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1.
The low and unstable yields of rainfed lowland rice in Central Java can be attributed to drought, nutrient stress, pest infestation or a combination of these factors. Field experiments were conducted in six crop seasons from 1997 to 2000 at Jakenan Experiment Station to quantify the yield loss due to these factors. Experimental treatments—two water supply levels (well-watered, rainfed) in the main plots and five fertilizer levels (0-22-90, 120-0-90, 120-22-0, 120-22-90, 144-27-108 kg NPK ha−1) in the subplots—were laid out in a split-plot design with four replications. Crop, soil, and water parameters were recorded and pest infestations were assessed.
In all seasons, rice yield was significantly influenced by fertilizer treatments. Average yield reduction due to N omission was 42%, to K omission 33–36%, and to P omission 3–4%. Water by nutrient interactions did not affect rice yield and biomass production. In two of the three dry seasons, an average of 20% of the panicles were damaged by pests and estimated yield loss from pests was 56–59% in well-watered and well-fertilized treatments. In one out of six seasons, yields under rainfed conditions were 20–23% lower than under well-watered conditions. Drought, N and K deficiencies, and pest infestation are the major determinants for high yields in rainfed environments in Jakenan. Supplying adequate nutrient and good pest control are at least as important as drought management for increasing crop productivity of rainfed rice-growing areas in Central Java. The relative importance of drought, nutrient and pest management may vary in other rainfed areas. Yield constraints analysis should be systematically carried out to identify appropriate management strategies. 相似文献
2.
《Field Crops Research》1995,40(2):67-86
Drought is a major problem for rice grown under rainfed lowland and upland conditions, but progress in breeding to improve drought resistance has been slow. This paper describes patterns of water-stress development in rice fields, reviews genetic variation in physio-morphological traits for drought resistance in rice, and suggests how knowledge of stress physiology can contribute to plant breeding programmes that aim to increase yield in water-limiting environments. To provide a basis for integrating physiological research with plant-breeding objectives we define drought resistance in terms of relative yield of genotypes. Therefore, a drought-resistant genotype will be one which has a higher grain yield than others when all genotypes are exposed to the same level of water stress.A major reason for the slow progress in breeding for drought resistance in rice is the complexity of the drought environment, which often results in the lack of clear identification of the target environment(s). There is a need to identify the relative importance of the three common drought types; early-season drought which often causes delay in transplanting, mild intermittent stress which can have a severe cumulative effect, and late stress which affects particularly late-maturing genotypes. In addition, in rainfed lowland rice, flooded and non-flooded soil conditions may alternate during the growing season, and affect nutrient availability or cause toxicity.Several drought-resistance mechanisms, and putative traits which contribute to them, have been identified for rice; important among these being drought escape via appropriate phenology, root characteristics, specific dehydration avoidance and tolerance mechanisms, and drought recovery. Some of these mechanisms/traits have been shown to confer drought resistance and others show potential to do so in rice. The most important is the appropriate phenology which matches crop growth and development with the water environment. A deep root system, with high root length density at depth is useful in extracting water thoroughly in upland conditions, but does not appear to offer much scope for improving drought resistance in rainfed lowland rice where the development of a hard pan may prevent deep root penetration. Under water-limiting environments, genotypes which maintain the highest leaf water potential generally grow best, but it is not known if genotypic variation in leaf water potential is solely caused by root factors. Osmotic adjustment is promising, because it can potentially counteract the effects of a rapid decline in leaf water potential and there is large genetic variation for this trait. There is genotypic variation in expression of green leaf retention which appears to be a useful character for prolonged droughts, but it is affected by plant size which complicates its use as a selection criterion for drought resistance.There is a general lack of drought related research for rice in rainfed lowland conditions. This needs to be rectified, particularly considering their importance relative to upland conditions in Asian countries. We suggest that focussing physiological-genetic research efforts onto clearly defined, major target environments should provide a basis for increasing the relevance of stress physiology and the efficiency of breeding programmes for development of drought-resistant genotypes. 相似文献
3.
