Study of water stress effects in different growth stages on yield and yield components of different rice (Oryza sativa L.) cultivars

A field experiment was conducted during 2001-2003 to evaluate the effect of water stress on the yield and yield components of four rice cultivars commonly grown in Mazandaran province, Iran. In northern Iran irrigated lowland rice usually experiences water deficit during the growing season include of land preparation time, planting, tillering stage, flowering and grain filing period. Recently drought affected 20 of 28 provinces in Iran; with the southeastern, central and eastern parts of the country being most severely affected. The local and improved cultivars used were Tarom, Khazar, Fajr and Nemat. The different water stress conditions were water stress during vegetative, flowering and grain filling stages and well watered was the control. Water stress at vegetative stage significantly reduced plant height of all cultivars. Water stress at flowering stage had a greater grain yield reduction than water stress at other times. The reduction of grain yield largely resulted from the reduction in fertile panicle and filled grain percentage. Water deficit during vegetative, flowering and grain filling stages reduced mean grain yield by 21, 50 and 21% on average in comparison to control respectively. The yield advantage of two semidwarf varieties, Fajr and Nemat, were not maintained under drought stress. Total biomass, harvest index, plant height, filled grain, unfilled grain and 1000 grain weight were reduced under water stress in all cultivars. Water stress at vegetative stage effectively reduced total biomass due to decrease of photosynthesis rate and dry matter accumulation.     

Herbicide evaluation studies in transplanted chilli pepper (Capsicum frutescens L.) in the Nigerian savanna

Field trials were conducted in the Nigerian savanna to evaluate the performance of various herbicide mixtures for weed control in chilli pepper (Capsicum frutescens L. var. Serrano chilli) during the wet seasons of 1982 to 1984 and in the 1982/83 dry season. Linuron at 0·5 kg or 0·75 kg a.i./ha in mixture with either alachlor at 1·5 kg, metolachlor at 1·5 kg, oxadiazon at 1·5 kg, or diphenamid at 3·0 kg, as well as metolachlor plus metobromuron at 1·0 + 1·0 kg and 1·5 + 1·5 kg a.i./ha all followed by supplementary hoe-weeding at 6 weeks after transplanting combined effective weed control with high chilli pepper fruit yields comparable to the hoe-weeded control in all the trials. Unchecked weed growth throughout the crop life cycle resulted in an 86–90% reduction in potential chilli pepper fruit yields.     

Effects of salicylic acid on growth, biochemical constituents in pepper (Capsicum annuum L.) seedlings

In the present study, the effect of different concentrations of salicylic acid which is an endogenous organic acid in plants and which is commonly cited as a hormone, on the growth and some other parameters of pepper (Capsicum annuum L. cv.) seedlings was investigated. The solutions were applied to the roots of seedlings using hydroponic method. In general, 1.5 mM concentration of salicylic acid had a stimulating effect while 5 and 10 mM concentrations had varying degrees of inhibitive effects on the seedlings. Although 0.3 mM SA application produced prominent results in the case of all parameters, the difference was not found statistically significant. The inhibitive effect produced by high SA was found much more dominant than the stimulating effect of low SA concentrations. Thus, it was established that SA had a bidirectional physiological effect on the seedlings in a concentration-dependent manner.     

Performance of a ring-shaped emitter for subsurface irrigation in bell pepper (Capsicum annum L.) cultivation

Paddy and Water Environment - A low-cost subsurface irrigation system with ring-shaped emitters has been applied and considered as a way to improve water irrigation efficiency in a region where...     

Impact of managing cover crop residues on the floristic composition and species diversity of the weed community of pepper crop (Capsicum annuum L.)

