Acta Agronomica Sinica最新文献

Chlorophyll deficient mutants are ideal materials to study photosynthetic mechanism, pathways of chlorophyll biosynthesis and degradation, and the genes related to photosynthesis. A chlorophyll-deficient mutant of wheat (Triticum aestivum L.), Mt135, was obtained by space mutagenesis. The main agronomic traits and photosynthetic characteristics of this mutant were compared with its wild type in field experiment. The leaf color of Mt135 showed albino, striped, and green phenotypes. The albino plants with entire albino leaves died at seedling stage. The plants with green-and-white striped leaves usually matured 5–7 d later than the wild type, and had lower plant height, shorter spike length, fewer grain number, and smaller grain weight per plant and 1000-grain weight. In contrast, the green plants of the mutant had similar agronomic traits to the wild type. Preliminary genetic analysis showed that the inheritance of leaf color in Mt135 was controlled by nucleocytoplasmic interaction. When exposed to photosynthetic active radiation (PAR) at 110 μmol m⁻² s⁻¹, the green tissue of striped plant (S-G) had a similar value of maximum photosystem II quantum yield to the wide plant, but a significantly lower potential activity of photosystem II; the photochemical quenching, nonphotochemical quenching, effective quantum yield, regulated nonphotochemical energy dissipation, and nonregulated energy dissipation varied differently at seeding, elongation, and heading stages. In addition, for electron transport rate, photochemical quenching, and effective quantum yield, the differences between S-G plant and the wild plant varied under different PAR conditions. Nevertheless, the other 2 types of the mutant, white tissue of striped plant and albino plant, showed complete losses of photosynthetic function. As a result, the photosynthesis of Mt135 was greatly restricted. High photosynthetic active radiation had tremendous impact on the mutant at elongation stage and relatively weak impact at heading stage. The changes of photosynthetic function of striped plants are in accordance with the reduction of their plant height, spike length, and yield related traits.

Rice blast, caused by Magnaporthe oryzae, became more severe in Heilongjiang Province, China during the past few years. The objectives of this study were to understand the race and virulence gene compositions of local M. oryzae populations, and purposefully select blast resistance genes for efficient development and deployment of resistant rice cultivars. A total of 173 isolates, collected from different rice-cropping districts of the province in 2006, were tested for their pathogenicity against 9 Japanese and 7 Chinese differential varieties (DVs) together with 31 rice monogenic lines (MLs) with different blast resistance genes and 12 local leading cultivars. Out of these 173 isolates, 55 Japanese pathotypes were identified using the Japanese DVs, and the predominant races were 017, 077, 037, 377, and 047, which accounted for 38.15% of all isolates tested. The comparison of differential ability between Japanese and Chinese DVs testified that the former one was much more suitable for M. oryzae pathotyping in Heilongjiang Province. Among the 12 leading cultivars tested, only Longjing 14 and Longdun 104 still kept good resistance to blast disease. The resistance gene Pi9 showed the broadest resistance spectrum (on average 94.80%) to all the blast isolates tested, and was of the highest utilization value in rice blast resistance breeding. The resistance genes Pi-z5(CA), Pi-z5(R), Pi-ta2(R), Pi-ta2(P), Pi-12(t), and Pi20(t) also showed high utilization values due to their resistance spectra of around 70%. The most effective breeding strategy for blast resistance should be as follows: 1) to use rationally Longjing 14, Longdun 104, and Pi9 as resistance donors, and pyramid one to several broad-spectrum resistance genes into elite leading cultivars by means of marker-assisted selection; 2) to strengthen monitoring of predominant virulent races and their temporal and spatial variation; and 3) to explore new resistance resources extensively and transfer the new broad-spectrum resistance genes into leading cultivars purposefully.

The objective of this study was to develop new molecular markers and locate them into the existing genetic map of upland cotton (Gossypium hirsutum L.). Exon-targeted intron-exon splice junction (ET-ISJ) maker primers were designed according to the conserved sequences of intron-exon splicing junction. A total of 1280 ET-ISJ primer combinations were used to screen polymorphism between upland cotton cultivars Yumian 1 and T586. Sixty-nine primer combinations were polymorphic, which accounted for 5.4% of the total primer combinations. A mapping population of F_2:7 from Yumian 1 × T586 were tested using the 69 ET-ISJ markers, and 70 ET-ISJ loci were obtained. Linkage analysis was conducted using the 70 ET-ISJ loci as well as 523 simple sequence repeat (SSR), 59 intron-tageted intron-exon splice junction (IT-ISJ), 29 sequence-related amplified polymorphism (SRAP), and 8 morphological loci. The linkage map obtained was composed of 59 linkage groups and 673 loci including 68 ET-ISJ, 510 SSR, 58 IT-ISJ, 29 SRAP, and 8 morphological loci. This linkage map covered 3216.7 cM (72.3%) of cotton genome with an average interval of 4.8 cM between 2 adjacent markers. Sixty-eight ET-ISJ loci were located on 20 chromosomes. The present study showed that ET-ISJ markers are relatively stable, highly polymorphic, and effective in constructing genetic map of upland cotton.

