Inheritance of glandular trichomes in crosses withSolanum berthaultii

The inheritance of trichome density and droplet size was investigated in diploid and tetraploid crosses. In haploidTuberosum ×Solanum berthaultii and (S.phureja ×haploid Tuberosum) × S.berthaultii crosses, droplet size on type B trichomes was small or droplets were lacking on F₁ hybrids. Parental phenotypes were recovered in the F₂ and backcross generations. Trichome density was more variable within a clone that was droplet size. Density of both type A and type B trichomes appears to be under the control of small numbers of genes, as parental phenotypes were recovered in the F₂ and backcross generations. The variation observed for each of the three traits studied could not be explained by hypotheses based on the segregation of one or two loci. The insect resistance ofSolanum berthaultii appears to be due to the interaction of several chemical and physical factors, thus potato breeders should handle it as a quantitatively inherited trait.     

Genetic analysis for resistance to the green leafhopper, Nephotettix virescens (Distant), in some cultivars of rice, Oryza sativa L.

The genetics of resistance to green leafhopper Nephotettix virescens (Distant) was studied in 17 cultivars of rice (Oryza sativa L.). Seedlings at the one-leaf stage were infested with second- and third-instar nymphs of green leafhopper. Reactions to seedling injury were recorded 7–8 days after infestation. The reactions of F₁, F₂, and F₃ populations from the crosses of resistant varieties with susceptible parent TN1 revealed that resistance of Tilakkachray, Kalimekri 77-5, and Tilockkachari was governed by two dominant genes and resistance of IR42 was conveyed by a single recessive gene. Single dominant genes govern resistance in the remaining 13 cultivars. Allele tests revealed that a single dominant gene of Segon Perak and one of the two genes of Kalimekri 77-5 are allelic to Glh 1. The single dominant gene of Ernest, Bignou and ARC614 and one of the two genes of each of Tilakkachray, Kalimekri 77-5, and Tilockkachari are allelic to Glh 2. A single dominant gene, which is allelic to Glh 3, conditions resistance in Arai and IR30. The single recessive gene which conveys resistance in IR42 appears to be allelic to glh 4. The allelic relationships of one of the two genes of Tilakkachray and Tilockkachari and single dominant genes of Fulkari 653, Chao Pho Kha, Amoule Borome, Kabero, Aus Murali, IR28 and IR34, with each other and with Glh 5 are not known.     

Genetic analysis for resistance to bean fly (Ophiomyia phaseoli) and seed yield among common bean genotypes in a semi-arid environment

Bean fly (Ophiomyia spp.) is a major field pest limiting common bean production in eastern Africa. The genetic enhancement of beans for resistance to insect pests is essential for minimizing yield losses arising from crop damage. The objectives of this study were to (1) assess combining ability for bean fly resistance and seed yield accumulation in common bean and (2) estimate genetic parameters associated with resistance for formulating further breeding strategy. Four parents with known reaction to bean fly were crossed with four locally adapted genotypes in an 8 × 8 half diallel mating design. Parents and F₂ progenies were grown in an alpha-lattice design replicated twice in an open-field and subjected to natural populations of bean fly for two cropping seasons under semi-arid conditions. Similarly, two resistant and two susceptible parents were selected and crossed to produce populations for generation means and variances components analysis. Results revealed that both general combining ability (GCA) and specific combining ability (SCA) mean squares were significant (p ≤ 0.05) for all four traits studied except SCA for stem damage during one cropping season. Among the parents, GBK 047858 was the best general combiner for all the traits studied across seasons except for stem damage during long rains (LR) 2009. Besides, genotypes GBK 047821 and Kat × 69 (a locally adapted variety) were generally good general combiners for resistance traits as well as seed yield. General predictability ratio (GPR) values ranging from 0.63 to 0.90 were obtained for plant mortality, stem damage, pupae in stem and seed yield across cropping seasons. These results established the predominance of additive gene effects (fixable variation) over the non-additive effects in controlling the traits. Low to moderate narrow sense heritability values ranging from 0.22 to 0.45 were obtained for pupae in stem. Such heritability estimates indicate that although additive gene components were critical in the inheritance of resistance for the trait, non-additive gene action were also important in addition to the environmental effects.     

