Leaf type is not associated with ascochyta blight disease in chickpea (Cicer arietinum L.)

The three major leaf types in chickpea are normal compound leaf, simple leaf and multipinnate. Simple leaf types are less commonly cultivated worldwide and are often reputed to be susceptible to ascochyta blight disease, whereas other leaf types range from resistant to susceptible. This study determined the association between host plant resistance to ascochyta blight and different leaf types in segregating populations derived from crosses between disease resistant and susceptible chickpea genotypes. In addition, the inheritance of disease resistance and leaf type was investigated in intraspecific progeny derived from crosses between two resistant genotypes with normal leaf type (ICC 3996 and Almaz), one susceptible simple leaf type (Kimberley Large) and one susceptible multipinnate leaf type (24 B-Isoline). Our results showed that, in these segregating populations, susceptibility to ascochyta blight was not linked to multipinnate or simple leaf types; resistance to ascochyta blight depended more on genetic background than leaf shape; leaf type was controlled by two genes with a dihybrid supplementary gene action; normal leaf type was dominant over other leaf types; and inheritance of ascochyta blight resistance was controlled by two major genes, one dominant and one recessive. Since there was no linkage between ascochyta blight susceptibility and leaf type, breeding various leaf types with ascochyta blight resistance is a clear possibility. These results have significant implications for chickpea improvement, as most current extra large seeded kabuli varieties have a simple leaf type.     

Genetical analysis of resistance to Mycosphaerella pinodes in pea seedlings

Summary In studies of the inheritance of resistance, pea seedlings of seven lines in which stems and leaves were both resistant to Mycosphaerella pinodes were crossed with a line in which they were both susceptible. With seven of the crosses resistance was dominant to susceptibility. When F₂ progenies of five crosses were inoculated on either stems or leaves independently, phenotypes segregated in a ratio of 3 resistant: 1 susceptible indicating that a single dominant gene controlled resistance. F₂ progenies of one other cross gave ratios with a better fit to 9 resistant: 7 susceptible indicating that two co-dominant genes controlled resistance. The F₂ progeny of another cross segregated in complex ratios indicating multigene resistance.When resistant lines JI 97 and JI 1089 were crossed with a susceptible line and leaves and stems of each F₂ plant were inoculated, resistance phenotypes segregated independently demonstrating that leaf and stem resistance were controlled by different genes. In two experiments where the F₂ progeny of the cross JI 97×JI 1089 were tested for stem and leaf resistance separately, both characters segregated in a ratio of 15 resistant:1 susceptible indicating that these two resistant lines contain two non-allelic genes for stem resistance (designated Rmp1 and Rmp2) and two for leaf resistance (designated Rmp3 and Rmp4). Evidence that the gene for leaf resistance in JI 1089 is located in linkage group 4 of Pisum sativum is presented.     

Screening for Fusarium resistance in seedling populations of Asiatic hybrid lily

A test to select Fusarium resistant seedlings of the Asiatic hybrid lily is described. Young seedlings of 28 populations, obtained from an incomplete diallel between eight parents with different levels of Fusarium resistance, were tested for resistance. Significant differences in Fusarium resistance between and within populations were detected. The average percentage of selected seedlings ranged from 34% in resistant × resistant crosses to 2% in susceptible × susceptible crosses. Although resistant descendants were obtained in susceptible × susceptible crosses, using at least one resistant parent produced higher percentages of resistant seedlings. The resistance level of the parents correlated highly with the general combining ability for Fusarium resistance based on the seedling test. For eight populations, seedlings selected for Fusarium resistance and non-tested (control) seedlings of the same cross were compared, after propagation, in a clonal test. Variation between and within populations, found at seedling level, was confirmed at clonal level. A positive selection response was found for all eight populations. In the seedling test, approximately 18% of the seedlings were selected as resistant of which 15% (2.7% of seedlings tested) appeared to be susceptible escapes. Comparison between selection at seedling level and at clonal level indicated that approximately 25% of the seedlings tested were missed (rejected resistant plants) in the seedling test. The practical use of a seedling test for Fusarium resistance in lily breeding programs is discussed.     

