Reciprocal effects in anther cultures of wheat hybrids

This study was conducted to determine the reciprocal effects for anther culture response in wheat (Triticum aestivum L.) using a set of 4 × 4 full diallel crosses. Both reciprocal and nuclear genetic effects were highly significant for anther culture response and useful for selection and breeding purposes. General combining ability (GCA) effects were predominant for all investigated anther culture traits. Also, significant differences for specific combining ability (SCA) effects were detected between reciprocal crosses. Although significant reciprocal differences for responding anther, callus number and green plant regeneration were recorded in some reciprocal crosses, there were no significant reciprocal differences for albino plant regeneration. The use of one parent as male or female could lead to change at the production of green plants from the F₁ hybrids and screening of inbred lines for response to anther culture, without reciprocal effects, could decrease the utilization of breeding material.     

Combining ability for resistance in peanut (Arachis hypogaea) to Peanut bud necrosis tospovirus (PBNV)

The combining abilities of field resistance to peanut bud necrosis disease (PBND) caused by Peanut bud necrosis tospovirus (PBNV) were examined to understand the type of gene action governing resistance to the disease, and to identify peanut lines suitable for use as parents in a PBND‐resistance breeding programme. The Ft and F2 progenies from a six‐parent diallel cross and their parents were evaluated under field conditions. They were assessed for disease incidence at 30, 40, 50 and 60 days after planting (DAP), and reactions of the lines to the disease could be best differentiated at 50 and 60 DAP. Results indicated highly significant general combining ability (GCA) effects for PBND incidence in F₁ and F₂ generations. Specific combining ability (SCA) and reciprocal effects were also found to be significant, but their relative contributions to variation among crosses were much less than those of GCA effects. These results suggested that the type of gene action governing resistance to PBND was mainly additive, and selection for PBND resistance in these populations should be effective. Strong correlation coefficients between parental means and GCA effects for disease incidence were seen in both Ft and F2 generations, suggesting that per se performance of the parental line could be used as a predictor of the capability of the line to transmit its PBND‐resistant attribute to progenies. The reciprocal effects were in favour of using resistant lines as female parents. The peanut lines ICGV 86388, 1C 10 and 1C 34 were found to be suitable for use in a PBND–resistance breeding programme.     

Evaluation of circulant partial diallel crosses in maize

Summary The present study was conducted in maize (Zea mays L.) on crosses among 20 diverse parents. The materials were evaluated in four different environments for eight characters. Combining ability analysis was carried out following diallel and partial diallel crosses. The number of crosses per parent (s) varied from 3 to 19 and the results were studied to identify the critical value of s that would provide an adequate information with minimum resources. The S₅ partial diallel was as good as the S₁₉ for the detection of differences among general combining ability (GCA) effects. Even the S₃ gave adequate information in the case of characters with high heritability. However, partial diallel analysis was less efficient in detecting the differences due to specific combining ability (SCA) effects. These results varied with environments, and characters with low heritability were more prone to misinterpretation. GCA effects showed fluctuations in partial diallel analysis which were more pronounced in S₅ and S₃, particularly for characters with low heritability. The average standard error of difference between GCA effects increased with a decrease in s, with a steep slope for s < 7. The partial diallel analysis was more efficient for the estimation of the variance component of GCA than for SCA, as the estimate of SCA was biased upwards. Estimates of broad sense heritability obtained from the partial diallels agreed with the full diallel analysis better than the narrow sense estimates. Smaller partial diallels gave erratic estimates of heritability, particularly for the characters with low heritability.     

Combining Ability of Different Agronomic Traits and Yield Components in Hybrid Barley

Selection of parents based on their combining ability is an effective approach in hybrid breeding. In this study, eight maintainer lines and nine restorer lines were used to obtain 72 crosses for analyzing the general combining ability (GCA) and special combining ability (SCA) for seven agronomic and yield characters including plant height (PH), spike length excluding awns (SL), inter-node length (IL), spikes per plant (SP), thousand kernel weight (TKW), kernel weight per plant (KWP) and dry matter weight per plant (DWP). The results showed that GCA was significantly different among parents and SCA was also significantly different among crosses. The performance of hybrid was significantly correlated with the sum of female and male GCA (TGCA), SCA and heterosis. Hu1154 A, Mian684 A, 86F098 A, 8036 R and 8041 R were excellent parents with greater general combining ability. Five crosses, Hu1154 A×8032 R, Humai10 A×8040 R, Mian684 A×8037 R, Mian684 A×8041 R and 86F098 A×8037 R, showed superior heterosis for most characters.     

