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1.
We investigated heat tolerance at the reproductive stage in six spring‐type B. rapa accessions and one B. juncea accession as a control. Plants were subjected to two temperature treatments for seven days in controlled environmental rooms, beginning one day before the first open flower on the main stem inflorescence. The high‐temperature treatment ranged from 25 °C to 35 °C during 16 h light and 25 °C during 8 h dark. The control temperature treatment was set at 23 °C during 16 h light and 15 °C during 8 h dark. Soil moisture was maintained at close to field capacity to avoid drought stress. Main stem buds that emerged during the treatment period were tagged, and pod and seed production was recorded at each reproductive node. Leaf temperature depression and leaf conductance increased in the high‐temperature treatment which indicated that plants were not drought stressed. A leafy vegetable type of B. rapa from Indonesia was the most tolerant to high temperature, as defined by its ability to set seed equally well in the control and high‐temperature treatments, followed by an oilseed type from Pakistan. Pollen viability remained above 87 % in all accessions and treatments. We conclude that bud number and length, and pod number produced under high temperatures, might provide a useful preliminary screen for high‐temperature tolerance and that B. rapa may be a valuable source of heat tolerance in canola (B. napus).  相似文献   

2.
Cytoplasmic male sterility (CMS), a maternally transmitted failure in pollen formation, is an effective pollination control system in hybrid rapeseed (Brassica napus) breeding. However, CMS is not widely used in the related oilseed species Brassica rapa. In the past years, several male sterile plants have been isolated from the B. rapa landrace ‘0A193’, collected in Shaanxi, China, in 2011. It is noteworthy that the fertility expression of 0A193‐CMS was affected by temperature. In contrast to pol CMS, fertility tests with 18 B. rapa and 9 B. napus accessions suggest that a different system of maintaining and restoring is responsible for the observed phenotype. Further on, genetic investigation evidenced that fertility of 0A193‐CMS is controlled by both cytoplasmic and one pair of nuclear recessive genes. Interestingly, plants of the 0A193‐CMS type possess a highly specific fragment of the mitochondrial gene orf222, a crucial regulator of male sterility in nap CMS. Our study broadens the CMS resources in B. rapa and provides a highly applicable alternative to pol CMS and ogu CMS for hybrid breeding production.  相似文献   

3.
Balanites aegyptiaca is a drought‐tolerant tree naturally distributed in Africa and has a high potential for biofuel production and livelihood. To understand the plant tolerance to drought stress, B. aegyptiaca plants collected from five provenances were subjected for 4 weeks to drought stress through different regimes of soil volumetric water content (VWC, i.e. 25% control, 15% as moderate and 5% as a severe drought stress) followed by 2‐week recovery. Morpho‐physiological responses as well as the changes in antioxidant defences under water stress and recovery were investigated. Drought stress significantly reduced plant biomass‐related parameters, stomatal conductance, quantum efficiency and increased leaf temperature. Each provenance showed specific patterns of stress response reactions that were detected in a cluster analysis. The large leaf area and a high level of lipid peroxidation in Cairo provenance increased its sensitivity to severe drought. For provenances El‐Kharga and Yemen, the highest tocopherol contents and the highest catalytic activities of ascorbate peroxidase (SOD), catalase (CAT), glutathione reductase (GR) and dehydroascorbate reductase (DHAR) were recorded. These traits contributed to the high drought tolerance of these two provenances in comparison with the other provenances. All plants recovered from stress and showed specifically increased activity of glutathione‐S‐transferase (GST) as a repair mechanism. Results showed that the drought tolerance level in B. aegyptiaca is provenance‐dependent.  相似文献   

4.
A microspore mutagenesis protocol was developed for Brassica rapa, Brassica napus and Brassica juncea for the production of double haploid lines with novel fatty acid profiles in the seed oil. Freshly isolated Brassica microspores were first cultured with ethyl methane sulphonate (EMS) for 1.5 h. The EMS was removed and the microspores were then cultured according to the standard Brassica microspore culture protocol. This protocol was used to generate over 80 000 Brassica haploid/double haploid plants. Field evaluation of B. napus and B. juncea double haploids was conducted between 2000 and 2003. Fatty acid analysis of the B. napus double haploid lines showed that saturated fatty acid proportions ranged from 5.0% to 7.7%. For B. juncea, saturate proportions ranged from 5.4% to 9.5%. Of the 7000 B. rapa lines that were analysed, 197 lines had elevated oleic acid (>55%), 69 lines had reduced α‐linolenic acid (<8%) and 157 lines had low saturated fatty acid proportions (<5%), when compared with the parental lines.  相似文献   

