GENETICS OF SLOW- RUSTING RESISTANCE TO LEAF RUST IN BREAD WHEAT

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1 Indian J. Agric. Res., 43 (4) : , 2009 AGRICULTURAL RESEARCH COMMUNICATION CENTRE / indianjournals.com GENETICS OF SLOW- RUSTING RESISTANCE TO LEAF RUST IN BREAD WHEAT V.J. Bhatiya, M.A. Vaddoria, D.R. Mehta and B.A. Monpara Department of Agricultural Botany, College of Agriculture Junagadh Agricultural University, Junagadh , India ABSTRACT Genetic architecture of slow-rusting resistance to leaf rust was studied using generation mean analysis involving six basic generations (P 1,P 2, F 1, F 2, BC 1 and BC 2 ) of two bread wheat crosses viz., J 24 x HD 2189 and J 24 x HS 347. The individual and joint scaling tests revealed the presence of digenic epistasis for inheritance of slow-leaf rusting in both the crosses. The best fitting model revealed the significance of only additive (d) gene effect in cross J 24 x HD 2189 where simple selection could be effective for exploiting slow rusting phenomenon. In case of cross J 24 x HS 347, all the gene effects except (m) were significant indicating importance of additive and non-additive gene effects. Therefore, improvement through reciprocal recurrent selection, biparental mating or diallel selective mating could be employed for improvement of this trait. However, number of gene pairs controlling slow-leaf rusting was quite variable in both the crosses. Key words: Bread wheat genetics, Slow-rusting, Resistance, Leaf rust. INTRODUCTION Wheat is the world s most widely cultivated foodgrain crop, known for its remarkable adoption to wide range of environments and its role in providing food security to millions of people across the globle. India is the second largest producer of wheat in the world contributing about 72.1 million tonnes of grains from an area of 26.6 million hectares (Annonymous, 2005). One of the most important factors that limit the grain yield in wheat is the damage due to diseases in general and rusts in particular. Leaf rust (Puccinia triticina Eriks) of wheat is an important disease in all the wheat growing areas of the world and cause serious damage to wheat crop. The phenomenon of slowrusting has been seen as one of the strategies to provide resistance against rust disease for longer duration. The term slow-rusting was coined by Coldwell (1969) as a type of resistance where disease progress at a retarded rate resulting in intermediate to low disease levels against all the pathotypes of a pathogen. Breeding for slow-rusting resistance has special significance for developing cultivars, which performs longer period and entails enormous expenditure on limited resources. Characterization of resistant wheat is terms of nature, number and usefulness of new leaf rust resistant genes is of paramount importance for the use of these new genes in breeding cultivars with slow-rusting resistance. Hence, present investigation deals with the characterization and inheritance of slow leaf-rusting using generation mean analysis with best fitting model in the line of Cavalli (1952).

