Wide compatibility in rice (Oryza sativa L.)

Summary Wide compatible varieties (WCVs) show normal spikelet fertility in crosses with Indica and Japonica rice varieties. Crosses of Indica and Japonica varieties frequently show high spikelet sterility which prevents exploitation of heterosis for grain yield. We screened 41 rice varieties for the wide compatibility trait by crossing each with three Indica and three Japonica testers. Varieties giving fertile F₁ hybrids with both groups of testers were classified as WCVs. Seven varieties viz., BPI-76 (Indica); N 22; Lambayeque-1 and Dular (Aus); Moroberekan, Palawan and Fossa HV (Japonicas), were identified as WCVs. The frequency of WCVs was higher among Aus and Japonicas. The wide compatibility trait in varieties: Dular and Moroberekan was controlled by a single dominant gene linked with the Est-2 and Amp-3 loci (mean recombination 32.0%). Est-2 and Amp-3 showed complete linkage. Pgi-2 was found to be linked with Est-2 and Amp-3 (mean recombination 16.1%). Est-2 and Amp-3, showed a tighter linkage with C ⁺ (mean recombination 4.1%). Pgi-2 showed a lower linkage with C ⁺ (mean recombination 17.3%). The recombination values between the WC gene in Dular and C ⁺ was much higher than those reported in Japan for the WC gene (S₅ ⁿ) from Ketan Nangka. It is possible that the WC gene from Dular is different from that in Ketan Nangka. Linkage intensities with the WC gene were not strong enough to be of use for indirect selection for the wide compatibility trait. A search for a more closely linked isozyme or DNA marker was proposed.