Improvement of Rice Resistance to Sheath Blight by Pyramiding QTLs Conditioning Disease Resistance and Tiller Angle

Rice resistance to sheath blight （SB） is controlled by polygenes or quantitative trait loci （QTLs） and affected by plant morphological traits, qSB-9^TQ and TAG1^TQ, which control SB resistance and tiller angle （TA）, respectively, were employed to test whether the combination of the two genes will further improve rice SB resistance and reduce yield loss rather than only one of them or neither. Using two pairs of near isogenic lines （NILs）, TAC1^TQ was confirmed to contribute to SB resistance. However, its effect was less considerable than that of qSB-9^TQ. Subsequently, the two genes were introduced into two commercial rice varieties to develop a series of NILs. The NILs carrying both TAG1^TQ and qSB-9^TQ showed more resistance than the NILs containing only one of them. Comparing the grain yield per plant （GYP） under the three different SB disease conditions, namely slight, moderate and severe conditions, NILs carrying both genes apparently lost lower GYP than the NILs without the two genes and the NILs carrying only TAC1^TQ. Under slight disease condition, no significant differences were found on morphology, development and GYP associated traits except for TA between the NILs carrying both genes and either of them, indicating that the two genes have no inferior effect on rice agronomic traits. Results indicated that mAC1^TQ and qSB-9^TQ have high breeding potential, and pyramiding SB resistance QTL and morphological trait QTL is a potential approach in improving rice SB resistance.     

水稻耐金属离子胁迫的QTL分析

【目的】 本研究旨在筛选与水稻苗期耐不同金属离子连锁的分子遗传标记,为探讨水稻耐不同金属离子胁迫的遗传研究提供参考。【方法】 以典型籼粳交(春江06/台中本地1号)双单倍体(DH)群体为材料,系统考查该群体及其双亲耐4种金属离子(Fe²⁺、Cd²⁺、Al³⁺、Na⁺)胁迫的情况,利用业已构建并完善的该群体加密的分子连锁图谱,对耐这4种金属离子胁迫的QTL进行检测分析。另外,利用实时定量PCR技术检测处理前后相关基因的表达变化情况。【结果】 发现耐各种金属离子胁迫的QTL共8个,分别位于水稻第1、2、4、6、9、10和11染色体上,其中Fe²⁺处理后检测到的QTL贡献率最大,达到24.47%(阈值为7.78),位于第1染色体上RM1297–RM1061,同时对该区间与耐胁迫相关基因的表达分析发现这些基因在处理前和处理后表达水平存在不同程度的差异;Cd²⁺处理后检测到1个QTL,位于第1染色体上;Al³⁺处理后检测到QTL共5个,分别位于第2、4、6、10、11染色体上;Na⁺处理后检测到QTL有1个,位于第9染色体上。【结论】 根据不同金属离子胁迫处理后DH群体的表型差异进行QTL分析,发现耐各种金属离子胁迫的QTL共8个,并初步定位于各染色体的遗传标记区间,这为精细定位并克隆相应QTL,进而探明水稻耐金属离子胁迫QTL的分子调控机制奠定了基础。     

Genotypic variation in rice varieties screened for deep rooting under field conditions in West Africa

In this study, to identify deep rooting accessions, we assessed the differences in root depth based on the length of the longest primary root among 586 different rice accessions: 511 Oryza sativa and 75 O. glaberrima. Malagkit Pirurutong and Binicol were identified as the two rice accessions with deepest roots through four field experiments conducted at two different locations in West Africa. For these two accessions, root depths reached 35.6 and 41.4 cm, respectively, in the first experiment at Bamako; on the other hand, their depths only reached 22.6 and 18.6 cm, respectively, in the second and third experiments at Ibadan, leading to inconsistent genotypic ranking based on root depth between the two locations. However, Malagkit Pirurutong was identified as deep rooting in both locations; in addition, it showed deep rooting in the fourth experiment in a 20-mm irrigation treatment, even when compared with the deep rooting reference Azucena. Nonetheless, this pattern was not found under a 10-mm irrigation treatment. Malagkit Pirurutong kept developing deep roots even following 60 days after sowing (DAS), whereas other shallower rooting accessions ceased deepening by 60 DAS. The longer period for deepening roots would be beneficial for terminal drought stress.     

