Wild Crop Relatives: Genomic and Breeding Resources

In the Meiji era we had two serious Bruchid pests, Callosobruchus chinensis and Bruch us pisorum in Japan. In 1926 B. rulimanus was found in Kyushu. Urgent countermeasures were taken to meet the new pest: biology of and control measures against the weevil were studied extensively especially by Kamito. In 1937 the basis of classification of Bruchids in Japan was established by Chujo. Recently the introduction of C. maculatus was noticed. During and after World War II Ishii started his pioneering study on biochemical resistance to Bruchid attack in legume seeds. Also, Utida was carrying on his continuing study of experimental populations of C. chinensis. The range of his study was enlarged from density effect to interspecific competition, host-parasite relationship and phase dimorphism in Callosobruchus spp. The new pheromones of "oviposition marker" and "erectin" were identified and synthesized by Yamamoto and his school in the bean weevils. Some authors took a growing interest in the life history strategy of Bruchids, coevolution between bean and weevil, and evolution or domestication of the bean weevils. Dealing with the increase of imported beans from foreign countries into Japan, the techniques of bean fumigation with methyl bromide and phosphine for quarantine fumigation was developed. In the laboratories of Universities and the private laboratories of agricultural Chemicals Companies many investigations were carried on using the bean weevil as an experimental insect to develop new chemicals without environmental disruption.

Bruchids and Legumes: Economics, Ecology and Coevolution

The Asian Vigna

Mungbean [Vigna radiata (L.) R. Wilczek var. radiata] is an important food and cash legume crop in Asia. Development of short duration varieties has paved the way for the expansion of mungbean into other regions such as Sub-Saharan Africa and South America. Mungbean productivity is constrained by biotic and abiotic factors. Bruchids, whitefly, thrips, stem fly, aphids, and pod borers are the major insect-pests. The major diseases of mungbean are yellow mosaic, anthracnose, powdery mildew, Cercospora leaf spot, halo blight, bacterial leaf spot, and tan spot. Key abiotic stresses affecting mungbean production are drought, waterlogging, salinity, and heat stress. Mungbean breeding has been critical in developing varieties with resistance to biotic and abiotic factors, but there are many constraints still to address that include the precise and accurate identification of resistance source(s) for some of the traits and the traits conferred by multi genes. Latest technologies in phenotyping, genomics, proteomics, and metabolomics could be of great help to understand insect/pathogen-plant, plant-environment interactions and the key components responsible for resistance to biotic and abiotic stresses. This review discusses current biotic and abiotic constraints in mungbean production and the challenges in genetic improvement.

Biotic and abiotic constraints in mungbean production-progress in genetic improvement.

A species level germplasm collection representing 76% of known taxa in the genus Vigna subgenus Ceratotropis was evaluated for resistance to two species of bruchid beetles, Callosobruchus chinensis and C. maculatus. Seven taxa consisting of 29 accessions were found to be resistant to C. chinensis and 4 taxa consisting of 24 accessions were found to be resistant to C. maculatus. This compared with no resistant accessions being found in several hundred landrace accessions of mungbean, V. radiata var. radiata, in the same subgenus. Sometimes resistance was found in all accessions of a particular taxon, such as complete resistance to both C. chinensis and C. macualtus in V. umbellata. Other taxa showed intra taxon variation for resistance such as V. reflexo-pilosa andV. minima. The levels and patterns of resistance among taxa were diverse. The results suggest that various factors cause resistance to bruchid in the subgenus Ceratotropis. While the number of eggs laid on seeds generally reflected seed size, one small seeded cultivar of V. mungo var. mungo, black gram, had an unusually high number of eggs laid per seed. No correlation was found between seed size and levels of resistance. The species level germplasm collection, which reflects the core collection concept in trying to maximize genetic diversity in a limited number of accessions, has enabled a large number of potentially useful sources of resistance to bruchid beetles to be found efficiently.

The effectiveness of evaluating wild species: searching for sources of resistance to bruchid beetles in the genus Vigna subgenus Ceratotropis

Infestation Resistance of Wild Legumes (Vigna sublobata) to Azuki Bean Weevil, Callosobruchus chinensis (L.) (Coleoptera : Bruchidae) and Its Relationship with Cytogenetic Classification

Koichi Fujii

Papers

Infestation Resistance of Wild Legumes (Vigna sublobata) to Azuki Bean Weevil, Callosobruchus chinensis (L.) (Coleoptera : Bruchidae) and Its Relationship with Cytogenetic Classification