The Ligon lintless-1 mutant (Li₁) mutant discovered by Griffee and Ligon in 1929 is characterized with its short lint fiber, contorted leaf laminae, and a twisted appearance of branches and stems. The Li₁ mutant has never been observed to produce homozygous phenotype Li₁ by selfing since it was introduced in China. From the cross Li₁ × XZ142 FLM, a recombinant with all distorted leaves and short lint fibers was obtained, and there was no segregation in their F₂ progeny. Thus, the mutation was homozygous of Li₁ gene, which was named as Ligon lintless recombinant (Li-R). Three fibreless mutants, XZ142FLM, MD17, and SL1-7-1, were crossed with Li-R to study the allelic relationship between the fibreless mutant genes and Li₁ gene. Segregation of the 4 F₂s derived from Li-R × XZ142FLM, Li-R × TM-1, Li-R × Hai 7124, and Li-R × Li₁ indicated that the segregation of the homozygous-dominant-surviving phenotype of Li-R fit a 2-locus inheritance model. One locus was the dominant Li₁ and another was a novel recessive locus derived from XZ142 FLM, which was named li_a. Therefore, the genotype of homozygous-dominant-surviving plant in Li-R is li_ali_aLi₁Li₁, and that of homozygous-dominant-leathal plant of Li₁ is Li_aLi_aLi₁Li₁. The genotype of XZ142 FLM is li_ali_ali₁li₁, and the genotype of the heterozygous Li₁ mutant found in 1929 is Li_aLi_aLi₁li₁. Segregation analysis of F₂-derived F₃ families from Li-R × TM-1 revealed that li_a is non-allalic to li₃ and n₂, both genes leading to fibreless seed phenotype.

Wheat (Triticum aestivum L.) line M8003-5 is selected from the hybrid progenies of the common wheat variety Chinese Spring and Secale cereale L., which exhibits not only resistance to Puccinia striiformis West. f. sp. tritici (Pst) but also high yield, early maturity, and resistance to drought. To develop molecular markers for Pst resistance gene(s) in M8003-5, a segregation population was constructed by crossing M8003-5 with a highly susceptible variety Mingxian 169. Seven prevalent Pst races in China were inoculated in greenhouse at seedling stage phenotyping individuals from the F₁, F₂, and F₃ generations. The results showed that M8003-5 was resistant to all races tested, whereas Mingxian 169 was highly susceptible to all inoculates. Genetic analysis indicated that the resistance of M8003-5 against Sun11-4 was conferred by a dominant gene, which was tentatively designated as YrM8003. This gene was linked to simple sequence repeat (SSR) markers Xbarc5, Xwmc463, Xwmc405, Xbarc126, Xgwm295, Xgwm44, Xwmc702, Xwmc438, Xwmc121, Xgwm111, and Xbarc128, which were all located on chromosome arm 7DS. The closest flanking makers were Xwmc702 and Xwmc438 with the genetic distances of 3.5 cM and 4.3 cM, respectively. Gene YrM8003 differs from any other known Pst resistance genes on 7DS, and is probably a novel gene. This gene is primarily inferred to originate from S. cereale based on analyses of pedigree and molecular markers data. Markers Xwmc702 and Xwmc438 were used to test 43 wheat cultivars from Huang-Huai Winter Wheat Region, and 20% cultivars were amplified with the target bands. These cultivars require further tests to validate the presence of YrM8003.

The sterile gene of YM-type thermo-sensitive male sterile wheat (Triticum aestivum L.) line has been mapped on chromosome arm 1BS, which was more than 10 cM distant from the adjacent molecular markers. For detecting markers with short distances to this gene, a population with 200 F₂ plants was constructed from the cross between ATM3314 and the restorer line Chinese Spring. Among 20 simple sequence repeat (SSR) markers distributing evenly on 1BS, 5 SSRs showed polymorphism between the parents and between the male sterile and fertile bulks. A 1BS partial linkage map carrying the 5 markers was obtained and QTLs for the male sterility were identified using composite interval mapping method. One major QTL and one minor QTL were detected and designated rfv1-1 and rfv1-2, respectively. QTL rfv1-1 (LOD = 8.80) was located between markers Xgwm18 and Xwmc406 with the genetic distances of 6.0 cM and 4.6 cM to the adjacent markers, respectively. On this locus, the additive and dominant effects were 23.87 and 10.44, respectively, which accounted for 23.9% of the phenotypic variation. QTL rfv1-2 (LOD = 3.10) was mapped between markers Xwmc406 and Xbarc8 with the genetic distances of 4.0 cM and 3.4 cM, respectively. This locus had additive effect of 17.59 and dominant effect of 5.99, and explained 7.8% of the phenotypic variation. These results are propitious for fine mapping and positional cloning of this male sterile gene.