利用分子育种技术改良水稻稻瘟病抗性

为选育具有稻瘟病持久抗性的水稻新品系提供可利用资源,1993 年以小粒野生稻为外源DNA供体,采用花粉管通道法,将其稻瘟病抗性导入栽培稻24D中。经过4 年连续6 代的选择,成功地将小粒野生稻稻瘟病抗性转移到栽培稻中,获得了9 份苗叶瘟和穗颈瘟均得到改良的抗性材料。因此,利用分子育种技术改良水稻抗病性是可行的。     

利用QTL-Seq定位粳稻整精米率QTL

[目的]稻米整精米率是加工品质的重要评价指标之一,其QTL定位将为提升稻米品质提供理论依据.[方法]通过两个粒型相近、整精米率差异极大的粳稻材料构建的F2分离群体为材料,利用QTL-Seq方法对分离群体中的高整精米率单株和低整精米率单株进行混池重测序以定位粳稻整精米率QTL位点.[结果]经过QTL-Seq分析发现在第8...     

Mapping of QTLs for Germination Characteristics under Non-stress and Drought Stress in Rice

Identification of genetic factors controlling traits associated with seed germination under drought stress conditions, leads to identification and development of drought tolerant varieties. Present study by using a population of F2：, derived from a cross between a drought tolerant variety, Gharib （indica） and a drought sensitive variety, Sepidroud （indica）, is to identify and compare QTLs associated with germination traits under drought stress and non-stress conditions. Through QTL analysis, using composite interval mapping, regarding traits such as germination rate （GR）, germination percentage （GP）, radicle length （RL）, plumule length （PL）, coleorhiza length （COL） and coleoptile length （CL）, totally 13 QTLs were detected under pole drought stress （-8 MPa poly ethylene glycol 6000） and 9 QTLs under non-stress conditions. Of the QTLs identified under non-stress conditions, QTLs associated with COL （qCOL-5） and GR （qGR-1） explained 21.28% and 19.73% of the total phenotypic variations, respectively Under drought stress conditions, QTLs associated with COL （qCOL-3） and PL （qPL-5） explained 18.34% and 18.22% of the total phenotypic variations, respectively. A few drought-tolerance-related QTLs identified in previous studies are near the QTLs detected in this study, and several QTLs in this study are novel alleles. The major QTLs like qGR-1, qGP-4, qRL-12 and qCL-4 identified in both conditions for traits GR, GP, RL and CL, respectively, should be considered as the important and stable trait-controlling QTLs in rice seed germination. Those major or minor QTLs could be used to significantly improve drought tolerance by marker-assisted selection in rice.     

水稻苗期抗旱性的QTL分析

利用251个株系组成的Maybelle/白叶秋的加倍单倍体群体,构建了由226个SSR分子标记组成的遗传图谱。通过两年抗旱棚苗期抗旱性鉴定,应用复合区间作图法和QTLNetwork2.0对水稻苗期抗旱性进行QTL定位及互作效应分析。利用前者在两年共检测到5个抗旱性相关QTL,分别位于第2、3、5、6和8染色体;而通过后者在第2、3、5和6染色体上也找到了抗旱性相关的QTL,并且通过两种方法检测到的第3、5、6染色体上的3个QTL所在区间吻合;还发现4个具有上位性的QTL。所有抗旱性QTL的加性效应均为正值,表明来自父本白叶秋的这些抗旱性位点可以提高水稻的抗旱性。     

Improvement of Upland Rice Variety by Pyramiding Drought Tolerance QTL with Two Major Blast Resistance Genes for Sustainable Rice Production

Varalu is an early maturing rice variety widely grown in the rainfed ecosystem preferred for its grain type and cooking quality. However, the yield of Varalu is substantially low since it is being affected by reproductive drought stress along with the blast disease. The genetic improvement of Varalu was done by introgressing a major yield QTL, qDTY_12.1, along with two major blast resistance genes i.e. Pi54 and Pi1 through marker-assisted backcross breeding. Both traits were transferred till BC₂ generation and intercrossing was followed to pyramid the two traits. Stringent foreground selection was carried out using linked markers as well as peak markers (RM28099, RM28130, RM511 and RM28163) for the targeted QTL (qDTY_12.1), RM206 for Pi54 and RM224 for Pi1. Extensive background selection was done using genome-wide SSR markers. Six best lines (MSM-36, MSM-49, MSM-53, MSM-57, MSM-60 and MSM-63) having qDTY_12.1 and two blast resistance genes in homozygous condition with recurrent parent genome of 95.0%-96.5% having minimal linkage drag of about 0.1 to 0.7 Mb were identified. These lines showed yield advantage under drought stress as well as irrigated conditions. MSM-36 showed better performance in the national coordinated trials conducted across India, which indicated that improved lines of Varalu expected to replace Varalu and may have an important role in sustaining rice production. The present study demonstrated the successful marker-assisted pyramiding strategy for introgression of genes/QTLs conferring biotic stress resistance and yield under abiotic stress in rice.     