Rice (<i>Oryza sativa</i> L.) Breeding among Hassawi Landrace and Egyptian Genotypes for Stem Borer (<i>Chilo agamemnon</i> Bles.) Resistance and Related Quantitative Traits

Rice stem borer (Chilo agamemnon Bles.) is a primary insect pest of rice and is a major limiting factor to rice production. Breeding for insect-resistant crop varieties has been an economic way of integrated pest management (IPM) as it offers a viable and ecologically acceptable approach. This study was aimed to evaluate rice genotypes for their resistance against rice stem borer. Seven parental genotypes with twenty one F1 crosses were evaluated for genotypic variation in field experiments. Analysis of variance revealed significant differences for the studied traits in almost all crosses and parents. In addition, the mean squares of parents versus their crosses were signifi- cant for stem borer resistance and other associated traits. Moreover, both general combining ability (GCA) and specific combining ability (SCA) variances were highly significant for all characters studied in the F1 generation. Based on GCA, 4 genotypes (Sakha101, Gz6903-3-4-2-1, Gz9577-4-1-1 and Hassawi) exhibited highly significant negative values for stem borer resistance (–0.53, –1.06, –0.18 and –0.49, respectively) indicating they are the best combiners for stem borer resistance. Based on SCA analysis, nine cross combinations showed highly significant negative effects for stem borer resistance. Similarly, the cross Giza178 Hassawi was the best combination with significantly highest value for early maturity. In addition, seven crosses showed highly significant negative SCA for plant height trait. On the other hand, for panicle length, number of primary branches/panicle, panicle weight and 1000-grain weight, seven, four, eight and six crosses showed highly significant positive SCA, respectively. The result further revealed that the non-additive dominance genetic variance was higher than the additive variance for all evaluated traits indicating that non-additive genetic variances have a role in their inheritance. The broad-sense heritability estimates were high for all the studied traits. The stem borer resistance was significantly correlated with panicle weight and 1000-grain weight, which also showed a highly significant correlation with grain yield/plant. Thus these traits can be effectively employed in a breeding program to confer resistance against stem borer infestation in rice. It was further supported by biplot analysis, which clustered these potentially important traits into two quadrants showing their importance in any future breeding program to control stem borer infestation. This study has contributed valuable information for evaluation of genetic diversity in the local rice germplasm and its utilization in futuristic rice genetic improvement programs.     

Population-based diallel analyses among nine historically recognized alfalfa germplasms

Identification of heterotic groups and patterns among breeding populations provides fundamental information to help plant breeders more knowledgeably manipulate heterosis. A diallel analysis was conducted among nine alfalfa (Medicago sativa L.) germplasms, commonly referred to as African, Chilean, Flemish, Indian, Ladak, M. falcata, M. varia, Peruvian, and Turkistan, which represent a significant proportion of the genetic diversity present in US cultivars. Heterotic responses were determined by evaluating forage yield of the germplasms and their 36 half-diallel hybrids in seeded plots that were harvested five times in each of 2 years. Commercially acceptable yields were obtained from some hybrids of unimproved parents, where at least one parent was adapted to the study environment. Variation among crosses was attributed primarily to general combining ability (GCA) effects; however, specific combining ability effects were also significant. GCA estimates for African, Chilean and Peruvian were positive, while those for Ladak, M. falcata, and M. varia were negative. Estimates for variety heterosis effects were positive for Peruvian and M. falcata and negative for Indian and M. varia. Significant mid-parent heterosis [(MPH) range of –21% to 55%] and high-parent heterosis [(HPH) range of –33% to 23%] was detected. M. falcata hybrids exhibited the highest MPH values. However, this likely reflects the poor yield of M. falcata per se in the study environment and consequently, low MPH values. Peruvian hybrids demonstrated the highest cross mean performance, significant positive MPH in all crosses, and positive HPH in five out of eight crosses. The results indicate that Peruvian should be recognized as a heterotic group. Alfalfa breeders may wish to explore opportunities for heterotic yield gains that are likely to exist in hybrids between the Peruvian germplasm and elite breeding populations, in particular, those adapted to the southwestern United States. MPH results suggest that alfalfa breeders may have capitalized on the heterotic response between Flemish and M. varia during past development of alfalfa synthetics adapted to the central and northern latitudes of the United States.     