2 280 INDIAN JOURNAL OF AGRICULTURAL RESEARCH MATERIAL AND METHODS Wheat cultivar J 24 as a susceptible parent was crossed with resistant parents HD 2189 and HS 347 during rabi Two F1s viz., J 24 x HD 2189 and J 24 x HS 347 along with three parents (J 24, HD 2189 and HS 347) were grown in rabi 2003 to perform BC 1 crosses. The F 2 generation was developed by selfing F 1 generation in the same season. The experimental material consisting of six basic generations viz., P 1, P 2, F 1, F 2, BC 1 of two crosses were grown during rabi The experiment was laid out in compact family block design with three replications using single row plot for each of the parents and F 1 s; two rows for each BC 1 and BC 1 and five rows for growing F 2 generation. The rows of 2.5 m length were spaced 22.5 cm apart by keeping 10 cm distances between two plants within each row. Infector rows of Agra Local were provided in and around the experimental area to ensure uniform inoculum load of brown rust. The 15 days old seedlings of infector were inoculated with a mixture of most prevalent races of leaf rust. The field was irrigated same day in the evening to provide sufficient humidity. In addition, fresh ureadospores collected from rust nursery were suspended in water with three drop of the surfactant Tween 20 and sprayed in experimental field. The material was reinnoculated second time 10 days after the first inoculation. Leaf rust infection based on the modified Cobb s scale for cereal rust (Paterson et al., 1948) was recorded for individual plants at five different dates starting from 2nd February to 2nd March, 2005 with an interval of seven days (i. e. 2nd, 9th, 16th, 23rd February and 2nd March). The observations were recorded on five randomly selected plants for each of parents and F1s; 20 plants of BC 1 and 50 plants of F 2 generation for recording rust infection in per cent. The area under the disease progress curve was determined for each plant using the formula suggested by Paterson et al., (1948). Data were transformed by using angular transformation of Fisher and Yates (1938). The data were first subjected to statistical analysis of variance to compact family block design (Panse and Sukhatme, 1967) followed by application of individual scaling tests of Mather (1949) to detect the presence of epistasis. Further, the data were subjected to joint scaling test of Cavalli (1952). The six-parameter model was also fitted following Jinks and Jones (1958). When any one of the epistatic parameters of digenic interaction found nonsignificant, the analysis was done as per the best possible estimates by omitting the nonsignificant interaction parameter(s) in the line of Cavalli (1952) using least square technique. The formula proposed by Wright (1968) was used to estimate the number of genes segregating for the trait. RESULTS AND DISCUSSION The result revealed from field observations on leaf rust reaction in both crosses that first parent (J 24) had higher degree of leaf rust susceptibility, whereas second parent (HD 2189 and HS 347) had higher degree of resistance (Fig. 1 and Table 1). Mean rust infection levels of other four generations were quite variable in both crosses. Mean performance indicated that F1 was intermediate between two parents indicating partial dominance for both these crosses. Besides, in case of cross J 24 x HD 2189, mean values of F 1 and F 2 were equal and differed significantly from both the parents, indicating influence of additive gene action for this trait (Table 1). Back cross generations revealed that leaf rust was higher in BC 1 as compared to BC 2 in both the crosses and differed significantly from respective parental mean.

3 Vol. 43, No. 4, Table 1: Mean performance, estimation of scaling test and genetic parameters for percent leaf rust infection measured in term of area under disease progress curve (AUDPC) in two bread wheat crosses Parameters Crosses J 24 x HD 2189 J 24 x HS 347 Mean Performance P ± ± 1.07 P ± ± 0.07 F ± ± 0.47 F ± ± 1.28 BC ± ± 1.39 BC ± ± 1.74 CD (5%) CV % Scaling tests A ± **± 3.03 B 11.25**± ± 3.52 C 11.58* ± * ± 5.31 Joint 2 (3 df) ** 39.32** Gene effects (m) 27.67** ± ± 6.81 (d) 21.79** ± * ± 0.54 (h) ± ** ± (i) ** ± 6.79 (j) ** ± ** ± 2.30 (l) ** ± ** ± (1df) for best fitting model *, ** Significant at 1 and 5 % levels, respectively The individual scaling tests B and C were significant in cross J 24 x HD 2189 and scaling tests A and C were significant in cross J 24 x HS 347. The similar results were also confined by joint scaling test in both the crosses (Table 1) indicating the presence of epistasis. The estimates of gene effects for the best fitting model in both the crosses are given in Table 1. The analysis of gene effects indicated the significance and importance of additive genes among main effects, in cross J 24 x HD 2189, while among the digenic effects additive x dominance (j) and dominance x dominance (l) effects were negative and significant. However, the relative magnitude of additive (d) was higher than the nonadditive gene effects in this cross indicating the preponderance of additive gene effects over non-additive gene effectst. Therefore, simple selection could be utilized for the improvement of slow leaf-rusting in early segregating generations. These results are akin with results reported by Tandon et al., (1989), Jacobs and Brores (1989) and Das et al., (1992). In case of cross J 24 x HS 347, all the five parameters of gene effects viz., additive (d), dominance (h), additive x additive (i), additive x dominance (j) and dominance x dominance (l) were found significant indicating importance of additive as well as non-additive gene effects. The relative magnitudes of nonadditive gene effects were higher than the additive gene effect indicating the preponderance of non-additive gene effects for slow leaf-rusting. Therefore, the successful breeding methods will be the ones, which can mop-up the gene to form superior gene constellations interacting in favorable manner, some forms of recurrent selection namely diallel selective mating design (Jenson, 1970) or