Inheritance of resistance to the chlorosis component of tan spot of wheat caused by Pyrenophora tritici-repentis, races 1 and 3

The fungus Pyrenophora tritici-repentis, causal agent of tan spot of wheat, produces two phenotypically distinct symptoms, tan necrosis and extensive chlorosis. The inheritance of resistance to chlorosis induced by P. tritici-repentis races 1 and 3 was studied in crosses between common wheat resistant genotypes Erik, Hadden, Red Chief, Glenlea, and 86ISMN 2137 and susceptible genotype 6B-365. Plants were inoculated under controlled environmental conditions at the two-leaf stage and disease rating was based on presence or absence of chlorosis. In all the resistant × susceptible crosses, F₁ plants were resistant and the segregation of the F₂ generation and F₃ families indicated that a single dominant gene controlled resistance. Lack of segregation in a partial diallel series of crosses among the resistant genotypes tested with race 3␣indicated that the resistant genotypes possessed␣the same resistance gene. This resistance gene was effective against chlorosis induced by P.␣tritici-repentis races 1 and 3.     

Diallel analysis of partial resistance to powdery mildew caused by Erysiphe graminis f. sp. hordei in spring barley (Hordeum vulgare L.)

Summary Six spring barley genotypes with growth stage dependent expression of partial resistance to powdery mildew were crossed following a half diallel scheme. Data for percentage infected leaf area at different growth stages from the F1 and F2 generation and the F2 offspring were analyzed. The absence of a contrast between parents and offspring indicated that dominance effects were not important at the young growth stages. Diallel analysis showed that general combining ability effects (GCA) were important at all growth stages. Although significant, specific combining ability effects were of minor importance. The cross between the most resistant parents with the largest, negative GCA resulted in the most resistant progeny.     

Inheritance of resistance to angular leaf spot in Nicotiana tabacum L. cultivars burley 21 and kentucky 14

Summary The genetics of resistance to angular leaf spot caused by Pseudomonas syringae pv. tabaci in Nicotiana tabacum cultivars Burley 21 and Kentucky 14 was investigated by studying disease reactions to three isolates of parental, F₁, F₂ and backcross generations derived from crosses between the resistant cultivars and the susceptible cultivar Judy's Pride. Studies were conducted in the greenhouse and in field plant beds. Chi-square values were computed to determine whether the observed ratios for disease reactions deviated from expected Mendelian ratios for a single, dominant gene controlling resistance to angular leaf spot in tobacco. Based on the resistance of the F₁ and the backcross generation to the resistant parent (BC-R), a 3 resistant: 1 susceptible segregation ratio in the F₂, and a 1 resistant: 1 susceptible segregation ratio in the backcross generation to the susceptible parent (BC-S), it was concluded that resistance to three isolates of Pseudomonas syringae pv. tabaci is governed by a single, dominant gene.     

Reciprocal recurrent selection for multitrait indices in maize

Summary Reciprocal recurrent selection was carried out with two populations of maize (Zea mays L.) having good combining ability. We selected for higher grain yield, early maturity, shorter plant height and lodging resistance. Two cycles were completed in two years (four seasons), by resorting to late planting of S1 lines for recombination in the main season in which top-cross families were assessed. Top-crosses and selfings were made in the off-season. The original and improved versions of the populations and their crosses were evaluated in multilocation trials. The superiority of the population hybrid was 10.3% for grain yield, 5.5% for plant height and 1.8 days to silk. The improved hybrid had delayed leaf senescence and better resistance to lodging and post-flowering stalk rots. Among the yield components, only ear girth showed improvement. Syn 2 of the improved population cross showed a yield reduction of 6.2% in comparison to Syn 1. Intrapopulation gains were not significant except for lodging resistance in one population.     