The decline of farmland biodiversity is mainly attributed to the intensive use of chemical inputs in agriculture. Cover crop residues may contribute to improve weed management while maintaining a high level of weed diversity. A 2-year field experiment was carried out in central Italy to study the effect of cover crop species and their residue management on weed community composition and weed species diversity in a winter cover crop – pepper sequence. Hairy vetch (Vicia villosa Roth.), oat (Avena sativa L.) and canola (Brassica napus L.) were sown in September 2009 and 2010 and grew undisturbed during the winter season until spring when they were suppressed one week before pepper transplanting. Cover crop residues were: (i) green manured at 30 cm depth (conventional tillage, CT), (ii) green manured at 10 cm depth (minimum tillage, MT), and (iii) left on the soil surface as mulch strips covering 50% of the ground area in no-tilled soil (NT). A winter weedy fallow and a bare soil without cover crop in NT, MT and CT were also included as controls. Weed plant density data in pepper were used for calculating weed species richness. Compared to weedy fallow, oat, hairy vetch and canola consistently reduced the weed density and weed aboveground biomass by the time of their suppression (on average 3.6, 21.5, and 41.3 plants m⁻² and 11.0, 49.2, and 161.8 g m⁻² of DM, respectively). In pepper, oat residues generally determined a higher reduction of weed density and species richness compared to hairy vetch and canola regardless the residue management treatments. Converting cover crop aboveground biomass into mulch strips greatly reduced weed species density but did not always imply a reduction of weed species diversity in pepper compared to MT and CT. The weed species richness was reduced inside the mulch strips, while a richer and more diverse weed community was found outside the mulch strips in NT. Weed community in pepper was mainly composed of annual dicot weeds such as Amaranthus retroflexus, Chenopodium album, Solanum nigrum, Polygonum aviculare which were mostly associated with MT and CT tillage systems, while in NT an increase of perennial species such as Rumex crispus was observed. These results suggest that it is possible to manage cover crop residues in NT in order to obtain a lower weed density and consequently a higher yield in pepper compared to MT and CT while maintaining a high level of weed diversity.     

The study of seed yield and seed yield components of lentil (Lens culinaris Medik) under normal and drought stress conditions

In this study yield and seed yield components of twenty lentil (Lens culinaris Medik) genotypes were compared in a split plot RCBD based design with 3 replications at the Zanjan University Research Farmland in 2004. The main plots were lentil planted under drought stress and non stress (irrigation) condition and subplots were twenty of genotype lentil. There were significant differences between traits in lentil genotypes. The seed yield per plant was sensitive to drought stress but 100 seed weight was more tolerance and stable trait in drought condition. As correlation analysis of traits in various stress condition, the harvest index, seed yield per plant, pods per plant and biological yield were correlated with grain yield. In addition harvest index, seed yield per plant, pods/plant and biological yield were the most important traits that have a relationship with grain yield.     

The effect of ecological conditions on yield and quality traits of selected peppermint (Mentha piperita L.) clones

The commercial production of peppermint (Mentha piperita L.) depends on the genetic structure and ecological conditions affecting yield and oil composition. To determine yield and quality characters of two peppermint clones (Clone-3 and Clone-8), field experiments were carried out at four different locations (Ayd?n, Bursa, Izmir and Tokat) in Turkey during 2007 and 2008. Locations with warmer climate gave higher fresh herbage yield (Ayd?n and Izmir 37.0 t/ha and 36.8 t/ha, respectively). Although vigor canopy caused maximum fresh herbage yield, it decreased dried leaf yield due to the defoliation of leaves near to the ground. The main components menthol and menthone showed significant variation with different ecologies. Menthol contents were higher in temperate locations (Bursa and Tokat), while menthone contents were lower. The differences in oil composition of Clone-3 were lower than that of Clone-8 according to different climates, thus Clone-3 can be grown widely in various ecological conditions for oil productions as compared to the Clone-8. It was also concluded that temperate location was more suitable for peppermint oil production with high menthol contents.     