Cadmium is a nonessential heavy metal that is extremely toxic to plants and animals. Previous studies have shown that several proteins associated with the Activity of the bc1 complex (ABC1) family participate in plant response to cadmium. An ABC1-like gene, ZmABC1-10, was cloned from maize (Zea mays L.). The full-length of cDNA was 2519 bp, which contained an open reading frame of 2250 bp encoding a membrane-binding protein with a predicted localization in the chloroplast. A promoter scan detected numerous cis-elements implicated in abiotic stress, light, and phytohormone responses. Expression profile analysis indicated most expression of this gene occurred in green tissues. Cadmium treatment revealed that expression of this gene could be induced and was correlated with plant development. In addition to cadmium, ZmABC1-10 expression was also affected by a broad range of abiotic factors, such as abscisic acid, H₂O₂, drought, and darkness. A total of 19 members of maize ABC1 family were identified with the B73 maize genomic sequence. Phylogenetic analysis using 148 ABC1 proteins from 8 representative species of plant kingdom revealed that divergence occurred and species-specific expansion contributed to the evolution of this family in plants. Collectively, ZmAbc1-10 is suggested to be a cadmium-responsive factor and may play potential roles in plant adaption to diverse abiotic stresses.

A forward cDNA-SSH library was constructed from a drought-tolerant cotton (Gossypium hirsutum L.) inbred line, Handan 177, to understand the expressions of drought-induced genes. Using suppression subtractive hybridization method, a total of 2300 positive clones were obtained, of which 300 clones were selected for PCR validation and sequencing. Among these clones, 284 were available sequences. According to clustering analysis of the expressed sequence tag (EST), 202 uniESTs were found, including 28 contigs and 174 singlets. The result of BlastN showed that 156 uniESTs had homologous sequences in GenBank database. The result of BlastX indicated that 116 uniESTs had high homology with proteins with known functions, and 40 uniESTs showed high similarities with unknown proteins or putative proteins. Thirty-three uniESTs were located into 55 KEGG pathways using KOBAS software, including 23 pathways at a significant level (P < 0.05). These significant pathways were mainly related to pyruvate metabolism (15%) and glyoxylate and dicarboxylate metabolism (12%). A large group of drought-induced genes were detected in the cDNA library, which were involved in signal transduction, energy metabolism, protein metabolism, nucleic acid metabolism, photosynthesis, and transmembrane transport. Some of them were associated with drought tolerance, such as malate synthase genes (MS1, 0001_C12 and MS2, 0002_F01), malate dehydrogenase genes (Md1, 001_C12 and Md2, 002_F01), NAC type transcription factor (001_C08), BZR1/BES1 (003_G04), zinc finger protein gene (zfp, 003_C06), and translationally controlled tumor protein gene (tctp, 002_C04).

For disclosing the effects of seed priming with water and polyethylene glycol (PEG) on physiological characteristics in rice (Oryza sativa L.), the seeds of 4 rice cultivars were treated with H₂O and different concentrations of PEG before germination. Primed or nonprimed (control) seeds were then germinated under drought stress conditions simulated with PEG in a serious of concentrations. The contents of proline, soluble protein (SP), total soluble sugar (SS), malonicdialdehyde (MDA), and the activities of phenylalanine ammonia lyase (PAL), superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD) in the seeds or seedlings after 10-day stress were tested, and the indices for seed germination and seedling characteristics were determined. In seeds with priming treatments, the contents of proline and SP were significantly higher than those in the corresponding controls, and the contents of SS and MDA were significantly lower than those in the controls. Seed priming accelerated the process of glucose metabolism, enhanced the activities of PAL, SOD, CAT, and POD in the stressed seeds of all cultivars. Compared to hydro-priming, priming with PEG in a proper concentration had a better effect on seed germination and seedling growth under drought stress, and the optimal priming concentrations of PEG were 20% for Gangyou 527 (indica hybrid rice) and 10%–15% for Nongken 57 (conventional japonica rice). Even higher concentrations of PEG had negative effects on seed germination. Moderate priming intensity improved metabolism of rice seed, germination indices, seedling quality, and drought tolerance of seedlings under drought stress for all cultivars. However, such effects had limited capability, and severe drought stress inhibited germination and caused damages of rice seedlings. Rice cultivars had significant impact on priming effect, and indica rice showed better performance than japonica rice.

Based on molecular marker data from 112 microsatellites, the genetic structure of 97 maize inbred lines was analyzed using distance-based and model-based clustering methods. The dendrograms produced by both methods showed similar categories but the model-based dendrogram sorted the uncertain lines in the distance-based cluster tree, which provided reasonable explanation of the category. The analysis of genetic structure and model-based cluster showed that the 97 inbred lines were classified into 4 subpopulations, which were known as Reid, Lüda Red Cob (LRC), PB, and Sipingtou (SPT). Many inbred lines in a subpopulation contained certain genetic component from other subpopulations. According to Nei's genetic distance, the Reid subpopulation was the closet to the LRC subpopulation and the farthest to the SPT subpopulation. For simplifying the heterotic groups, the subpopulations Reid and LRC could be integrated into one group, or even Reid, LRC, and PB could be integrated into one group.