Development and characterization of chromosome segment substitution lines derived from backcross between japonica donor rice cultivar Yukihikari and japonica recipient cultivar Kirara397

Grain yield-related traits and grain quality-related traits are important for rice cultivars. The quantitative trait loci (QTLs) involved in controlling the natural variation in these traits among closely related cultivars are still unclear. The present study describes the development of a novel chromosome segment substitution line (CSSL) population derived from a cross between the temperate japonica cultivars Yukihikari and Kirara397, which are grown in Hokkaido, the northernmost limit for rice cultivation. Days to heading, culm length, panicle length, panicle number, brown grain weight per plant, thousand brown grain weight, brown grain length, brown grain width, brown grain thickness, apparent amylose content, and protein content were evaluated. Panicle length, brown grain length and amylose content differed significantly in the parental cultivars. Thirty-five significant changes in the evaluated traits were identified in the CSSLs. A total of 28 QTLs were located on chromosomes 1, 2, 3, 4, 5, 6, 8, 9, 10, 11 and 12. These findings could be useful for breeding rice cultivars in the northernmost limit for rice cultivation.     

Linkage analysis of rice bacterial blight resistance gene xa20 in XM6, a mutant line from IR24

Bacterial blight caused by Xanthomonas oryzae pv. oryzae (Xoo) is an important disease constraining rice (Oryza sativa L.) production worldwide. The XM6 line was induced by N-methyl-N-nitrosourea from IR24, an Indica cultivar that is susceptible to Philippine and Japanese Xoo races. XM6 was confirmed to carry a recessive gene named xa20, resistant to six Philippine and five Japanese Xoo races. The chromosomal gene location was found using 10 plants with the shortest lesion length in an F₂ population consisting of 298 plants from a susceptible Japonica variety Koshihikari × XM6. Analysis using PCR-based DNA markers covering the whole rice genome indicated the gene as located on the distal region of the long arm of chromosome 3. The IKC3 line carries IR24 genetic background with Koshihikari fragment on chromosome 3 where a resistance gene was thought to be located. The F₂ population from IKC3 × XM6 clearly showed a bimodal distribution separating resistant and susceptible plants. Further linkage analysis conducted using this F₂ population revealed that xa20 is located within the 0.8 cM region flanked by DNA markers KIC3-33.88 (33.0 Mb) and KIC3-34.06 (33.2 Mb). This study yields important findings for resistance breeding and for the genetic mechanism of Xoo resistance.     

Trisomic genetic analysis of aroma in three Japanese native rice varieties (Oryza sativa L.)

Information on the genetics of aroma in rice facilitates breeding and selection of new aromatic varieties with high yield and good quality. Objective of the present study was to make clear the number of genes controlling aroma, and the allelism of aroma genes and the location of aroma gene(s) on the chromosome in three Japanese native aromatic rice varieties (Kabashiko, Shiroikichi and Henroyori). Lack of leaf aroma in all F₁ plants of non-aromatic/aromatic crosses indicated the recessive nature of aroma, and the segregation ratios (3:1) of non-aromatic to aromatic plants in its F₂ populations from Nipponbare/aromatic varieties crosses revealed that each of the three aromatic varieties contains a single recessive gene for aroma. Through trisomic analysis, the segregation of non-aromatic and aromatic plants in all F₂ populations from the crosses between trisomics lines NT8, with an extra chromosome 8, and aromatic varieties deviated significantly from disomic segregation of 3:1 ratios, and fitted to trisomic segregation, however, in other F₂ populations derived from other 7 types of trisomic F₁ plants, the segregation ratios of non-aromatic to aromatic were 3:1, indicating that the single recessive aroma gene was located on chromosome 8 in three aromatic varieties. This revised version was published online in July 2006 with corrections to the Cover Date.     

Genetic analysis of ion-beam induced extremely late heading mutants in rice

Two extremely late heading mutants were induced by ion beam irradiation in rice cultivar ‘Taichung 65’: KGM26 and KGM27. The F₂ populations from the cross between the two mutants and Taichung 65 showed clear 3 early: 1 late segregation, suggesting control of late heading by a recessive gene. The genes identified in KGM26 and KGM27 were respectively designated as FLT1 and FLT2. The two genes were mapped using the crosses between the two mutants and an Indica cultivar ‘Kasalath’. FLT1 was located on the distal end of the short arm of chromosome 8. FLT2 was located around the centromere of chromosome 9. FLT1 might share the same locus as EHD3 because their chromosomal location is overlapping. FLT2 is inferred to be a new gene because no gene with a comparable effect to that of this gene was mapped near the centromere of chromosome 9. In crosses with Kasalath, homozygotes of late heading mutant genes showed a large variation of days to heading, suggesting that other genes affected late heading mutant genes.     

