Acta Agronomica Sinica最新文献

Late embriogenesis abundant (LEA) protein is one of the hot topics in plant stress physiology. In this study, an RNAi expression vector harboring MsLEA3-1 gene fragment from alfalfa (Medicago sativa L.) was constructed. Two pairs of specific primers with different enzyme sites were designed based on the sequence of MsLEA3-1 (GenBank accession number EU665182). With the template of PMD-LEA plasmid constructed, positive-sense strand and antisense strand were obtained, which were separately inserted into the expression vector pART27. A hairpin structure in the RNAi vector pART-F-R was confirmed by the digestion of restriction enzymes. pART-F-R was transformed into tobacco via Agrobacterium-mediated transformation system, and 16 transgenic plants were obtained after PCR validation.

Aimengniu (hereafter AMN), cultivated by Shandong Agricultural University, is a renowned Chinese winter wheat germplasm. The purpose of this study was to dissect the genetic difference among the 7 AMN-derived types in homoeologous group 1. The translocation between chromosomes 1B and 1R was identified in the 7 AMN-derived types (AMNI to AMNVII) using molecular markers and genomic in situ hybridization (GISH). Amplified with the specific primers for 1R and 1B, the AMNI and AMNIII plants showed the presence of normal 1B chromatin, and the remaining types had both 1RS and 1BL but not 1BS and 1RL chromatin. The GISH result confirmed the replacement of 1BS by 1RS in AMNII, AMNIV, AMNV, AMNVI, and AMNVII plants; and the typical common wheat karyotype was observed in AMNI and AMNIII plants. In addition, genetic differences among the 7 AMN-derived types in homoeologous group 1 were detected using 138 polymorphic markers. Three markers, Xwmc336 and Xmag1884 on chromosome 1A and Xgwm124 on chromosome 1B, amplified specific segments of AMNV. Loci of Xwmc336 and Xmag1884 originated from the parent Neuzucht and that of Xgwm124 from the parent Aifeng 3.

Mapping consensus genomic regions for drought-tolerance is of great importance in molecular breeding of maize (Zea mays L.). This study aimed to integrate published quantitative trait loci (QTLs) relevant to drought tolerance under water stress that were identified in different experiments. Based on the high-density linkage map of IBM2 2008 Neighbors, a total of 79 Meta-QTLs (MQTLs) were screened out through the methods of “overview” and meta-analysis, of which 43 (54.4%) contained information of genes conferring drought tolerance according to bioinformatic analysis. By integrating the genetic map and the physical map of maize via Genome Brower in maize genome database (http://www.maizegdb.org/), the physical map distance of MQTLs was estimated and the function of these candidate drought tolerance-related genomic regions was analyzed based on sequence information from the maize sequence database (http://www.maizesequence.org/). The results showed that these regions contained abundant sequences of transcription factors such as MYB, bZIP and DREB, and a number of functional genes of LEA family.

Wheat (Triticum aestivum L.) lines with similar traits are often found in the National Winter Wheat Regional Trials. Molecular markers have been regarded potential tools to efficiently and accurately identify wheat lines with genetic similarity. In this study, 681 wheat cultivars and lines were assessed using 63 genome-SSR, 21 EST-SSR, and 21 AFLP-SCAR markers. These markers were classified into core primer (21 pairs), first-grade standby primer (29 pairs), and second-grade standby primer (55 pairs). The cultivars and lines tested consisted of 134 released cultivars and 547 lines evaluated in the National Winter Wheat Regional Trials from 2005 to 2009. Cultivars and lines were primarily screened with the core primers, and those with similar fingerprint on 19–21 loci were further tested with the first-grade standby primers, and only the cultivars with genetic similarity (GS) larger than 0.90 were subjected to the detection by the second-grade standby primers. The molecular evaluation was based on at least 100 loci, and cultivars (lines) with total GS larger than 0.90 were suspected to be similar genotypes. These cultivars (lines) were continuously evaluated based on main morphological characteristics and agronomic traits before final decision. The GS of most cultivars and lines tested was larger than 0.90 according to molecular data. The molecular markers used in this study are effective in bulk screening similar cultivars and lines in wheat regional trials.

The objective of this study was to construct a linkage map of sweetpotato [Ipomoea batatas (L.) Lam.] based on Chinese cultivars with higher marker density than previous maps. Cultivars Luoxushu 8 (female parent) and Zhengshu 20 (male parent) with obvious differences in starch content, yield, β-carotene content, and disease resistance were crossed to produce a segregation population with 240 F₁ individuals. Among the total 800 sequence-related amplified polymorphism (SRAP) markers, 770 and 523 markers showed polymorphism in the female and male parents, respectively. Using the “double pseudo testcross” strategy, 2 linkage maps were constructed by means of JoinMap 3.0. The linkage maps were composed of 473 markers in 81 linkage groups for Luoxushu 8 and 328 markers in 66 linkage groups for Zhengshu 20. The former map covered 5802.46 cM with an average marker interval of 10.16 cM, and latter one covered 3967.90 cM with an average of 12.02 cM. Both linkage maps may facilitate marker-assisted selection, gene localization, and gene cloning in sweetpotato.

