Stem rot was recorded as one of serious diseases of red-fleshed dragon fruit, (Hylocereus polyrhizus), in Malaysia. Fusarium fujikuroi was recovered from stem rot lesion of H. polyrhizus and the species was identified using TEF1sequence and mating study. From maximum likelihood phylogenetic tree using combined TEF1-and -tubulin sequences, the F. fujikuroi isolates from stem rot were grouped according to three geographical locations, namely Peninsular Malaysia, Sabah and Sarawak. Phylogenetic analysis indicated that F. fujikuroi isolates from stem rot of H. polyrhizus were clustered separately from F. fujikuroi isolates from rice because of intraspecific variation. From amplification of MAT allele-specific primers, 20% of the isolates carried MAT-1 allele while 80% carried MAT-2 allele. From isolates that carried MAT-1 allele, 65% crossed-fertile with MP-C (mating population of F. fujikuroi) tester strain while for MAT-2 allele, 56% crossed-fertile with MP-C. None of the isolates were identified as MP-D (mating population of F. proliferatum). Pathogenicity test conducted on 40 representative isolates showed that the stem rot symptoms were similar with the symptoms observed in the field, and can be categorized as low, moderate and high aggressiveness, which indicated variation in pathogenicity and virulence among the isolates. This study provides novel findings regarding Fusarium species associated with stem rot of H. polyrhizus and indicated that F. fujikuroi as a new causal pathogen of the disease.

Silicon is one of the beneficial elements to the rice plant for plant growth and the effects could be detected particularly under the biotic and abiotic stress conditions. Plants take up silicon in a form of monosilicic acid from various sources of silicon. A pot experiment was conducted under a greenhouse condition to study the uptake of silicon by local Malaysian rice variety MR284 in a form of silicic acid. The experiment was carried out under 2 x 4 factorial design consist of two methods of silicic acid application namely foliar spray and drench method and four silicic acid rate at 0, 0.02, 0.04 and 0.06 mol L−1-set up in Complete Randomized Design (CRD) with four replications. Parameters measured were plant growth, yield component and grain yield. Paddy with foliar spray application of silicic acid had a better performance than of paddy with drench method in term of yield increment. The application of silicic acid did not have significant effects on panicle length, plant height and thousand grain weight. The number of tillers and number of panicles had increased with an increasing silicic acid rate, while percentage of filled grain and grain yield decreased with the increasing of silicic acid rate. The findings suggest that the ideal amount of silicic acid for optimum effects on growth and yield of paddy can be used at 0.02 mol L−1 as foliar spray application.