4 282 INDIAN JOURNAL OF AGRICULTURAL RESEARCH biparental mating design in early segregating generation (Joshi and Dhawan, 1966) might prove to be effective as an alternative approach. Parental mean and F 2 range in both the crosses reveled that transgressive segregation in F 2 in desirable direction could be possible for AUDPC in cross J 24 x HS 347 (Table 2). Therefore, selection of slow leafrusting plants as well as high yielding ability from F 2 generation in cross J 24 x HS 347 could be possible. Number of gene pairs controlling slow leaf-rusting in both the crosses J 24 x HD 2189 and J 24 x HS 347 in both the methods (n 1 and n 2 ) was (12.47 and 1.20) and (3.71 and 2.07), respectively, indicating that the HD 2189 possessed 2 to 13 and HS 347 possessed 3 to 4 genes for the differences in slow leaf-rusting. HD 2189 had more numbers of resistance Table 2: Number of gene groups, parental mean and F 2 range for per cent leaf rust infection measured as area under disease progress curve (AUDPC) in two bread wheat crosses Parameters Crosses J 24 x HD 2189 J 24 x HS 347 Number of n Gene groups n P L P H Range in F 2 plants 7.10 to to n 1, n 2 = Number of segregating genes calculated according to Wright (1968) P L = low mean value of respective parent, P H = high mean value of respective parent.

5 gene pairs as compared to HS 347. Therefore, it could be better to utilize it for developing new slow leaf-rusting genotypes. Quite variable results were also found for number of gene pairs controlling slow-rusting in wheat. Two Vol. 43, No. 4, to 12 genes by Ohm and shaner (1976); 2 to 3 genes by Bjarko and Line (1986); 0.1 to 19.6 genes by Jacobs and Broers (1989) and 4 to 5 genes by Zhang et al., (2001) were reported for slow-leaf rusting in wheat. REFERENCES Anonymous (2005). CMIE, Andheri (East), Mumbai. Bjarko, M.E. and Line, R.F. (1988). Phytopathology, 78: Caldwall, R.M. (1969). In Int. Wheat Genet. Symp. 3rd ed. (Finalay, K.W. and Shepherd, K.W,ed.) Cavalli, L.L. (1952). Quantitative inheritance. H.M.S.O., London Das, M.K.et al. (1992). Crop Sci., 32: Fisher,R.A. and Yates, F.(1938). Statistical Tables for Biological, Agricultural and Medical Research. Jacobs, Th. and Broers, L.H.M. (1989). Euphytica, 44: Jensen, A. B. (1970). Crop. Sci., 42: Jinks, J.L. and Jones, R.M. (1958). Genetics, 43: Joshi, A.B. and Dhawan, N.L. (1966). Indian J. Genet., 26(A): Mather, K. (1949). Biometrical Genetics. Mathuen and Company Ltd., London. Ohm, H.W. and Shaner, G.E. (1976). Phytopathology, 66: Panse, V.G. and Sukhatme,V.P. (1967). Statistical Methods for Agricultural Workers. ICAR, New Delhi. Peterson, R.F. et al. (1948). Can. J. Res. Sect. C., 26: Tandon, G. et al. (1989). Haryana Agric. Univ. J. Res., 19: 1-5 Wright, S. (1968). Evaluation and Genetics of Populations. 1.: 5-9 Zhang, R.J. et al. (2001). Phytopathology, 91: