高粱[Sorghum bicolor(L.)Moench.]叶面积校正值(K 值)的初步研究

通过对两个高粱品种叶面积校正值(K 值)的初步研究,提出了在高粱叶面积测算中采用叶面积校正值K=0.72的建议,并对K 值在应用中的可靠性进行了分析。

Effect of Planting Date on Yield and Yield Components of Grain Sorghum Hybrids

In Kansas, productivity of grain sorghum [Sorghum bicolor (L.) Moench] is affected by weather conditions at planting and during pollination. Planting date management and selection of hybrid maturity group can help to avoid severe environmental stresses during these sensitive stages. The hypothesis of the study was that late May planting improves grain sorghum yield and yield components compared with late June planting. The objectives of this research were to investigate the influence of planting dates yield and yield components of different grain sorghum hybrids, and to determine the optimal planting date and hybrid combination for maximum biomass and grains production. Three sorghum hybrids (early, medium, and late maturing) were planted in late May and late June without irrigation in Kansas at Manhattan/Ashland Bottom Research Station, and Hutchinson in 2010;and at Manhattan/North Farm and Hutchinson in 2011. Data on dry matter production, yield and yield components were collected. Grain yield and yield components were influenced by planting date depending on environmental conditions. At Manhattan (2010), greater grain yield, number of heads per plant, were obtained with late-June planting compared with late May planting, while at Hutchinson (2010) greater yield was obtained with late May planting for all hybrids. The yield component most affected at Hutchinson was the number of kernels∙panicle−1 and plant density. Late-May planting was favorable for late maturing hybrid (P84G62) in all locations. However, the yield of early maturing hybrid (DKS 28-05) and medium maturing hybrid (DKS 37-07) was less affected by delayed planting. The effects of planting dates on yield and yield components of grain sorghum hybrids were found to be variable among hybrid maturity groups and locations.

Characterization of subunits encoded by Sn RK1 and dissection of combinations among these subunits in sorghum(Sorghum bicolor L.)

Sucrose nonfermenting-related protein kinase 1(SnRK1)is one of the critical serine/threonine protein kinases.It commonly mediates plant growth and development,cross-talks with metabolism processes and physiological responses to biotic or abiotic stresses.It plays a key role in distributing carbohydrates and sugar signal transporting.In the present study,eight SnRK1 coding genes were identified in sorghum(Sorghum bicolor L.)via sequences alignment,with three forαsubunits(SnRK1α1 to SnRK1α3),three forβ(SnRK1β1 to SnRK1β3),and one for bothγ(SnRK1γ)andβγ(SnRK1βγ).These eight corresponding genes located on five chromosomes(Chr)of Chr1–3,Chr7,and Chr9 and presented collinearities to SnRK1s from maize and rice,exhibiting highly conserved domains within the same subunits from the three kinds of cereals.Expression results via qRT-PCR showed that different coding genes of SnRK1s in sorghum possessed similar expression patterns except for SnRK1α3 with a low expression level in grains and SnRK1β2 with a relatively high expression level in inflorescences.Results of subcellular localization in sorghum leaf protoplast showed that SnRK1α1/α2/α3/γmainly located on organelles,while the rest four of SnRK1β1/β2/β3/βγlocated on both membranes and some organelles.Besides,three combinations were discovered among eight SnRK1 subunits in sorghum through yeast two hybrid,includingα1-β2-βγ,α2-β3-γ,andα3-β3-γ.These results provide informative references for the following functional dissection of SnRK1 subunits in sorghum.

Regulations on Planting Techniques of Harmless Feeding Sorghum bicolor(L.) Moench in Hebei

According to many years of experimental summary, regulations on planting technique of harmless feeding Sorghum bicolor （L.） Moenchwere studied from the application scope, basic demands of planting, preparation be fore seeding, demands of seeding, field management, clipping and harvesting, transportation, storage, ledger management and other technical requirements, and specific measures and technical indicators of the technical regulations were analyzed, so as to provide normalized, standardized, industrial and marketization technical support for the planting of harmless feeding S. bicolor （L.） Moench.

