Tomato: a crop species amenable to improvement by cellular and molecular methods

Tomato is a crop plant with a relatively small DNA content per haploid genome and a well developed genetics. Plant regeneration from explants and protoplasts is feasable which led to the development of efficient transformation procedures. In view of the current data, the isolation of useful mutants at the cellular level probably will be of limited value in the genetic improvement of tomato. Protoplast fusion may lead to novel combinations of organelle and nuclear DNA (cybrids), whereas this technique also provides a means of introducing genetic information from alien species into tomato. Important developments have come from molecular approaches. Following the construction of an RFLP map, these RFLP markers can be used in tomato to tag quantitative traits bred in from related species. Both RFLP's and transposons are in the process of being used to clone desired genes for which no gene products are known. Cloned genes can be introduced and potentially improve specific properties of tomato especially those controlled by single genes. Recent results suggest that, in principle, phenotypic mutants can be created for cloned and characterized genes and will prove their value in further improving the cultivated tomato.

IR varieties and their impact

Project number related to IDRC support could not be determine

Inheritance of resistance to bacterial blight in ten rice (oryza sativa l.) cultivars

Tanzania Journal of Agricultural Sciences 2000, Vol. 3(1) : 39-46Ten rice cultivars from the International Rice Germplasm Centre originating from Bangladesh were analysedfor the~r genetics of resistance to bacterial blight. The test cultivars were selected on the basis of their high level ofresistance to races IV & VI ofXanthomonas oryzae pv. oryzae. The mode ofinheritance was studied by crossing the test cultivars with Taichung Native 1 (TNI) which is highly susceptible to the races 1,2,3;4 & 6 of X. Oryzae pv. oryzae. The genetic analysis revealed that the test cultivars have two recessive genes conferring resistance to races 1 (PX 061) and 6 (PX 079) of X. oryzae pv oryzae, respectively. The allelic relationship of genes conferring resistance with xa-S and xa-13 was studied in progenies derived from crosses between the cultivars and IRBBS and IRBB13 which are near isogenic lines carrying genes xa-S and xa-13 respectively. The Chi-square analysis of F2 populations revealed that resistance ilJ these cultivars to race 1 was conferred by xa-S. Resistance to race 6 was found to be conferred by another gene which was non-allelic to xa-13