Inheritance and selection of field resistance to sheath brown rot disease in rice
1995
Sthapit, B.R. | Pradhanang, P.M. | Witcombe, J.R.
Chilling temperatures induce sheath brown rot disease (ShBR) in rice (Oryza saliva) caused by Pseudomonas fuscovaginae. The major symptoms of the disease are poor exsertion of the panicle from the boot and spikelet sterility. The inheritance of field resistance was studied in F3 families derived from three rice crosses involving a field-resistant (R) parent, two intermediate (1) parents, and a susceptible (S) parent. Each cross was assessed at a different altitude to give three independent data sets. Heritability (h2) estimates of disease resistance traits were determined by analysis of F3 family means in crosses Raksali (S) X Makwanpur-15L (I), Makwanpur-3L (I) X Chhomrong (R), and IR36 (S) X Chhomrong (R). There were highly significant differences between F3 family means in all cases and heritabilities were consistently high (0.72 to 0.84). High h2 estimates and high variance between F3 families resulted in high predicted genetic gains from selection, so field screening in the F3 generation for ShBR resistance should be effective. Mean, additive, and dominance gene effects were estimated from generation means analyses. A statistically significant model could be fitted in all three crosses, and additive effects were always important. Dominance was also an important genetic effect, and its direction was significantly toward resistance in two of the crosses but, with lower significance, toward susceptibility in the third. Significant correlations were found between ShBR field resistance and plant height and panicle exsertion from the boot. Selection, in the presence of the disease, for taller plants and better panicle exsertion will give a genetic gain for greater chilling tolerance and higher ShBR field resistance.
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