高粱黄色籽粒基因Yellow Seed 2的定位及候选基因分析

高粱在我国农业结构调整和酿酒行业中具有重要的作用。籽粒颜色是高粱重要的性状之一,但有关高粱籽粒颜色的研究并不多。本研究观察了高粱黄色籽粒材料GLB41的籽粒发育过程,花后1~16 d为快速生长期,17~24 d进入缓慢膨大期,第25天开始进入转色期,绿色逐渐褪去,籽粒颜色由乳白色或苍白色逐渐变成浅黄色,随后颜色加深,40 d后籽粒颜色变为深黄色。利用黄色籽粒GLB41和白色籽粒6E16两个材料构建的群体,使用重测序BSA方法,将控制黄色籽粒性状的基因初定位在1号染色体15.6 Mb区间内,利用3215株分离个体将该基因定位在BR13和P2两个标记之间,区间内有7个候选基因,对这些基因的功能注释进行分析并测序,结果表明GLB41、6E16两个材料中未被报道过的基因Yellow Seed 2(Sobic.001G397900)的编码区内第619~621位插入CTG 3个碱基,导致增加了1个Leu(亮氨酸),第819位C突变为G,导致Cys(半胱氨酸)突变为Trp(色氨酸);第912位C突变为T,但氨基酸序列无变化。因此推测Yellow Seed 2可能参与这两份亲本材料籽粒颜色的形成。本研究为高粱籽粒颜色性状的研究提供了新的基因。

Genome-wide identification,expression and functional analysis of sugar transporters in sorghum(Sorghum bicolor L.)

Sugar transporters are essential for osmotic process regulation,various signaling pathways and plant growth and development.Currently,few studies are available on the function of sugar transporters in sorghum(Sorghum bicolor L.).In this study,we performed a genome-wide survey of sugar transporters in sorghum.In total,98 sorghum sugar transporters(SSTs)were identified via BLASTP.These SSTs were classified into three families based on the phylogenetic and conserved domain analysis,including six sucrose transporters(SUTs),23 sugars will eventually be exported transporters(SWEETs),and 69 monosaccharide transporters(MSTs).The sorghum MSTs were further divided into seven subfamilies,including 24 STPs,23 PLTs,two VGTs,four INTs,three p Glc T/SBG1 s,five TMTs,and eight ERDs.Chromosomal localization of the SST genes showed that they were randomly distributed on 10 chromosomes,and substantial clustering was evident on the specific chromosomes.Twenty-seven SST genes from the families of SWEET,ERD,STP,and PLT were found to cluster in eight tandem repeat event regions.In total,22 SSTs comprising 11 paralogous pairs and accounting for 22.4%of all the genes were located on the duplicated blocks.The different subfamilies of SST proteins possessed the same conserved domain,but there were some differences in features of the motif and transmembrane helices(TMH).The publicly-accessible RNA-sequencing data and real-time PCR revealed that the SST genes exhibited distinctive tissue specific patterns.Functional studies showed that seven SSTs were mainly located on the cell membrane and membrane organelles,and 14 of the SSTs could transport different types of monosaccharides in yeast.These findings will help us to further elucidate their roles in the sorghum sugar transport and sugar signaling pathways.

Genetic Diversity in the Environmental Conditioning of Two Sorghum (<i>Sorghum bicolor</i>L.) Hybrids

Sorghum metabolism continually adapts to environmental temperature as thermal patterns modulate diurnally and seasonally. The degree of adaptation to any given temperature may be difficult to determine from phenotypic responses of the plants. The present study was designed to see if the efficiency of quantum yield of photosystem II could be used as a measure of how well leaf tissue metabolism was able to withstand a prolonged respiratory demand caused by elevated temperatures. The efficiency of quantum yield values of Pioneer 84G62 and Northrup King KS585 commercial sorghum hybrids showed that when the hybrids were grown in a 28&deg;C/20&deg;C day/night cycle in the greenhouse or the field, Pioneer hybrid 84G62 withstood subsequent elevated thermal challenges better than Northrup King KS585. The same hybrids grown in a 39&deg;C/32&deg;C day/night cycle showed similar efficiency of quantum yield values when thermally challenged. Water-deficit stress increased the heat resistance of the tissue raising the efficiency of quantum yield of both lines to the same level. Upon recovery from the water deficit stress the differential efficiency of quantum yield values between the two lines re-appeared. The data provided in this study suggest a metabolic advantage of Pioneer 84G62 to environmental thermal challenges compared with the Northrup King KS585.