玉米组合M9916×D472抗镰孢茎腐病的六世代联合数量遗传研究

以玉米自交系M9916×D472组成的六世代群体为材料,利用六世代数量性状主基因+多基因混合遗传模型多世代联合分析方法,研究玉米茎腐病抗性的遗传机制。结果表明,分离世代的次数频率分布在F2群体中呈近似于抛物线状的正态分布,在B1和B2群体中呈偏正态分布。通过AIC值适合性检验,该性状符合1对加-显主基因+加-显-上位性多基因遗传D模型,主基因加性效应值为5.29,显性效应值为6.79,两者效应值均相对较高,加性与显性效应比率为78%;多基因加性效应值为2.98,明显低于显性效应值6.88,说明显性效应起主导作用。多基因加性互作效应明显,加、显互作上存在一定抑制作用,显性互作效应不明显,加性互作效应在上位性方面起主导作用。回交群体中主基因的遗传率介于39.9%~41.3%,多基因遗传率介于33.8%~36.7%,主基因遗传率相对较高;自交群体中多基因遗传率为53.8%,大于主基因遗传率32.8%,说明在进代过程中主基因遗传率不断下降。在抗茎腐病的育种中,应注重早代抗病材料的选择,对现有重要的感病材料可利用回交方法进行有效改良。     

玉米茎秆抗倒伏相关性状的遗传效应分析

利用主基因+多基因混合遗传多世代联合分析的方法,对玉米自交系K12和A7110组配的正反交组合进行6个世代(P1、P2、F1、B1、B2、F2)联合分析。结果表明,茎粗正交组合中的最适模型为D-1模型(1对加性-显性主基因+加性-显性多基因),茎粗的反交组合的最适模型均为E-1模型(2对加性-显性-上位性主基因+加性-显性多基因),茎粗在正交组合中表现出基因的加性效应大于显性效应。反交组合中主基因互作效应较高,正反交组合中,多基因的遗传率大于主基因的遗传率,在B2、F2代达到最大值,分别达到78.74%、71.22%。抗推力的正反交组合最适模型为C模型(加性—显性—上位性多基因),正交组合中回交世代多基因遗传率较低,分别为6.22%和19.94%;反交组合中回交世代多基因遗传率较高,分别为68.81%和52.78%。在玉米育种过程中,以多基因遗传为主控制的性状,在遗传率较高的世代进行轮回选择的方法富集目的基因,有利于提高育种效率。     

Simultaneous selection for stem borer resistance and forage related traits in maize (Zea mays ssp. mays L.) × teosinte (Zea mays ssp. mexicana L.) derived populations

Maize spotted stalk borer (Chilo partellus Swinhoe Pyralidae) (MSSB) is a serious pest of the maize (Zea mays ssp. mays L.) crop in Pakistan. This study was conducted to introgress resistance in maize against MSSB by exploring wild sources of resistance for the development of a resistant maize variety. To achieve this, teosinte (‘PI566674’) × maize (‘Sargodha-2002’) crosses were conducted and three populations (F₁, F₂ and F₃) were established. These populations were screened at various locations and in a contrasting artificial insect infestation experiment. Teosinte species ‘PI566674’, following screening, was shown to be highly resistant to MSSB and had the ability to produce a high biomass (5 times higher than susceptible genotypes) under high temperatures (36–40 °C). The biomass of the F₁ hybrid, which was highly susceptible to MSSB, was significantly reduced (P ≤ 0.05) following infestation by MSSB in all experiments. The introgression from teosinte for genes conferring resistance to MSSB was screened in segregating F₂ and F₃ generations. Despite a susceptible F₁ population, F₂ was resistant to MSSB. Twenty new recombinant plants with resistance to MSSB and a high leaf soluble solid (16 °Brix) content were identified. They were selected to grow the F₃ population. Mean values of F₃ progenies showed similar resistance to the F₂ population but a high percentage (60%) of resistant plants was recovered.     