Association between AFLP-based genetic distance and hybrid performance in tropical maize

Identifying the best inbred combinations for the development of commercial hybrid maize varieties remains the main challenge to maize breeders. The aim of this work was to study associations between the genetic distance (GD) of 21 inbreds and the corresponding F₁ phenotypic data. Furthermore, the impact of grouping lines into genetically similar clusters was investigated. The 21 inbred lines were fingerprinted using amplified fragment length polymorphism markers. Parents and 210 F₁ progeny were evaluated in the field. Joint data analysis mostly revealed a tighter association between GD and the F₁ performance or mid parent heterosis in the intergroup than in the intragroup crosses. Despite these correlations, intergoup crosses should always be field‐tested before their release. Crosses showing low GD values should be discarded to avoid field‐testing costs. Better F₁ hybrid performance predictions can be achieved by integrating molecular and F₁ phenotypic data.     

Inheritance of high palmitic acid content in the sunflower mutant CAS-12 and its relationship with high oleic content

CAS‐12 is a sunflower mutant with increased levels of palmitic (C16: 0 = 30%) and oleic (C18: 1 = 55%) acids in its seed oil, hence it has a reduced linoleic acid content (C18: 2 < 5%). This study was conducted to determine the inheritance of high C16: 0 content and its relationship with high C18: 1 content in CAS‐12. Reciprocal crosses involving CAS‐12, CAS‐5 (high C16: 0 content), HAOL‐9 (high C18: 1 content) and HA‐89 (standard fatty acid profile) were made. The F₁, F₂ and BC₁F₁ generations were obtained. The genetic control of the high C16: 0 trait in CAS‐12 was partially recessive and gametophytic. In all cases, this character segregated in the ratio 19: 38: 7 (low: intermediate: high C16: 0 content) in the F₂ generation. These results, together with the lack of segregation for C16: 0 content in crosses between CAS‐12 and CAS‐5, indicated that the genetic control of the high C16: 0 trait in CAS‐12 was similar to that in CAS‐5 in being controlled by partially recessive alleles (p1, p2, and p3) at three loci. Crosses between HA‐89 and CAS‐12, and HAOL‐9 and CAS‐5 (segregating for C16: 0 and C18: 1) demonstrated that the high C16: 0 and the high C18: 1 traits were independently inherited. However, C18: 1 segregation in these crosses exhibited reversal of dominance. Apparently, the low C18: 1 parental lines carried modifier genes causing the deviation.     

Characterization and fine mapping of <Emphasis Type="Italic">qPE12</Emphasis>, a new locus controlling rice panicle exsertion

Panicle exsertion is an important agronomic trait involved in pollination and hybrid rice seed production. The identification of genes controlling panicle exsertion will play a central role in hybrid rice breeding. C115, a chromosome segment substitution line carrying introgression segments of Nipponbare in genetic background of indica variety 9311, had significantly shortened panicle exsertion, uppermost internode length and plant height. Genetic analysis in F₂ and F₃ populations derived from a cross of C115 and 9311 indicated that the shortened panicle exsertion of C115 was recessive and controlled by a single Medelian factor, and the allele from Nipponbare decreased the phenotypic value. Primary mapping suggested qPE12, the Nipponbare introgression segment locating on the long arm of chromosome 12, was responsible for this phenotypic variation. Based on map-based cloning strategy, fine mapping was carried out with a total of 1130 recessive individuals selected from F₂ and F₃ populations, delimiting qPE12 to a 190-kb region. This result provides important information for isolation of a new gene controlling panicle exsertion in the future.     

