Selection for juice quality and red rot disease index in sugarcane (Saccharum officinarum L.)

Abstract

Red rot, caused by Colletotrichum falcatum Went, is the most important disease of sugarcane (Saccharum officinarum L.) in India, which had caused the complete failure of many commercial varieties. In general, it is believed that red rot susceptibility is correlated with high juice quality (1). However, Ram et al., (2) found no correlation between HR Brix and disease index in seedlings of seven crosses. Considering these contradictory reports 230 progenies of 40 crosses, 7 general crosses and 7 poly crosses were evaluated in an RBO with 2 replications. The plot size was a 6m row spaced at 90 cm. Five canes/plot were inoculated by the most virulent race (Cf08) of red rot pathogen during August 2004. The reaction of each clone was recorded during October 2004 by following the internationally accepted 0-9 scale. Observations were recorded on hand refractmeter Brix (HR Brix) at the time of inoculation (August 2004) and evaluation (October 2004) and pol % in juice during January 2005 and red rot disease index to study the relationship among these traits. Clones were grouped as low «(+x-cr), medium (+x-cr) «(+x-cr) and high) (+ x + cr) on the basis of juice quality at the three growth stages. Mean and genotypic coefficients of variation (GCV) and genotypic correlations were computed amongst the four traits studied in the population as well as in low, medium and high juice quality groups.