Utilizing the frost resistance of diploid solanum species

Introductions of 13 frost-resistant diploid (2n=2x=24)Solanum species (2 non-tuberous) were inter-crossed to produce F₁ hybrids involving two frost resistance sources. Successful F₁ combinations were: (i) inter-crossed to produce hybrids involving 3 to 4 frost resistance sources, (F₁×F₁); and (ii) crossed with haploids (2n=24) of frost-susceptible tetraploid (2n=4x=48)S. tuberosum subsp.tuberosum, (F₁×tbr). Thirty-five of the 75 crosses between the 13 species produced viable seed. The F₁ and F₁×F₁ progenies segregated to yield plants more resistant to freezing temperatures than the parental species. All attempts to cross these hybrids with 24-chromosometbr were successful. Although tuber production improved following the first cross totbr, the frequency of resistant plants decreased approximately 50%. Thus far, all first back-cross attempts, (F₁×tbr)×tbr, have succeeded. Utilizing hybrids synthesized from several sources of frost resistance as the donor parents, and clonal selections of 24-chromosometbr as the recurring parents, may provide a high order of resistance throughout the backcrossing program and implement selection of frost-resistant, long-day tuberizing parental stocks acceptable to the potato breeder.     

The inheritance of resistance to soft rot (Erwinia carotovora subsp.atroseptica) in diploid potato families

Soft rot of potato tubers, caused byErwinia (Pectobacterium), is a serious disease affecting potato crops during storage. Studies on the inheritance of resistance to tuber soft rot were undertaken on diploid potato hybrids. A total of 480 clones, derived from 12 families, were examined for resistance to soft rot in laboratory tests over 3 years and for basic agronomic traits in field experiments over 2 years. General (GCA) and specific (SCA) combining abilities were significant in the inheritance of resistance to soft rot; however, GCA for female parents were significant in 1 or 2 years during 3 years of evaluation and SCA was significant for eight, two, and six families out of 10 tested in 1994, 1995, and 1996, respectively. There were also significant differences between years. Moreover, marked interactions for GCA_females × year and SCA × year in the variation of soft rot resistance were found. Broad-sense and narrowsense heritability of resistance, measured as diameter of rotten tissue, was estimated as 0.92 and 0.89, respectively. The maternal effect, evaluated in two sets of reciprocal crosses, was not significant for the genetic determination of resistance to soft rot. No significant relationships were found between resistance to soft rot and the main agronomic traits in the tested diploid families. These results suggest that diploid potato clones with resistance to soft rot can be selected after being evaluated over a few seasons. It is also possible to select clones combining good resistance to soft rot with high yield, superior tuber characteristics, and acceptable starch content. These resistant diploids can be used as male parents in 4x-2x crosses in breeding tetraploid potato resistant to soft rot.     

Identification and Genetic Analysis of Fertility Restoration Ability in Dongxiang Wild Rice （Oryza rufipogon）

Two populations of Dongxiang wild rice (Oryza rufipogon), Shuitaoshu and Dongtangshang, were crossed with five male sterile rice lines with different cytoplasmic backgrounds (B06S, Zhenshan 97A, Xieqingzao A, Zhong 9A, and Yuetai A), and the seed setting rate of the F₁ was used to judge the fertility restoration ability in the Dongxiang wild rice. With P₁, F₁, P₂, and F₂ populations as materials, the Akaike's Information Criterion (AIC) was used to identify the major genes affecting quantitative traits, and when the major genes existed, the genetic effects of the major gene and the polygene and their genetic variance were estimated through segregation analysis. The seed setting rates of the F₁ generation varied from 45.98% to 76.57%, suggesting that the Dongxiang wild rice had the fertility restoration ability. One major gene plus polygene mixed inheritance model was the most fitted genetic model for this trait in all the F₂ populations. The heritability values of the major genes varied from 56.63% to 88.29% and those of the polygenes from 2.74% to 30.97%, and the total heritability values were from 63.17% to 94.01%. The major gene inheritance of the combination Zhong 9A/Dongtangshang was controlled by the additive effect without dominant effect, and the other nine combinations were by the completely dominant inheritance.     