Genetic Variation and Combining Ability Analysis of Bruising Sensitivity in Agaricus bisporus

Advanced button mushroom cultivars that are less sensitive to mechanical bruising are required by the mushroom industry, where automated harvesting still cannot be used for the fresh mushroom market. The genetic variation in bruising sensitivity (BS) of Agaricus bisporus was studied through an incomplete set of diallel crosses to get insight in the heritability of BS and the combining ability of the parental lines used and, in this way, to estimate their breeding value. To this end nineteen homokaryotic lines recovered from wild strains and cultivars were inter-crossed in a diallel scheme. Fifty-one successful hybrids were grown under controlled conditions, and the BS of these hybrids was assessed. BS was shown to be a trait with a very high heritability. The results also showed that brown hybrids were generally less sensitive to bruising than white hybrids. The diallel scheme allowed to estimate the general combining ability (GCA) for each homokaryotic parental line and to estimate the specific combining ability (SCA) of each hybrid. The line with the lowest GCA is seen as the most attractive donor for improving resistance to bruising. The line gave rise to hybrids sensitive to bruising having the highest GCA value. The highest negative SCA possibly indicates heterosis effects for resistance to bruising. This study provides a foundation for estimating breeding value of parental lines to further study the genetic factors underlying bruising sensitivity and other quality-related traits, and to select potential parental lines for further heterosis breeding. The approach of studying combining ability in a diallel scheme was used for the first time in button mushroom breeding.     

Use of seedling progeny tests for genetical studies as part of a potato (Solanum tuberosum subsp. tuberosum) breeding programme

A diallel set of crosses, including selfs and some reciprocal crosses, was made between 15 parents chosen for their male fertility from those included in a tetraploid potato (Solanum tuberosum subsp. tuberosum) breeding programme at the Scottish Crop Research Institute. Seedling progeny tests were used to evaluate the progenies for non-race-specific resistance to late blight (Phytophthora infestans) in both foliage and tubers, quantitative resistance to the white potato cystnematode (PCN) (Globodera pallida) and the commercial worth of their tubers as judged by breeders' visual preference. No reciprocal differences were found. Comparisons of the selfs and crosses revealed inbreeding depression for breeders' preference, which varied among the parents from negligible to severe, whilst there were also statistically significant differences for foliage and tuber blight, but not for PCN. When the selfs were omitted from the combining ability analyses, large differences in general combining ability (GCA) were found for all four traits, and smaller differences in specific combining ability for tuber blight and breeders' preference. The only statistically significant correlation between GCAs for different traits was a favourable one of r = 0.56 between foliage and tuber resistance to late blight. It was concluded that prospects were good for simultaneously improving all four traits by multitrait genotypic recurrent selection.     

Evaluation of genetic behavior of some Egyption Cotton genotypes for tolerance to water stress conditions