Effect of sowing dates on yield and yield components of spring safflower (Carthamus tinctorius L.) in Isfahan region

In order to study the effect of sowing dates on the yield and yield components of two safflower varieties, an experiment was conducted at Agriculture Research Station of Isfahan Kabotar Abad in 2004. A split plot layout within randomized complete block design with three replications was used in the experimentation. Eight sowing dates were in the main plots, consist March 6, March 21, April 6, April 21, May 6, May 21, June 6 and June 21 and two varieties (Isfahan 14 and I.L111) were in the sub plots. The results showed that the number of seed per capitulum and seed yield were decreased significantly as the sowings dates were delayed. The Isfahan 14 variety in comparison with I.L111 produced more fertile capitulum in square meter and also, respectively seed per capitulum. The second sowing date (March 21) produced the highest seed yield (2306.2 kg ha(-1)), whereas the 7th sowing date (June 6) produced the lowest seed yield (622 kg ha(-1)). The effect of variety for seed yield was not significant. Farmers in the Kabotar Abad of Isfahan and in other areas with similar conditions are recommended to plant the Isfahan 14 variety on March 21.     

Estimation of combining ability for yield and yield components in rice (Oryza sativa L.) cultivars using diallel cross

In order to estimate combining ability and gene action of a number of rice cultivars, a 5 x 5 half a diallel cross genetic design has been used. Parents and their hybrids have been evaluated in a randomized complete block design with 3 replicates for yield and 6 yield components in 2007 in Rice Research Station of Iran-Amol. Mean squares of genotypes for all traits were highly significant (p < 0.01). Significant mean squares of combining ability for all traits showed additive and non-additive effects in control of the related traits. Having nonsignificant MS(GCA)/MS(SCA) ratio for all traits but 1000-grain weight show higher importance of nonadditive effects in comparison with additive effects of controlling genes. High relative importance of specific combining ability indicated that all traits but 1000-grain weight are highly affected by impacts of specific combining ability. Generally, Dasht, Neda and Binam were the best parents for general combining ability and Binam x IR62871-175-1-10 and Mashhad Domsiah x Binam were the best hybrids for grain yield and its components.     

Post-harvest development of anthracnose in pepper (Capsicum spp): Etiology and management strategies

Chilli anthracnose, caused by Colletotrichum spp, is one of the main causes for post-harvest decay of chilli. It can develop on the field, during long distant transport, cold storage and shelf-life. In conventional agriculture, the whole plant including the fruits, are sprayed with fungicides as a prerequisite for post-harvest control of chilli anthracnose. Due to consumer concerns regarding the use of synthetic fungicides and the demand for safer storage methods, the use of synthetic fungicides is no longer allowed for the post-harvest control of chilli anthracnose. As a result, studies on alternative methods to control post-harvest decay have been developed over the years along with the demand for safer storage methods. In this review, results published within the last decade have been summarized and alternative approaches to synthetic fungicides for post-harvest control of chilli anthracnose were discussed in detail. Overall, the use of natural antimicrobials, biocontrol agents, resistant cultivars and ozone shows promise as treatments that can be adopted on a commercial scale to control post-harvest chilli anthracnose caused by Colletotrichum species.     

Yield response of rice (Oryza sativa L.) genotypes to different types of drought under rainfed lowlands: Part 1. Grain yield and yield components

Responses of rice genotypes to drought stress may be different when characteristics of the drought stress environments differ. The performance of 128 genotypes was examined under irrigation and four different types of drought stress, to determine genotypic consistency in yield and factors determining yields under different drought stress conditions. The different drought conditions were mild drought during grain filling, short and severe drought at flowering, prolonged severe drought during the reproductive to grain filling, and prolonged mild drought during vegetative and grain filling.Genotypic grain yield under mild stress conditions was associated with yield under irrigated conditions, indicating the importance of potential yield in environments where the yield reduction was less than 50%. However, yields under irrigated conditions differed over time and locations.Under prolonged or severe drought conditions, flowering time was an important determinant of grain yield. Earlier flowering genotypes escaped the severe stress and had higher grain yields indicating large genotype by environment (G×E) interactions which have implications for plant breeding even for mild stress. It is suggested that variations in flowering time, potential yields and drought patterns need to be considered for development of drought-resistant cultivars using specific physiological traits.     