Inheritance of resistance to race F of broomrape in sunflower lines of different origins

A new race F of broomrape overcomes all known resistance genes in cultivated sunflower, but recently, sources of resistance against race F have been developed. The objective of the present research was to study the inheritance of resistance to race F in crosses between 12 resistant sunflower breeding lines, derived from three different sources of resistance, and the susceptible male‐sterile line P‐21. Parental lines and F₁, F₂, F₃ and BC₁ generations were evaluated for broomrape resistance. Segregations in the F₂ and BC₁ to resistant parent approached resistant to susceptible ratios of 1: 15 and 1: 3, respectively, in most of the crosses, suggesting a double dominant epistasis. However, segregations of 3: 13 and 1: 1 for F₂ and BC₁, respectively, indicating a dominant‐recessive epistasis, were also found. The F₃ data confirmed these results. Owing to the recessive nature of this resistance, it must be incorporated into both parental lines for developing resistant hybrid cultivars.     

水稻黄绿叶突变体ygl209的遗传分析与目标基因精细定位

水稻叶色突变体是研究高等植物光合作用、叶绿体发育和叶绿素代谢的重要材料。从水稻转基因育种材料中国91与镇稻88的BC4F3后代中分离到稳定遗传的粳型黄绿叶突变体ygl209,与野生型亲本镇稻88相比,突变体ygl209在苗期、分蘖期及抽穗期叶片中叶绿素a、叶绿素b和类胡萝卜素含量均显著降低,其中叶绿素b降幅最大;其他农艺性状中抽穗期、株高、有效穗数、主茎穗总粒数、结实率和千粒重无显著变化。遗传分析表明,ygl209的黄绿叶突变性状由1对核隐性基因控制。应用(ygl209/9311)F2、F3分离群体,将ygl209的叶色突变基因定位于第1染色体着丝粒附近571.6 kb的染色体区段内。对区段内与叶绿体发育有关的基因LOC_Os01g31110序列测定,ygl209突变体中LOC_Os01g31110基因的编码区1390位(位于第5外显子)上碱基由C转换成G,使编码蛋白序列由丙氨酸(Ala)变成了甘氨酸(Gly),推测LOC_Os01g31110即为ygl209的候选基因。     

Linkage relationships of some genes for disease and insect resistance and semidwarf stature in rice

Summary Two-way classification of 400 F₃ families from the rice cross IR2153-159-1 x Babawee for plant stature and for resistance to brown planthopper, green leafhopper, and bacterial blight indicated that Glh 3 (dominant gene for resistance to green leafhopper) and bph 4 (recessive gene for resistance to brown planthopper) are linked with a map distance of 34 units. The bph 4 gene also appears to be linked with sd ₁ (recessive gene for semidwarf stature) although the linkage is less strong. However, bph 4 and Xa 4 (dominant gene for bacterial blight resistance) are inherited independently of each other. No segregation for susceptibility was observed among F₃ families of crosses between varieties having Bph 3 and bph 4 genes for resistance to brown planthopper. Apparently, Bph 3 and bph 4 are either allelic or closely linked.     

A dominant gene in rice for resistance to white-backed planthopper and its relationship to other plant characteristics

Summary The inheritance of resistance to white-backed planthopper, Sogatella furcifera Horvath, was investigated in a rice, Oryza sativa L., cultivar N22. Resistance to the white-backed planthopper in the cross IR30×N22 appears to be governed by a single dominant gene-designated Wbph. The classification for various characteristics of 397 F₃ families of the IR30×N22 cross confirmed earlier results about the monogenic dominant control of resistance to brown planthopper, green leafhopper, and bacterial leaf blight, and about the monogenic recessive control of short stature. Additionally, the genes governing plant height and resistance to white-backed planthopper, brown planthopper, green leafhopper, and bacterial leaf blight were found to segregate independently of each other in these 397 F₃ families.     

Inheritance of Resistance to Yellow Mosaic Virus in some Vigna Species

Inheritance of resistance to Yellow Mosaic Virus (YMV) was studied in crosses of mungbean, black-gram and their interspecific crosses with Vigna sub-lobata. Resistance to YMV was recessive in the three Vigna species. The segregation ratios in F₂ and back crosses indicated that the resistance was digenic recessive in the crosses of mungbean and in interspecific crosses of mungbean with blackgram and Vigna subiobata but YMV resistance was monogenic recessive in blackgram crosses.     

Derivation of superior F5 lines from heterotic hybrids in pea

Summary F₅ seeds from six highly heterotic F₁ hybrids were produced to determine whether the superior performance of F1 hyrids could be fixed in pure-line derivatives of pea (Pisum sativum L.). For each cross, 24–31 F₅ lines derived from single seed descent were compared with F₁ hybrids and their parents in two environments. The F₁ hybrids out-yielded the best parent by up to 11%. All crosses produced F₅ lines which were as high in yield as the F₁ hybrids indicating that pure-line derivatives equivalent in yield to the heterotic F₁ hybrid could be developed by conventional breeding. Heterosis of the F₁ hybrids over the best commercial cultivar was thus a useful indicator of the future performance of the pure-line derivatives. These results indicate that overdominance was not an important component of heterosis in peas.     