水稻抗白叶枯病微效QTL的定位分析

以不携有抗白叶枯病主效基因的中感籼粳双亲(窄叶青8号和京系17）及其花培DH群体为材料,接种白叶枯病菌浙9612后,考察了该DH群体的白叶枯病抗性,并进行了数量性状座位（QTL）分析。共检测到控制白叶枯病的4个QTL,分别位于第3、4、5和6染色体上,其中第3和第4染色体上的qBBR-3和qBBR-4,其加性效应为正值;而位于第5和第6染色体上的为负值,4个QTL的总效应是38.6%。方差分析和差异显著性比较表明,具有4个QTL抗性等位基因水稻株系的白叶枯病抗性与不含QTL抗性等位基因的株系相比,差异达极显著水平（P<0.01)。说明通过微效基因的聚合可以获得对白叶枯病的一定抗性。     

水稻胚芽鞘长度与抗旱性的关系及QTL定位

对由水稻品种珍汕97B和旱稻品种IRAT109构建的重组自交系195个株系的胚芽鞘长度及抗旱系数的研究表明,水分胁迫下水稻重组自交系群体的胚芽鞘长度与抗旱系数的相关系数为0.2206**。应用由213个SSR标记构建的遗传连锁图对控制胚芽鞘长度和抗旱系数的QTL进行了定位。检测到胚芽鞘长度和抗旱系数的主效QTL各为13个和5个,单个QTL对表型的贡献率为2.28%～22.65%;在第9染色体上两者的QTL出现在相同的分子标记区间（RM160-RM215）。检测到胚芽鞘长度和抗旱系数的互作位点分别为17对和3对,影响胚芽鞘长度的互作位点联合贡献率为5835%;影响抗旱系数的互作位点联合贡献率为11.93%。控制胚芽鞘长度和抗旱系数的QTL分别与其他研究中控制根系性状（深根干质量、根深、根长、根数等）的QTL位于相同的标记区间。     

直播稻生产概况与品种选育策略

近年,直播稻面积在我国迅速扩大。本文结合国内外直播稻生产概况,指出了直播稻在抗倒伏、出苗率、耐冷性、防治杂草以及生育期等方面存在的问题,提出了培育“生育期适中、抗倒伏、耐低温、耐低氧萌发”的适合直播的水稻新品种选育策略。     

水稻抗恶苗病微效QTL的定位

对粳稻品种春江06和籼稻品种TN1以及由它们构建的加倍单倍体（DH）群体,采用芽期接菌方法接种恶苗病菌,进行抗恶苗病微效QTL的定位分析。共检测到2个QTL:qB1和qB10,分别位于第1和第10染色体上,2个QTL的抗性基因都来自春江06,贡献率相近。     

江苏省水稻新品种（系）对稻瘟病的抗性评价

对1996～2000年的335份江苏省水稻新品种（系）进行了抗稻瘟病性的分析,江苏省新品种（系）中常规中籼和杂交籼稻对江苏省稻瘟病菌有很好的抗性,对参试菌株的全抗率分别为76.6％和85.1％,中粳稻和单季晚粳稻对江苏省稻瘟病菌的抗性相对较差,全抗率为18.2％和32.1％。感病的籼稻品种对参试的稻瘟病菌代表菌株中的1个菌株感病频率较高,对2个或2个以上的菌株同时感病的频率很低,而感病的中粳稻和单季晚粳稻品种同时对参试的稻瘟病菌代表菌株3个或3个以上的菌株表现感病频率较高,并表现出感病谱的多样性。从参试的品种对江苏省稻瘟病菌感病分布情况来看,中G1小种对大多数品种保持了比较稳定的侵染率。     

水稻穗型的遗传和育种改良

 穗型是与水稻株型和产量密切相关的重要农艺性状,大穗型理想株型的创新已经成为今后水稻超高产育种的重要内容。简要介绍了水稻穗型的“穗直立程度、单穗粒数、单穗重和着粒密度”等六大类和19个亚类的分类;至少200多种水稻穗型突变体被创制、1386个水稻穗部QTL（涉及穗长、穗数、穗重、粒宽、每穗粒数、每穗结实率等多个性状）被定位,Dep1、Ghd7、Gn1a、Ipa1和GW2等16个穗型QTL已被成功克隆;综合评述了直立穗型、大穗型、重穗型和后期功能型的四个水稻穗型育种改良方向,及利用新克隆的穗型基因进行Gn1/sd1或Gn1/DEP1双基因聚合的分子育种策略。穗型研究的不断深入,将为今后大穗型的理想株型水稻、直立大穗型超级稻的高产分子育种提供更多的方法与思路。     

Crop Technology Introduction in Semiarid West Africa: Performance and Future Strategy

SUMMARY

The periodic food crises in agricultural production in semiarid sub-Saharan Africa have been the main public view of the subcontinent since the media perpetuates a Gloom and Doom perception. Actually the agricultural systems of sub-Saharan Africa have made some impressive achievements and there is potential to make more impact even in the more difficult regions where the poor are concentrated. In this paper the focus is on the successes, a strategy for introduction of new technologies in semiarid regions of West Africa, and supportive policy. More rapid technological change, with supportive policy, would have a substantial effect on rural poverty.     