《Plant Production Science》2013,16(3):381-389
AbstractScarcity of water and N fertilizer are major constraints to rice production, particularly in developing countries where rainfed upland condition dominates. Improvement of genetic adaptability to inadequate water and N fertilizer is one option to maintain productivity in these regions. NERICAs are expected to yield higher under low input conditions, but growth and yield responses of the cultivars to different ecosystems and N levels remain unknown. The objectives of this study were to characterize the growth and yield performance of NERICAs, in comparison with selected Japanese rice cultivars. The two NERICAs (NERICA 1 and NERICA 5), two Japanese upland cultivars (Toyohatamochi and Yumenohatamochi), and a Japanese lowland cultivar Hitomebore were grown under two ecosystems (irrigated lowland (IL) and rainfed upland (RU)) with two N levels (high (H) and low (L)) for two years. The cultivar difference in the aboveground dry weight and grain yield was the largest in the in RU × L plot, where the values of NERICAs were similar to those in the other plots, but the values of other cultivars were substantially reduced. Regardless of cultivar, N contents of the plants at maturity correlated significantly with the aboveground dry weight at maturity, spikelet number and grain yield per area. These results indicate that NERICAs, compared with the selected Japanese upland cultivars that were bred for drought tolerance, have a higher ability to absorb N under upland conditions, which may contribute to higher biomass production and sink formation, resulting in increased gain yield. 相似文献
4.
沪优2号由上海市农业生物基因中心选育,2010年通过国家品种审定,具有株型好、抗倒、抗旱、耐肥、耐高温、结实率高、米质优、穗足产量高的特点,不但可以在建瓯市水田大面积推广,还是缺水的望天田种植水稻的首选品种。 相似文献
5.
《Field Crops Research》2002,73(2-3):169-180
Drought frequently reduces grain yield of rainfed lowland rice. A series of experiments were conducted in drought-prone northeast Thailand to study the magnitude and consistency of yield responses of diverse, rainfed lowland rice genotypes to drought stress environments and to examine ways to identify genotypes that confer drought resistance. One hundred and twenty-eight genotypes were grown under non-stress and four different types of drought stress conditions. The relationship of genotypic variation in yield under drought conditions to genetic yield potential, flowering time and flowering delay, and to a drought response index (DRI) that removed the effect of potential yield and flowering time on yield under stress was examined.Drought stress that developed prior to flowering generally delayed the time of flowering of genotypes, and the delay in flowering was negatively associated with grain yield, fertile panicle percentage and filled grain percentage. Genotypes with a longer delay in flowering time had extracted more water during the early drought period, and as a consequence, had higher water deficits. They were consistently associated with a larger yield reduction under drought and in one experiment with a smaller DRI. Genotypes, however, responded differently to the different drought stress conditions and there was no consistency in the DRI estimates for the different genotypes across the drought stress experiments. The results indicate that with the use of irrigated-control and drought test environments, genotypes with drought resistance can be identified by using DRI or delay in flowering. However, selections will differ depending on the type of drought condition. The inconsistency of the estimates in DRI and flowering delay across different drought conditions reflects the nature of the large genotype-by-environment interactions observed for grain yield under various types of drought in rainfed lowland conditions. 相似文献
6.
Vaiphot KANJOO Kanchana PUNYAWAEW Jonaliza L.SIANGLIW Suwat JEARAKONGMAN Apichart VANAVICHIT Theerayut TOOJINDA 《水稻科学》2012,19(2):117-124
Drought is a major abiotic constraint to rice production in rainfed lowland and insufficiently irrigated areas.The improvement of drought tolerant varieties is one of the strategies to reduce the negative effects of drought.Quantitative trait loci(QTLs) for primary and secondary traits related to drought tolerance(DT) on chromosomes 1,3,4,8 and 9 that determined from double haploid lines derived from a cross between CT9993 and IR62266 were introgressed and dissected into small pieces in the genetic background of Khao Dawk Mali 105(KDML105) to develop chromosome segment substitution line(CSSL) population.The CSSLs were evaluated at the reproductive stage for their agronomic performance and yield components under drought stress,and results were compared with irrigated condition.The flowering of CSSL lines was 6 to 7 d earlier than KDML105.The mean values of grain yields in the CSSLs were higher than KDML105 under drought and irrigated conditions.At irrigated condition,the grain yields of introgression lines carrying DT-QTLs from chromosomes 4 and 8 were higher than that of KDML105,whereas other traits showed little difference with KDML105.Analysis indicated that grain yield has positive correlation with plant height,tiller and panicle number per plant,and total grain weight per plant under drought stress while negatively correlated with days to flowering.As mentioned above,CSSLs showing good adaptation under drought stress can be used as genetic materials to improve drought tolerance in Thai rainfed lowland rice breeding program,and as materials to dissect genes underlying drought tolerance. 相似文献
7.