5.
Six accessions belonging to four subspecies of Brassica rapa, including three accessions of B. rapa subsp. sylvestris, were crossed with B. oleracea subsp. alboglabra in order to develop a series of synthetic B. napus lines with a common C genome but contrasting A genomes. Different A genomes had significant effects on the efficiency of B. napus resynthesis and the sexual compatibility of the synthetic lines with oilseed rape cultivars. The synthetic lines were used to investigate the effect of A genome substitution on the resistance of B. napus to infection by Leptosphaeria maculans, and to explore the potential for the use of wild forms of B. rapa in oilseed rape breeding programmes. Synthetic lines derived from two wild accessions of B. rapa, and their F1 hybrids with oilseed rape cultivars, expressed high levels of resistance to L. maculans in glasshouse experiments. One of these lines also expressed high levels of resistance in field experiments in England and Australia when exposed to a genetically diverse pathogen population. All other synthetic lines and cultivars were highly susceptible in both glasshouse and field experiments. F1 hybrids between oilseed rape cultivars and synthetic lines derived from B. rapa subsp. chinensis were significantly more susceptible than either parent.  相似文献   

6.
The primary aim of this study was to optimize in vitro culture protocols to establish an efficient reproducible culture system for different Brassica interspecific crosses, and to synthesize yellow-seeded Brassica napus (AACC) for breeding and genetical studies. Reciprocal crosses were carried out between three B. rapa L. ssp. oleifera varieties (AA) and five accessions of B. oleracea var. acephala (CC). All the parental lines were yellow-seeded except one accession of B. oleracea. Hybrids were obtained through either ovary culture from crosses B. rapa × B. oleracea, or embryo culture from crosses B. oleracea × B. rapa. A higher rate of hybrid production was recorded when ovaries were cultured at 4–7 days after pollination (DAP). Of different culture media, medium E (MS with half strength macronutrients) showed good response for ovaries from all the crosses, the highest rate of hybrid production reaching 45% in B. rapa (1151) × B. oleracea (T2). In embryo culture, the hybrid rate was significantly enhanced at 16–18 DAP, up to 48.1% in B. oleracea (T3) × B. rapa (JB2). The combinations of optimal DAP for excision and media components increased recovery of hybrids for ovary and embryo culture, and constituted an improved technique for B. rapa × B. oleracea crosses. In addition, yellow seeds were obtained from progenies of two crosses, indicating the feasibility of developing yellow-seeded B. napus through the hybridization between yellow-seeded diploids B. rapa and B. oleracea var. acephala.  相似文献   

7.
W. Qian  R. Liu  J. Meng 《Euphytica》2003,134(1):9-15
This study was conducted to estimate the genetic effects on biomass yield in the interspecific hybrids between Brassica napus and B. rapa, and to evaluate the relationship between parental genetic diversity and its effect on biomass yield of interspecific hybrids. Six cultivars and lines of oilseed B. napus and 20 cultivars of oilseed B. rapa from different regions of the world were chosen to produce interspecific hybrids using NC design II. Obvious genetic differences between B. rapa and B. napus were detected by RFLP. In addition, Chinese B. rapa and European B. rapa were shown genetically differences. Plant biomass yield from these interspecific hybrids were measured at the end of flowering period. Significant differences were detected among general combining ability (GCA) effects over two years and specific combining ability (SCA) effects differences were detected in 2000. The ratios of mean squares, (σ2 GCA(f) + σ2 GCA(m)) / (σ2 GCA(f) + σ2 GCA(m) + σ2 SCA), were 89% and 88% in 1999 and 2000, respectively. This indicates that both additive effects and non-additive effects contributed to the biomass yield of interspecific hybrids and the former played more important role. Some European B. rapa had significant negative GCA effects while many of Chinese B. rapa had significant positive GCA effects, indicating that Chinese B. rapa may be a valuable source for transferring favorable genes of biomass yield to B. napus. Significant positive correlation between parental genetic distance and biomass yield of interspecific hybrids implies that larger genetic distance results in higher biomass yield for the interspecific hybrids. A way to utilize interspecific heterosis for seed yield was discussed. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