Glycoalkaloid content in foliage of hybrid and backcross populations from aSolanum tuberosum X S. chacoense cross

The glycoalkaloid contents of foliage were measured in populations derived from a cross ofSolanum chacoense Bitter (PI 472810) with a composite sample of genotypes from a randomly matedSolanum tuberosum L. population. The mean total glycoalkaloid contents of the parent PI 472810 andtuberosum populations, and the F₂ and F₄ populations were 856, 121, 286, and 279 mg/100g fresh weight, respectively. The total glycoalkaloid content of the first backcross population, F₂ xtuberosum, was 290 mg/100 g, close to the content of the F₂. In a second backcross totuberosum, the mean total content was 148 mg/100 g, close to the content of the parenttuberosum population. Only the glycoalkaloids α-solanine and α-chaconine were found in PI 472810, whereas in the parenttuberosum, hybrid, and backcross populations, the glycoalkaloids α & β-solamarine also were found in a small number of genotypes. The ratios of chaconine to solanine contents were significantly (P≤.05) different in the parent PI 472810 andtuberosum populations, 2.55 and 2.12, respectively. The ratios in the F₂ and F₄ populations were similar to that of PI 472810, whereas the ratios in the backcross populations were closer to that of thetuberosum parent. The levels of foliage glycoalkaloids in the hybrid and backcross populations paralleled the levels of potato leafhopper,Empoasca fabae Harris, resistance measured in a previous study.     

水稻品种五丰占2号的白叶枯病抗性遗传分析

研究了五丰占2号的白叶枯病抗性遗传及在回交世代中的抗性表现。结果表明,用白叶枯病菌株浙173（Ⅳ型）接种,五丰占2号表现中抗,IRBB5表现抗;五丰占2号的白叶枯病抗性受微效多基因控制,基因效应分析表明,该性状符合加性-显性模型,以加性效应为主;隐性主效基因xa5控制的IRBB5对白叶枯病菌株浙173的遗传符合隐性主基因的分离比。对白叶枯病菌株浙173的抗性反应与xa5基因的PCR检测结果一致。在五丰占2号2/IRBB5 B1F1群体中,基因型Xa5Xa5与Xa5xa5的分离比为1∶1;在五丰占2号2/蜀恢162 B1F1群体中,白叶枯病抗性达到五丰占2号水平的植株数占群体总数的68.3%。如果要将IRBB5中的xa5基因与五丰占2号的微效基因聚合,用五丰占2号回交1次是必要的。     

Delineation of Inheritance Pattern of Aleurone Layer Colour Through Chemical Tests in Rice

Background

Rice aleurone layer develops different colours with various chemical tests that may help to develop some rapid tests for identification/grouping of rice varieties. Understanding the colour inheritance pattern could enable to develop chemical clues that may help for genetic purity analysis along with grow-out-test.

Results

In this study, inheritance pattern of aleurone layer colour was studied in parents, F₁ and F₂ progenies derived from the crosses IR 36 × Acc. No. 2693 and IR 64 × Acc. No. 2693. The parent IR 36 showed light yellow (NaOH/KOH) and brown (phenol/modified phenol test) colour; whereas, Acc. No. 2693 revealed wine red/dark wine red (NaOH/KOH) and light brown colour/no reaction (phenol/modified phenol test). In contrary, another parent IR 64 exhibited light yellow (KOH/NaOH) and dark brown (phenol, modified phenol) colour. Both the F₁ showed an intermediate light wine red colour (NaOH/KOH) and dark brown (phenol and modified phenol) colour, which is dominant over their one of the parents. The colour pattern with standard phenol/modified phenol, NaOH and KOH tests in F₂ progenies of both the crosses showed 9:7 (complementary gene interaction) and 11:5 ratios (reciprocal dominance modification of recessive alleles), respectively.

Conclusions

Our findings clearly elucidate the colour inheritance pattern in rice that may facilitate to develop rapid chemical tests to identify/ group the varieties for genetic purity analysis.

     

Genetic analysis of resistance to whitebacked planthopper, Sogatella furcifera (Horvath), in some rice varieties

