Authors:M.A. Adebayo, A. Menkir, S. Hearne and A.O. Kolawole
The quest for precise and rapid phenotyping of germplasm is increasing the interest of breeders and physiologists in the application of remote sensing techniques in maize breeding. Twenty-four drought-tolerant maize inbred lines were crossed using a modified North Carolina II mating scheme to generate 96 single-cross hybrids. The parents and the hybrids were evaluated under full irrigation and drought stress conditions in the dry seasons of 2010 and 2011 at Ikenne, southwest Nigeria. Normalized difference vegetation index (NDVI) was recorded at 3- and 8-leaf growth stages. Hybrids differed significantly for NDVI. Both general (GCA) and specific (SCA) combining ability effects were significant for NDVI measured at 8-leaf stage under both irrigation regimes, with GCA accounting for 53% of the total variation under full irrigation. Both additive and non-additive genetic effects played significant roles in the inheritance of NDVI. The females GCA effects for grain yield was positively correlated with females GCA effects for NDVI (r = 0.72, p < 0.0001) and the male GCA effects for grain yield was also correlated with males GCA effects for NDVI (r = 0.78, p < 0.0001) at 8-leaf stage under full irrigation. These results indicate that live green biomass accumulation in maize could be identified through early screening of a large number of genotypes using NDVI for developing productive hybrids.
Authors:T. Spitkó, L. SÁgi, J. Pintér, C. Marton and B. Barnabás
The breeding of hybrid maize now has a history of over 100 years. In 1908, George H. Shull was the first to report on the high yields, great uniformity and homogeneity of hybrids derived from a cross between two inbred lines. Following this discovery, consistent self-fertilisation over a period of six to eight generations was found to be an extremely efficient method for developing maize lines. From the mid-1970s, however, with the elaboration of the monoploid (
) and microspore culture (
) techniques, it became possible to develop homozygous lines within a year.With the help of an efficient plant regeneration system based on anther culture, large numbers of doubled haploid (DH) lines can be produced. In the course of the experiments the seed of DH plants selected over several years was multiplied and crossed with Martonvásár testers, after which the hybrids were included in field performance trials in three consecutive years (2005–2007). The aim was to determine whether the field performance of hybrids developed in this way equalled the mean yield of standards with commercial value. The data also made it possible to calculate the general (GCA) and specific (SCA) combining ability of the parental lines, indicating the usefulness of the parental components in hybrid combinations and expressing the extent to which a given line contributes to yield surpluses in its progeny.A total of 52 maize hybrids were evaluated in the experiments in terms of yield and grain moisture content at harvest. The combinations, resulting from crosses between 12 DH lines, one control line developed by conventional inbreeding and four testers, were found to include hybrids capable of equalling the performance of the standards, and four DH lines were identified as improving the yield level of their progeny. As the experiment was carried out on a very small number of genotypes, the results are extremely promising and suggest that, if the range of genotypes used to develop DH lines is broadened and the sample number is increased, it will be possible in the future to find maize hybrids, developed with
DH parental components, that surpass the performance of commercial hybrids.
Combining ability and heterosis were calculated for fourteen lines of linseed in a line × tester mating design using twelve lines and two diverse testers in two different environments. The hybrids and parental lines were raised in a completely randomized block design with three replications to investigate seed and fibre yield and their component traits. Genetic variation was significant for most of the traits over environments. Combining ability studies revealed that the lines KL-221 and LCK-9826 were good general combiners for seed yield and most of its components, whereas LMH-62 and LC-2323 were good general combiners for yield components only. Moreover, KL-221 was also a good general combiner for fibre yield. Similarly, B-509 and Ariane were good general combiners for fibre yield and most of its components. Among the specific cross combinations, B-509 × Flak-1 was outstanding for seed yield per plant and B-509 × KL-187 and LC-2323 × LCK-9826 for fibre yield per plant, with high SCA effects. In general, the hybrids excelled their respective parents and the standard checks for most of the characters studied. Based on the comparison of mean performance, SCA effects and the extent of heterosis, the hybrids LC-2323 × LCK-9826 and B-509 × KL-221 appeared to be the most promising for both seed and fibre yield. Other promising combinations were LC-2323 × KL-210 and B-509 × Ariane for seed and fibre yield, respectively. The superiority of LC-2323, LCK-9826, KL-221, B-509 and Ariane as good general combiners was further confirmed by the involvement of these parents in the desirable cross combinations.