PCR Amplification，Cloning and Sequencing of RbcL Coding Region in Mesophyll Cell and Bundle Sheath Cell of Sorghum（Sorghum bicolor L．）

The Primacy question addressed in our study is: Is the difterntial expression of rbcL gene in mesophyll cells and in bundle sheath cells related to the sequence of the gene per se?An enzymatic approach was fist established to separate the two groups of cells. Microscopic examination revealed satisfactory separation effect: minimal mutual contamination was found so that no mistake might be introduced into biochemical or molecular biological expeitments using such preparations. CpDNA were isolated from mesophyll cells and from bundle sheath cells and coding region of rbcL gene was obtained from each by PCR ampilfication.Cloning and sequencing were then done on them.Compartive analysis , however, revealed identical sequence, with a length of 1,368 bp, encoding 456 amino acids. Since sequences of the non-coding regions of rbcL gene in masephyll sad bundle sheath have not been obtained, it can not yet be concluded that the differential expression is not related to the sequence itself. Nevertheless,It sesems justifiable to infer that whatever difference there may be between the sequences of rbcL gene in two groups of cells can only be found in the non-coding regions(including promoter and the 3' down stream region).

Transcriptomic profiling of sorghum leaves and roots responsive to drought stress at the seedling stage

Drought stress affects the growth and productivity of crop plants including sorghum.To study the molecular basis of drought tolerance in sorghum,we conducted the transcriptomic profiling of sorghum leaves and roots under drought stress using RNA-Seq method.A total of 510,559,and 3 687 differentially expressed genes(DEGs)in leaves,3 368,5 093,and 4 635 DEGs in roots responding to mild drought,severe drought,and re-watering treatments were identified,respectively.Among them,190 common DEGs in leaves and 1 644 common DEGs in roots were responsive to mild drought,severe drought,and re-watering environment.Gene Ontology(GO)enrichment analysis revealed that the GO categories related to drought tolerance include terms related to response to stimulus especially response to water deprivation,abscisic acid stimulus,and reactive oxygen species.The major transcription factor genes responsive to drought stress include heat stress transcription factor(HSF),ethylene-responsive transcription factor(ERF),Petunia NAM,Arabidopsis ATAF1/2 and CUC2(NAC),WRKY transcription factor(WRKY),homeodomain leucine zipper transcription factor(HD-ZIP),basic helix-loop-helix transcription factor(bHLH),and V-myb myeloblastosis viral oncogene homolog transcription facotr(MYB).Functional protein genes for heat shock protein(HSPs),late-embryogenesis-abundant protein(LEAs),chaperones,aquaporins,and expansins might play important roles in sorghum drought tolerance.Moreover,the genomic regions enriched with HSP,expansin,and aquaporin genes responsive to drought stress could be used as powerful targets for improvement of drought tolerance in sorghum and other cereals.Overall,our results provide a genome-wide analysis of DEGs in sorghum leaves and roots under mild drought,severe drought,and re-watering environments.This study contributes to a better understanding of the molecular basis of drought tolerance of sorghum and can be useful for crop improvement.

Pseudogamous Apomixis in Maize and Sorghum in Diploid-Tetraploid Crosses

Apomictic seed development is a complex process including formation of unreduced embryo sac,parthenogenetic embryo development from the egg cell,and endosperm formation either autonomously,or due to fertilization of polar nuclei by the sperm(under pseudogamous form of apomixis).In the latter case,an obstacle to the normal endosperm development is disturbance of maternal(m)-to-paternal(p)genomic ratio 2m:1p that occurs in the cases of pollination of unreduced embryo sac with haploid sperms.Usage of tetraploid pollinators can overcome this problem because in such crosses maternal-to-paternal genomic ratio is 4m:2p that provides formation of kernels with plump endosperm.Using tetraploid lines as pollen parents we observed formation of plump kernels on the ears and panicles of diploid maize and sorghum accessions.These kernels had hybrid endosperm and diploid maternal-type embryo or hybrid embryo with different ploidy level(2n,3n,4n).The frequencies of plump kernels on the ear ranged from 0.2-0.3%to 5.7-6.2%counting from the number of ovaries.Maternal-type plants were found in two maize lines,their frequency varying from 10.7 to 37.5%of the progeny plants.In CMS-lines of sorghum pollinated with tetraploid sorghum accessions,the frequency of plump kernels ranged from 0.6 to 14.0%counting from the number of ovaries;the frequency of maternal-type plants varied from 33.0 up to 96.1%.The hybrid nature of endosperm of the kernels that gave rise to maternal-type plants has been proved by marker gene expression and by SDS-electrophoresis of endosperm proteins.These data testify to variable modes of seed formation under diploid×tetraploid crosses in maize and sorghum both by amphi-and by apomixis.Therefore,usage of tetraploid pollinators might be a promising approach for isolation of apomixis in maize and sorghum accessions.