Lowland rice production in the Mekong region is generally low because crops are cultivated under rainfed conditions and often exposed to drought. To examine how field water availability affects productivity of different genotypes in rainfed lowland rice, the field experiments were carried out for six years at eight locations in Cambodia. We classified 34 genotypes used in the experiments into photoperiod-insensitive [short (IS) and medium (IM) maturity] and sensitive [medium (SM) and long-duration (SL) maturity] genotype groups. Mean days-to-flower from sowing was 87 in IS, 112 in IM, 112 in SM and 132 in SL and mean grain yield was 2.0, 2.8, 2.5 and 2.4 t ha−1, respectively. Drought environment was quantified for each experiment by determining whether free water level was observed to be less than the soil surface during three growth stages: GS1 (maximum tillering), GS2 (panicle development) and GS3 (grain filling). The drought frequency estimated from 44 field experiments was 18% in all IM, SM and SL at GS1, 23%, 25% and 32% in IM, SM and SL, respectively at GS2, and 43%, 45% and 57% at GS3. Thus, the drought occurred more frequently after flowering, particularly in the SL group. Based on the results, the IM genotypes may be grown to escape from drought during the GS2 and GS3 periods by sowing early (June) in the drought environment. When sown late (August), the SM genotypes are exposed to less drought risk because they flower earlier than the IM genotypes. Compared with the SM genotypes, the SL genotypes are highly exposed to water stress during the GS3 period, resulting in yield reduction. SM and IM had similar occurrence of drought environment, but yield reduction due to drought was less in SM than in IM. Thus, photoperiod-sensitive cultivars with medium maturity are preferred in drought-prone lowland fields, particularly when sowing is delayed. In the favourable water environment, the SM genotypes can be better than the IM genotypes when sown early in the season, while the IM genotypes performs better than the SM genotypes with late sowing. This suggests that for lowland fields without drought photoperiod-insensitive cultivars are recommended and photoperiod-sensitive cultivars can be preferred if sown early. 相似文献
8.
《Field Crops Research》2007,102(1):9-21
We evaluated the genotypic differences in grain yield of 14 rice (Oryza sativa L.) genotypes with different phenology under four growing conditions: transplanting (TP) or direct-seeding (DS) in a toposequentially lower (with favorable water conditions) or upper (drought at around flowering stage) field at Ubon Ratchathani, northeastern Thailand. Thirteen of the genotypes – five early-maturing, four intermediate, and four late – had been bred for rainfed lowlands in northern and northeastern Thailand. IR24, a semi-dwarf, high-yielding, and early-maturing genotype bred for irrigated lowlands, was included for comparison. Genotypic differences in grain yield were significant in a combined analysis of all 4 growing conditions, and both high sink size (spikelet number per area) and high ripened grain percentage were associated with high yield. IR24 did not out-yield the rainfed-lowland genotypes, and its yield was particularly low in DS, owing to poor shoot dry matter production and low spikelet number per panicle. In the lower field, the interaction between cultivation method and genotype was also significant. In the lower field, late maturity was more strongly related to high shoot dry weight at maturity in TP than in DS; some of the early- to intermediate-maturing genotypes in DS produced shoot dry weights at maturity that were comparable to those of the late-maturing genotypes. High shoot dry matter production and large spikelet number per panicle were associated with high grain yield in DS genotypes in the lower field, whereas in TP genotypes with large numbers of panicles were required for high grain yield. Although the field location–genotype interaction and the field location–cultivation method–genotype interaction were not significant, regression analysis showed that late-maturing genotypes yielded less than earlier maturing genotypes, owing to the smaller ripened grain percentage resulting from late-season drought, in the upper field but not in the lower field. The presence of a trade-off between number of ripened grains and grain size in the lower field indicated the possibility of increasing the yield in rainfed-lowland genotypes by increasing assimilation capacity during grain filling. Phenology is important in the development of higher-yielding genotypes for different cultivation methods and different toposequential positions. 相似文献
9.