Gene action and reciprocal effects for ear rot resistance in crosses derived from five tropical maize populations

Devastating maize grain yield and quality losses are caused by Aspergillus flavus, Fusarium verticillioides and Stenocarpella maydis ear rots especially in tropical countries. Therefore, combining ability of tropical maize populations for ear rot severity and ear rot-related traits was investigated. Ten full-sib progenies, comprising one resistant and one susceptible from each of the five populations, were selected for mating in a 10 × 10 full diallel. The full-sib progeny crosses were evaluated across two environments with two replications in Zambia. To determine resistance across three ear rots that occur together in Zambia, the crosses were artificially inoculated with a mixture of Aspergillus flavus, Fusarium verticillioides and Stenocarpella maydis isolates. There were marked differences between environment main effects and their interaction with GCA and SCA effects were highly significant, suggesting observation of genotype × environment interaction effects. Both additive and non-additive gene effects were significant for ear rot severity. Highly significant reciprocal differences were also revealed, suggesting that cytoplasmic gene effects and their interaction with nuclear genes were responsible in modifying resistance across the three ear rot diseases in the full-sib progenies that were derived from the five tropical maize populations.     

Variation in inheritance of resistance to sorghum midge, Stenodiplosis sorghicola across locations in India and Kenya

Sorghum midge [Stenodiplosis sorghicola (Coquillett)] is an important pest of grain sorghum, and host plant resistance is one of the important components for the management of this pest. We studied the inheritance of resistance to this insect involving a diverse array of midge-resistant and midge-susceptible genotypes in India and Kenya. Testers IS 15107, TAM 2566, and DJ 6514, which were highly resistant to sorghum midge in India, showed a greater susceptibility to this insect in Kenya. The maintainer lines ICSB 88019 and ICSB 88020 were highly resistant to sorghum midge in India, but showed a susceptible reaction in Kenya; while ICSB 42 was susceptible at both the locations. General combining ability (GCA) effects for susceptibility to sorghum midge for ICSA 88019 and ICSA 88020 were significant and negative in India, but such effects were non-significant in Kenya. The GCA effects of ICSB 42 for susceptibility to sorghum midge were significant and positive at both the locations. The GCA effects were significant and positive for Swarna, and such effects for IS 15107 and TAM 2566 were negative at both the locations. GCA effect of DJ 6514 were significant and negative in India, but non-significant and positive in Kenya; while those of AF 28 were significant and positive during the 1994 season in India, but significant and negative in Kenya. Inheritance of resistance to sorghum midge is largely governed by additive type of gene action. Testers showing resistance to sorghum midge in India and/or Kenya did not combine with ICSA 88019 and ICSA 88020 to produce midge-resistant hybrids in Kenya. Therefore, it is essential to transfer location specific resistance into both parents to produce midge-resistant hybrids.     

Diallel analysis of barley for resistance to leaf stripe and impact of the disease on genetic variability for yield components

Barley breeders in Syria attempting to develop barley (Hordeum vulgare L.) cultivars resistant to barley leaf stripe (BLS) disease caused by Pyrenophora graminea Ito & Kuribayashi [anamorph Drechslera graminea (Rabenh. Ex. Schlech. Shoem.)]. Information on the combining ability for BLS resistance in Syria is not available. This study was conducted to evaluate, in 10 genetically diverse barley parents, general combining ability (GCA) and specific combining ability (SCA) effects towards the determination of the genetic basis of disease resistance and to estimate genetic variability for yield components and its modification by BLS. Ten parental genotypes varying in their reactions to BLS were crossed in a half-diallel mating design to generate 45 full-sib families. The families and the parents were inoculated with P. graminea and evaluated for resistance in replicated field tests (three inoculated and three non-inoculated plots). The parents chosen showed wide variations for resistance to BLS. Genetic component analysis showed significant effects for both GCA and SCA for resistance to BLS, suggesting that additive as well as non-additive genetic mechanisms were involved in the expression of resistance in these parents. GCA effects were more important than SCA effects. Resistant parents exhibited high negative GCA indicating that additive gene effects were more predominant, and suggesting their prime suitability for use in barley breeding programs to improve resistance to BLS. Narrow-sense heritability was 58% and broad-sense heritability was 99% indicating that selection for BLS resistance should be effective in these crosses. A high genetic variability for the agronomic traits studied was observed. Yield components decreased significantly in inoculated plants and more pronounced in diseased plants. Significant GCA was observed for all traits. Values for GCA were, in some cases, significantly modified by BLS. This indicates that attention must be paid to the danger of drawing conclusion in quantitative genetics studies dealing with both diseased and healthy plants. Two genotypes, Banteng and Igri, had high negative GCA effects and are promising parents for enhancement of BLS resistance.     