For genetic analysis of resistance to the whitebacked planthopper, Sogatella furcifera (Horvath) (Homoptera: Delphacidae), in 13 rice varieties, seedlings at the one-leaf stage were artificially infested in the greenhouse with second; and third-instar nymphs of this planthopper. Reactions of the seedlings were recorded 7–10 days after infestation when the susceptible check (control variety) TN1 was completely killed. The reactions of the F₁, F₂, and F₃ populations from the crosses of resistant varieties with TN1 revealed that single dominant genes condition resistance in the varieties Sinnanayam, ARC 13349, MGL 1, Sukhwel 20, Bam 3, Hornamawee, Senawee, A1, T1432, W128, and Chuvanna Kumbolum. The resistance in NP130 and CI-5662-2 was conditioned by two independent dominant genes. The allelic relationships of the latter genes for resistance in the test varieties to resistance genes Wbph 1 and Wbph 2 were determined. Reactions of the F₂ and F₃ progenies from the crosses of test varieties with IR13475-7-3-2 which is homozygous for Wbph 1, and with IR30659-2-165, which is homozygous for Wbph 2, showed that the resistance genes in Sukhwel 20, Senawee, T1432, and W128 are allelic to Wbph 1. The resistance genes in Sinnanayam, ARC 13349, MGL 1, Bam 3, A1, and Chuvanna Kumbolum are allelic to Wbph 2. The two independent dominant genes for resistance in NP130 and CI-5662-2 are Wpbh 1 and Wbph 2. However, there is a single dominant gene for resistance in Hornamawee which is independent and non-allelic to Wbph 1 and Wpbh 2.     

Introgression and stabilization oferwinia tuber soft rot resistance into potato after somatic hybridization ofsolanum tuberosum ands. brevidens

Resistance to potato tuber soft rot caused byErwinia carotovora was transferred fromSolanum brevidens to the cultivated potato over the course of four backcross generations originating from a somatic hybrid. Soft rot reactions were determined via a tuber plug inoculation method developed during the course of these experiments. Soft rot resistance was highest in the somatic hybrid (only ca. 20% of tubers and plugs showed evidence of severe rotting) and lowest among progeny of control potato x potato crosses (ca. 80% of tuber plugs showed severe rot). Backcross generations involving somatic hybrids were intermediate in their reaction, and resistance stabilized to about 60% of tuber plugs showing severe rot in the BC₂ through the BC₄. Reciprocal crosses showed no difference in the inheritance of soft rot resistance, indicating that neitherS. brevidens norS. tuberosum donor cytoplasm had a significant effect on the expression of resistance. Crosses between BC₃ siblings where noS. brevidens genetic markers were detected but resistance was segregating demonstrated a dosage effect for soft rot resistance. We conclude that introgression of soft rot resistance has occurred and that at least one locus responsible for resistance inS. brevidens now resides in theS. tuberosum genome.     

玉米纹枯病抗性的主基因+多基因混合遗传分析

利用自交系CML429(高抗)、CI23(中抗)、DM9(高感)和478(高感)组配得到6对正反交组合以及抗感组合CML429×DM9的P₁(CML429)、P₂(DM9)、B₁、B₂、F₁和 F₂ 6个世代材料进行玉米纹枯病抗性鉴定,研究分析这些抗感组合的抗性遗传特性。结果表明：玉米纹枯病抗性基本不存在胞质效应,抗性遗传符合两对加性-显性-上位性主基因+加性-显性-上位性多基因遗传模型;主基因间表现为加性-显性-上位性作用,两对主基因的加性效应分别为-1.228 4和-1.228 4,显性效应分别为-0.206 5和-0.206 3,其遗传效应值大小基本相同,且两对主基因间的加性效应与显性效应互作的上位性效应也相差不多,分别为0.293 1和0.293 5,两对主基因的遗传效应基本相同。抗感组合不同世代中F₂的主基因遗传率最高(70.22%);多基因遗传率在B₂最高(10.17%)。因此,在F₂的选择效率最高。     

Use of stomatal index as a marker to screen backcross populations of two wild potato species segregating for freezing tolerance

The purpose of this study was to investigate differences in stomatal index among backcross progeny ofSolanum commersonii (freezing tolerant) andSolanum cardiophyllum (freezing sensitive) to assess the feasibility of using this trait as a marker for screeningSolanum populations for freezing tolerance. Measurements were taken on three terminal fully-expanded leaflets per genotype by completing microscopic examination of epidermal impressions made in partially dissolved cellophane tape. Freezing tolerance was estimated in parallel studies on the same plant material. Values of SI were significantly greater (Fisher T-test, 0.05) for theS. cmm. group (parent + backcross progeny) compared with theS. cph. group. Stomatal index of the F₁ was significantly greater than SI ofS. cph. parents and similar toS. cmm. parents. Values of SI for both backcross progenies were greater than parental values. Non-acclimated relative freezing tolerance values were in the following order:S. cmm. parents >S. cmm. backcrosses > F₁ >S. cph. back-crosses >S. cph. parents. Stomatal index values followed a similar pattern with the exceptionS. cmm. backcross >S. cmm. parents. These data suggest: a) increased SI is inherited as a dominant trait, b) SI may be a useful screening marker in breeding programs interested in improving freezing tolerance.     

