Resistance to rust (Puminia arachidis Speg.) and late leafspot (Cercospridium personaturn (Berk. & Curt.) Deighton) in some peanut genotypes was studied under field conditions. Late leafspot development was also assessed in the glasshbuse and the parameters lesion diameter, defoliation percentage and sporulation gave highly significant correlations with the field disease scores. Several genotypes were found to be resistant to both rust and late leafspot and should be useful sources of multiple diseaseresistance in a breeding program.

7'hcc~ulti~utedpc~a,r1~/ (Arachis hypogaea. Fubaccac) is belic~ved to have orlginutcjd ulorrg I/?(, C~U S I C~I I slo/)c,s (?f ihr ..lnrl(s in Bo111.ia und northerr1 Argentina. The crop 1s t~orc groLt,tr thronghout i r o~~i c~u l utid warm tonpiJralr regron.c. .4rnong diseases uttac.krn,q pc,ut~lrrs, rlitr cwlr.,c~/ hjl Puccinia arachidis arid larr, Ieuf'spot cuuscd hj, Phaeoisariopsis personata urea flic r?io.sl rt?iportan/ and dcstrurttvc~ on a ~, o r l d~, i d r .\c,olc. noti? pa//iogc,tr~, rr,stric./cd rn host run@, to Arachis, prohahly originated and c,oc,vol\,ed irl .Siiut/r .,ltnrriiu alclt~y ~i'ith thrir /~ost.s. In rcwnr years there has heen 1?11i(./r ~rtlphusr.\

No abstract

Arachis hypogaea, genetic divergence, heterosis, combining ability, diallel crosses, D 2 statistic . SUMMARYThe frequency and magnitude of heterosis were examined in relation to genetic divergence among parents in two diallel cross experiments in groundnut . The parents were grouped into clusters based on their divergence . The range, mean and standard deviation of the intra-and inter-cluster divergence were used to define four divergence classes . The frequency of heterotic crosses and the magnitude of heterosis for yield and its components were found to be higher in crosses between the parents in intermediate divergence classes than extreme ones . The results agreed well with the overall status of the specific combining ability of these crosses .

SUMMARY Twenty groundnut genotypes were grown with various spray treatments which controlled either, only rust, or only leaf spot diseases, or all of these diseases or none of them. The genotypes varied in their resistance to these diseases, some having resistance to only one disease and some having resistance or susceptibility to all the diseases. Chemical control of the diseases resulted in variations in leaf area protection and in yield which were specific to each genotype. For some genotypes the diseases had little influence on yield and foliage, while for others yield and remaining green leaf were varied greatly by the control of diseases. For many of the genotypes the yield achieved was well related to variations in the green leaf remaining at maturity as a result of the spray treatments. Genotypes with good levels of genetic resistance did not have high yield potentials while those with the best yields when diseases were controlled were the most susceptible to these diseases.