EVALUATION OF GROUNDNUT (ARACHIS HYPOGAEA L.) GERMPLASM FOR RESISTANCE TO LEAF DISEASES AND RELATED CYTOPLASMIC FACTORS, TESTA COLOUR AND CUP LEAF

• Main Author: Pretorius, Alana Elmarie
• Other Authors: Dr MM Liebenberg
• Format: Others
• Language: en-uk
• Published: University of the Free State 2007
• Subjects: Plant Sciences
• Online Access: http://etd.uovs.ac.za//theses/available/etd-02282007-084640/restricted/

Early leaf spot (ELS) caused by Cercospora arachidicola, late leaf spot (LLS) caused by Cercosporidium personatum, web blotch (WB) caused by Phoma arachidicola and rust caused by Puccinia arachidis, are serious diseases of groundnut in South Africa. The aims of this study were to evaluate ARC-GCI germplasm for resistance to the important foliar diseases such as ELS, LLS, WB, and rust and to ascertain if cytoplasmic factors influence the pattern of inheritance of resistance to ELS, LLS, and WB, testa colour and mutations such as the one responsible for cupleaf phenotypes. Twenty-one reciprocal crosses were made to study the cytoplasmic factors but the F1 progenies gave no evidence of cytoplasmic factors directly responsible for any of the above-mentioned traits. During 2003/04, 138 ARC-GCI germplasm entries were evaluated for resistance to ELS, LLS, WB and rust at Potchefstroom (North West Province; Highveld), Burgershall (Mpumalanga Province), Brits (North West Province), Vaalharts (Northern Cape Province) and Cedara (Kwazulu Natal Province). No fungicides were used to control the foliar diseases. In trials at Vaalharts, Cedara, and Burgershall entries 1, 10-13, 18-21, 23, 30, 52 and 56-58 were resistant to two of the three (LLS, WB, and rust) foliar diseases and entries 18, 19 and 20 (best) to LLS, WB and rust. At Brits, Elite (E) and ICRISAT (I) short/medium growth entries 8I and 7E, were resistant to LLS and WB and the long growth entries 1E and 3E were resistant to WB, LLS and rust. In micro-plots at Potchefstroom entries 6, 9, 10 and 13-15 were resistant to LLS and WB and in the brick plots 1-3, 6 and 7 to ELS and LLS. Entries with resistance to ELS, LLS, WB, and rust as well as other favourable traits, such as a high yield and oleic acid percentage, from the 2003/04 trials were included in the 2004/05 trials for further assessment. All the entries were evaluated for resistance to ELS, LLS, WB and rust, were graded and grouped by using the Canonical Variate Analysis (CVA). From the results on the five locality trials (2004/05) medium growth entries 1, 3, 7, 10, 14, 15, 20-22, 26, 27, 30, 32 and 33 were resistant to three or four of the foliar diseases, gave good yields and choice grade kernels. The CVA identified separate groups, containing entries 3, 20, 21 and 32, with resistance to two or more foliar diseases and with high yield. No choice grade entries were reported for unsound blemished and soiled (UBS) kernels with an UBS>13%. In the Elite short/medium trials at Brits (2004/05) entries 3 and 8 were resistant to rust, 1, 2, 4, 7, 11-13, 15, 17, 19-22, 24 and 25 gave choice grade kernels, and 10, 13 and 12 the highest yield. Entries 1-6, and 8-15 (Elite long) were resistant to LLS, 1-15 to WB, and 1, 4 and 15 to rust, 4, 10 and 12 gave choice grade kernels and 4, 1 and 10 the highest yields. ICRISAT (long) entries 5 and 7 gave choice grade kernels, and 1, 6 and 3 the highest yields. The CVA identified the groups containing medium growth entries 10, 12, 13, 22 and 23, Elite long 1, 4, 10 and 15 and ICRISAT long 5, 8 and 9 as groups with resistance to two or more foliar diseases (ELS, LLS, WB, and rust) and good yield. Twenty-three medium and 11 long growth entries in the Elite trials at Vaalharts (an extra trial planted where fungicides were used to control foliar diseases) gave choice grade kernels and good yields. In this study, some ARC-GCI germplasm entries were resistant to ELS, LLS, WB, and rust, but climatic factors influenced the severity of infection. Foliar diseases lowered the quality and grade of the kernels and resulted in lower yields. CVA simplifies the evaluation and grouping of new germplasm entries and will save valuable research resources.