MORPHO-PHYSIOLOGIC EVALUATION OF GROUNDNUT (Arachis hypogaea L.) GENOTYPES FOR DROUGHT TOLERANCE AND ASPERGILLUS INFECTION IN CENTRAL ZONE OF TIGRAY, ETHIOPIA

Abstract

Understanding the underlying mechanisms of drought tolerance and Aspergillus infection resistance and the correlation among different surrogate traits are suitable breeding strategies for groundnut improvement. Forty groundnut genotypes were evaluated under field condition at Rama using alpha lattice design with two replications. For the drought stress screening, the genotypes were tested under three water regimes (25%CWR, 50% CWR, and 100% CWR). There was significant difference among the genotypes for most of the traits related to drought tolerance and yield and yield components in the three irrigation treatments. In the stressed treatment (25% CWR highly significant (P<0.01) differences among genotypes were observed for number of leaves per main stem, root dry mass and pod width. Drought stress significantly affects yielding potential of the groundnut genotypes in which the mean BLUP yield of genotypes under 25% CWR treatment is 355.35 kg/ha where as it is 746.63 kg kg/ha and 1222 kg/ha under 50% CWR and 100% CWR respectively. Under the severe drought treatment (25% CWR) kernel yield showed positive and significant (P<0.01) genotypic correlation with number of leaves per main stem(r=0.337), leaf length (r=0.332), plant height (r=0.579), root dry weight (r=0.354), pod length (r=0.596), 100 seed weight(r=0.625) and shelling percentage. Therefore, any improvement of these characters would result a substantial increment on kernel yield in groundnut. The highest kernel weight record in the stress and non-stress condition was noted by genotypes ICGV 91328 (891.5 Kg/ha) and ICGV 00308 (1405.74 Kg/ha) respectively. The GGE-biplot also supported the superiority of the 11 genotypes particularly ICGV 91328 in the stress environment. A. flavus were predominantly isolated (63.08%) and A. niger was less frequent (6.12%) in the three irrigation water treatments. 79.1% and 20.9% of the samples was found infected and non-infected respectively in 25% CWR by Aspergillus Spp. Whereas, the minimum frequency of infection was found under the 100% CWR treatment. Four different stress indices, MP, % yield reduction, DSI and DTI along with yield under stress and optimal conditions was used to determine the comparative performance of genotypes under different soil moisture levels. Correlation between the indices and average yields under stress and optimal conditions is mostly highly significant. The most drought tolerant genotype according to the drought tolerance index (DTI) is ICGV 91328 followed by ICGV 00308 and ICGV 86015whereas; the least drought tolerant was the local variety followed by Roba and Werer-963. Thus, genotypes such as ICGV 91328, ICGV 00308, ICGV 9114, ICGV 86015 and ICGV 01276 can be a good source of parents for further groundnut improvements and can be alternatively developed into superior groundnut genotypes with moderate resistance to Aspergillus infection. Although interesting results are recorded in this study that could assist better production of the crop in the area, drought and Aspergillus contamination are influenced by many traits that continuous and integrated efforts are mandatory for enhancing productivity and quality of the crop.