Water stress is a critical abiotic stress for plant reduction in arid and semiarid zones and, has been discovered to be detrimental to the development of seedlings as well as the growth and physiological characteristics of many crops such as cotton. The objectives of our study were to determine the combining ability and genetic components for five quantitative traits [(leaf area (LA), leaf dry weight (LDW), plant height (PH), fiber length (2.5 percent SL), and lint cotton yield/plant (LCY/P)] under water shortage stress, a half diallel cross between six cotton genotypes representing a wide range of cotton characteristics was evaluated in RCBD with four replications. The genotype mean squares were significant for all traits studied, demonstrating significant variation among genotypes for all characters under water shortage stress. LCY/P had the highest phenotypic and genotypic correlation co-efficient with PH, LDW, and LA shortage. The highest direct effect on lint cotton yield was exhibited by leaf area (3.905), and the highest indirect effects of all traits were through LA, with the exception of 2.5 percent SL, which was through LDW. The highest dissimilarity (Euclidean Distance) between parental genotypes was between G.87 and G.94, followed by G.87 and Menoufi. G.94 was also a well-adapted genotype, and the combinations G.87 x G.94 and G.87 x Menoufi may outperform their parents. The combining ability analysis revealed highly significant differences between parental GCA effects and F1 crosses SCA effects. The variation of GCA and SCA demonstrated the assurance of additive and non- additive gene action in the inheritance of all traits studied. In terms of general combining ability (GCA) effects, parental genotype G.94 demonstrated the highest significant and positive GCA effects for all traits studied, with the exception of 2.5 percent SL, where G.87 revealed the highest significant and positive GCA effects. The effects of specific combining ability (SCA) revealed that the cross (G.87 x2G.94) revealed stable, positive, and significant SCA for all of the studied traits.     

Diallel and generation means analyses for the components of resistance to Cercospora arachidicola in peanut

Summary The inheritance of the components of partial resistance to Cercospora arachidicola Hori in peanut (Arachis hypogaea L.) was examined in two five-parent diallels and in the six generations of two single crosses in greenhouse tests. The Griffing (1956) analysis indicated general combining ability (GCA) to be of most importance, yet large ratios of SCA/GCA sum of squares suggested nonadditive genetic variance as well. Reciprocal effects were found for lesion area and lesion number/10 cm² leaf area. The importance of nonadditive genetic variance was substantiated by the lack of fit for the additive-dominance model in the Hayman's analysis (1954 a, b). Further evidence from the Hayman's analysis indicated that epistasis may be important in determining the inheritance of some of the components of resistance. Additive gene effects alone accounted for the genetic variability observed among the generation means from two single crosses for all components of resistance except latent period. There was evidence that epistasis was an important mode of gene action for the inheritance of latent period.Paper No. 10172 of the Journal Series of the North Carolina Agricultural Research Service, Raleigh, NC 27601, USA     

Prediction of hybrid performance in maize using molecular markers and joint analyses of hybrids and parental inbreds

The identification of superior hybrids is important for the success of a hybrid breeding program. However, field evaluation of all possible crosses among inbred lines requires extremely large resources. Therefore, efforts have been made to predict hybrid performance (HP) by using field data of related genotypes and molecular markers. In the present study, the main objective was to assess the usefulness of pedigree information in combination with the covariance between general combining ability (GCA) and per se performance of parental lines for HP prediction. In addition, we compared the prediction efficiency of AFLP and SSR marker data, estimated marker effects separately for reciprocal allelic configurations (among heterotic groups) of heterozygous marker loci in hybrids, and imputed missing AFLP marker data for marker-based HP prediction. Unbalanced field data of 400 maize dent × flint hybrids from 9 factorials and of 79 inbred parents were subjected to joint analyses with mixed linear models. The inbreds were genotyped with 910 AFLP and 256 SSR markers. Efficiency of prediction (R ²) was estimated by cross-validation for hybrids having no or one parent evaluated in testcrosses. Best linear unbiased prediction of GCA and specific combining ability resulted in the highest efficiencies for HP prediction for both traits (R ² = 0.6–0.9), if pedigree and line per se data were used. However, without such data, HP for grain yield was more efficiently predicted using molecular markers. The additional modifications of the marker-based approaches had no clear effect. Our study showed the high potential of joint analyses of hybrids and parental inbred lines for the prediction of performance of untested hybrids.     

