H. A. Van Rheenen

Induction and inheritance of determinate growth habit in chickpea (Cicer arietinum L.)

SummaryThe character of determinate plant growth has not been reported for chickpea and has not been observed in the world germplasm collection at ICRISAT, Patancheru, India. A determinate growth habit would be desirable where growing conditions often lead to excessive vegetative growth. We attempted to generate this trait by mutation breeding. Seeds of the cultivar ICCV 6 were exposed to varying irradiation treatments, M1 and M2 populations were raised, and in the latter one plant was detected that showed the determinate growth habit and female sterility. The character of determinate growth segregated in a postulated digenic epistatic 3:13 fashion in the F2 and confirmed its digenic mode of inheritance in the F3 and F4. The symbol cd is proposed for the allele conditioning for determinancy and Dt for the allele expressing the determinate trait. Continued mutation breeding with this and other material may result in identifying fully fertile, determinate plant types.

Male sterility in beans (Phaseolus vulgaris L.)

SummaryMale sterile bean plants were discovered at Embu Agricultural Research Station, Kenya. The character is controlled by one recessive gene.

Breeding research in sweet potato, Ipomoea batatas poir

As the sweet potato, Ipomoea batatasPoir, is propagated vegetatively its selection is comparatively simple. Choice of parents and selection procedures were carried out on the basis of yield capacity, resistance or tolerance to a fungus and virus disease, resistance to Cylas formicarius F. and the shape and size of tubers. Because insufficient data were available the protein content played no important role in the choice of parents. In the selection procedures, also this character could not yet be taken into account because the laboratory equipment was insufficient. This might have changed in the future.In the selection fields the new clones were planted by the side of a well-known test-clone, in such a way, that every new clone had a test on either side. At every selection cycle 25% of the new clones was kept for further research while the rest was rejected. On two generations the visible disease symptoms of new clones increased considerably while their production capacity decreased. For various characters a clear relation could be demonstrated between the phenotype of the parents and their offspring.

Mode of inheritance of resistance to ascochyta blight (Ascochyta rabiei [Pass.] Labr.) in chickpea (Cicer arietinum L.) and its consequences for resistance breeding†

A disease‐rating data set collected for ascochyta blight (Ascochyta rabiei [Pass.] Labr.) on chickpea (Cicer arietinum L.) in different environments and with different isolates of the pathogen showed that resistance against the disease is quantitative, with a significant vertical component. Lower mean environmental disease ratings will enhance effective selection for resistance. It is proposed that gene pyramiding, using diverse germplasm and pathogenic isolates be used to combat the disease.

Root-knot nematode disease of chickpea in Nepal

The root-knot nematode disease of chickpea (Cicer arietinum) caused by Meloidogyne spp. was found to be widespread in the Tarai region of Nepal. The disease was moderate to severe in Bhairahawa, Gadari, Gopalkoti, and Rampur. In Nawalpur, Nepalganj and Parwanipur, the disease incidence was low. Leucas aspera, a common weed in chickpea fields, was found to harbour the root-knot nematode

Addressing farmers’ constraints through on-farm research: chickpea in Maharashtra state of India

On-farm research on irrigated and rainfed chickpea in ten states of India (mostly in the state of Maharashtra) was conducted during 1988/89 and 1989/90. Results showed that under residual moisture conditions, extra short-duration chickpeas had a 30% yield advantage over commonly grown long-duration cultivars. Local and improved cultivars produced similar yields when irrigated, but improved management provided a 19% yield advantage when compared to traditional cultivation practices.

Future breeding strategies for pea, lentil, faba bean and chickpea

Larger and more stable seed yields are often the principal objectives of breeding in each of pea, lentil, faba bean and chickpea. Pea, lentil and chickpea are self-pollinated, while faba bean is partially cross-pollinated. The breeding of all four species has followed mainly conventional methods; a brief description and evaluation of those methods is given. The scope for changes in traditional breeding methods and the application of biotechnology for crop improvement are discussed. Special reference is made to mutation breeding and to different tissue culture techniques. In all four crops, the objective of these novel methods and techniques is to generate new and useful variation and to accelerate the breeding process.

Flowering stimulation in sweet potato

Flower formation of most sweet potato clones in the collection at Manokwari was poor and when seed for breeding purposes was desired flowering had to be stimulated accordingly.Of various methods applied to stimulate the flowering some proved to be satisfactory. Good results were obtained in training tendrils to racks and grafting on different species of the genus Ipomoea.