The wheat (Triticum aestivum L.) line Tian 95HF2 shows low infection to most of current Chinese pathotypes of Puccinia triticina at seedling stage. With the objective of identifying leaf rust resistance genes in Tian 95HF2, F₁ and F₂ plants from a cross between resistant line Tian 95HF2 and susceptible line Zhengzhou 5389 were inoculated with pathotypes FHTT and PHTS in the greenhouse. The infection types were scored 15 d after inoculation and molecular markers were used for mapping the resistance genes. When inoculated with pathotype FHTT, only one resistance gene was detected. After screening 1274 primer pairs in the parents and the resistant and susceptible bulks, the resistance gene was located between a sequence tag site for Lr1 (WR003) and a simple sequence repeat locus Xwmc443 on chromosome arm 5DL. The genetic distances to WR003 and Xwmc443 were 2.9 cM and 3.1 cM, respectively. This resistance gene was likely to be Lr1. The segregation of infection type showed that there were 2 resistance genes in Tian 95HF2. One was inferred as Lr1, and the other was likely to be LrZH84, which is located on chromosome 1BL.

The enhancement of resistances to aflatoxin contamination and bacterial wilt is one of the major objectives in peanut (Arachis hypogaea L.) breeding for high oil content. In this study, 117 recombinant inbred lines (RILs) were developed through crossing peanut varieties Yuanza 9102 and Zhonghua 5. Genetic analysis revealed that aflatoxin resistance was controlled by 2 major genes plus additive polygenes and seed oil content controlled by 2 suppressive major genes plus additive polygenes. The RILs showed transgressive segregations in aflatoxin and oil content compared to their parents. Eighteen high oil content lines with resistance to aflatoxin contamination or bacterial wilt were selected from the RILs population. Among them, line J091 exhibited resistance to both diseases. The 18 RILs had genetic diversity based on phenotyping and molecular marker analyses.

The objective of this study was to understand the genetic basis underlying the relationship between mesocotyl elongation and plant hormone gibberellin (GA) in rice (Oryza sativa L.). Using a recombinant inbred line (RIL) population derived from a cross between 2 japonica rice cultivars, Shennong 265 (long mesocotyl) and Lijiang Xintuan Heigu (short mesocotyl), quantitative trait loci (QTLs) for mesocotyl length were detected under both water and GA germination conditions. The treatment of 1.50 μmol L⁻¹ of GA dramatically stimulated the mesocotyl elongation of rice. A total of 5 QTLs for mesocotyl length were identified on chromosomes 1, 2, 3, 6, and 11 under water and GA germination conditions, which accounted for 7–33% of the phenotypic variance, respectively. The LOD value of each QTL ranged from 3.65 to 15.52. Among the 5 QTLs, qML3, qML6, and qML11 were common in both germination conditions, whereas qML1 and qML2 were detected only under water germination condition. qML3 was usually detected in several experiments using different populations, indicating that it might be a major QTL for mesocotyl elongation of rice.

Scarcity of restorer line with high combining ability is a crucial restraint in the extension of japonica hybrid rice (Oryza sativa L.). This study aimed to screen simple sequence repeat (SSR) marker genotypes that can efficiently reveal high combining ability of hybrid parents. A total of 115 candidate markers were amplified in 6 BT-type cytoplasmic male sterile (CMS) lines and 12 restorer lines. Daily yield per plant (DYP), number of productive panicle per plant (PP), total number of spikelet per panicle (TSP), number of filled spikelet per panicle (FSP), and thousand-grain weight (TGW) were investigated in the 18 parents and 72 F₁s derived from the crosses under an NCII design. Twenty marker genotypes were significantly associated with combining abilities (CA) of the parents. Among them, 12 marker genotypes were related to CA for more than one trait simultaneously, and the remaining 8 marker genotypes were only related to CA for one trait. The effect direction of marker genotype on combining ability of multiple traits was either positive or negative. RM152-165/170 was a marker genotype with the largest combining ability of PP and DYP, which increased DYP and PP in F₁ by 20.6% and 12.7%, respectively. The marker genotypes with positive effect on increasing yield can be applied directly in the combining ability improvement of japonica rice restorer lines.

Screening indexes for drought resistance in crops is a puzzler characterized with a few samples, multiple indexes, and nonlinear. Rationality of linear regression model and indexes obtained by linear screening based on empirical risk minimization are controversal. On the contrary, support vector machine based on structural risk minimization has the advantages of nonlinear characteristics, fitting for a few samples, avoiding the over-fit, strong generalization ability, and high prediction precision. In this paper, setting the survival percentage under repeated drought condition as the target and support vector regression as the nonlinear screen tool, 6 integrated indexes including plant height, proline content, malondialdehyde content, leaf age, area of the first leaf under the central leaf and ascorbic acid were highlighted from 24 morphological and physiological indexes in 15 paddy rice cultivars. The results showed that support vector regression model with the 6 integrated indexes had a more distinct improvement in fitting and prediction precision than the linear reference models. Considering the simplicity of indexes measurement, the support vector regression model with only 6 morphological indexes including shoot dry weight, area of the second leaf under the central leaf, root shoot ratio, leaf age, leaf fresh weight, and area of the first leaf under the central leaf was also feasible. Furthermore, an explanatory system including the significance of regression model and the importance of single index was established based on support vector regression and F-test.