Genetic studies on resistance to Valsa canker in apple: genetic variance and breeding values estimated from intra- and inter-specific hybrid progeny populations

Malus sieboldii Rehd. exhibits high levels of resistance to Valsa canker caused by Valsa ceratosperma (Tode ex Fr.) Maire while cultivated apples (Malus domestica Borkh.) are susceptible to the disease. In this study, progenies from 23 full-sib families derived from both inter- and intra-specific hybridization among 16 Malus genotypes as parents were assessed for resistance to V. ceratosperma (Vc) for two seasons using an excised shoot assay to determine the pattern of inheritance of the resistance and to also estimate the variance components, narrow-sense heritability, and breeding values of parental genotypes. Generally, M. sieboldii × M. domestica and its reciprocal crosses had more resistant progenies to Vc than intra-specific crosses of M. domestica. Resistance to Vc expressed as the relative lesion length among progenies showed continuous variation irrespective of cross, suggesting the quantitative nature of the resistance to the three virulent isolates of Vc that were tested. Resistance to Vc using the progeny population was analyzed using a mixed linear model based on restricted maximum likelihood. The parental effect (general combining ability (GCA)) was significant while the interaction effect between parents (specific combining ability (SCA)) was relatively small and non-significant. The ratio of SCA/GCA variance was about 32%, suggesting that additive genetic variance had a major contribution to the total genetic variance for resistance to Vc. There was a positive correlation (r = 0.49, p < 0.01) between mid-parental GCA and SCA predictions among 23 full-sib families for the resistance. Narrow-sense heritability estimated by sib analysis was moderate ( [^(h)]² = 0.29 ) \left( {{{\hat{h}}^2} = 0.29} \right) . The predicted breeding values (BV) of the 16 parents indicated that M. sieboldii “Sanashi 63” and “Hayanarisanashi 1” would be useful for breeding for high levels of resistance to Vc.     

抗除草剂杂交籼稻亲本的配合力分析

本试验以6份新育成的抗除草剂籼型恢复系为父本,5份生产上广泛应用的不育系为母本,采用不完全双列杂交设计配制了30份杂交组合,对其苗期除草剂抗性和主要农艺性状配合力进行了分析。除草剂抗性鉴定表明,亲本恢复系及三系杂交组合抗性接近完全,两系杂交组合抗性达90%以上。配合力分析表明,不育系除单株有效穗数外其他农艺性状的一般配合力均达到极显著差异;恢复系间一般配合力在所有性状中均达到显著或极显著差异;杂交组合间特殊配合力方差仅在单株产量、结实率、播始历期和千粒重4个性状中达到显著或极显著差异。不育系中,金科1A在单株产量、结实率等7个性状上的一般配合力均为最高,但其特殊配合力方差最小;广占63-4S在千粒重性状上具有最高的一般配合力、最大的特殊配合力方差,在播始历期上具有最高的一般配合力负效应;C815S在株高上的一般配合力负效应最大,同时特殊配合力方差较高。恢复系中,华抗恢101在单株有效穗数上具有最高的一般配合力和特殊配合力方差;华抗恢104在穗长上具有最高的一般配合力,在播始历期上具有最高的一般配合力负效应;华抗恢105在单株产量、结实率等性状上具有最高的一般配合力,在株高上具有最高的一般配合力负效应;华抗恢106在千粒重性状上具有最高的一般配合力和特殊配合力效应方差。利用抗除草剂恢复系配制杂交组合,不仅可以改良其除草剂抗性,也可以通过广泛测配,选择一般配合力强、特殊配合力方差大的亲本配组育成强优势组合。     

优质蛋白玉米黄粒系产量配合力及其杂种优势模式的分析

研究玉米种质的遗传关系及其杂种优势模式对玉米育种者有着极为重要的指导意义.本研究对从国际玉米小麦改良中心(CIMMYT)引入的及国内自育成的10个优质蛋白玉米(QPM)黄粒优良系进行了配合力分析及杂优模式的初步研究.这10个QPM优良系中有5个来自CIMMYT的热带、亚热带系;5个为国内自育成的骨干系.通过部分双列杂交获得45个杂交组合,将这些组合种植在云南省及广西自治区的三种不同生态条件下进行观察鉴定.产量的方差分析结果表明,品种之间、环境之间的差异达到极显著水平,而重复之间不显著;产量的一般配合力差异达极显著水平,而特殊配合力的差异不显著.杂交组合CML166×齐205具有最高产量(10880kg/hm2),杂交组合长631/02×中系096/02具有最低产量(5496kg/hm2).自交系CML161产量的一般配合力效应值最高(1010.53),自交系CML166产量的一般配合力效应值其次(947.11);而自交系中系096/02产量的一般配合力效应值最低(-1119.98).自交系CML194与忻9101/02具有最高的产量特殊配合力效应值(1813.50),自交系CML166与齐205产量的特殊配合力效应值也较高(1272.00);而自交系忻9101/02与齐205产量的特殊配合力效应值最低(-1670.96).根据杂交组合产量性状的配合力分析,可初步将这10个优质蛋白玉米自交系划分为4个杂种优势群和4种杂种优势模式.     