8.
C. M. Lu    B. Zhang    L. Liu  M. Kato 《Plant Breeding》2004,123(5):495-496
The effect of genome composition and cytoplasm on petal size was studied in Brassica. Two accessions of Brassica rapa (2n = 20, AA) were reciprocally crossed with three accessions of Brassica oleracea (2n =18, CC) to produce resynthesized B. napus (2n = 38, AACC or CCAA) and sesquidiploids (2n = 29, AAC or CAA). Petal size was measured and compared among diploids (AA and CC), sesquidiploids (AAC and CAA) and amphidiploids(AACC and CCAA). The results showed that petal size is a genome‐dependent and highly heritable character. The heritability of petal length is as high as 96.3%. The addition of each C‐genome to the AA genomic background increased the petal length by 4‐5 mm. Cytoplasm of B. oleracea showed a positive effect on petal length by about 1.3 mm over that of B. rapa. Petal width was positively correlated with petal length at a highly significant level (r= 0.806, df = 81). Resynthesized B. napus (AACC) showed significantly larger flower petals than natural rapeseed cultivars (AACC).  相似文献   

9.
Use of self‐incompatibility (SI) as a pollination control method for Brassica napus hybrid production requires the development of a sufficient number of S‐alleles that are expressed consistently in a range of B. napus lines. Self‐incompatibility (SI) alleles have been transferred from Brassica oleracea and Brassica rapa into B. napus var. oleifera. An understanding of expression of these alleles in B. napus is essential for their commercial use. Four SI B. napus doubled haploids containing the B. oleracea S‐alleles S2, S5, S13 and S24 were crossed to three B. napus cultivars to measure the B. napus genetic background effect on S‐allele expression. A line x tester analysis indicated that the largest source of variation in the expression rate of SI was the S‐allele itself. The B. napus genotypes tested contained modifier gene(s), some that enhanced SI expression and others that inhibited SI expression. The B. napus Canadian cultivar ‘Westar’ generally had a negative effect on SI expression while the European cultivar ‘Topas’ had a positive effect on the B. oleracea S‐allele expression. The B. oleracea S‐allele S24 was very similar in expression to the B. rapa allele W1. The application of these results for the use of B. oleracea S‐alleles for hybrid production in B. napus is discussed.  相似文献   

10.
A diversity arrays technology (DArT) map was constructed to identify quantitative trait loci (QTL) affecting seed colour, hairy leaf, seedling anthocyanin, leaf chlorosis and days to flowering in Brassica rapa using a F2 population from a cross between two parents with contrasting traits. Two genes with dominant epistatic interaction were responsible for seed colour. One major dominant gene controls the hairy leaf trait. Seedling anthocyanin was controlled by a major single dominant gene. The parents did not exhibit leaf chlorosis; however, 32% F2 plants showed leaf chlorosis in the population. A distorted segregation was observed for days to flowering in the F2 population. A linkage map was constructed with 376 DArT markers distributed over 12 linkage groups covering 579.7 cM. The DArT markers were assigned on different chromosomes of B. rapa using B. rapa genome sequences and DArT consensus map of B. napus. Two QTL (RSC1‐2 and RSC12‐56) located on chromosome A8 and chromosome A9 were identified for seed colour, which explained 19.4% and 18.2% of the phenotypic variation, respectively. The seed colour marker located in the ortholog to Arabidopsis thaliana Transparent Testa2 (AtTT2). Two QTL RLH6‐0 and RLH9‐16 were identified for hairy leaf, which explained 31.6% and 20.7% phenotypic variation, respectively. A single QTL (RSAn‐12‐157) on chromosome A7, which explained 12.8% of phenotypic variation was detected for seedling anthocyanin. The seedling anthocyanin marker is found within the A. thaliana Transparent Testa12 (AtTT12) ortholog. A QTL (RLC6‐04) for leaf chlorosis was identified, which explained 55.3% of phenotypic variation. QTL for hairy leaf and leaf chlorosis were located 0–4 cM apart on the same chromosome A1. A single QTL (RDF‐10‐0) for days to flowering was identified, which explained 21.4% phenotypic variation.  相似文献   