Heterosis in crisphead lettuce (Lactuca sativa L.) hybrids

Summary Six of 16 F₁ hybrids from diverse crosses of crisphead lettuce with butterhead, cos or other crispheads significantly outyielded their respective better parent. Four were crosses between crisphead and cos parents, one was a butterhead × crisphead cross and one, a winter crisphead × winter crisphead cross. This latter hybrid plus one other also proved heterotic in a subsequent trial of ten crosses involving five winter crisphead parents, with yield excesses over better parent of 16 and 19%. It appeared significant that the heterotic crosses were given by parents of dissimilar origin. Trials of F₂ segregants from one of these heterotic hybrids enabled predictions to be made for 10.2 to 24.1% yield increases over better parent by the retention and clonal multiplication of the 10% highest yielding selections. Heterosis demonstrated in these trials may constitute the first reported cases in lettuce.     

Mapping and validation of QTLs for rice sheath blight resistance

Sheath blight, caused by Rhizoctonia solani, is one of the most serious diseases of rice. Among 33 rice accessions, mainly from National Institute of Agrobiological Sciences (NIAS) Core Collection, we found three landraces from the Himalayas—Jarjan, Nepal 555 and Nepal 8—with resistance to sheath blight in 3 years’ field testing. Backcrossed inbred lines (BILs) derived from a cross between Jarjan and the leading Japanese cultivar Koshihikari were used in QTL analyses. Since later-heading lines show fewer lesions, we used only earlier-heading BILs to avoid association with heading date. We detected eight QTLs; the Jarjan allele of three of these increased resistance. Only one QTL, on chromosome 9 (between markers Nag08KK18184 and Nag08KK18871), was detected in all 3 years. Chromosome segment substitution lines (CSSLs) carrying it showed resistance in field tests. Thirty F₂ lines derived from a cross between Koshihikari and one CSSL supported the QTL.     

水稻斑马叶突变体zebra1349的表型鉴定及基因精细定位

从恢复系育种材料[R128//(R318/R1025)F1]F6中获得一个新的斑马叶突变体zebra1349,突变体秧苗期如果不移栽,与野生型一样表现绿色,移栽后5 d新抽出的叶片包括叶鞘会呈现出与叶脉垂直的黄绿相间的条纹,移栽后30 d抽出的叶片又表现正常绿色,成熟期主要农艺性状与野生型无明显差异。与野生型相比,突变体六叶期斑马叶黄区部位的总叶绿素、叶绿素a、叶绿素b和类胡萝卜素的含量分别下降了55.86%、61.02%、39.34%和47.03%。透射电镜(TEM)观察表明,突变体斑马叶绿区部位叶绿体发育正常;黄区部位叶肉细胞中叶绿体结构异常,类囊体膜退化和分解严重,类囊体基粒片层数量明显减少,片层间距拉大,排列疏松。对zebra1349与正常叶色品种杂交F1、F2代的遗传分析表明该性状受1对隐性核基因调控。利用1192株zebra1349/02428 F2隐性定位群体,最终把ZEBRA1349基因定位在水稻第12染色体In Del标记indel39和indel44之间,其遗传距离分别为0.04 c M和0.17 c M,根据日本晴基因组序列推测,两标记之间的物理距离约为89 kb。本研究为ZEBRA1349基因的图位克隆和功能研究以及分子标记辅助育种奠定了基础。     

