flowering and a cytogenetic approach to discover the reason for uniform 36 chromosomes. Could cassava be an aUopolyplold? Is Brazil harbouring same 18 chromosome diploid ancestors? These are basic questions needing answers to facilitate further breeding and genetic Improvement. POSSIBLE ACTION: TIssue culture can be used to control Ught Intensity. photoperiod. physiological status and hormone balances. and help us to improve our understanding of the process. Phytotrum studies may also help (ZImbabwe has facility). This Is baslc research to support all other developments. Cobalt -60 irradiation and tn vitro flower Induction were also suggested for the shy-flowering type.
6. MealybUC and green Iplder mite. Can genes be found to discourage these InSects. or Is biologICal control the method of choICe?
NEEDS: Cassava Mealybug Is the Single biggest pest problem. Biological control Is proving effective. Varieties that have some level of resistance to mealybug and green spider mlte were Identified and being Incorporated Into Improved cassava varieties. Pubescence In the young leaves Is highly correlated with reststance to both pests. Spider mtte needs an appropriate paraslte which Is yet to be tested. POSSIBLE ACTION: (a) It IS not clear whether genes are avallable. Tbe BT gene wlll not be suitable; Is the trypSin inhibitor gene effective? Are there others? Again. we depend on advances In tissue culture to succeed In transferring any suitable genes: (b) Wide crosses to Introduce pubescence also depend on basIC studies of regeneration. Cytogenetics wlll open the door for future reassessment.
7. Browning. physiological problems and postharvest loss. Can we arrest postharvest deterioration and so extend storage life? NEEDS: Local experience counsels use of ash to slow brownlng. Does this have to do with "wounds bonds" or adsorbing oxldases? There are no clear Ideas about the possibilities for action. beyond looking at enzymes and genes Involved. polyphenol oxldases and tannic acid production. The Issues hold a low priority because the problems have not been clearly defined. Basic physiological/biochemical studies are needed.
& Blick Sigatoka disease.
Can we control the black Sigatoka disease
In plantain and banana? NEEDS: African countries are Increasingly facing problems of this disease In plantain and banana production. A genetic source of 58