A new gene located on chromosome 2 causing hybrid sterility in a remote cross of rice

‘Ketan Nangka’, the donor of the wide compatibility gene (WCG) showed typical hybrid sterility when crossed to a landrace, ‘Bai Mi Fen’, of Yunnan province in China. A genome‐wide analysis was performed for a backcrossed population of ‘Ketan Nangka’/‘Bai Mi Fen’//‘Ketan Nangka’ using a total of 143 simple sequence repeat markers and an expressed sequence tagged marker to cover the entire rice linkage map. As a result, two independent loci were found to cause hybrid sterility via female gamete abortion. The locus on chromosome 4 may correspond to S9, but the other, on chromosome 2, was different from all the previously reported hybrid sterility loci and was designated as S29(t) following the hybrid sterility nomenclature. On the basis of allelic interaction which causes female gamete abortion, two alleles were found: S29^kn(t) in ‘Ketan Nangka’ and S29^bi(t) in ‘Bai Mi Fen’. In the heterozygote, S29^kn(t)/S29^bi(t), which was semi‐sterile, female gametes carrying S29^bi(t) were aborted. An Aus variety from the Indian subcontinent, ‘Dular’, was found to have a neutral allele, S29ⁿ(t). Two molecular markers, RM185 and RM425, linked to S9 and S29(t), respectively, will be useful for marker‐aided transfer of WCGs in hybrid rice breeding.     

A gamete abortion locus detected by segregation distortion of isozyme locus Est-9 in wide crosses of rice (Oryza sativa L.)

Summary A locus for male gamete abortion in hybrids for Japonica and Indica rice was identified with the aid of marker genes Rc and Est-9 on chromosome 7. In an Indica-Japonica cross, AKAMAI 1/IR50, the Indica allele Est-9 ² was transmitted via the male gamete with a ratio of 0.29 instead of the normal 0.5, whereas no segregation distortion was observed for the Rc locus. The recombination value (p) for Est-9 and Rc was estimated to be 0.38 by a least square method after adjusting Mendelian segregation ratios with the male transmission ratios of 0.29 (Tr) for Est-9 ² and 0.71 (1-Tr) for Est-9 ¹. The recombination value (q) for the new locus for male gamete abortion, ga-11, and Est-9 was estimated to be 0.23 by using 56 F₃ lines from F₂ plants which were heterozygous for the Est-9 locus. No linkage for Rc and ga-11 was found. Therefore, the two markers and ga-11 were located in the order of ga-11-Est-9-Rc. Using the estimated recombination value (q), the male transmission rate (k) of ga-11 ^a was estimated to be 0.11 with the F₂ data and-0.07 with the F₃ line data. Thus, it was apparent that male gametes possessing ga-11 ^a were frequently aborted in the Indica-Japonica hybrid.     

水稻亚种间广亲和性及其酯酶同工酶特点

通过与籼粳测验种测交，考察了9个待测品种的亲和性表现。结果表明品种Dular、Aus449、0046、CPSL－17、KetanNangka、02428具有广亲和性，水源287可能具有广亲和性。比较广亲和性品种和不具有广亲和性品种的酯酶同工酶，得出所有供试广亲和品种都具有特异酶带9A，某些广亲和性品种具有酶谱的中间型特点。因此，可以将酯酶同工酶9A或中间型酶谱作为筛选广亲和性品种的一个生化指标。     

粳稻品种4502与广亲和品种间杂种F1不育性的遗传分析

利用９个籼、粳稻品种，７个广亲和品种，配制单交Ｆ１、回交及三交组合，研究了粳稻品种４５０２与广亲和品种间Ｆ１不育性的遗传。根据与品种４５０２杂交Ｆ１的亲和性，可将参试的广亲和品种分为两组，Ｉ组是４５０２亲和的品种，如Ｄｕｌａｒ和０２４２８；Ⅱ组是与４５０２不亲和的品种，如热研１号、Ｍｏｒｏｂｅｒｅｋａｎ和ＣＰＳＬＯ１７。回交和三交组合的育性分离表明，４５０２和Ⅱ组广亲和品种间杂种Ｆ１花粉不育性受单     

