Development of new cytoplasmic lines with good flowering behavior for hybrid rice breeding

Abstract

Intensive use of single source of male sterile cytoplasm (i.e. wild abortive or WA) in developing hybrid rice might lead to genetic vulnerability associated with susceptibility to pests and diseases. The research aim was to develop new cytoplasmic genetic male sterile lines (CMS) from 3 different cytoplasmic sources (WA, Gambiaca and Kalinga). Anther culture and successive backcrosses were conducted to develop new CMS. The screening of bacterial leaf blight to each CMS was done through artificial inoculation using three isolates i.e. pathotype III, IV and VIII. The results showed that combination of anther culture and backcrosses obtained 6 CMS lines of WA type, 3 CMS lines of Kalinga type, and 1 CMS line of Gambiaca type. The lines showed complete and stable sterility from first to fifth backcross generations. Some of them also showed resistance to certain Xanthomonas oryzae pathotypes. The new CMS lines with WA, Kalinga and Gambiaca cytoplasm were early in maturity with flowering behavior better than IR58025A (check CMS), such as larger stigma, higher stigma exertion, wider angle and longer duration of glume opening during anthesis. The accumulation of good flowering behavior increased seed set of the new CMS lines yielded from outcrossings. It ranged from 4.75–25.9%, meanwhile IR58025A seed set only reached 2.98%. Corellation analysis showed high positive and significant value between seed set of the new CMS lines and stigma width (r = 0.44*), stigma exertion (r = 0.54*) and angle of glume opening during anthesis (r = 0.42*), respectively. The seed set was also affected by some flower characters of the maintainer lines such as filament length and angle of glume opening during anthesis. The results indicated that the new CMS lines with diferent cytoplasm sources could be used in hybrid rice breeding.