Yield and yield components of saffron under different cropping systems

This study was conducted to evaluate yield and yield components of saffron (Crocus sativus L.) in response to (i) production system (PS) (irrigated vs. non-irrigated); (ii) corm size (CS) (medium −2.25 to 3 cm diameter vs. small corms <2.25 cm diameter); (iii) planting depth (PD) (10 cm vs. 20 cm); and iv) planting density (PDEN) (51 corms m⁻² vs. 69 corms m⁻²).This fully replicated multifactorial design was started in August 2000, and carried through November 2003, when the fourth saffron harvest took place. The total and average fresh weight of stigmas, and the number of flowers were measured at each harvest.Results indicate that three of the four factors tested (PS, CS and PD) had a significant effect on the quantitative yield during the two most productive flowering years (2001 and 2002) and on the total flowering. Irrigated cultivation, medium size corms and 10 cm planting depth had the greatest effect in increasing the quantitative production of saffron.Yield was also affected by planting density in contrasting ways. Whereas at high PDEN yield increased per unit of surface, at low PDEN, yield increased with respect to the initial number of corms planted.The fresh weight of stigmas per flower yield component, an important aspect that determines the quality of the spice, was enhanced when corms were planted at 20 cm depth and when irrigation was applied to the crop.     

不同种植密度下大豆产量性状的QTL分析

利用大豆重组自交系soy01群体的255个家系为作图群体,在不同年份、不同种植密度下进行了大豆产量性状的QTL分析。结果表明,采用复合区间作图法,2年2种处理组合下检测到单株荚数、单株粒数、每荚粒数等5个产量性状相关QTL共43个,分布于A2、F、I等14个连锁群,其中qNP-15-1等3个QTL在4种环境中均检测到,qNP-19-1等5个QTL在3种环境中均检测到,qNP-1-1等10个QTL在2种环境中均检测到,为较稳定的QTL。每荚粒数QTL qNSP-19-1和qNSP-19-2在多种环境中均检测到,贡献率均超过60%,为稳定主效QTL;百粒重QTL qSW-19-1在4种环境中均检测到,贡献率均超过20%,为稳定主效QTL。这些稳定的主效QTL可应用于精细定位和分子标记辅助育种研究。     

Essential oil variation among and within six Achillea species transferred from different ecological regions in Iran to the field conditions

The compositions of essential oils of 19 accessions belonging to six different Achillea species, transferred from the natural habitats in 10 provinces of Iran to the field conditions, were assessed. The relationship between the leaf areas of selected accessions with their essential oil content was also investigated. Essential oil yield of dried plants obtained by hydro-distillation ranged from 0.1 to 2.7% in leaves. Results indicated a significant variation in oil composition among and within species. Total of 94 compounds were identified in 19 accessions belonging to the six species of A. millefolium, A. filipendulina, A. tenuifolia, A. santolina, A. biebersteinii and A. eriophora. The major constituents of the leaves in the tested genotypes were determined as germacrene-D, bicyclogermacrene, camphor, borneol, 1,8-cineole, spathulenol and bornyl acetate. According to the major compounds, four chemotypes were defined as: (I) spathulenol (1.64–34.31%) + camphor (0.2–15.61%) (7 accessions); (II₁) germacrene-D (18.78–23.93%) + borneol (7.93–8.26%) + bornyl acetate (11.56–14.66%) (5 accessions); (II₂) germacrene-D (13.28–36.28%) + bicyclogermacrene (5.93–8.4%) + 1,8-cineole (15.26–19.41%) + camphor (14.95–23.32%) (2 accessions); (III) borneol + camphor (52.04–63.27) (2 accessions); (IV) germacrene-D (45.86–69.64%) (3 accessions). The relationships of chemotypes with soil type and climatic conditions of collected regions were assessed, as probable reasons of high variations in essential oil components, and discussed.     