Effect of drought stress on male fertility restoration in A3 CMS-inducing cytoplasm of sorghum

Use of cytoplasmic male sterility (CMS) in hybrid breeding requires effective male fertility-restoring lines. In sorghum, very few restoring lines that can restore fertility in A_3 CMS have been reported. To identify the reasons for this deficiency, F_1 and F_2 hybrids of an A_3 CMS line crossed with the line IS1112C, a donor of fertility-restoring (Rf) genes for A_3 cytoplasm, and testcrosses of fertile plants to A_3CMS lines were grown under contrasting water availability regimes in dryland and irrigated field plots. In the irrigated plots the frequency of fertile plants in testcrosses was twice that in dryland plots (P < 0.05). Fertile plants from the F_2 family grown in the irrigated plots showed significantly higher restoration ability than fertile plants from the same family grown in dryland plots. F_3 plants from the F_2 family grown in irrigated plots yielded on average a sixfold higherfrequency of fertile plants in testcrosses than F_3 plants derived from dryland plots (P < 0.01).Fertility of testcross hybrids correlated negatively with air vapor pressure deficit (VPD) at flowering (r = - 0.96; P < 0.01) suggesting that VPD is a trigger for downregulation of Rf genes for A_3 cytoplasm.

Apomictic symptoms in the aspect of embryology in a sorghum line 296B

The presence of facultative apomixis In line 296B was proved by the embryologicalstudy.The twin embryosacs were observed at florescence.The autonomous development of em-bryo was confirmed by multiple cell proembryo existing with undeveloped polar nuclei In one embryosac.Cell structure and size of apomictic proembryo were different from sexual proembryo.The structural feature of proembryo can be used to distinguish apomictic proembryo with devel-oped endosperm from sexual embryo.The apomictic development in this line is attributed toaposporous type.The frequency of apomixis Is at least 16—21%.The apomictic characters andthe potential for fixing heterosis in line 296B was dlscussed in the present paper.

Cytological Investigation of Pollen Development in Sorghum Line with Male Sterility Induced by Sodium Ascorbate in Tissue Culture

Investigation of male sterility mutations is an effective approach for identification of genes involved in anther and pollen development. The comparison of “cytological phenotypes” of newly induced mutants with phenotypes determined by already known genes favors elucidation of genetic control of diverse microsporo- and gametogenesis stages. In this paper, we describe pollen development in the grain sorghum line Zh10-asc1 with mutation of male sterility. This line was obtained from callus culture treated by sodium ascorbate. A wide spectrum of abnormalities in microsporogenesis have been found, such as cytomixis, chromosomal laggards, chromosome disjunction, adhesion of chromosomes, disturbed cytokinesis, and others. In tapetum, the cells with one nucleus, with unequal nuclei, and with micronuclei have been observed. During pollen grain (PG) maturation abnormalities in starch accumulation and delay of development often took place. In mature anthers, a variety of pollen grain types have been revealed: fertile, of irregular shape, incompletely filled with starch, PGs delayed at the uni-nucleate or bi-nucleate gametophyte stages, with partially or fully degenerated contents, and with abnormal coloration. Variation in spectrum and the frequency of disturbances between the flowers of one and the same plant have been revealed. The reasons for significant genetic and epigenetic instability are discussed.