Authors:Chu Jinfeng, Wang Xuebin, Lv Gongxu, Zhao Yi, Zhang Junbo, Wang Jincheng, Mi Hongzhi and Yang Hao
The purpose of the investigation was to evaluate the feasibility of imaging inflammatory lesions with five small molecular weight complexes of 99mTc. The labeling yields of D-glucaric acid (D-Gca), citric acid (Cit), DL-malic acid (DL-Mal), L-malic acid (L-Mal) and tartaric acid (Tar) were all more than 90%. The percentage uptake/g tissue of them and 99mTc-pertechnetate (P) in mice with turpentine-induced abscesses and abscess/muscle (A/M), blood (A/B), liver (A/L), kidney (A/K) concentration ratios were calculated. The maximum A/M ratios were 4.02±0.21 (Cit, 3h), 4.30±0.77 (D-Gca, 3h), 4.04±0.21 (DL-Mal, 6h), 3.50±0.23 (L-Mal, 1h), 3.20±0.17 (Tar, 1h) and 3.23±0.41 (P, 1h) respectively. The scintigram was obtained in a rabbit with turpentine-induced abscess after 99mTc-D-Gca i.v. injection. Results demonstrated they all can accumulate in inflammatory lesions. Of them, 99mTc-D-Gca is probably a potential imaging agent on inflammatory lesions.
The fruit yield and quality of hot pepper, Capsicum annuum L., is very low in Ethiopia mainly due to the lack of improved cultivars. The objective of this study was to evaluate the combining ability for yield and yield contributing characters in order to apply an appropriate breeding methodology for the improvement of yield and the contributing characters. Seven diverse cultivars, two local cultivars and five introduced promising inbred lines, were crossed in a half-diallel. The parents and F1s were grown at Melkasa Agricultural Research Center in 1999 and 2000. The experiment was arranged in a randomized complete block design with three replications of ten plants per row. The green fruit yield and eight yield contributing characters were recorded from eight plants in each replication. The analysis of variance and estimates of GCA and SCA were significant for most of the characters studied. Significant GCA and SCA values were recorded for most of the characters, revealing that both additive and non-additive gene effects were involved in genetic control. A lower average degree of dominance was also recorded for some of the characters. Although none of the parents was a good general combiner for all the traits, some parents showed high GCA effects for some of the economic traits, suggesting that these parental lines could be considered simultaneously while formulating a breeding programme for improving fruit yield and yield contributing characters. The majority of the crosses also depicted significant SCA effects in the desirable directions.
Combining ability analysis was carried out in the F1 and F2 generations of a 10 × 10 parents half diallel for peduncle length and flag leaf area in spring wheat under three environments. The mean squares for both general combining ability (GCA) and specific combining ability (SCA) were significant for peduncle length in both the generations, indicating the involvement of both additive and non-additive gene actions in the inheritance. However, the high values of GCA variance showed the greater importance of additive gene action in the inheritance of this trait. Flag leaf area was observed to be controlled by non-additive gene action. The environment played a significant role in the expression of both the traits. The GCA × environment interaction exhibited greater sensitivity in all cases than the SCA × environment interaction. The varieties Kharchia 65 and Durgapura 65 emerged as desirable general combiners for peduncle length, whereas Pavon and Moncho had high mean performance for flag leaf area. These parents could be used as donors in future breeding to develop a physiologically efficient wheat genotype with high production. The crosses Moncho × Brochis and Durgapura 65 × Raj 821 were the most desirable specific combinations for flag leaf area and Kharchia 65 × Chiroca for both the traits. Desirable transgressive segregants can be expected from these crosses. Diallel selective mating or bi-parental crossing could be useful for the genetic improvement of these physiological traits.