Additive inheritance of resistance to pod rot caused by Phytophthora palmivora in cocoa

Summary Quantitative inheritance of resistance to Phytophthora pod rot (Ppr) was studied in cocoa hybrid progeny from 12 Trinitario x Amazonian crosses and their reciprocal crosses. The crossing scheme was similar to a factorial design. Disease was assessed by the number and percentage of infected pods on each tree. Highly significant differences due to general combining abilities (GCA) were obtained for all characters, except for the GCA of Trinitario on total pod production. Differences for specific combining ability (SCA) were not significant for all characters. There were no significant differences between reciprocal crosses. The Trinitario clone K82 provided the only source for the hybrid progenies of strong Ppr resistance to the hybrid progenies, while K20 provided moderate resistance. Other parental clones — KA2-101, KA5-201, KEE 2, KEE 5, and KEE 52 — produced progenies which were susceptible to Ppr. It is evident that resistance to Ppr in cocoa is inherited additively. Maternal and cytoplasmic effects were assumed to have no influence on inheritance of resistance. It is also concluded that resistance to Ppr of the kind shown by K82 is likely to be horizontal resistance. Breeding for high-yielding cultivars combined with Ppr resistance is the most effective way of controlling Ppr of cocoa on the crops of growers with small holdings in Papua New Guinea.     

Micronuclei frequency and character coherence inAvena sativa L./A.fatua L. crosses

Summary The use of micronuclei frequency per microspore quartet (MF) has been proposed to indicate the relative reduction in chromosome homology among interspecific oat (Avena L.) hybrids. Hybrids with lower MF would presumably undergo greater genetic recombination, providing greater opportunity for breaking linkages that contribute to association, or coherence, of desirable and undesirable characters in progenies. Microspore quartets from 63A. sativa/A. fatua hybrids were observed. Character coherence was examined in progenies of the four hybrids with the highest MF (2.22 to 2.82 micronuclei/quartet) and four hybrids with the lowest MF (0.23 to 0.31 micronuclei/quartet) to determine whether a relationship existed between MF and character coherence. Coherence of seed disarticulation with quantitative characters that differentiate the parental species was more frequent in high MF crosses as was expected if high MF is indicative of reduced recombination. However, incidence of coherence between seed color and the quantitative characters was not related to MF differences among the crosses. Likewise, the degree of coherence among the quantitative characters, as measured by coefficients of concordance, was not associated with differences in MF among the crosses. Thus, coherence of the characters studied was not associated consistently with differences in MF.     

Nuclear genes affecting albinism in wheat (Triticum aestivum L.) anther culture

Summary Inheritance of the ability to respond in wheat anther culture was studied from 6×2 reciprocal crosses between six varieties with high and two varieties with low capacity for green plant formation and their parents, replicated in two environments. Effects of genotypes dominated embryo formation and percentages of green plants, accounting for 78.4% and 85.4% of total variation, respectively, while smaller genetic effects were indicated for regeneration. Nuclear genes could explain almost all the genotype effects in this material. Embryo formation showed heterosis over high parent for 5 of the 12 hybrids, while percentages of green plants from the hybrids were intermediate to the parents. General Combining Ability (GCA) could explain 78.8% of the variation for embryo formation among the hybrids, whereas differences in percentage of green plants were dominated by Specific Combining Ability (SCA), accounting for 67.9% of hybrid variation. A positive correlation (r=0.81^**) was observed between the genetic capacity for regeneration and green plant formation. Analysis of covariance indicated that effects causing GCA for green plant formation were mainly responsible for this correlation. A regression model with two parallel lines divided the six parent lines with high green plant formation into three groups with respect to their reactions with the two testers. The results are discussed with regard to possible involvement of two sets of nuclear genes affecting the percentage of green plants obtained in wheat anther culture: one set consisting of mainly additive effects affecting green plant percentage through an initial effect on regeneration ability, and another set of two or a few more major genes with dominance or epistatic effects uncorrelated with regeneration.     