4个籼粳杂种的亲和性分析

Ｂｅｌｌｅｍｏｎｔ，ＣＢ－８０１，３２６４，浙湖１１４与籼，粳稻杂交亲和性比较表明：Ｂｅｌｌｅｍｏｎｔ，ＣＢ－８０１表现出广谱，偏籼型的亲和性，基中Ｂｅｌｌｅｍｏｎｔ亲和性优于ＣＢ－８０１。它们均不携带不育胞质的恢复基因，综合考虑株型，开花散粉习性，其更适宜 于转充和不育系；３２６４，浙湖１１４为窄谱，偏粳型广亲和品种，它闪对粳稻ＢＴ型不育胞质具有恢复能力，可以作为转育广亲和恢复系的基础材料。系谱     

Developing rice lines possessing neutral alleles at sterility loci to improve the width of compatibility

To improve the width of compatibility for overcoming various sterilities in inter‐subspecific hybrid rice, some elite lines combining several sterility‐neutral genes were developed and the effects on mitigating various hybrid sterilities were tested. From Akihikari// IR36/Dular, neutral genes at ga11 and six sterility loci, S5, S7, S8, S9, S15 and S16, were combined and elite lines were obtained in their successive progeny. Four of the lines tested were confirmed to combine the neutral alleles S5‐n, S7‐n, S8‐n, S9‐n, S15‐n and S16‐n at the sterility loci and, among them, two harboured an additional gamete abortion‐neutral allele, ga11‐n. F₁s, which used the lines and various testers as parents, mitigated the spikelet sterilities by six sterility loci and gamete abortion by a gametophyte gene, ga11. These lines could be selectively used as parents or donors to increase the width of compatibility of rice varieties for improving fertility in inter‐subspecific hybrid rice breeding.     

Increased regeneration from NaCl-tolerant callus in rice

Summary NaCl-tolerant calli were selected from two Japonica and two Indica rice (Oryza sativa L.) cultivars on basal media containing 6,000, 9,000, 12,000 or 15,000 ppm NaCl. Frequency of callus formation decreased with the increase of NaCl in the medium, especially in Indica. About half of the calli of Japonica cultivars selected on NaCl-ammended media survived 20,000 ppm NaCl but none of the Indica callus survived. In Japonica, more plants were regenerated from calli selected on all concentrations of NaCl media than from NaCl-free medium. Concentration of Cl^- in callus increased dramatically with increased NaCl content but peroxidase activity decreased.     

Photosynthetic ability,grain yield and an esterase band in rice genotypes

Summary Four Indica and one Japonica (Tainung 67) of rice (Oryza sativa L.) varieties had an esterase band (tentatively designated as E₁), and also had higher photosynthetic ability than other five Japonica varieties without E₁ band. The F₁ plants of Tainung 67 × Mineyutaka (low photosynthetic ability, no E₁ band) showed E₁ band and a low photosynthetic ability. Of 34 F₂ plants, 28 had E₁ band, but 6 had no E₁ band of which 5 plants showed a low photosynthetic ability. These results suggest that an esterase gene and one of the photosynthesis gene are linked, and the gene for low photosynthetic ability is dominant.Among 42 new Japonica strains and 2 control varieties bred in Taiwan, most genotypes with E₁ band showed higher grain yield potential (grain field/growth days) in local test.Esterase band may be used as a marker for high photosynthesis and grain yield ability in breeding.     

A Novel Breeding Approach in Quest of Temperature Sensitive Genic Male Sterile Lines Among Rice Intersubspecies Derivatives

Summary An investigation was made to exploit an innovative tool viz., thermosensitive genic male sterile (TGMS) system in twoline inter-subspecies rice hybrids using 132 hybrids involving four TGMS lines viz., TS15, TS16, TS18 and TS29 and thirty three testers viz., 17 indicas, 7 japonicas and 9 javanicas by line × tester method at Paddy Breeding Station, Tamil Nadu Agricultural University, India. Pre-ponderence of non-additive gene action for yield and yield attributing traits was observed by analysing combining ability. TGMS lines TS18, TS29 and the testers CB96073, CB96026, CB94247, TNAU 94241 (indicas), Gohykumangoku (japonica), Dular, PRR16 (javanicas) were good general combiners. The hybrids TS29 × TNAU 94241 (indica/indica), TS 18 × Yamadanishiki (indica/japonica) and TS29 × Dular, TS29 × PRR16 (indica/javanica) were promising for heterosis breeding programme. The japonica tester Gohykumangoku and javanica testers Dular and CPSL0-17 exhibited strong heterosis for spikelet fertility when crossed with TGMS lines TS 16, TS 18, TS 29 indicated that these lines may possess wide compatible gene (WCG) for spikelet fertility. Based on mean performance, standard heterosis and sca for yield and yield traits, the inter – subspecies hybrids viz., TS29 × TNAU 94241, TS18 × TNAU 94241, TS29 × CB96073, TS29 × CB94247, TS29 × CB96026 (indica/indica) TS18 × Yamadanishiki, TS29 × Gohykumangoku (indica/japonica), TS29 × Dular, TS29 × PRR16 (indica/javanica) exhibited high heterosis over check hybrid CORH2 and the above hybrids can be exploited commercially. The present investigation revealed that the TGMS system may utilized as an innovative tool for developing inter subspecies two line hybrids with strong heterosis in rice.     