Under terminal drought conditions, cereal varieties with limited tillering have been suggested to be advantageous, because they have fewer nonproductive tillers, thereby limiting water consumption prior to anthesis. In this study, four field trials were conducted over two growing seasons in southern Spain, under rainfed and irrigated conditions. Twenty-five genotypes were studied to evaluate the contribution of the main stem (MS) and tillers to grain yield and its components. Significant differences were found among genotypes for these contributions under non-stressed environments, but these differences were not significant under water-stress conditions. The contribution of the MS to plant grain yield was higher than that of tillers (68% vs. 32%) and was stable between years in irrigated trials. However, in the rainfed trials, MS contributed differently depending on year-to-year climate variations. Thus, under favorable weather conditions the contribution of MS to grain yield was higher than in the unfavorable year (85% vs. 59%). In irrigated environments, MS and tiller grain yield depended on the number of grains per spike, spikelets per spike, and thousand kernel weight (TKW). Under water-limited conditions, MS yield depended on the number of grains per spike and grains per spikelet, whereas the number of spikelets and TKW had less influence on MS grain yield. Furthermore, under water-stress conditions, high tillering genotypes showed yield levels similar to the genotypes with restricted tillering. Additionally, there was no significant evidence of a positive or negative effect of maximum tiller number on grain yield under rainfed conditions. 相似文献
10.
《Field Crops Research》2004,88(1):11-19
Drought is recognized as a primary constraint for rainfed rice production. In this study, the spatial distribution of heading date of rainfed rice and its relation to field water conditions were investigated for 2 years in mini-watersheds called Nong in Northeast Thailand, in order to clarify the toposequential variation in the degree of water stress of rice. Although the difference in the relative field elevation in the mini-watersheds was only a few meters, the water availability in terms of standing water and soil moisture markedly decreased with ascending elevation. Rice cultivars, KDML 105 and RD 6, the two dominant genotypes in Northeast Thailand, reached the heading stage at nearly the same day in the absence of water stress, independent of transplanting or seeding date under customary management. As the water availability decreased with ascending field elevation, the heading date of rice was markedly delayed. The delay seemed to be related to the cumulative water stress before heading of rice. The rice harvest index and yield at farmers’ fields decreased linearly with the delay of heading. The observed toposequential distribution of heading date indicated that quite severe water stress was imposed in the uppermost fields of the mini-watersheds, while practically no water stress occurred in the lower fields, at least in the lower half of the mini-watersheds. These results suggest that the delay of heading is a good index for rice water stress in rice in Northeast Thailand and can be applicable to field classification with respect to drought risk. 相似文献
11.