Mapping QTLs for Drought Tolerance at Seedling Stage in Rice Using Doubled Haploid Population

QTLs for drought tolerance at the rice seedling stage were analyzed using a doubled haploid (DH) population consisted of 251 lines from the cross between a japonica parent Maybelle and an indica parent Baiyeqiu. A genetic linkage map with 226 SSR marker loci was constructed. Single-locus analysis following composite interval mapping (CIM) detected a total of five QTLs located on five different chromosomes of rice. Four QTLs were also detected following two-locus analysis, resolving two pairs of epistatic QT...     

利用重测序的水稻染色体片段代换系群体定位剑叶形态QTL

 剑叶形态性状（剑叶长、剑叶宽和剑叶面积）是水稻理想株型育种的重要目标性状之一。发掘新的控制水稻剑叶形态性状的基因资源,准确鉴定和定位水稻剑叶形态性状QTL,对开展水稻剑叶形态性状分子生物学研究和理想株型分子育种都具有重要意义。 以通过高通量测序而准确获知代换片段位置及长度的一套用籼稻品种9311为受体、粳稻品种日本晴为供体构建的,包括128个染色体片段代换系群体为材料,对剑叶形态性状及其与主穗颖花之间的相关性进行分析,结果表明剑叶面积与剑叶长、宽呈极显著正相关,主穗颖花数与剑叶长、剑叶面积呈极显著正相关。利用多元回归分析方法,结合Bin map,共鉴定出与水稻剑叶长、宽和面积相关的QTL分别为4、4和6个,贡献率介于4.08%~60.40%。上述QTL的准确定位,为进一步精细定位及克隆相应QTL以及开展水稻剑叶形态性状分子育种奠定了基础。     

氮、磷节约高产型水稻品种筛选

为筛选氮、磷节约高产型水稻品种,以正常施肥条件下的F优498和宜香2115作为对照,选取贵州省水稻研究所近年来选育的12个杂交籼稻新品种(组合)为材料,设置不同减氮处理和减磷处理,比较这些新品种(组合)在减肥条件下的产量和肥料利用率。结果表明,成优981、成优33、汕优108、D44/QR35、成优489等5个品种(组合)在减氮45 kg/hm^2的条件下较正常施氮的对照品种平均增产3.97%,属节氮高产型品种;汕优108和D44/QR35在减磷37.5 kg/hm^2的条件下较正常施磷的对照品种平均增产3.20%,属节磷高产型品种。节肥高产型水稻品种具有较多的每穗粒数和更大的群体颖花量。     

北方粳稻新品种培育与发展

北方粳稻生产直接影响我国粳米市场稳定,承载着国家粮食安全和社会稳定的历史重任。种子是粮食生产的基础,粮食丰收则需要优质的种子。近几十年来,北方粳稻新品种培育极大促进了北方粳稻生产的快速发展。新形势下,北方粳稻新品种培育应采用“高产与优质并重、轻简高效广适高抗相结合、常规育种和生物育种相结合、商业化育种与公益性育种并重”的策略,把优质的北方粳稻种子牢牢攥在自己手里,筑牢国家粮食安全之基。     

Association and Heritability Studies for Drought Resistance under Varied Moisture Stress Regimes in Backcross Inbred Population of RiceAssociation and Heritability Studies for Drought Resistance under Varied Moisture Stress Regimes in Backcross Inbred Population of Rice

Drought stress is one of the major constraints affecting rice production and yield stability in the rainfed regions. To understand the physiological basis of drought resistance related component traits, we used a backcross inbred population of rice under three kinds of moisture regimes viz., non-stress, moderate （24.48%） and severe stress （73.97%） conditions which reflect the differential responses of the genotypes to varying stress intensities. The plot yield, 1000-grain weight, panicle exsertion and canopy air temperature difference exhibited high heritability under the control conditions, whereas spikelet sterility and single plant yield exhibited high heritability under the moderate stress conditions. Traits such as days to 50% flowering, plant height and osmotic potential showed high heritability under the severe stress conditions. Plot yield under stress was significantly and positively correlated with harvest index and 1000-grain weight, but negatively associated with leaf rolling score and days to 50% flowering. The drought susceptibility index and drought response index were negatively correlated between each other both under the moderate and severe stress conditions. The derived traits viz., difference in panicle length between the control and the severe stress was associated with osmotic adjustment measured under field conditions. Difference in plant height and panicle length was negatively associated with plot yield under stress.