming approximately three to four weeks prior to the average first autumn freeze to allow for maximum growth. 相似文献
18.
A 20-year field experiment was employed with the aim of evaluating the effect of tillage systems on biological, chemical and physical aspects of the soil, and to establish whether there was a correlation of these parameters with the incidence of charcoal rot (Macrophomina phaseolina) of soybean and crop yield. The tillage systems evaluated were direct seeding (DS), DS + scarifier (DS + S), minimum tillage (MT) and conventional tillage (CT). DS presented higher values than CT in culturable total fungi (26.33 × 105 vs. 2.33 × 105 CFU g−1 dry soil), total bacteria (182 × 107 vs. 64 × 107 CFU g−1 dry soil), microbial respiration (0.77 mg CO2 g−1 week−1 vs. 0.45 mg CO2 g−1 week−1) and fluorescein diacetate (FDA) hydrolysis (4.17 ug fluorescein g−1 h−1 vs. 1.70 ug fluorescein g−1 h−1 in CT. Fungal and bacterial community fingerprints, by terminal restriction fragment length polymorphism (T-RFLP) analysis, of Intergenic spacer regions of rRNA and 16S rRNA genes, respectively, were influenced by the tillage system. Also FAME (fatty acid methyl ester) profiles showed that microbial community structure in DS and CT was clearly different. DS samples contained significantly higher total microbial biomass than the other tillage treatments, but there were no significant differences in fungal biomass or any consistent trend with respect to stress index. Our results showed that microbial communities were more abundant and active in DS than in CT in response to high nutrient content in soil. Indeed, DS systems presented higher soil OM, total N, K and Ca than CT. Electrical conductivity and aggregate stability (AS) were also improved by DS. Soybean grown in high-quality soil was not affected by charcoal rot, however, under CT, disease incidence in soybean was 54%. These differences were correlated to the higher microbial abundance and activity under DS, the biological component being a key factor determining soil capacity to suppress the soilborne pathogen. 相似文献
19.
《Field Crops Research》1999,63(3):187-198
Rice is subjected to excessive waterlogging and flash-flooding on large areas in south and south-east Asia. Besides cultivars, submergence tolerance of plants is influenced by various agronomic practices. A field experiment was conducted at Cuttack, India during 1994–1995 to study the effect of method of stand establishment (direct seeding and transplanting), vigour of seed (low and high-density) or seedlings (N-fertilized and unfertilized), plant population (normal and 50% more) and N fertilizer (single basal and split application) on yield performance of lowland rice under conditions of natural submergence and simulated flash-flooding (impounding up to 90 ± 3 cm depth for 10 days at vegetative stage). Flooding reached a maximum depth of 80 cm in 1994 and 52 cm in 1995 under natural submergence. The crop performance was better in 1994 due to timely sowing in dry soil and delayed accumulation of water (43 days after sowing) than in 1995 when sowing was done late in saturated soil followed by early water accumulation (28 days after sowing). Grain yield of rice decreased by 30.0–33.6% due to simulated flash-flooding compared with natural submergence, and by 21.4–33.1% due to transplanting in July compared with direct seeding in May-end/early June. The yield of direct-sown crop increased by using high-density seed of 22.9–23.0 mg weight (5.2–9.0%), higher seed rate of 600 m−2 (2.2–2.3%) and basal fertilization at 40 kg N ha−1 (19.4–25.7%) compared with low-density seed (19.4–20.1 mg), 400 seed m−2 and no N, respectively. The yield of transplanted crop increased by using N-fertilized seedlings of 0.49–1.65 g weight (29.5–38.5%), higher number of seedlings at 155 m−2 (3.5–16.7%) and basal fertilization at 40 kg N ha−1 (31.9–32.5%) compared with unfertilized seedlings (0.19–0.79 g), 115 seedlings m−2 and no N. Split application of 40 kg N ha−1 — 50% each at basal and top dressing (105–115 days of growth after flash-flooding) — improved yield significantly (10.1–13.1%) over single basal application under simulated flash-flooding, but not under natural submergence conditions. Regression analysis indicated that relative contribution of various factors in increasing grain yield was in order: N fertilizer > seed density > seed m−2 in direct-sown rice, and N fertilizer > seedlings m−2 > seedling dry weight in transplanted rice. It was concluded that grain yield of flood-prone lowland rice can be increased by establishing the crop early through direct seeding using high-density seed and basal N fertilization. 相似文献
20.
《Field Crops Research》2001,69(1):1-11
Agricultural intensification through the application of mineral fertilizers, the recycling of crop residues and animal manures and through plant breeding are the only means to increase food supply in the poverty ridden West African Sahel, where pearl millet (Pennisetum glaucum (L.) R. Br.) is the dominant staple. Research on the effects of soil amendments on the quality of millet straw and grain is scarce, comparative studies of possible quality differences in traditional landraces versus improved varieties and hybrids are lacking. This paper reports results from 22 landrace populations, 22 improved varieties, six inbred×variety hybrids (IVHs, fertile inbred×open-pollinated varieties) and four topcross hybrids (TCHs, male-sterile line×open-pollinated varieties), whose grains were analyzed for protein concentration and amino acid composition, macro- and micronutrients (total and phytate P, K, Ca, Mg, Zn, Cu), metabolizable energy (ME), fat and β-carotene. At similar yield levels, landraces showed a 2.9 and 3.5% higher protein concentration compared with improved varieties and hybrids without a detrimental effect on protein quality as determined by the relative amount of lysine and threonine. Landrace populations also had the highest fat concentrations and the largest micronutrient densities. However, in-vitro digestibility and ME were (79.8% and 12.2 MJ kg−1 respectively) larger for both groups of hybrids. The concentration of β-carotene was (0.13 μmol kg−1) highest in the improved varieties, but appeared overall too low to significantly contribute to vitamin A nutrition in local diets. While the results of this genotype screening need to be verified in replicated multi-location trial studies, they underline the potential of including landraces in breeding programs to concurrently improve grain yield and grain quality in this area of the world. 相似文献