Reena Sellamuthu Gui Fu Liu Chandra Babu Ranganathan Rachid Serraj 《Field Crops Research》2011,124(1):46-58
Drought is a major constraint for rice production and yield stability in rainfed ecosystems, especially when it occurs during the reproductive stage. Combined genetic and physiological analysis of reproductive-growth traits and their effects on yield and yield components under drought stress is important for dissecting the biological bases of drought resistance and for rice yield improvement in water-limited environments. A subset of a doubled haploid (DH) line population of CT9993-5-10-1-M/IR62266-42-6-2 was evaluated for variation in plant water status, phenology, reproductive-growth traits, yield and yield components under reproductive-stage drought stress and irrigated (non-stress) conditions in the field. Since this DH line population was previously used in extensive quantitative trait loci (QTLs) mapping of various drought resistance component traits, we aimed at identifying QTLs for specific reproductive-growth and yield traits and also to validate the consensus QTLs identified earlier in these DH lines using meta-analysis. DH lines showed significant variation for plant water status, reproductive-growth traits, yield and yield components under drought stress. Total dry matter, number of panicles per plant, harvest index, panicle harvest index, panicle fertility, pollen fertility, spikelet fertility and hundred grain weight had significant positive correlations with grain yield under drought stress. A total of 46 QTLs were identified for the various traits under stress and non-stress conditions with phenotypic effect ranging from 9.5 to 35.6% in this study. QTLs for panicle exsertion, peduncle length and pollen fertility, identified for the first time in this study, could be useful in marker-assisted breeding (MAB) for drought resistance in rice. A total of 97 QTLs linked to plant growth, phenology, reproductive-growth traits, yield and its components under non-stress and drought stress, identified in this study as well as from earlier published information, were subjected to meta-analysis. Meta-analysis identified 23 MQTLs linked to plant phenology and production traits under stress conditions. Among them, four MQTLs viz., 1.3 for plant height, 3.1 for days to flowering, 8.1 for days to flowering or delay in flowering and 9.1 for days to flowering are true QTLs. Consensus QTLs for reproductive-growth traits and grain yield under drought stress have been identified on chromosomes 1 and 9 using meta-QTL analysis in these DH lines. These MQTLs associated with reproductive-growth, grain yield and its component traits under drought stress could be useful targets for drought resistance improvement in rice through MAB and/or map-based positional analysis of candidate genes. 相似文献
12.
Yasuhiro Tsujimoto Tovohery Rakotoson Atsuko Tanaka Kazuki Saito 《Plant Production Science》2013,16(4):413-427
ABSTRACTIn sub-Saharan Africa (SSA), rice production from smallholder farms is challenged because of a lack of fertilizer inputs and nutrient-poor soils. Therefore, improving nutrient efficiency is particularly important for increasing both fertilizer use and rice yield. This review discusses how to improve the return from fertilizer input in terms of agronomic N use efficiency (AEN), that is, the increase in grain yield per kg of applied N, for rice production in SSA. The AEN values we summarized here revealed large spatial variations even within small areas and a certain gap between researcher-led trials and smallholder-managed farms. Experimental results suggest AEN can be improved by addressing spatial variations in soil-related factors such as P, S, Zn, and Si deficiencies and Fe toxicity in both irrigated and rainfed production systems. In rainfed production systems, differences in small-scale topography are also important which affects AEN through dynamic changes in hydrology and variations in the contents of soil organic carbon and clay. Although empirical evidence is further needed regarding the relationship between soil properties and responses to fertilizer inputs, recent agricultural advances have generated opportunities for integrating these micro-topographical and soil-related variables into field-specific fertilizer management. These opportunities include UAV (unmanned aerial vehicle) technology to capture microtopography at low cost, database on soil nutrient characteristics at high resolution and more numbers of fertilizer blending facilities across SSA, and interactive decision support tools by use of smartphones on site. Small-dose nursery fertilization can be also alternative approach for improving AEN in adverse field conditions in SSA.ABBREVIATIONS: AEN: agronomic nitrogen use efficiency; FISP: farm input subsidy program; VCR: value cost ratio; SOC: soil organic carbon; SSA: sub-Saharan Africa; UAV: unmanned aerial vehicle 相似文献
13.