Increased yield stability of field-grown winter barley (Hordeum vulgare L.) varietal mixtures through ecological processes

Crop variety mixtures have the potential to increase yield stability in highly variable and unpredictable environments, yet knowledge of the specific mechanisms underlying enhanced yield stability has been limited. Ecological processes in genetically diverse crops were investigated by conducting field trials with winter barley varieties (Hordeum vulgare), grown as monocultures or as three-way mixtures in fungicide treated and untreated plots at three sites. Mixtures achieved yields comparable to the best performing monocultures whilst enhancing yield stability despite being subject to multiple predicted and unpredicted abiotic and biotic stresses including brown rust (Puccinia hordei) and lodging. There was compensation through competitive release because the most competitive variety overyielded in mixtures thereby compensating for less competitive varieties. Facilitation was also identified as an important ecological process within mixtures by reducing lodging. This study indicates that crop varietal mixtures have the capacity to stabilise productivity even when environmental conditions and stresses are not predicted in advance. Varietal mixtures provide a means of increasing crop genetic diversity without the need for extensive breeding efforts. They may confer enhanced resilience to environmental stresses and thus be a desirable component of future cropping systems for sustainable arable farming.     

辣椒花器性状的遗传分析

估算辣椒(Capsicum annuum L.)花器性状的遗传变异系数和遗传力,结果表明,柱头外露长、柱头宽和花宽的遗传变异系数较大,花宽、花长/花宽、花药长和柱头宽的遗传力较大,且遗传型变异系数较大的性状,它的遗传力不一定大。相关和通径分析结果表明,辣椒柱头外露长与花长、柱头长和花长/花宽间的遗传相关达显著或极显著水平,大多数情况下都是遗传型相关系数绝对值大于表型相关系数绝对值,花宽和花长/花宽对柱头外露长的直接作用较大。估算26个辣椒品种、9个花器性状的主成分值,并将其分为6类,数量分类的结果符合实际情况。当主成分的特征值的累计贡献率接近85%时,主成分值就能基本反映花器性状的遗传特征。比较不同的系统聚类方法,离差平方和法较好地适合用于辣椒品种花器性状的数量分类。     

Seed-yield and yield components response to source-sink ratio in annual and perennial species of Lesquerella (Brassicaceae)

Although the annual Lesquerella fendleri is the prime candidate for the development of a lesquerolic rich oil-seed crop, within this genus there are other species available to breeders, some of which are perennials. However, the feasibility of a perennial crop of Lesquerella is not clear because increases in seed-yield tend to reduce perennially. The objective of this work was to determine the effect of the source-sink ratio on seed yield and yield components in annual and perennial species of Lesquerella. We predicted that (i) due to differences in allocation patterns of annual and perennial species, seed-yield and yield components in perennials would be less affected by the source-sink ratio (higher stability) than in annuals and (ii) since seed-weight has been found to be the most stable yield component in other crops and their wild relatives, most of the variation in seed-yield as a consequence of source-sink ratios would be determined by changes in the number fruits per plant and the number of seeds per fruit. A field experiment was carried out in Chubut, Patagonia Argentina in a complete randomized design with four treatments to examine source-sink relationships in four species of Lesquerella, two annuals (L. angustifolia, L. gracilis) and two perennials (L. pinetorum, L. mendocina). We used either shading (reduction of source) or removal of flower-buds (reduction of sink) to develop a range of source-sink relationships. All four species showed a similar yield response to source-sink variations. Seed-yield was lower in shaded plants, although the timing of shading influenced this response. Flower-bud removal resulted in a significant increase in seed-yield. Seed-yield differences among source-sink treatments were best explained by changes in the number of fruits per plant than by the number of seeds per fruit. Source-sink manipulations had no affect on seed weight. Flower-bud removal significantly increased the number of fruits per plant in all species except for L. mendocina. The number of seeds per fruits increased only in L. pinetorum. Our results show that carbon stored during pre-anthesis plays a key role in reproduction both in annual and perennial Lesquerella. The increase in the seed-yield components found with bud removal could potentially reduce longevity in perennial species. The results also show that the number of fruits per plant is a good proxy for seed-yield within a species.     