Monosomic analysis of Helminthosporium leaf blight resistance genes in wheat

A set of 21 monosomic (2n ‐ 1) and the disomic (2n) lines of the ‘Chinese Spring’ cultivar were crossed with ‘Chirya‐3′, the CIMMYT synthetic wheat line which has been identified as highly resistant for Helminthosporium leaf blight disease (HLB), in order to locate the genes governing disease resistance. The F₁ and segregating populations were challenged and screened against the most virulent pure mono‐conidial HLB isolate KL‐8 (Karnal, India). The F₁ progenies of the crosses were found to be susceptible because of the recessive nature of resistance. The F₂ progeny of the control cross (‘Chinese Spring’בChirya‐3’), segregated in the ratio of 1: 15 (resistant: susceptible), indicating that resistance to HLB was controlled by a pair of recessive genes. While the F₂ progeny of 19 monosomic crosses segregated in the ratio of 1: 15 (resistant: susceptible), the progeny of the remaining two crosses, 7B and 7D, deviated significantly from the ratio, revealing that 7B and 7D were the critical chromosomes for resistance genes that were located one on each chromosome. Moreover, the critical lines, 7B and 7D, confirmed the digenic complementary recessive nature of gene action by fitting well with the overall pooled F₂ segregation ratio of 13: 51 (resistant: susceptible) as expected for digenic complementary recessive resistance. The F₃ segregation ratios of the critical crosses, based on their pooled F₂ analysis, was estimated as 19: 32: 13 (non‐segregating susceptible: segregating as susceptible and resistant: non‐segregating resistant). F₃ progenies when tested with these ratios showed goodness‐of‐fit, confirming that the two pairs of recessive resistance genes were located on chromosomes 7B and 7D.     

Semi-lethality in hybrid offspring of wheat

Summary Seven of the wheat crosses which were performed in 1954 and 1955 produced a uniform semi-lethal F₁. Among these were four combinations with the spring wheat Koga and two with the Turkish winter wheat Eskischir. The degree of withering in the F₁ appeared to be dependent on the variety with which Koga or Eskischir were combined. In the F₂ of the Koga crosses carried out in 1954 a 9 : 7 ratio of semi-lethals and normal plants was found. The almost continuous gradation in semi-lethality within the group of semi-lethal plants of every F₂ was conspicuous.The facts are explained as follows: Two complementary genes determine the semi-lethality as such, while modifying genes are responsible for the different degrees of semi-lethality of the different F₁'s and for the variation in degree of semi-lethality within every F₂. In the discussion this explanation is given in detail.It is pointed out that it is perhaps possible, with the aid of the phenomenon of semi-lethality, to discover or confirm relationships between species and/or varieties.Finally it is suggested that the rejection of F₁'s with withering symptoms is premature.     

Component analysis of duration from seeding to heading in rice by the basic vegetative phase and the photoperiod-sensitive phase

Summary Inheritance of the duration from seeding to heading in rice was analyzed by dividing the vegetative growth period into the basic vegetative phase (b.v.p.) and the photoperiod-sensitive phase (p.s.p.). Concurrent determination of the two physiologic phases on pure lines and hybrids was facilitated by testing vegetative tillers of the same plant under two photoperiods.In nine crosses of photoperiod-sensitive by insensitive arieties where the parents differed appreciably in b.v.p. estimates obtained under a 10-hour photoperiod, two to three Ef genes of relatively discrete effect controlled the F₂ variation in b.v.p. Short b.v.p. was controlled by dominant genes of cumulative but unequal effect. In three other sensitive × insensitive crosses where the parents differed less in b.v.p., the F₂ segregation could be ascribed to two to four pairs of metrical alleles with equal or unequal effect.Concurrent data obtained from sensitive × insensitive crosses grown under a 16-hour photoperiod indicate the action of one or two (duplicate) dominant Se genes in controlling strong sensitivity to a long photoperiod. One insensitive variety appeared to carry a recessive inhibitor, i-Se. The Se gene(s) is epistatic to the Ef genes in the expression of earliness under a short photoperiod. Pooled data also suggest an association between photoperiod sensitivity and a short b.v.p. in a large proportion of F₂ plants.Field data on the two principal components of the vegetative growth period obtained under natural daylength generally indicated agreement with duplicate plantings grown under controlled photoperiods. Segregation for the optimum photoperiod and critical photoperiod under a changing photoperiod in the field plantings probably resulted in modified expression of the Se and Ef genes.Research supported in part by grant GB-2417 from the U.S. National Science Foundation.     

Use of radiations for breaking hybrid necrosis in wheat

Summary This report deals with a method of precluding hybrid necrosis lethality in wheat crosses by treatment of F₁ hybrid seeds with gamma rays from ⁶⁰Co source. Two crosses i.e. C306 × Kalyan 227 and C306 × U.S.A. 190 showing severe necrosis were treated with 15 kr and 20 kr doses and plants having mutated chimeras at tiller level and at leaf level were obtained, setting adequate seed for growing F₂ generation. The merits of the method have been discussed.