11.
W. Rygulla    W. Friedt    F. Seyis    W. Lühs    C. Eynck    A. von Tiedemann    R. J. Snowdon 《Plant Breeding》2007,126(6):596-602
Resynthesized (RS) forms of rapeseed (Brassica napus L.; genome AACC, 2n = 38) generated from interspecific hybridization between suitable genotypes of its diploid progenitors Brassica rapa L. (syn. campestris; genome AA, 2n = 20) and Brassica oleracea L. (CC, 2n = 18) represent a potentially useful resource to introduce resistance against the fungal pathogen Verticillium longisporum into the gene pool of oilseed rape. Numerous cabbage (B. oleracea) accessions are known with resistance to V. longisporum; however, B. oleracea generally has high levels of erucic acid and glucosinolates in the seed, which reduces the suitability of resulting RS rapeseed lines for oilseed rape breeding. In this study resistance against V. longisporum was identified in the cabbage accession Kashirka 202 (B. oleracea convar. capitata), a zero erucic acid mutant, and RS rapeseed lines were generated by crossing the resistant genotype with two spring turnip rape accessions (B. rapa ssp. olerifera) with zero erucic acid. One of the resulting zero erucic acid RS rapeseed lines was found to have a high level of resistance to V. longisporum compared with both parental accessions and with B. napus controls. A number of other zero erucic acid RS lines showed resistance levels comparable to the parental accessions. In the most resistant RS lines the resistance and zero erucic acid traits were combined with variable seed glucosinolate contents. Erucic acid‐free RS rapeseed with moderate seed glucosinolate content represents an ideal basic material for introgression of quantitative V. longisporum resistance derived from B. oleracea and B. rapa into elite oilseed rape breeding lines.  相似文献   

12.
Brassica napus is an important oil species with short history and narrow genetic background. Interspecific hybrids from crosses between B. oleracea and different B. rapa were obtained. We found the hybrids with white petal resembling B. oleracea, the flavonoid and phenolic content decreased in hybrids, agreeing with the expressional changes of flavonoid biosynthesis genes. Seed coat of hybrids resembled diploid parents, or partly resembled to each parent with a clear outline. The palisade layer in hybrids was thicker than parents, with similar pigment accumulation as B. oleracea but more than B. rapa. Differentially sized protein bodies (PBs) were found in hybrids. The radical and inner cotyledon of all hybrids were identified with larger but less PBs than parents. The average size of PBs in outer cotyledon of resynthesized B. napus was also larger than parents, but the number of PBs was not significantly reduced. The phenotypic and seed structural variations after polyploidization of B. napus would be interesting for genetic broadening and breeding of rapeseed.  相似文献   

13.
Production of yellow-seeded Brassica napus through interspecific crosses   总被引：12，自引：0，他引：12  
M. H. Rahman   《Plant Breeding》2001,120(6):463-472
Yellow‐seeded Brassica napus was developed from interspecific crosses between yellow‐seeded Brassica rapa var.‘yellow sarson’ (AA), black‐seeded Brassica alboglabra (CC), yellow‐seeded Brassica carinata (Bbcc) and black‐seeded B. napus (AACC). Three different interspecific crossing approaches were undertaken. Approaches 1 and 2 were designed directly to develop yellow‐seeded B. napus while approach 3 was designed to produce a yellow‐seeded CC genome species. Approaches 1 and 2 differed in the steps taken after trigenomic interspecific hybrids (ABC) were generated from B. carinata×B. rapa crosses. The aim of approach 1 was to transfer the yellow seed colour genes from the A to the C genome as an intermediate step in developing yellow‐seeded B. napus. For this purpose, the ABC hybrids were crossed with black‐seeded B. napus and the three‐way interspecific hybrids were self‐pollinated for a number of generations. The F7 generation resulted in the yellowish‐brown‐seeded B. napus line, No. 06. Crossing this line with the B. napus line No. 01, resynthesized from a black‐seeded B. alboglabra x B. rapa var.‘yellow sarson’ cross (containing the yellow seed colour genes in its AA genome), yielded yellow‐seeded B. napus. This result indicated that the yellow seed colour genes were transferred from the A to the C genome in the yellowish‐brown seed colour line No. 06. In approach 2, trigenomic diploids (AABBCC) were generated from the above‐mentioned trigenomic haploids (ABC). The seed colour of the trigenomic diploid was brown, in contrast to the yellow seed colour of the parental species. Trigenomic diploids were crossed with the resynthesized B. napus line No. 01 to eliminate the B genome chromosomes, and to develop yellow‐seeded B. napus with the AA genome of ‘yellow sarson’ and the CC genome of B. carinata with yellow seed colour genes. This interspecific cross failed to generate any yellow‐seeded B. napus. Approach 3 was to develop yellow‐seeded CC genome species from B. alboglabra×B. carinata crosses. It was possible to obtain a yellowish‐brown seeded B. alboglabra, but crossing this B. alboglabra with B. rapa var.‘yellow sarson’ failed to produce yellow seed in the resynthesized B. napus. The results of approaches 2 and 3 demonstrated that yellow‐seeded B. napus cannot be developed by combining the yellow seed colour genes of the CC genome of yellow‐seeded B. carinata and the AA genome of ‘yellow sarson’.  相似文献   

