Inheritance of Submergence Tolerance in Lowland Rice Variety

About 70% of the rain-fed lowland rice farms in Nigeria are prone to seasonal flooding, which is a major constraint to rice production in some major rice producing areas. Each year that there is flooding, rice farmers in these parts of the country lose their entire crop. This research focuses on developing a submergence tolerant rice variety to overcome crop loss due to flooding. A study of the inheritance pattern of submergence tolerance in rice was carried out using four parental lines, namely two submergence tolerant varieties collected from IRRI (IR05F102 and IR07F102) and two susceptible Nigerian varieties (WITA 4 and TOX 4004). Crosses of tolerant x susceptible and susceptible x tolerant varieties were made. The resulting progenies were screened for submergence tolerance and the number of susceptible and tolerant plants was counted. Data obtained were subjected to Chi-square test to determine their goodness of fit to various genetic ratios. The cross involving WITA 4 and IR05F102 parents produced 187 F2 progenies that segregated into 143 tolerant and 44 susceptible. The reciprocal cross also produced 168 F2 progenies that segregated into 132 tolerant and 36 susceptible. The results of both crosses fitted into 3:1 ratio of 275 tolerant and 80 susceptible as indicated by the chi-square goodness of fit analysis. The 157 F2 progenies derived from the cross (TOX 4004 X IR07F102) segregated into 126 tolerant and 31susceptible. The 179 progenies of the reciprocal cross also segregated in the same pattern with 142 tolerant and 37 susceptible. The 336 F2 progenies from all the crosses and reciprocal crosses segregated into 268 tolerant and 68 susceptible in the ratio 3:1, suggesting the involvement of one major gene. No difference in the reciprocal crosses in both F1 and F2 populations was detected in all the crosses. Hence, either of the genotypes could be used as the female parent in breeding programmes.