杂交水稻苗瘟抗性的配合力和遗传力分析

采用7×7不完全双列杂交设计,对反映杂交水稻苗瘟抗性的5个指标进行了配合力和遗传力分析.结果表明,杂交水稻苗瘟抗性遗传力高,受加性和非加性基因效应共同控制,但以加性效应为主;恢复系的苗瘟抗性一般配合力效应明显相对重要于不育系,不育系苗瘟抗性一般配合力效应对F1代的抗性有显著的影响;14个供试亲本中,多恢1号、成恢149、K42A、K40A具有较好的苗瘟抗性一般配合力效应.因此,在杂交水稻抗苗瘟育种中,对恢复系的抗性GCA选择和对亲本的抗性GCA评鉴至关重要,但不应忽视不育系对组合的抗性贡献和对组合的抗性评鉴;多恢1号、成恢149、K42A和K40A可作为优良抗苗瘟亲本加以利用.     

Evaluation of inheritance to leaf rust in wheat using area under disease progress curve

Six varieties, Kundan (K), Galvez-87 (G), Trap (T), Chris (C), Mango (M) and PBW-348 (P) along with fast ruster, Agra Local (AL), were screened for seedling reaction and adult pant response to leaf rust. Seedlings of all six varieties were susceptible while adult plants showed lower susceptability response than Agra Local. The F1s among the varieties, and also with Agra Local, showed the values lesser than the respective mid parental values for AUDPC suggesting a polygenic mode of inheritance. ANOVA for combining ability effects indicated variation due to the GCA and SCA effects, which indicated that both additive as well as non-additive type of genetic variances, govern AUDPC. The higher values for the GCA variance over the SCA variance indicated the predominance of an additive component over the dominance component for AUDPC. Significant values for GCA effects indicated that Kundan, Galvez-87 and Trap can be used as good general combiners for AUDPC. The crosses, KxAL, GxAL and TxAL showed significant sca effects for AUDPC, which indicated the predominance of non-additive gene effects in these crosses. Additive x additive and dominance x dominance components of the 5- parameter model were highly significant and contributed maximum extent compared to the additive and dominance components in the cross KxG, while dominance and dominance x dominance components contributed maximum in the remaining crosses. Under such a situation, improvement in the character may be expected through standard selection procedure, which may first exploit the additive gene effects and simultaneously care should be taken to see that the dominance effects are not dissipated, but rather they should be concentrated.     

Genetic analysis of the anther-culture response of three spring wheat crosses

Summary Anther-culture response was examined among three spring wheat (Triticum aestivum L.) cultivars to evaluate the genetic component of response and to determine whether androgenetic performance could be improved by selection. The three lines, the three possible F₁'s among the three lines, their F₂'s, and the backcrosses to the parents were evaluated for callus production and regeneration capacity. Significant variation was observed among the generations of the three crosses for callus formation. Genetic variation for regenerability was nonsignificant. Callus production was negatively correlated (-0.24) with regeneration capacity. The random variation in the study was too great to determine whether major-gene differences for antherculture response exist among the three lines by examining population distributions. When the material was evaluated for quantitative gene effects, the estimates for the additive gene effects were generally greater than the estimates for the dominance gene effects for callus formation. Only the Pavon x Chris cross, however, exhibited a significant narrow sense heritability estimate for callusing response (0.94). Due to the large component of random variation and the varying selection potential among crosses for androgenetic performance, improving anther-culture response in wheat by selection could prove difficult unless the anther-culture process itself selects for response traits at the gametic level.