Dynamic and adaptive membrane lipid remodeling in leaves of sorghum under salt stress

Salt stress limits plant growth and development.In this study,changes in membrane lipids were investigated in leaves of sorghum seedlings subjected to salt stress(150 mmol L^(-1)NaCl).Galactolipids(DGDG and MGDG)accounted for more than 65%of the total glycerolipids in sorghum leaves.The predominance of C36 molecular species in MGDG suggested that sorghum is an 18:3 plant.Under Na Cl treatment,the content of major phospholipids(PC and PE)increased,accompanied by the activation of their metabolism pathways at the transcriptional level.In contrast,the proportion of MGDG and PG dropped drastically,leading to a decreased ratio of plastidic to non-plastidic lipids.An adjustment of glycerolipid pathway between the cytosolic and plastidic compartments was triggered by salt stress,as reflected by the increased conversion of PC to PA,providing precursors for galactolipid synthesis.The elevated DGDG resulted in increased DGDG/MGDG and bilayer/non-bilayer lipid ratios.The double-bond index of PC,PE,and DGDG increased markedly,evidently owing to the increased expression of FAD3 and FAD8.These findings will be helpful for understanding dynamic membrane lipid changes and adaptive lipid remodeling in sorghum response to salt stress.

Productivity and Water-Use Efficiency of Sorghum in Rainfed Regime in the Semi-Arid Region of Brazil

Sorghum has become ever more prominent on the global energy scene, with studies in the area becoming extremely important. Agricultural production in the semi-arid region of the Brazilian Northeast is intrinsically dependent on rainfall in the region. However, on both inter- and intra-annual scales, the rainfall regime is quite irregular. The aim of this study was to evaluate the productivity of sorghum grown under a rainfed regime, and the water-use efficiency of crops in the semi-arid region of the northeast of Brazil. The work was carried out in the city of Tabuleiro do Norte in the semi-arid region of the State of Ceará. Mean productivity of the sorghum was 919.42 kg&middot;ha-1, with maximum values being recorded for lot 02 (1032 kg&middot;ha-1), lot 03 (1102 kg&middot;ha-1), lot 04 (2143 kg&middot;ha-1) and lot 12 (1367 kg&middot;ha-1). The greatest value for water-use efficiency, 1.13 m3&middot;kg-1, was found for lot 04, while the smallest value, 4.83 m3&middot;kg-1 was seen in lot 02. It was found that the low productivity of sorghum in a rainfed regime shows that the lack of success in production systems in semi-arid regions is not due to the total amount of rainfall, but rather the spatial and temporal distribution of the rains, as well as the occurrence of hot, dry spells. Furthermore, it can be seen that the best ratio of grain production to water demand shows a strong correlation with the distribution of water throughout the cycle, and not only with the total volume.

Binary Vector Construction for Site-Directed Mutagenesis of <i>Kafirin</i>Genes in Sorghum

Sorghum (Sorghum bicolor (L.) Moench) is one of the world’s leading cereal crops in agricultural production, which has a special importance in the arid regions. However, unlike other cereals, sorghum grain has a lower nutritional value, which is caused, inter alia, by the resistance of its seed storage proteins (kafirins) to protease digestion. One of the effective approaches to improve the nutritional value of sorghum grain is to obtain mutants with partially or completely suppressed synthesis or altered amino acid composition of kafirins. The employment of genome editing may allow to solve this problem by introducing mutations into the nucleotide sequences of the α- and γ-kafirin genes. In this study, genomic target motifs (23 bp sequences) were selected for the introduction of mutations into the α- and γ-KAFIRIN genes of sorghum. The design of the gRNAs was conducted using the online tools CRISPROR and CHOPCHOP. Two most suitable targets were chosen for α-KAFIRIN (k1C5) and two for γ-KAFIRIN (gKAF1) genes. The insertion of respective sequences in the generic vector pSH121 was performed at the BsaI (Eco31I) sites. Validation of the cloning procedure was performed by DNA sequencing. Subcloning of the resulting constructs was performed using the SfiI restriction sites into the compatible binary vector B479p7oUZm-LH. The correct assembly of binary vectors was confirmed by restriction analysis using the MluI and SfiI cleavage sites. The four vectors created (1C - 4C) were transferred by electroporation into the Agrobacterium tumefaciens strain AGL0. Currently, this vector series is used for stable transformation of sorghum using immature embryo explants.