Relationship of growth parameters and nutrients uptake with canola (Brassica napus L.) yield and yield contribution at different nutrients availability

A field experiment was conducted to evaluate the effect of different nutrients on canola (Brassica napus L.) growth parameters, nutrient uptake and ultimately on seed yield. For this purpose a split plot experimental design, with 10 treatments in 4 replications was carried out in 2004-2005, in silt-clay soil at Baiecola Agricultural Research Station, Mazandaran Iran. Canola seed yield, growth parameters (CGR, LAI, RGR and NAR), dry matter accumulation and HI and nutrient content of the leaf were examined. NPK fertilizers together with S and Zn, singly or in combination were applied. The results showed that at treatments T5 (NP), T8 (NPK), T9 (NPKS) and T10 (NPKZn) the higher seed yield (> 2600 kg ha(-1)) coincided with TDM > 880 g m(-2) the peak CGR > or = 13.9 g m(-2) day(-1) and the maximum LAI > or = 4.1. The higher seed yield at T5, T8, T9 and T10 coincided with higher concentrations of nutrients: N, P, K, S and Zn in leaf at flowering having > or = 3.40%, > or = 0.25%, > or = 1.53%, > or = 110 ppm and > or = 22.7 ppm, indicating substantial levels of translocation of nutrients at various stages of plant growth and higher number of pods per plant (> or = 179). Combined application of NPKZn at T10 resulted in maximum seed yield (3090 kg ha(-1)), coinciding with the maximum number of pods per plant (230), maximum TDM (1043 kg ha(-1)), maximum CGR (20.09 g m(-2) day(-1)) and maximum LAI (4.69).     

Genetic analysis of early-maturing maize (Zea Mays L.) inbred lines under stress and nonstress conditions

Early-maturing maize (Zea Mays L.) germplasm developed from diverse sources has the potential for use in developing maize hybrids suitable for increasing maize production in the dry ecologies of eastern Africa. A diallel study was conducted to estimate general combining ability (GCA) of 12 early-maturing maize inbred lines, identify potential single-cross hybrids for use as parents, assess genetic diversity among the inbred lines, and relate genetic distance to specific combining ability (SCA) and hybrid performance. Sixty-six F₁ diallel hybrids were evaluated under optimal and drought stress conditions at four locations in Kenya and Uganda. The parental inbred lines were genotyped using 94 single nucleotide polymorphism (SNP) markers. Additive gene action was more important than nonadditive gene action for inheritance of grain yield (GY) under optimal conditions. However, nonadditive gene effects were more important in the inheritance of GY under drought and across all environments. Inbred lines CKL0722, VL058014, and CZL0724 were among the best with positive GCA effects for GY across both optimal and drought stress conditions. The correlation between SCA and both genetic distance and F₁ GY was significant under both drought stress and across all environments. Inbred lines with desirable GCA effects for GY and other agronomic traits and hybrids with good performance under both optimal and drought stress conditions are potential parents for development of various types of high-yielding, stress-tolerant, and early-maturing hybrids.     

Performance of high-protein mutant lines of Triticum aestivum (L.) under semi-arid conditions of Syria

The agronomical characters of nine high-protein mutant lines of T. aestivum produced by the IAEA were studied along with their mother line Mex22A and four local cultivars. The experiments were carried out under rainfed conditions in 1990 and 1991 in southern Syria. Statistical analysis revealed significant differences among the lines in all characters. Genotype by environment interaction was significant for all characters except for N yield. There was a negative correlation between grain nitrogen concentration (GNC) and yield. However, two of the check cultivars and seven mutant lines had similar yield to Mex22A with greater GNC. The other two mutant lines, 5074M and E296, were very late in heading and were characterized by low yield with extremely high GNC. Spikes per square meter contributed most to grain yield followed by number of seeds per spike and lastly seed weight. SDS sedimentation test values were negatively correlated with GNC.Polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulphate (SDS-PAGE) was used to assay for high molecular weight (HMW) glutenin protein subunits of the grain endosperm. The results showed the presence of HMW glutenin GluD1 subunits 2 + 12 in Mex22A and all IAEA genotypes. Check varieties L92-6, Buhuth 4 and Cham 2 contain the good quality allelic GluD1 subunits 5 + 10. Nevertheless, 4 of 9 IAEA mutant lines were characterized by having higher SDS sedimentation values due to the presence of Glu-B1 subunits 17 + 18 when compared to those that had subunits 7 + 8.