4个非洲玉米地方种育种潜力初步研究

为进一步改良和有效利用4个非洲玉米种质提供理论依据,以中国常用的5个自交系为测验种,采用不完全双列杂交设计(NCⅡ),对在四川地区能正常散粉结实的4个非洲玉米地方种进行配合力和育种潜力分析。结果表明,20个顶交组合的株高、穗位高及生育期趋向于对四川生态条件的适应,具有较强的抗病性和抗倒折性,其中来自几内亚比绍编号FDP1种质具有较高的一般配合力,与中国温带血缘的‘丹340’有较强的对照优势,对拓展中国西南地区玉米种质资源、创新杂优模式有一定利用价值。     

Genetical relationships between reactions to bacterial leaf spot,yellow mosaic and Cercospora leaf spot diseases in mungbean (Vigna radiata)

Summary Studies on the inheritance pattern of bacterial leaf spot (BLS), yellow mosaic (YM) and Cercospora leaf spot (CLS) reactions in crosses of BLS and YM resistant/tolerant but CLS susceptible × CLS resistant but BLS and YM susceptible parents indicated that resistances to BLS and CLS were governed by single dominant genes, whereas YM tolerance was a monogenic recessive character. The studies also indicated that these three genes were inherited independently. The simple inheritance pattern and independent assortment of the genes governing resistance/tolerance to these diseases suggest that the usual breeding methods will be adequate to develop multi-disease resistant mungbean cultivars.Paper XII in the series Studies on resistance in crops to bacterial diseases in India.     

转Bt基因玉米对亚洲玉米螟的抗性评价

转Bt基因抗虫玉米为诺华公司含Bt11转化系的杂交种NX4777,能全株表达Cry1Ab杀虫蛋白,以其非转基因受体玉米品种NX4906为对照。在玉米生长至心叶中期(50~60cm高)、抽雄前期和抽丝散粉期分别进行人工接亚洲玉米螟[Ostrinia furnacalis (Guenée)]初孵幼虫40~60头。以食叶级别、存活幼虫数、蛀孔数、隧道长度和雌穗被害级别等,分别作为评价玉米心叶期和穗期的抗性标准。结果表明,Bt玉米食叶级别仅为1级,显著低于对照的7级。Bt玉米平均每株存活幼虫0.04~0.20头、蛀孔0.11~0.15个、隧道长度0.13~0.41cm,雌穗被害级别为0,植株折茎率为0,而对照玉米平均每株存活幼虫6.19~12.41头、蛀孔4.48~7.05个、隧道长度12.41~24.09cm,雌穗被害级别为5.9,植株折茎率高达73.6%~95.5%。室内生测结果亦表明,取食Bt玉米心叶、雄穗的初孵幼虫3d全部死亡,取食花丝7d死亡率达到99%,相比之下取食常规玉米的存活率在88.7%以上。表明表达Cry1Ab杀虫蛋白的Bt对亚洲玉米螟具有很高的抗虫性,能够保护玉米全生育期免受玉米螟的危害。     

Genetics of resistance to 3 isolates of Ascochyta fabae on Faba bean (Vicia faba L.) in controlled conditions

