J. Hort. Sci. Vol. 2 (2): 104-107, 2007 INTRODUCTION French bean (Phaseolus vulgaris L.) is one of the most important legume vegetables grown for its tender green pods. Globally it is grown in an area of 0.68 million ha with total production of 4.7 million metric tonnes and productivity is 6.91 tonnes / ha. In India, it is grown in an area of 0.15 million ha with annual production of 0.42 million metric tonnes (Anonymous, 2006). The crop is susceptible to various biotic and abiotic stresses. Among the various biotic stresses, rust caused by Uromyces phaseoli (Reben Wint) has become endemic in bean producing areas. The yield loss due to this disease is 78 to 90 % (Grafton et al, 1985) and it is serious during rabi. The disease incidence will be less during kharif season. The disease is more severe in tropics than in the temperate region and the pathogen will be more active under moderate temperature of 17 to 270 C and relative humidity of more than 95 %. The popular varieties like Contender, Pant Anupama, Pusa Parvathi, Arka Komal, Arka Suvidha etc., are susceptible to rust disease. Although chemical control using sulphur fungicides and propioconozole are recommended, the induction of genetic resistance will have Breeding French bean (Phaseolus vulgaris L.) for resistance to rust (Uromyces phaseoli Reben Wint.) T. S. Aghora, N. Mohan, R. G. Somkuwar1 and Girija Ganeshan Division of Vegetable drops Indian Institute of Horticultural Research Hessaraghatta Lake Post, Bangalore-560089, India E-mail: aghor@iihr.ernet.in ABSTRACT French bean is an important legume vegetable grown for its tender, green pods for both fresh consumption and processing. Rust, caused by Uromyces phaseoli, limits successful cultivation of this crop. Popular varieties like Contender, Pant Anupama, Pusa Parvathi, Arka Komal, Arka Suvidha, etc., are susceptible to this disease. The french bean variety, Arka Bold, having resistance to rust was used in hybridization with Arka Komal, a popular bush variety with high yield and slender, long green pods but susceptible to rust. Inheritance studies indicated that resistance to rust was controlled by a single, dominant gene. Pedigree method of breeding was followed for incorporating rust resistance in to commercially cultivated varieties. Breeding lines with resistance to rust were selected to F 2 generation onwards. These were advanced up to F 7 , wherein, a promising line, (Arka Bold x Arka Komal) 99-17-2-1-4-12-3, with resistance to rust with high pod yield and good pod quality was selected and named Arka Anoop and released for commercial cultivation. Keywords: French bean, rust resistance, the greater merit over the chemical control. Hence, the present study was taken up with the objective of developing a french bean variety with resistance to rust disease along with high yield and good pod quality and also to study the genetics of disease resistance. MATERIAL AND METHODS The source of resistance to rust was found in Arka Bold (Mohan et al, 1997). The hybridization was done between Arka Bold and Arka Komal (a bushy variety with high yield and slender long pods) in both combinations during 1999 at IIHR, Bangalore. Subsequently, F 1, F 2, B 1 and B 2 populations were raised and evaluated for resistance to rust. Artificial screening for rust was done by spraying uredospore suspension uniformly on both sides of the leaves. The concentration of spore suspension was maintained at 107 spores / ml. Percent disease index (PDI) was calculated as per the method given by Stavely (1983). The disease scoring was done on a 0- 9 scale where 0 = no pustules; 1 = small brown pustules covering less than 1% of leaf area; 3 = typical pustules covering 1-10 % of leaf area; 5= typical pustules covering 11- 25 % of leaf area; 7= typical pustules covering 1Present address:National Research Center for Grapes, Pune, Maharashtra 104 105 26 - 50 % of leaf area and 9= typical pustules covering more than 51 % of leaf area combined with withering of leaves. Per cent disease index (PDI) was calculated by using the formula given by Wheeler (1969), PDI = Where χ represents the diseased leaves within the sample plants in the respective class such as 0, 1, 3, …9. Data obtained from the two crosses and two testcrosses were subjected to χ2 analysis. Based on the disease reaction in F 1, F 2, B 1 and B 2 population, the inheritance of resistance to rust was worked out. The plants with PDI less than 5 % were considered as resistant and those showing PDI more than 5 % as susceptible for formation of classes for test. Data of two crosses and two testcrosses were subjected to analysis to test the goodness of fit against assumed phenotypic ratio of 3:1(resistant and susceptible respectively) for single dominant gene controlling rust resistance. Pedigree method of selection was followed up to F 7 generation. Replicated yield trials were conducted for selected breeding lines. RESULTS AND DISCUSSION All the F 1 plants in the cross Arka Bold (R) and Arka Komal (S) and its reciprocal were resistant indicating the dominance over susceptibility and had shown that cytoplasmic genes are not involved in resistance. In F 2 population of 196 plants, observed segregation ratio for resistance to susceptibility, was 146: 50 as against expected ratio of 147:49 (Table 1). In the reciprocal cross, 216 plants were resistant and 68 were susceptible as against expected ratio of 213:71 respectively. Further, the test cross progeny of Arka Bold (R) and Arka Komal (S) segregated in the ratio of 55 resistant to 50 susceptible plants as against the expected ratio of 53: 53 respectively out of 106 test cross plants. In another test cross progeny of Arka Komal (S) and Arka Bold (R), the ratio was 54:48 as against 51:51. The calculated χ2 value for both the F 2 and testcrosses were non significant with high probability of 0.87 to 0.89 and 0.55 to 0.63, respectively. F 2 population of both the crosses showed a good fit of 3:1 between resistant and susceptible and test cross progeny indicated the segregation in 1:1 ratio (Table 2). The cross, Arka Bold x Arka Komal indicated dominance of resistance to rust over susceptibility in F 1 progeny. This was similar in the reciprocal cross also. The pattern of segregation in F 2 population along with the two test cross generations followed Mendelian ratio of dominance and application of χ2 test for F 2 and test cross generations indicated that resistance to rust was inherited as a single dominant gene in french bean variety, Arka Bold. These findings are in conformity with Augustin et al, (1972a, b), Stavely (1984), Stavely and Grafton (1985), Grafton et al, (1985), Finke et al, (1986), Sayler et al, (1995) and Yuebin (1995) who reported that the resistance to rust is monogenically controlled. Further, Pedigree method of breeding was followed and segregants with resistance to rust were selected from F 2 generation onwards and were advanced up to F 7 generation, wherein, a promising line (Arka Bold x Arka Komal)-99-17-2-1-4-12-3 possessing resistance to rust with high yield and good pod quality was selected and named as Table 1. Frequency of resistant and susceptible plants in parents and F 1 ’s Sl Crosses First parent Second parent F 1 F 2 Test BC with No. Cross R Parent. R S R S R S R S R S R S 1 B x A 87 0 0 89 78 0 147 49 55 50 91 0 2 A x B 0 89 87 0 85 0 216 68 54 48 105 0 R=Resistant, S=Susceptible, A=Arka Komal, B=Arka Bold, BC=Back cross. Table 2. Frequencies of F 2 and test cross progenies with their χχχχχ2 estimates Sl No Crosses Observed Expected Total Chi Square Probability ratio ratio R S R S 1 B x A 146 50 147 49 196 0.03 0.87 2 A x B 216 68 213 71 284 0.02 0.89 Pooled 350 120 360 110 470 0.18 0.68 Test crosses 1 (B x A) x A 55 51 53 53 106 0.24 0.63 2 (A x B) x A 54 48 51 51 102 0.35 0.55 Pooled 109 99 104 104 208 0.96 0.33 Table χ2 @ 1df. 3.84 R=Resistant, S=Susceptible, C=Contender, A=Arka Komal, B=Arka Bold, K=KPV-1, BC=Back cross. Rust resistance in French bean J. Hort. Sci. Vol. 2 (2): 104-107, 2007 106 Arka Anoop (Fig 1 and 2). Replicated yield trials conducted at IIHR, Hessaraghatta for three years from 2003 to 2005) during rabi season showed that the new variety, Arka Anoop had a significantly higher number of pods per plant (42.50) as compared to check (Table 3). It also recorded an average pod yield of 19.78 t /ha, as against a yield of 14.29 and 8.24 t/ha in the check varieties Arka Komal and Contender, respectively. The percent yield increase in Arka Anoop over check varieties Arka Komal and Contender was 38.42 and 140.05 respectively. Arka Anoop was completely resistant Fig 1. Arka Anoop a new french bean variety Fig 2. French bean var. Arka Anoop (on either side) showing resistance to rust with susceptible check in the middle Table 3. Average plant and pod characters of french bean var. Arka Anoop compared with parents and checks Sl. No. Characters