《Plant Production Science》2013,16(4):488-496
Environmental resources for rainfed rice production show large variability even within a small area in Northeast Thailand, and it is said that farmer’s management is well adapted to the variability. This study evaluated transplanting date and nitrogen (N) fertilizer rate in the management to improve rice productivity. The effect of transplanting date and N fertilizer rate on rice productivity was analyzed by investigating rice growth, and also by dividing rainfed rice fields located in a mini-watershed into 4 subecosystems: (1) medium deep water, waterlogged (MDW), (2) shallow water, favorable (SWf), (3) shallow water, drought- and submergence-prone (SWds), and (4) shallow water, drought-prone (SWd). Rice grew at almost a constant rate until maturity and the growth rate was higher at a lower field. The difference in productivity was derived from not only a water condition but also soil fertility, and was associated with the rate of N uptake. Small leaf area index was found to be one of the causes for low productivity in rice. Statistic analysis showed that earlier transplanting increased biomass production in all subecosystems. The biomass-increase resulted in a higher yield in SWds and SWd fields while it resulted in a reduced harvest index (HI) and did not increase yield in MDW and SWf fields. The effect of N fertilizer was apparent in the field where rice biomass was small due to later transplanting or unfertile soil, but the effect was generally small. Earlier transplanting in upper fields and later transplanting in lower fields in mini-watersheds were suggested to improve rice production, and proper distribution of N fertilizer use is considered necessary. 相似文献
14.
《Plant Production Science》2013,16(2):147-153
AbstractMini-watersheds called Nongin Thai are geographical components of rainfed lowland rice culture in Northeast Thailand, and constitute distinct units in understanding environmental constraints for low and unstable rainfed rice production there. The toposequential variation of soil fertility and its relation to rice productivity within mini-watersheds, was examined by phytometry of sampled soils and field measurements of rice growth and yield. The phytometry experiment with irrigated potted rice using soils sampled from various rice fields within each mini-watershed, revealed that soil fertility as evaluated by rice dry matter production showed a 5 times difference among the fields at most. The difference in the soil fertility was ascribed primarily to that in nitrogen (N) supply capacity, which itself had a strong correlation with soil organic carbon (SOC) content. Accordingly, the biomass production of pot-grown rice was proportional to SOC. content, which suggested the usefulness of SOC as an index for soil fertility evaluation. The effect of clay on the soil fertility was much less than that of SOC. The actual rice yield in each field also showed quite large field-to-field variation, most of which was explained by the SOC content, rice growth duration and fertilizer application rate even though water availability also affected the yield. The yield positively correlated with growth duration and hence with earlier transplanting. Both SOC and clay contents of fields showed steep gradients with ascending field elevation within mini-watersheds, resulting in a marked toposequential distribution of rice yield. The toposequential distributions of SOC and clay contents imply that rice culture after deforestation accelerated soil erosion from upper to lower fields. The large toposequential gradient in soil fertility requires different resource and crop management for each toposequential position, in order to improve rice productivity of the mini-watershed as a whole. 相似文献
15.
Genetic analysis of rainfed lowland rice drought tolerance under naturally-occurring stress in eastern India: Heritability and QTL effects 总被引：1，自引：0，他引：1
Drought tolerance is an important rainfed rice breeding objective, but because the heritability (H) of yield under drought stress is thought to be low, secondary physiological traits are considered better targets for selection than yield under stress per se. This assumption has rarely been tested, and there are no reports on H for yield under drought stress from experiments repeated over seasons in rainfed lowland rice. To assess the potential for improving yield under drought stress via direct selection, and to identify associated quantitative trait loci (QTL), doubled haploid lines with a narrow range of flowering dates, derived from the population CT9993-5-10-1-M/IR62266-42-6-2, were screened under full irrigation and severe drought stress induced by draining the paddy before flowering in 2000–2002 at Raipur, India. Drought stress reduced mean yield by 80%. H was similar in stress and non-stress trials, as was the relative magnitude of the genotype and genotype × year variances. The genetic correlation between yield in stress and non-stress conditions was 0.8, indicating that about 64% of the genetic variation for yield under stress was accounted for by differences in yield potential also expressed in irrigated environments. These results indicate that direct selection for yield under drought stress can produce yield gains under stress without reducing yield potential. There was no secondary trait for which selection resulted in greater predicted response in yield under stress than direct selection for stress yield per se. A QTL was detected on chromosome 1 near sd1 that explained 32% of the genetic variation for yield under stress, but only 4% under non-stress. Its effect was consistent across years. This QTL accounted for much of the variation in drought yield not accounted for by variation in yield potential. 相似文献
16.