Summary Genetics of resistance to Ascochyta fabae Speg. in Vicia faba L. was studied with a final objective to develop resistant faba bean varieties to Ascochyta blight. The study was conducted separately on 3 single spore isolates (AF10-2 and AF13-2 from Tunisia and AF4-3 from France) and belonging to different groups of virulence (GV1 and GV2). Important general combining ability (GCA) effects were found especially with isolates AF10-2 and AF4-3. Specific combining ability (SCA), although significant for the 3 isolates, was important only with AF13 -2, but less important than GCA. Additive gene effects were predominant to non-additive effects. Lines 29H and A8817 transmitted to their progenies resistance to the 3 isolates, whereas 14–12 and 19TB conferred resistance to their progenies only with isolates AF13-2 and AF4-3, respectively. In the material studied, resistance was generally controlled by dominant genes but also could be attributed to recessive genes although less frequent. Analysis of segregation in the F2 of 2 crosses between the resistant lines (A8817 and 29H) and the susceptible line (14–12) with isolate AF4-3 revealed dominant monogenic control at the level of leaves in the 2 resistant lines and, in addition, a recessive gene controlling resistance of stems. Non-allelic interactions were occasionally manifested and their origin appeared to be due to line 19TB. A recurrent selection scheme was proposed with the objective to develop improved open-pollination populations and synthetic varieties responding to the objective of the national Tunisian research programme on faba bean.     

Genetics of disease resistance in urdbean (Vigna mungo (L.) Hepper) to the leaf spots caused by Colletotrichum truncatum (Schw.) Andrus & Moore

Summary The resistance sources among various test cultivars of urdbean to Colletotrichum truncatum, a leaf spotting pathogen, were identified and genetics of resistance was worked out by studying F₁, F₂ and F₃ generations of crosses between resistant cultivars and the susceptible cv. Kulu 4 and of those among the resistant parents. The resistance was found to be controlled by single dominant genes and the resistance genes were non-allelic.     

Resistance to Septoria nodorum blotch in several Triticum species

Summary Resistance to septoria nodorum blotch in Triticum monococcum, T. tauschii, T. timopheevii, T. dicoccum and T. durum was evaluated on plants at the three-leaf stage in greenhouse tests. A high frequency of resistant genotypes was found in T. monococcum, T. tauschii and T. timopheevii, but not in T. dicoccum and T. durum. The resistance of F₁ plants of crosses of resistant T. monococcum (PI 289599) and T. timopheevii (PI 290518) accessions with susceptible common wheat cv. Park and durum wheat cv. Wakooma, respectively, was evaluated on the basis of percentage leaf necrosis, lesion number, lesion size and incubation period. No dominance was found for long incubation period, but various dominance relationships occurred for low percentage leaf necrosis, low lesion number and small lesion size, depending on the cross. Multiple regression analysis showed that lesion number contributed more to percentage leaf necrosis than lesion size or incubation period. Resistance to septoria nodorum blotch was transferred successfully from T. timopheevii to cultivated durum wheat. Resistant BC₁F₇ lines, recovered from the T. timopheevii (PI 290518) × Wakooma cross, showed normal chromosome behaviour at meiosis (14 bivalents) and were self-fertile. However, an effective level of resistance was not recovered in lines derived from the other interspecific crosses.     

Compensation in grain weight and volume in sorghum is associated with expression of resistance to sorghum midge, Stenodiplosis sorghicola

Sorghum midge, Stenodiplosis sorghicola (Coquillett) is one of the most important pests of grain sorghum worldwide. We studied the inheritance of resistance to sorghum midge and compensation in grain weight and volume in panicles of sorghum hybrids and their parents under uniform infestation (40 midges per panicle for two consecutive days). Sorghum midge damage ranged from 8.2 to 82.4% in the maintainer lines (B-lines) of the females parents (A-lines), and 9.0 to 67% in the male parents (restorer lines). Hybrids involving resistant × resistant parents were highly resistant, while those involving resistant ×susceptible and susceptible × resistant parents showed moderate susceptibility. Susceptible × susceptible hybrids were susceptible. Compensation in (percentage increase) grain weight and volume in midge-infested panicles of midge-resistant parents and their F₁ hybrids was greater than in midge-susceptible parents and hybrids. General combining ability effects for midge damage, and grain weight and volume were significant and negative for the midge-resistant females (ICSA 88019 and ICSA 88020), whereas those for the midge-susceptible females (ICSA 42 and 296A) were significant and positive. However, the reverse was true in case of compensation in grain weight and volume. Inheritance of compensation in grain weight and volume and resistance to sorghum midge is controlled by quantitative gene action with some cytoplasmic effects. Resistance is needed in both parents to realize full potential of midge-resistant hybrids. This revised version was published online in July 2006 with corrections to the Cover Date.     