Authors:M.I.E. Arabi, E. Al-shehadah and M. Jawhar
Powdery mildew, caused by Blumeria graminis f. sp. hordei (Bgh) is a common foliar disease of barley worldwide. The creation of new cultivars with durable resistance to Bgh is highly desirable. This work was undertaken to examine the resistance to Bgh in 10 genetically diverse barley parents, and to evaluate their general combining ability (GCA) and specific combining ability (SCA) effects toward determining the genetic basis of disease resistance. Two experiments, in a growth chamber on seedling and in the field on adult plant stages, were conducted using a randomized complete block design with three replicates. The parents expressing differences in their reactions to Bgh were crossed in a half-diallel mating design to generate 45 full-sib families. Genetic component analysis showed significant effects for both GCA and SCA under both experiments suggesting that additive as well as non-additive genetic mechanisms were involved in the expression of resistance in these parents. The estimate of narrow-sense heritability was 0.63 and broad-sense heritability was 98% indicating that selection for the disease resistance should be effective in these crosses. Resistant parents ‘Banteng, PK 30-136 and ‘Igri’ had significantly negative GCA effects, suggesting their prime suitability for use in barley breeding programs to improve resistance to Bgh.
Authors:F. S. Pelser, M.T. Labuschagne, B. Wentzel and A. van Biljon
The mixograph performs certain rheological measurements during dough mixing and is a good predictor of wheat end-use quality. The aim of this study was to determine the expression and the heritability of mixing characteristics measured with Mixsmart® software and some quality characteristics in hard red spring wheat parents and their F1 progeny. Six parents varying in midline peak time and envelope peak time were crossed in a half diallel design. Parents and progeny were planted in three different environments. General combining ability (GCA) was a significant source of variation for the measured characteristics, and parents differed widely in terms of GCA effects. Midline-development time, -peak integral and -peak time showed high narrow sense heritability. Envelope peak-integral and -tail width displayed high narrow sense heritability for some, but not all locations. High GCA:SCA (specific combining ability) ratios indicated the prevalence of additive gene effects for midline-development time, -peak integral and -peak time, indicating that these characteristics are largely genetically determined, and that selection for them should lead to genetic gain.
Salinity stress is one of the important abiotic stresses affecting rice germination and reduces establishment of seedlings in the field. Six varieties of rice were included in a full diallel mating design and together with their progenies were evaluated for salinity tolerance. General combining ability (GCA) effect was significant for germination percentage reduction (GP) and radicle length reduction (RL); whereas specific combining ability (SCA) were significant for all of traits contain GP, RL, germination rate reduction (GR) and coleoptile length reduction (CL). The negative value of heterosis, due to inverse relation of reduction of traits and salinity tolerance, indicated ideal heterosis. The highest value of negative heterosis for GP, GR, RL and CL were displayed in Shahpasand × Sepidrod, Hassani × Sepidrod, Shahpasand × IRFAON-215 and Sepidrod × IRFAON-215, respectively. The parents with negative GCA are superior for salinity tolerance traits. The Genotype, Genotype-by-Environment (GGE) biplot analysis showed that Sepidrod contributed resistance to GP, GR and IRFAON-215 was the best parent for RL and CL. Respondent this view, Sepidrod and IRFAON-215 can be used either as best parents for selection programs due to their GCA effects, or as a superior parent hybrid programs on their SCA effects.
This research was carried out in 1997 and 1998 in order to study the genetic structure of a hybrid population established from three CMS (cytoplasmic male sterile) lines and four pollen tester (restorer) lines, to identify the parents and crosses showing superior general and specific combining abilities and finally to evaluate F1 hybrid vigour. According to the results, the variance due to specific combining ability (SCA) was highly significant for seed yield, number of seeds per head and plant height. These traits of sunflower were influenced, mostly, by dominant gene actions. Neither general (GCA) nor specific combining ability (SCA) variances were found to be significant for head diameter and 1000-seed weight. most of the total genetic variation in these characteristics was caused by epistatic gene actions due to SCA variances, which were higher than GCA variances. The parental lines CMS381, CMS461, RHA684 and RHA892 had the highest positive GCA effects for seed yield and in terms of the other traits studied, but these effects were not significant for all the traits observed. The crosses CMS191×RHA723, CMS191×RHA892, CMS381×RHA684 and CMS461×RHA684 might be considered as promising combinations in terms of seed yield and yield components. The amounts of heterosis and heterobeltiosis ranged from -8.4 to +16.3% to -21.3 to +3.4% for plant height, from 46.3-82.3% to 20.3-48.3% for head diameter, from -14.8 to +52.6% to.-16.5 +46.9% for number of seeds per head, from -3.3 to +42.7 to -19.0 to +21.0% for 1000-seed weight and from 19.8-98.1 to 4.6-89.8% for seed yield.