Bacterial wilt of tomatoes severely limits production in the tropical and subtropical countries. Screening of known resistant cultivars introduced from North Carolina, viz., Venus and Saturn; breeding lines from Philippines and Hawaii, revealed only CRA 66 Sel-A (sent by Dr. Gilbert from Hawaii) to be resistant under our conditions, (Rao et al., 1975). Some SSD derivatives sent to us by Dr. Villareal from AVRDC, Taiwan in 1977, were observed to be generally resistant, a few of them highly so, viz., VC 8-1-2-1 (our no. IHR 663). Interestingly resistance in CRA 66 Sel-A has been observed to be conditioned by multiple recessive genes, while a single dominant gene controls the resistance in 663-12-3, when tested against a race-1 isolate being maintained here (Tikoo et al., 1983)
Following pedigree selection in crosses involving CRA 66 Sel-A with high yielding lines and pure line selection in Taiwanese breeding lines, many high yielding lines with varying levels of resistance have been obtained (Table 1). The results could be summarized as follows:
1) Derivatives with acceptable fruit weight from CRA 66 Sel-A crosses were obtained only when the susceptible line was large fruited (above 100 g).
2) None of the CRA 66 derivatives had absolute resistance, but survival beyond 80 days after inoculation in the field resulted in acceptable yields (Table 1).
3) The resistance in the Taiwanese derivates was very high, most lines having 100 percent survival even at 100 days after inoculation, i.p., 120 days after planting (Table 1).
4) Fruit size in the Taiwanese derivatives was generally high, one of them, 83 BWR 11 having an average fruit weight of 129 g (Table 1).
5) Per cent survival data at various stages of growth (Table 1) showed that stage-3 (coinciding with first harvest) was very closely correlated with survival rates at stage-4 (r = 0.81). Stage-3 also had the highest correlation with yield (r = 0.57). Hence, under our field conditions, the survival rates of first harvest seem to be the ideal stage to isolate true resistance and also select for yield and fruit traits.
Table 1. ANOVA for yield/plant, average fruit weight, percent survival at 4 stages of crop growth after inoculation with bacterial wilt inoculum. Season - December 1982 to April 1983.
______________________________________________________________
(% survival at 20 day intervals)
Yield/ Av. fr. _______________________________
plant weight Stage* Stage Stage Stage
Remarks (g) (g) 1 2 3 4
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Derivative
from Taiwan line
82 BWR 1 1.48^abc 50.2^f 100.0 100.0 100.0 78.1^c
2 " 1.10^c 54.0^ef 100.0 100.0 100.0 100.0^a
3 " 1.59^ab 70.3^cd 100.0 100.0 100.0 100.0^a
4 " 1.28^abcd 61.2^def 100.0 100.0 98.2 83.5^bc
5 " 1.64^a 59.5^def 100.0 100.0 100.0 100.0^a
CRA 66 derivative
6 1.37^abcd 60.7^def 100.0 100.0 100.0 90.5^bc
7 " 1.51^abc 63.0^de 100.0 100.0 100.0 92.1^b
8 " 1.27^abcd 67.2^d 100.0 96.2 92.3 31.1^d
9 " 1.46^abc 64.9^de 100.0 100.0 100.0 80.4^c
Taiwan
10 1.28^abcd 84.5^b 100.0 100.0 100.0 100.0^a
11 " 1.19^bcd 129.6^a 100.0 100.0 100.0 97.8^ab
Maya Guez Peru
12 1.02^d 91.9^b 100.0 100.0 97.9 97.9^ab
13 " 1.08^cd 82.7^bc 100.0 97.9 95.8 87.4^bc
Hawaii
**14 0.58^e 30.O^g 100.0 100.0 100.0 100.0^a
Taiwan
15 1.43^abcd 48.9^f 100.0 100.0 100.0 100.0^a
Pusa Ruby -
susceptible 0.30^e 32.1^g 74.4 57.1 4.7 0.0^a
check
Sel-4 " 0 0 84.1 17.2 3.6 0.0^e
IHR 709 " 0 0 73.6 8.3 0.0 0.0^e
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'F' value 5.84** 28.14** 6.14** 82.9** 373.6** 59.4**
C.D. 5% 0.43 13.0 10.34 9.2 5.5 14.1
* Stage-1 = 40 days after inoculation.
** CRA Sel-A - 8, resistant line from Hawaii.
Literature cited:Rao, MVB, H.S.Sohi & S.K.Tikoo, Pl. Dis. Rep., 1975.
Tikoo,S.K., N.Anand, R. Kishun, 15th Intl. Cong. Genet., New Delhi, Dec. 12-21, 1983, Abstr. 1338.