14.
Drought stress is a major limiting factor for crop production in the arid and semi‐arid regions. Here, we screened eighty barley (Hordeum vulgare L.) genotypes collected from different geographical locations contrasting in drought stress tolerance and quantified a range of physiological and agronomical indices in glasshouse trails. The experiment was conducted in large soil tanks subjected to drought treatment of eighty barley genotypes at three‐leaf stage and gradually brought to severe drought by withholding irrigation for 30 days under glasshouse conditions. Also, root length of the same genotypes was measured from stress‐affected plants growing hydroponically. Drought tolerance was scored 30 days after the drought stress commenced based on the degree of the leaf wilting, fresh and dry biomass and relative water content. These characteristics were related to stomatal conductance, stomatal density, residual transpiration and leaf sap Na, K, Cl contents measured in control (irrigated) plants. Responses to drought stress differed significantly among the genotypes. The overall drought tolerance was significantly correlated with relative water content, stomatal conductance and leaf Na+ and K+ contents. No significant correlations between drought tolerance and root length of 6‐day‐old seedling, stomatal density, residual transpiration and leaf sap Cl? content were found. Taking together, these results suggest that drought‐tolerant genotypes have lower stomatal conductance, and lower water content, Na+, K+ and Cl? contents in their tissue under control conditions than the drought‐sensitive ones. These traits make them more resilient to the forthcoming drought stress.  相似文献   

15.
The leaf subtending to a cotton boll (LSCB) is vital to boll development and biomass, but few studies have examined the effects of drought on the source capacity of LSCBs on different fruiting branches (FBs). To investigate the response of LSCB photosynthesis on different FBs and the relationship of boll biomass to drought, a drought experiment was performed with three treatments: well‐watered (WW, soil water relative content [SRWC] 75 ± 5%), mild drought (MD, SRWC 60 ± 5%), and severe drought (SD, SRWC 45 ± 5%). Despite photosynthetic active radiation increasing under drought conditions, the pre‐dawn leaf water potential, net photosynthesis rate (Pn), stomatal conductance (Gs), transpiration rate (Tr), and maximum quantum yield in PSII (Fv/Fm) under MD and SD significantly decreased when compared with WW, with a more pronounced decrease observed on upper FBs. Additionally, the maximum sucrose and hexose levels in LSCBs increased under drought conditions, whereas the maximum starch content decreased on FB10–11, but showed a varied trend on FB2–3 and FB6–7. Although carbohydrate levels in the LSCBs increased, biomass per cotton boll decreased. More importantly, the ratio of cotton boll biomass was significantly correlated to the maximum sucrose content ratio on each FB, indicating that sucrose allocation was important to cotton boll biomass. Cotton boll biomass notably decreased on upper FBs, but was maintained on lower FBs, indicating that drought promoted carbon allocation in older bolls. Thus, LSCBs and cotton bolls on upper FBs were more affected under drought conditions due to decreased photosynthesis and carbohydrate allocation.  相似文献   

16.
W. K. Heneen  K. Brismar   《Plant Breeding》2001,120(4):325-329
Most oilseed rape, Brassica napus, cultivars are black‐seeded. The progenitor species, Brassica rapa, has either yellow or black seeds, while known cultivars of the other progenitor species Brassica oleracea/alboglabra have black seeds. To determine which chromosomes of B. alboglabra are carriers of seed colour genes, B. rapaalboglabra monosomic addition lines were produced from a B. napus resynthesized from yellow‐seeded B. rapa and brown/black‐seeded B. alboglabra. Eight out of nine possible lines have been developed and transmission frequencies of the alien chromosomes were estimated. Three B. alboglabra chromosomes in three of these lines influenced seed colour. B. rapa plants carrying alien chromosome 1 exhibited a maternal control of seed colour and produced only brown seeds, which gave rise to plants with either yellow or brown seeds. However, B. rapa plants carrying alien chromosome 4 or another as yet unidentified alien chromosome exhibited an embryonal control of seed colour and produced a mixture of yellow and brown seeds. The yellow seeds gave rise to yellow‐seeded plants, while the brown seeds gave rise to plants that yielded a mixture of yellow and brown seeds, depending on the absence or presence, respectively, of the B. alboglabra chromosome. Consequently, both maternal and embryonal control of seed colour are expected to contribute to the black‐seeded phenotype of oilseed rape.  相似文献   