The rice stem nematode Ditylenchus angustus causes “Ufra” disease in rice resulting in substantial yield losses. Although it is predominant in deep water rice in South and Southeast Asia, this nematode also infects irrigated and rainfed low land rice. This study evaluated rice genotypes (irrigated, rainfed, deep water and landraces) for resistance to the Bangladeshi population of D. angustus. The experiment was executed using artificial inoculation, in both rainfed and irrigated ecosystems. The rice varieties were first scored at 28 days post inoculation (dpi), and ranked based on the postinfectional reactions and severity of symptoms on a 0–16 rating scale. The susceptibility of the varieties was also evaluated at a later time point, i.e. 55 dpi, based on the percentage of tiller infections, using a disease index scoring system ranging from 0 to 9. Both screening methods showed a similar ranking of the varieties for susceptibility/resistance against this nematode. The experiment was initially conducted in plastic pots, and the promising varieties were analyzed further in field conditions. Out of the 85 varieties, one landrace named ‘Manikpukha’ proved to be highly resistant, while 6 other varieties showed resistance and 13 varieties showed moderately resistant responses under both pot and field conditions. The promising varieties found in the present investigation can be used in rice breeding programs as well as for further detailed studies to develop a sustainable ufra management strategy. 相似文献
17.
Eric S. Ober Chris J. A. Clark Mich Le Bloa Andy Royal Keith W. Jaggard John D. Pidgeon 《Field Crops Research》2004,90(2-3):213-234
Drought is the major cause of sugar beet (Beta vulgaris L.) yield losses in the UK and many other regions where the crop is not normally irrigated. However, drought tolerance has not been a breeding target partly because the extent of the problem was not understood, it is difficult to design effective selection screens, and because of the suspicion that few varietal differences existed. The aim of this study was to evaluate the genetic resources necessary to improve drought tolerance. Specific objectives were to assess the degree of genotypic diversity for drought tolerance, characterise genotypic differences in response to drought, and identify sources of germplasm with greater drought tolerance than current commercial varieties. Over 3 years, 46 beet genotypes representing diverse genetic backgrounds were tested in the field under large polythene covers to impose a drought beginning approximately 40 days after emergence until harvest. Sugar, root and total dry matter yields were measured under drought and irrigated conditions. The percentage green crop cover was measured at regular intervals and used in the calculation of radiation use efficiencies for each genotype. Drought tolerance index (DTI) was computed as the fraction of irrigated yield maintained under drought, normalised by the mean yield across all genotypes in the trial. Seven genotypes were tested in all years, and the data on these were used to calculate yield stability statistics and to estimate broad-sense heritability. There were more than two-fold differences in droughted and irrigated yields between genotypes, and nearly a two-fold difference in DTI. According to an index that combines yield potential and drought tolerance, some genotypes performed better than the three locally adapted commercial varieties included in the test. There were significant effects for genotype, treatment and G×E interactions for yield components and radiation use efficiency. There were also significant genotype differences in harvest index but few significant G×E interactions. Droughted and irrigated yields were positively associated, but there was no close relation between yield potential and DTI. The seven genotypes common to all years differed in yield stability and in sensitivity to water availability. Thus, the genetic resources exist for germplasm improvement. Both yield potential and DTI (which may ensure better yield stability) should be considered simultaneously as breeding targets for drought-prone areas. 相似文献
18.