Genetic analysis of resistance to Karnal bunt (Tilletia indica (Mitra)) in bread wheat

Summary An analyis of an F1-based incomplete diallel was conducted involving 11 parents with different levels of resistance to Karnal bunt (Tilletia indica (Mitra)). It demonstrated that general combining ability (GCA) and thus additive or additive × additive gene effects were very important in the inheritance of resistance, accounting for 86.9% of the variation. Further analysis concentrated on F3 lines derived from individual random F2 plants from crosses with resistant varieties having the highest negative GCA effects. It was shown that the varieties Weaver and W499 have single dominant genes of resistance, which are different from each other, and which differ from a single allelic gene in varieties K342 and Cruz Alta. The majority of the crosses did not demonstrate a relationship between Karnal bunt infection and the number of days to heading. Resistant F3 lines varied in the number of days to heading from 80 to 100.     

A single dominant gene for downy mildew resistance in broccoli

Downy mildew, incited by Peronospora parasitica (Pers.: Fr.) Fr., is a destructive disease of broccoli (Brassica oleraceaL., Italica Group). Resistant cultivars represent a desirable control method to provide a practical, environmentally benign, and long-term means of limiting damage from this disease. Doubled-haploid (DH) lines developed by us exhibit a high level of downy mildew resistance at the cotyledon stage. To determine the mode of inheritance for this resistance, a resistant DH line was crossed to a susceptible DH line to make an F₁, from which F₂ and backcross (BC) populations were developed. All populations were evaluated for response to artificial inoculation with P. parasitica at the cotyledon stage. All F₁ plants (including reciprocals) were as resistant as the resistant parent, indicating no maternal effect for this trait. F₂ populations segregated approximately 3resistant to 1 susceptible, BC populations using the resistant parent as the recurrent parent contained all resistant plants, and the BC to the susceptible parent segregated 1 resistant to 1 susceptible. These results indicate that resistance is controlled by a single dominant gene. This gene should be easily incorporated into F₁ hybrids and used commercially to prevent downy mildew at the cotyledon stage. This revised version was published online in August 2006 with corrections to the Cover Date.     

Combining ability analysis of resistance to head blight caused by <Emphasis Type="Italic">Fusarium graminearum</Emphasis> in spring wheat

Fusarium head blight (FHB) caused by Fusarium spp. is one of the most important fungal diseases of wheat (Triticum aestivum L.) in regions with wet climatic conditions. Improvement of the FHB resistance by developing new varieties requires sound knowledge on the inheritance of resistance. An 8 × 8 diallel analysis was performed to estimate general (GCA) and specific (SCA) combining ability of resistance to FHB. The F₁s and parental lines were evaluated under artificial inoculation at the experimental field of IFA-Tulln, Austria during 2001 and 2002. Disease severity was evaluated by repeated scoring of the percentage of infected spikelets and calculating an area under the disease progress curve (AUDPC). The analysis of combining ability across two years showed highly significant GCA and non-significant SCA effects indicating the importance of additive genetic components in controlling FHB resistance. The significant GCA-by-year interaction presented the role of environmental factors in influencing the FHB reaction of wheat lines. The comparison of the crosses with low FHB infection and GCA effects of their parents showed that such crosses involved at least one parent with high or average negative GCA effect. The results revealed that it is feasible to use highly or moderately resistant genotypes and conventional breeding methods to achieve genetic improvement of FHB resistance in spring wheat.