Hugh Harries - Tropical Tree Crops Agronomist
TANZANIA
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1994-1996 Plant Breeder, ODA Cashew Research Project
To produce improved cashew clones to be vegetatively propagated by farmers; for use as parents in the breeders' crossing garden; and as parents in polyclonal seed gardens; the new material to produce economic crops when grown under good management despite powdery mildew (Oidium anacardii) or other diseases and Helopeltis spp. or other pests; the material to fit into practical intercropping systems on the poor soils and in the unreliable climates, where cashew is customarily grown with low inputs.
A CASHEW BREEDING PROGRAMME FOR TANZANIA
H.C. Harries, P.M. Kusolwa, K.J. Millanzi & P.A.L. Masawe
At Naliendele Agricultural Research Institute, Mtwara breeding programme to generate new cashew clones started in 1996 and is expected to continue for the foreseeable future. Crosses are planned annually and made using standard seed parents in a crossing garden where 101 selected clones are available. The pollen parents are individual trees, from both Tanzanian and overseas accessions, selected from the trials planted at Naliendele. The crosses aim to combine complementary qualities from parents with contrasting characteristics, taking care to prevent inbreeding depression by avoiding parents with a common ancestry. The seed produced is germinated and grafted onto mature seedling rootstocks to appraise, in one or two years, hypersensitivity to powdery mildew, bud vigour and kernel quality. A selection-rejection ratio of 1:20 is proposed for this stage. The selected plants are multiplied by budding or grafting for growing in progeny row trials within existing planted areas at Naliendele. The plants are appraised over three consecutive crop years for growth and vegetative habit, Helopeltis tolerance, powdery mildew resistance, with and without chemical control, yield in terms of nut weight and number and quality as percent kernel out-turn. The selection-rejection ratio at this point might be 1:50 and it may be possible to use some selections as pollinators in the crossing garden. The material remaining after the second selection is top-worked for performance testing in on-station and on-farm trials. These trials are also appraised for at least three consecutive crop years under regular farm and plantation management. Some selections may continue to be used as pollinators. Additional selection criteria at this stage includes evaluation by farmers and cashewnut buyers and takes GxE interactions into account. The final selections replace inferior clones - in the seed gardens to improve polyclonal seed production - in the scion gardens to be available for vegetative propagation and - in the crossing garden to become parents for the next cycle of crosses. The new clones will be named for release through the Ministry of Agriculture's Variety Release Committee. General information about them will be available to farmers in a Cashew Clone Catalogue and detailed performance data will be published. Now that the breeding programme has started, new material will become available for testing every year for as long as crossing continues. Unavoidably, the first round of crossing, appraisal and selection will take up to nine years to complete. Thereafter, new material should become available for release every year.
International Cashew & Coconut Conference, Dar es Salaam, 1997
1990-1993 Plant Breeder, NCDP Coconut Development Programme
To breed lethal disease resistant coconut varieties, tolerant to drought and to minimum input cultivation but able to respond to improved cultural techniques.
Consultant to IBPGR (IPGRI) to establish COGENT (Coconut Resources Network) on secondment from GTZ; Philippines, Indonesia, India, Sri Lanka, Brazil & Jamaica
THE VULNERABILITY OF THE COCONUT GENETIC RESOURCES OF AFRICA
If the African coconut germplasm is to be made less vulnerable to loss from disease or replacement by improved planting material it must first be properly assessed.
It is suggested that the wild type coconut has been on the coastal islands of the Indian Ocean for hundreds of thousands of years and that the domestic type was introduced by Indo-Polynesians, at least to Malagasy, about 1,500 years ago. Introgression between these two contrasting types was encouraged by Arab and Indian trading activities, about 700 years ago. The influence of Europeans, taking coconuts to West Africa for the first time only 500 years and perhaps making longer distance introductions by steamship only 100 years ago has great significance. When these influences are accounted for the recent activities of the last two decades can be put in perspective. The future activities of the next decade must not be allowed to obliterate the coconut genetic resources of Africa before they have been fully evaluated.
What needs to be done is to identify how much introduction, introgression, selection, genetic drift, mutation, etc., has occurred in the thousands of years that coconut may have been on the East African coasts and islands and the 500 years that it has been in West Africa. Within-country appraisals of endemic germplasm need to be made whenever inter-country comparisons are proposed or introductions are planned. Evaluation of national coconut germplasm, must be made in the field at the time of collection, as well as in the research establishments. It can be linked with programmes of selection for drought tolerance and disease resistance. Multiplication of good or interesting indigenous material should have equal or greater priority with the production and evaluation of new planting material.
BuroTrop Meeting, Arusha, Tanzania, February 1991