Arka Anoop Arka Komal Arka Bold Contender P=0.05 CV % 1 Days to 50 % flowering 32.50 32.00 33.0 32.50 1.41 2.05 2 Days to pod maturity 45.00 45.50 47.0 43.50 1.45 1.97 3 Plant height 58.50 57.50 55.0 52.50 2.33 4.72 4 Pod length (cm) 17.60 15.75 14.5 14.25 1.03 2.93 5 Pod width (cm) 1.00 1.05 1.55 1.00 0.11 4.24 6 Number of pods per plant 42.50 31.58 22.5 15.50 2.35 6.98 7 Ten pod weight (g) 88.50 56.00 75.0 51.00 11.00 5.79 Table 4. Average pod yield (t/ha) and rust index (PDI) of french bean var. Arka Anoop between 2003-2005 during rabi Sl. No. Varieties Pod yield (t/ha) Average Rust PDI Average % Yield % Yield increase increase over over Arka Contender Komal 2003 2004 2005 2003 2004 2005 1 Arka Bold (res. parent) 14.50 15.20 14.80 14.83 2.15 1.86 2.64 2.22 - - 2 Arka Komal (Susc. Parent) 17.11 16.10 9.67 14.29 27.90 36.45 56.84 40.40 - - 3 Arka Anoop 18.71 19.38 21.24 19.78 2.35 1.79 1.58 1.91 38.42 140.05 4 Contender (susc. check) 9.92 8.70 6.10 8.24 45.36 51.30 74.36 57.01 - - CD (P=0.05) 2.43 1.92 1.76 - 5.79 2.83 4.85 - - - CV % 14.04 5.92 5.20 - 7.66 11.26 9.53 - - - Aghora et al Table 5. Average pod yield (t/ha) of Arka Anoop during Kharif season Sl. No. Varieties 2003 2004 2005 Average % increase over increaseover Arka Komal % Contender 1 Arka Bold (res. parent) 15.50 14.30 14.90 14.90 - - 2 Arka Komal (Susc. Parent) 18.00 18.50 17.22 17.90 - - 3 Arka Anoop 18.83 21.13 19.90 19.95 15.85 69.00 4 Contender (susc. check) 10.50 12.25 12.69 11.81 - - CD(P=0.05) 0.71 2.82 3.59 - - - CV % 4.22 7.85 15.00 - - - J. Hort. Sci. Vol. 2 (2): 104-107, 2007 107 to rust with very low PDI of 1.91 whereas, the check varieties, Arka Komal and Contender were susceptible (Table 4). Yield trials were also conducted during kharif seasons for three years from 2003 to 2005 wherein, Arka Anoop gave an average green pod yield of 19.95 t /ha, while in parents Arka Bold and Arka Komal, the yields were 14.9 and 17.9 t/ha, respectively (Table 5). The per cent yield increase in Arka Anoop over check varieties Arka Komal and Contender was 15.85 and 69.00 in that order (Table 5). The yields in the check varieties were comparatively better during kharif due to low or no incidence of rust. The study confirmed that the resistance to rust in french bean variety, Arka Bold was controlled by single dominant gene. Further, it also revealed that the selected breeding line, Arka Anoop was resistant to rust with average yield potential of 19.8 t/ha. REFERENCES Anonymous, 2006. FAOSTAT. http://faostat.org Augustin E., Coyne, D. P and Schuster M. L. 1972a. Inoculation methods, sources of resistance and genetics of the reaction to Brazilian rust race B 11 in Phaseolus vulgaris. Ann Rep Bean Improvement Co- operative 15:44 Augustin E., Coyne, D. P and Schuster M. L., 1972b. Inheritance of resistance in Phaseolus vulgaris to Uromyces phaseoli var. typica Brazilian rust race B 11 and of plant habit. J. Amer. Soc. Hortl. Sci., 96:526-531 Grafton, K. F., Weiser, G. C., Littlefield, L. J and Stavely, J.R. 1985. Influence of resistance to two races of leaf rust in dry edible bean. Crop Sci. 25:537-539 Finke,M. L., Coyne,D. P. and Steadman, J. R. 1986. The inheritance and association of resistance to rust, common bacterial blight, plant habit and foliar abnormalities in Phaseolus vulgarisL. Euphytica 35:969-982 Mohan N., Aghora, T. S., Somkuwar R. G. and Girija, G. 1997. Sources of resistance to rust in french bean (Phaseolus vulgaris L.). Ind. J. Agril. Sci., 67:85-86 Sayler, R. J., Ewing, J. D., and McClean, P. E, 1995. Monogenic and epistatic resistance to bean rust infection in common bean. Physiol. Mol. Pl. Path., 47:173-184 Stavely, J. R., 1983. A rapid technique for inoculation of Phaseolus vulgaris with multiple pathotypes of Uromyces phaseoli. Phytopath., 73:676-679 Stavely, J. R., 1984. Genetics of resistance to Uromyces phaseoli in a Phaseolus vulgaris line resistant to most races of pathogen. Phytopath., 74:339-344 Stavely, J. R. and Grafton, K. F., 1985. Genetics of resistance to eight races of Uromyces appendiculatus in Phaseolus vulgaris , cultivar, Mexico-235 Phytopath., 75:1310 Wheeler, B. E. J., 1969. An Introduction to Plant Disease. John Wiley and Sons Ltd., London, p.301 Yuebin, 1995. Preliminary studies on kidney bean rust resistant breeding. Acta Hort., 402:115-119 (MS Received 13 November 2007, Revised 31 December 2007) Rust resistance in French bean J. Hort. Sci. Vol. 2 (2): 104-107, 2007