Genetic analysis of phosphoglucoisomerase isozymes in cultivated and wild species of section Cepa in Allium

Phosphoglucoisomerase (PGI) was studied to establish the genetic system of the isozymes in section Cepa of Allium. The results of isozyme analyses using 15 cultivars and clones in two cultivated species A. fistulosum and A. cepa, eight strains in four wild species A. altaicum, A. galanthum, A. oschaninii and A. vavilovii and a total of 10 hybrids between A. fistulosum and A. cepa and between the cultivated and wild species revealed that: 1) PGI was a dimeric enzyme; 2) the two cultivated and four wild species had a common gene locus Pgi-1 where six alleles were identified; and 3) A. fistulosum had Pgi-1 ^F-1 and Pgi-1 ^F-2, A. cepa had Pgi-1 ^A-1 and Pgi-1 ^A-2, A. altaicum had Pgi-1 ^F-1, A. galanthum and A. vavilovii had Pgi-1 ^A-1, and A. oschaninii had Pgi-1 ^A-1, Pgi-1^O-1 and Pgi-1 ^O-1. The intra- and inter-specific polymorphisms of PGI isozymes are expected to be valuable tools for the genetics and practical utilization of the wild species in section Cepa.     

Indica-Japonica differentiation of paddy rice and its relationship with heterosis

The Indica‐Japonica differentiation of three photoperiod‐sensitive and/or thermosensitive genetic male‐sterile rice (PGMS or TGMS, respectively) lines and 47 male parental lines from seven ecotypes were studied for their restriction fragment length polymorphism marker data to determine which ecotype crosses with the three PGMS and/or TGMS lines could lead to higher yield potential, and to estimate the relationship between the Indica‐Japonica differentiation of parents and heterosis in grain yield and its components. The results indicated that hybrids derived from ‘N422s’ and the early‐middle ripening Indica varieties from southern China, and hybrids between ‘Pei'ai64s’ and three Japonica ecotypes, including North‐eastern Japonica varieties, restoring lines of Japonica hybrid rice and north China Japonica varieties, showed the highest grain yields. There was less variation of yield among the F1s between ‘108s’ and the seven ecotypes than among the other F₁s. Highly significant positive correlations between heterosis of the F₁ yield and genetic distance of the parents were detected, although the correlation between F₁ yield performance and genetic distance did not reach a significant level. Considerable variation of correlation between heterosis and genetic distance was also detected in the Indica × Indica crosses and Indica × Japonica crosses. There was much higher correlation (r = 0.63) between the F₁ yield performance and the genetic distance of parents in the Indica × Indica crosses than in the others. It is proposed that a genetic distance of 0.4‐0.8 between the two parents of hybrid rice might be appropriate not only for F₁ performance, but also for heterosis.     

Effects of the two most common Wx alleles on different genetic backgrounds in rice

Wx^a and Wx^b are the most common alleles of the Wx gene in Asian cultivated rice. The difference between them is responsible for differences in the levels of the Wx gene product in the endosperm, as well as in amylose content, which is an important determinant of the quality of edible rice. Since Indica rice mostly carries the Wx^a allele, we introduced the Wx^b allele into Indica‐type rice (IR36) from a Japonica‐type rice (T65) by repeated backcrossing. In the near‐isogenic line (IR36 Wx^b), the level of the Wx gene product was reduced and, as expected, the level of amylose. However, IR36Wx^b had a lower amylose content than the recurrent parent of T65 with the Wx^b allele. The results suggest that the Indica (IR36) background might lower the amylose content more than the Japonica (T65) background when the Wx allele is the same. The possible importance of modifiers that regulate expression of the Wx gene is also discussed in relation to improvements in the grain quality of rice.     

Analysis on the spectra and level of wide-compatibility conferred by three neutral alleles in inter-subspecific hybrids of rice (Oryza sativa L.) using near isogenic lines

Wide‐compatibility varieties are a special class of rice germplasm that is able to produce fertile hybrids when crossed to either indica or japonica subspecies. Previous studies determined the f5 allele from ‘Dular’ (f5‐Du), f6 allele from ‘Dular’ (f6‐Du) and S5 allele from ‘02428’ (S5‐08) as neutral alleles conferring wide‐compatibility. However, the possible extent of the effect of the three neutral alleles has not been fully characterized because of the narrow range of the tester varieties used and the highly complex differentiation in Asian cultivated rice. In this study, we further developed the five near‐isogenic lines with higher recovery rates of the recurrent parent genome, and testcrossed to 14 japonica varieties, which have been widely used in rice breeding programmes in China. The results clearly revealed that all three neutral alleles exhibited substantial effects on spikelet fertility in most of the indica–japonica testcrosses, which indicated that these hybrid sterility loci have been extensively differentiated between indica and japonica varieties. The magnitudes of effects on spikelet fertility averaged over various crosses seem to be similar among the three neutral alleles, with f5‐Du, f6‐Du and S5‐08 alleles increasing spikelet fertility by 15.09%, 13.99% and 14.25%, respectively. The testcrosses involving f5‐Du allele generally showed much smaller variation in pollen fertility than others. The pyramiding lines with two neutral alleles showed a wider spectrum and a higher level of wide compatibility than others, whereas most of the increases in hybrid fertility couldn’t be simply explained by additive effects, suggesting the very complexity of wide compatibility and hybrid sterility. The indica–japonica hybrids involving restorer lines as one of their parents showed much higher pollen fertility (almost normal) and also higher spikelet fertility. The implications of the findings in rice breeding programmes are also discussed.     

Expression of Introduced Genes after Tuber Propagation of Transgenic Potato Plants

The linkage relationship between eighteen isozyme loci and the morphological markers hypocotyl colour (R-r), monogerm character (M-m), pollen fertility (X) and stem fasciation (Verb.) are tested. Three linkage groups could be set up, involving all morphological marker loci and eight of the isozyme loci. Est-2, R-r, Fdp-2, Got2 and Icd-1 belong to linkage group I, linkage group II includes the loci Fas-fas M-m, Est-3 and Aco-1, linkage group III contains the loci X, Mdh-1 and Est-5. When analysing the inheritance of isozymes and RFLPs, deviations are usually found in some lines from the expected frequencies of a 3 : 1 or 1 : 2 : 1 segregation at single marker loci. In many cases these data can still be used for the estimation of recombination values with linked loci under the control of selection. Procedures to estimate linkage in such cases are given and applied to experimental data in Beta vulgaris.     

Interspecific cytoplasm substitutions of an Indica strain of Oryza sativa L. and O. Glaberrima Steud

Summary To study differential nucleus-cytoplasm interactions between the two cultivated rice species, Oryza sativa and O. glaberrima, cytoplasmic substitution lines were made by using a glaberrima strain (G) and an Indica strain of sativa (S). The G cytoplasm had no adverse effect on pollen development when combined with the nucleus of S. On the other hand, when the S cytoplasm was combined with the G nucleus, the substitution line showed no seed set because of male sterility although the pollen grains were normally stained with I₂-KI solution. A dominant gene derived from S strain seemed to cause anther indehiscence in the substitution line. Further, a restorer gene (Rf _j)from Akebono of Japonica type was effective on pollen restoration in the male sterile line, suggesting that the S cytoplasm is the same as those of Japonica type in terms of a fertility-restoring system.This paper is Genetic studies of speciation in cultivated rice. 4.     

Inheritance of new genetic markers in lentil (Lens Miller)

Summary We report on the inheritance of 11 morphological markers and 17 isozymes in lentil (Lens culinaris). The monogenic inheritance of 11 morphological markers and 11 isozymes is confirmed. The inheritance of six isozymes (Aco-2, Enp, Est-3, Est-4, Lap-3, and Mdh-m) is reported for the first time in lentil. This brings the total number of described genes in lentil to 78. Cases of disturbed segregation were more frequent than expected by chance. It is suggested that disturbed segregation was in most cases caused by linkage with a piece of chromosome that showed preferential elimination in crosses between Lens culinaris ssp. odemensis and other subspecies. The prevalence of disturbed segregation in crosses with Lens culinaris ssp. odemensis could limit the usefulness of this subspecies in genetic and linkage studies.     

Genetic Analysis of DIA, GOT and PGI Isozyme Loci in Daucus carota L. ssp. sativas

Isozymes are useful biochemical markers in plant breeding. This paper presents the first results on the inheritance of three enzyme systems: diaphorase (DIA), glutamate oxalacetate transaminase (GOT) and phosphoglucoisomerase (PGI) from leaves of Daucus carota L. ssp. sativus and the linkage relationships among these isozyme loci, marked Dia, Got, and Pgi. Methods of extraction and electrophoresis are described. Segregation ratios indicated that the DIA system is controlled by three genes: Dia-1, Dia-2 and Dia-3, Dia-1 as invariant. Two codominant alleles and a null allele were found for Dia-2, and four codominant alleles for Dia-3-GOT isozymes are encoded by three genes; Got-1, Got-2 and Got-3. An active allele and a null allele were observed for Got-1, two codominant alleles for Got-2 and Got-3, respectively. PGI isozymes are controlled by a single gene, Pgi-1, with two codominant alleles. Altogether one invariant isozyme locus and six polymorphic loci are postulated. Test of joint segregation suggested a linkage of Dia-3 and Pgi-1. The recombination value is 0.04 ± 0.009.     

Methods for Detection and Estimation of Linkage between a Marker Locus and Quantitative Trait Loci

Several methods have been proposed over the years to detect linkage between a marker gene and quantitative trait locus (QTL). Use of isozymes and restriction fragment length polymorphisms as genetic markers, has encouraged the development of new methods to detect linkage. We present three methods to detect linkage and two methods to measure recombination frequency (r). The three methods that detect linkage can be used when a single QTL or a tightly linked cluster of QTLs control the quantitative trait. The two methods that measure recombination frequency could not be used in the latter case because r would not be properly estimated. Procedures to calculate the additive and dominance gene effects of the QTL and the respective variances of these estimates were also presented.     

QTLs and candidate genes for chlorate resistance in rice (Oryzasativa L.)

Chlorate resistance is one of the reliable characters in Indica/Japonica classification. To understand the genetic basis of chlorate resistance is very important for revealing the evolutionary mechanism of Indica/Japonica differentiation. In this study, a doubled haploid (DH) population derived from anther culture of ZYQ8/JX17, a typical Indica and Japonica hybrid, was used as the genetic material to investigate chlorate sensitivity of the parents and DH lines. The quantitative trait loci (QTLs) of chlorate resistance were analyzed based on the molecular linkage map of this population. Total of 3 QTLs (qCHR-2, qCHR-8 and qCHR-10) for chlorate resistance were detected on chromosomes 2, 8 and 10, respectively. A QTL × QTL epistatic interaction was detected between qCHR-2 and qCHR-10. Genes involved in nitrogen assimilation, such as nitrate reduction, molybdenum cofactor biosynthesis and nitrate transport were strong candidates of QTLs for chlorate resistance. A putative nitrate reductase gene (8611.t00011), and two putative nitrate reductase genes (9319.t00010 and 9319.t00012) were in the genomic region of qCHR-2, and qCHR-8, respectively, and a putative nitrate transporter gene (756.t00011) was in the region of qCHR-10. The expression of 8611.t00011, 9319.t00010 and 756.t00011 were confirmed by the corresponding cDNAs, and 2 in/del and 12 SNPs in the coding regions of these three genes were found between Indica (cv. 9311) and Japonica (cv. Nipponbare) in silico. These results indicated that these three genes were candidates of the chlorate resistance QTLs. An in/del in the coding region of 8611.t00011 was used to develop a new PCR marker. A polymorphism was detected between JX17/Nipponbare and ZYQ8/9311. This polymorphism corresponds to the chlorate sensitivity of Nipponbare and 9311. This marker was located between Y8007R and RM250 on chromosome 2 in the DH population, where qCHR-2 was also located.     

Genetic control of esterase-6 isozymes in hexaploid wheat and rye

Summary The EST-6 leaf esterase phenotypes from euploid, nullisomic-tetrasomic and rye chromosome addition and substitution lines of common wheat were determined using polyacrylamide gel electrophoresis. Evidence is presented to demonstrate that Est-6 is a new set of genes, that are expressed in the leaf. The Est-6 gene set were clearly distinguished from the Est-5 genes which are expressed in the grain. The three homoeoallelic loci, Est-A6, Est-B6 and Est-D6, were located on chromosomes 3A, 3B and 3D. An Est-R6 gene was located on chromosome 6R is involved in rye. Some considerations concerning homoeology between homoeologous group 3 of wheat and the rye chromosome 6R are made.