17.
Brassica napus is a most important oilseed grown worldwide with a limited genetic background, due to the short history of speciation, domestication and cultivation. To create novel germplasm for rapeseed breeding, we made interspecific crosses followed with chromosome doubling between B. rapa and B. oleracea to generate novel B. napus with favourable agronomic traits. The resynthesized (S0) hybrids were confirmed by SSR and cytogenetic analysis, and the fertility was increased from 32.7% in S0 generation to ~97.31% in S1 generation. The plant shapes of the progeny were dramatically improved compared to the diploid parents and B. napus cv. ‘Yangyou 6’, especially for the branch initiation height, branch number and pod number. The single‐plant yield was significantly improved in S1 progeny for the variations in branching sites and number. Significant improvement in plant shape and yield was observed on S2 generation compared to the local elite commercial open‐pollinated cultivar, which would be further fixed by intensive selection and pyramiding breeding. Such variation is of great value for breeding rapeseed with improved plant architecture and harvest index.  相似文献   

18.
Although strong intersubgenomic heterosis for seed production has been observed between “natural” domesticated Brassica napus (rapeseed, AACC) and a new type of rapeseed into which subgenomic components of Brassica rapa (AA) have been introgressed, the molecular genetic mechanism of this intersubgenomic heterosis is not understood. In this study, a recombinant inbred line population of new type rapeseed derived from a cross between B. napus and B. rapa, together with a population from a backcross with the parental line of B. napus, was used to identify single-locus quantitative trait locus (QTL) and interacting QTL pairs for yield and nine yield-related traits. More than half of single-locus QTLs and interacting QTL pairs detected were involved with the novel alleles induced by the introgression of B. rapa. The alleles directly from B. rapa A genome played a secondary role in contributing to intersubgenomic heterosis. Allelic and nonallelic interactions of both novel alleles generated by B. rapa introgression and the alleles directly from B. rapa A genome contributed to the intersubgenomic heterosis between “natural” domesticated rapeseed and new type rapeseed into which B. rapa had been introgressed. Six loci for fixed heterosis were identified and their possible applications are also discussed.  相似文献   

19.
Productivity and quality of crops of Brassica rapa L. in north‐western of Spain are highly affected by black rot, caused by the bacterium Xanthomonas campestris pv. campestris (Pammel) Dowson (Xcc). Several races of Xcc have been described in this area, being the race 6 the most frequent in B. rapa crops and races 1 and 4 the most frequent in B. oleracea crops. The control of the disease can be aided by the employment of resistant varieties. The aim of this work was to find sources of resistance to Xcc in a collection of open‐pollinated varieties of B. rapa from north‐western Spain. Resistance was evaluated in 191 landraces. Partial resistance to races 6, 1 and 4 and complete resistance to race 4 were identified in several landraces. Several accessions exhibited partial resistance to the three races. Sources of resistance were identified in landraces of different crops of the species (turnips, turnip greens and turnip tops). These landraces could be grown after selection for resistance or they can be donors of resistance genes in breeding programmes.  相似文献   

20.
Alfalfa (Medicago sativa L.) production is negatively affected by drought stress. This is particularly true for alfalfa grown on non‐irrigated rangelands. Thus, the development of drought‐tolerant alfalfa cultivars is of great significance. A greenhouse study was conducted to evaluate 11 alfalfa accessions including several that are adapted to rangeland conditions and two commercial accessions, for their performance under drought condition. Water supply was adjusted based on the transpiration rate of individual plants to compensate for 100, 75, 50 or 25 % of transpirational water loss. We found that RS, a naturalized alfalfa collected from the Grand River National Grassland in South Dakota, showed the best resistance to drought condition. It showed the smallest reduction in stem elongation (36 %), relative growth rate (14 %), and shoot dry mass (40 %) production under the severest drought tested in this study relative to the non‐drought treatment. While RS showed less biomass production under well‐watered conditions, it produced similar or more shoot biomass under drought conditions compared to other accessions. Associated with the drought resistance or less sensitivity to drought, RS showed greater capability to maintain root growth, shoot relative water content, and leaf chlorophyll content compared to other accessions. Different from other accessions, RS showed increasing water use efficiency (WUE) as water deficit became severe, reaching the greatest WUE among 11 accessions. Our results suggest that RS is a valuable genetic resource that can be used to elucidate physiological and molecular mechanisms that determine drought resistance in alfalfa and to develop alfalfa with improved WUE.  相似文献   

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