Identification and evaluation of resistance to rice blast in Guangxi wild rice resources.

Rice blast,caused by Magnaporthe grisea,is one of the most destructive diseases in rice worldwide.Exploitation of resistance gene resources for rice breeding is of most importance in control of this disease.Thirty-eight of 1500 accessions of Oryza rufipogon Griff.and 18 of 113 accessions of O.officinalis Wall.ex Watt.originated from Guangxi,China were found to be resistant to the disease.In natural field nursery assessment,there was no significant difference in the frequency distributions at different disease index levels in different years for O.rufipogon and O.officinalis.The frequency and resistance stability of resistant plants in O.officinalis were obviously higher than those in O.rufipogon,which indicated that the O.officinalis species was a specific resistant type to the blast,with new type of resistance genes of important value.The study also indicated that homozygosity by selfing could significantly enhance the mean resistance level of O.rufipogon and O.officinalis.In natural field nursery assessment,the ratio of resistant plants had not significant correlation with genetic diversity in the regional population groups of O.rufipogon.