Pandit Elssa Kumar Panda Rajendra Sahoo Auromeera Ranjan Pani Dipti Kumar Pradhan Sharat 《水稻科学》2020,27(2):124-132
Deeper rooting 1(Dro1) and Deeper rooting 2(Dro2) are the QTLs that contribute considerably to root growth angle assisting in deeper rooting of rice plant. In the present study, a set of 348 genotypes were shortlisted from rice germplasm based on root angle study. Screening results of the germplasm lines under drought stress identified 25 drought tolerant donor lines based on leaf rolling, leaf drying, spikelet fertility and single plant yield. A panel containing 101 genotypes was constituted based on screening results and genotyped using Dro1 and Dro2 markers. Structure software categorized the genotypes into four sub-populations with different fixation index values for root growth angle. The clustering analysis and principal coordinate analysis could differentiate the genotypes with or without deeper rooting trait. The dendrogram constructed based on the molecular screening for deep rooting QTLs showed clear distinction between the rainfed upland cultivars and irrigated genotypes. Eleven genotypes, namely Dular, Tepiboro, Surjamukhi, Bamawpyan, N22, Dinorado, Karni, Kusuma, Bowdel, Lalsankari and Laxmikajal, possessed both the QTLs, whereas 67 genotypes possessed only Dro1. The average angle of Dro positive genotypes ranged from 82.7° to 89.7°. These genotypes possessing the deeper rooting QTLs can be taken as donor lines to be used in marker-assisted breeding programs. 相似文献
19.
雨养和灌溉条件下施氮量对小麦干物质积累和产量的影响 总被引：3，自引：0，他引：3
为给冀东地区小麦高产栽培提供技术参考,以高蛋白质品种京冬8号和低蛋白质品种宝麦38为材料,设置0、120、240和360kg·hm-2三个施氮水平,研究了在灌溉和雨养条件下氮素营养对冬小麦干物质积累和产量形成的调控效应。结果表明,适量施氮提高了小麦干物质积累量、结实小穗数和穗粒数,促进了叶片、茎和鞘的花前贮存干物质在花后向籽粒中的转移,但过量施氮则抑制灌溉条件下营养器官花前贮存干物质在花后向籽粒的转移。施氮量对千粒重的影响因基因型和土壤水分状况不同而差异。随施氮量的增加,在雨养和灌溉条件下京冬8号千粒重分别呈降低和增加趋势,宝麦38千粒重均呈下降趋势。适当施氮可促进分蘖和分蘖成穗。与雨养栽培相比,灌溉可促进小麦干物质积累,增加穗数和延长灌浆时间,提高籽粒产量。随着施氮量的增加,两品种的氮肥生产效率和氮肥农学效率均降低。宝麦38和京冬8号籽粒产量达到最高的施氮量在雨养条件下均为120kg·hm-2,在灌溉条件下分别为120和240kg·hm-2。从产量和氮肥利用效率综合来看,宝麦38的适宜施氮量为120kg·hm-2,京冬8号的适宜施氮量为120~240kg·hm-2。 相似文献
20.
《Field Crops Research》2002,73(2-3):181-200
A series of experiments were conducted in drought-prone northeast Thailand to examine the magnitude of yield responses of diverse genotypes to drought stress environments and to identify traits that may confer drought resistance to rainfed lowland rice. One hundred and twenty eight genotypes were grown under non-stress and four different types of drought stress conditions.Under severe drought conditions, the maintenance of PWP of genotypes played a significant role in determining final grain yield. Because of their smaller plant size (lower total dry matter at anthesis) genotypes that extracted less soil water during the early stages of the drought period, tended to maintain higher PWP and had a higher fertile panicle percentage, filled grain percentage and final grain yield than other genotypes. PWP was correlated with delay in flowering (r=−0.387) indicating that the latter could be used as a measure of water potential under stress. Genotypes with well-developed root systems extracted water too rapidly and experienced severe water stress at flowering. RPR which showed smaller coefficient of variation was more useful than root mass density in identifying genotypes with large root system.Under less severe and prolonged drought conditions, genotypes that could achieve higher plant dry matter at anthesis were desirable. They had less delay in flowering, higher grain yield and higher drought response index, indicating the importance of ability to grow during the prolonged stress period.Other shoot characters (osmotic potential, leaf temperature, leaf rolling, leaf death) had little effect on grain yield under different drought conditions. This was associated with a lack of genetic variation and difficulty in estimating trait values precisely.Under mild stress conditions (yield loss less than 50%), there was no significant relationship between the measured drought characters and grain yield. Under these mild drought conditions, yield is determined more by yield potential and phenotype than by drought resistant mechanisms per se. 相似文献