Screening,Inheritance and Linkage Marker Analyses of Salt Tolerance in Mutated Scented Japonica Rice (Oryza sativa L.)

Abstract

We grew 1005 mutated scented japonica rice lines to the seventh steady genetic generation, and treated the seedlings with six true leaves with 300 mM NaCl for three days. Only the salt-tolerant line, SM61, survived. We obtained F₁, F₂ and F₃ populations from the cross between SM61 and a salt-susceptible indica variety, TCS17. After culture with 200 mM NaCl for five days, SM61 and F₁ (SM61×TCS17; TCS17×SM61) plants survived (R) while TCS17 plants did not (S). The R to S ratio in 513 F₂ plants showed a good fit to the Mendelian 3 : 1 segregation ratio by a Chi-square test indicating that the salt-tolerance of SM61 was governed by a single dominant gene. The mutated salt-tolerance gene explained close to 100% of the total phenotypic variation, and was tightly linked to RM223 (marker) located on chromosome 8, which was different from the results of previous studies investigating the relationship of QTLs with salt tolerance. This is the first report of mapping tightly linked markers of a single dominant mutated salt-tolerance gene.     

小麦农艺性状的主基因+多基因遗传分析

为明确小麦重要农艺性状的遗传组成,并筛选适于QTL的性状,以西农817和中国春为亲本,构建F2、F3群体,采用P1、P2、F1、F2、F3五世代联合分析方法,研究了株高、有效分蘖、小穗数、穗粒数、穗长、穗下节间距、小穗着生密度等产量相关性状的遗传模型.结果表明,7个性状不仅受基因的控制,同时也受到不同程度的环境影响.其中,穗长、穗粒数符合多基因遗传模型,无主基因存在;株高、小穗数、小穗着生密度符合一对加显性主基因+加性-显性多基因混合遗传模型;穗下节间距符合一对完全显性主基因+加性-显性多基因模型;有效分蘖符合一对负向完全显性主基因+加性-显性多基因模型.     

Phenotypic identification of peanut germplasm for resistance to southern stem rot

Southern stem rot, caused by Sclerotium rolfsii Sacc., is a destructive soil fungal disease of peanut in China and other countries. To evaluate resistant germplasm, a total of 256 peanut accessions were investigated on their resistance to southern stem rot in 3 environments by artificial inoculation. Variance analysis indicated that disease index was significantly influenced by environment, genotype and genotype ​× ​environment interactions. Peanut accessions of var. vulgaris type exhibited higher resistance to southern stem rot. Disease index was significantly negatively correlated with linoleic acid content, while positively correlated with oleic acid content. Six resistant accessions were identified, including Hua 28, Shandongzai, ICG 6326, Quanhua 7, Quanhua 9 and Guihua 836, with their disease indexes under 40 and mortality were less than 30% in the three environments. The identified resistant accessions showed the great potential to be applied in resistant peanut breeding, and would be good genetic resources for enhancing the resistance to southern stem rot.     

Selection before backcross during exotic germplasm introgression

Introgression of genes from exotic germplasm into breeding populations can broaden the genetic base of crop improvement. Only a very small percentage of genetic variability has been used in crop breeding programs. Traditionally, F₁ plants are used to backcross to the adapted lines or populations. An alternative approach is to backcross the F₂ individuals selected for agronomic acceptability. Our objective was to determine whether selection before backcross would lead to more progenies with both high yield and acceptable levels of agronomic performance than direct backcross without selection. To test the feasibility of the proposed approach, we conducted parallel experiments in which two exotic sorghum accessions were crossed to two adapted sorghum parents and further backcrossing was conducted with either F₁ or selected F₂ plants. Fifty random S₁ families were evaluated in three test environments. Although selection before backcross resulted in a higher frequency of families with maturity equal to or earlier than those of the adapted parents, no consistent changes in grain yield and plant height were observed between populations with and without selection. Similar results were found with either an inbred or a population as the recurrent parents. Given these findings and the extra generation required, we do not recommend selection before backcross in the process of introgression of exotic germplasm.