基于AFLP和SSR标记的高粱分子遗传连锁图构建

以茎秆糖份含量高的高粱自交系1095和低糖高粱自交系N3杂交获得的F2分离群体(205个个体)为材料,采用AFLP(amplified fragment length polymorphism)和SSR(simple sequence repeat)两种分子标记,构建了包含273个(232AFLP,41SSR)标记,覆盖基因组长度为978.1cM的高粱分子标记连锁遗传图。以SSR标记为锚标记,19个连锁群中,18个连锁群各自被归并于高粱的10个连锁群(A-J)中。该连锁图平均图距和最大图距分别为3.6cM和19.4cM,未出现大的空隙(gap>25cM),归并后的10个连锁群(A-J)分别对应于高粱染色体SBI-01、SBI-02、SBI-03、SBI-04、SBI-07、SBI-09、SBI-10、SBI-08、SBI-06、SBI-05。

高粱两步法厌氧发酵产己酸研究

研究以富含淀粉的高粱为原料,通过两步法厌氧发酵提高己酸生成效率,即第一步分别接种己酸复合菌液、接种嗜酸乳杆菌TYCA06、添加酿酒酵母制得丁酸发酵液、乳酸发酵液、乙醇发酵液,第二步将丁酸发酵液、乳酸发酵液、乙醇发酵液等3种发酵液混合,并接种己酸复合菌液,厌氧发酵制得己酸。研究发现:通过优化丁酸发酵液、乳酸发酵液、乙醇发酵液的发酵工艺,丁酸发酵液中的丁酸、乙酸产量达到20.16 g/L和8.47 g/L,淀粉转化率达到76.02%;乳酸发酵液中的乳酸产量和乳酸产率分别达到11.41 g/L和42.48%;乙醇发酵液中的乙醇产率可达95.06%。继续优化己酸发酵工艺,发现当乙醇发酵液和乳酸发酵液同时作为电子供体时,己酸产量和产率均显著提升,分别达到4.15 g/L和75.2 mg/g,且当乙醇发酵液和乳酸发酵液中乙醇与乳酸添加的质量浓度比为2∶1时,己酸产量和产率均达到最高,分别为6.65 g/L和99.78 mg/g。对己酸发酵过程中微生物与己酸的相关性分析发现,发酵过程中和己酸含量呈正相关的微生物有产己酸菌属(Caproiciproducens)、Clostridium_sensu_stricto_12、Pseudoclavibacter。其中Caproiciproducens随着发酵进行不断富集,到发酵后期相对丰度达到37.81%,是己酸形成的主要贡献者。希望研究可为无外源电子供体添加条件下,实现高粱两步法厌氧发酵生产己酸提供理论基础,为拓展高粱的资源化利用提供思路。

高粱不同器官生长对NaCl胁迫的响应及其耐盐阈值

用砂基培养研究高粱不同器官生长对NaCl胁迫的响应及其耐盐阈值。NaCl胁迫下，独角虎和糖高粱均表现为生长叶叶鞘鲜重下降最大，其次是生长叶叶片、成熟叶叶鞘和叶片变化最小。长期胁迫单株叶片数及叶面积也明显下降。相同胁迫情况下，糖高梁的生长抑制明显大于独角虎。独角虎和糖高粱耐盐阈值分别为135和82mmol／LNaCI。以上结果表明独角虎耐盐能力明显大于糖高粱。讨论了不同器官生长抑制的机制。

高粱苯丙氨酸解氨酶(SbPAL)编码蛋白的生物信息学分析

高粱是世界上一种重要的粮食作物,具有耐寒耐高温等优良性质,挖掘高粱抗病基因(如PAL),在基因水平上进行遗传改良,提高高粱对贫瘠土地的耐受性仍是研究热点之一。以高粱的苯丙氨酸解氨酶基因(SbPAL)为研究对象,运用生物信息学方法对其编码蛋白的结构、理化性质及功能结构域进行分析,以期揭示苯丙解氨酶的基本信息。结果表明,高粱SbPAL基因的编码序列(Coding sequences,CDS)全长为2 145 bp,编码714个氨基酸;高粱SbPAL蛋白主要位于细胞基质中,二级结构以无规则卷曲和α-螺旋为主,三级结构预测其为同源四聚体结构,由4个相同亚基对称性组成,各亚基之间由配体DTT共价连接。多序列比对结果表明,高粱SbPAL蛋白与拟南芥、水稻、葡萄、烟草等蛋白的同源性较高,为83.31%,SbPAL基因与玉米、水稻和大麦有着较近的亲缘关系,PAL在这些作物中主要参与木质素和植保素的合成。此分析结果将为后续进一步研究SbPAL对木质素、植保素等合成的分子机制与抗病性关系奠定一定的理论基础。