AGRICULTURE

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Browsing AGRICULTURE by Subject "(ARACHIS HYPOGAEA L.)"

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    GENETIC ANALYSIS OF AFLATOXIN AND AGRONOMIC TRAITS IN GROUNDNUT (ARACHIS HYPOGAEA L.)
    (2017-08) YAHAYA, Muhammad Ahmad
    Groundnut (Arachis hypogaea L.) is one of the major crops susceptible to Aspergillus flavus infection and subsequent aflatoxin contamination which adversely affects its production and utilization in the small holder setting. Although there are several management strategies that may reduce aflatoxin contamination of groundnuts, the pre-eminent strategy for the prevention of aflatoxin is to develop host resistance to A. flavus. The objectives of this study were to determine the level of resistance to A. flavus and aflatoxin accumulation among selected groundnut genotypes, to assess the mode of gene action controlling resistance to aflatoxin accumulation and agronomic traits and to estimate heritability for resistance to A. flavus and aflatoxin accumulation. Eight groundnut varieties comprising of three A. flavus resistant lines and five susceptible varieties were obtained from Institute for Agricultural Research, Samaru. The genotypes were crossed in a 3 x 5 North Carolina (NC II) design II fashion to generate 15 F1 hybrids. The F1 seeds were selfed to F2 and then evaluated alongside the eight parents for twelve quantitative characters using randomised complete block design (RCBD) with three replications at the Department of Plant Science screen-house under artificial A. flavus inoculation. Analysis of variance revealed significant (P≤0.05) differences among the groundnut genotypes for all traits except for 100-kernel weight and shelling percentage. The mean performance of the parents showed that SAMNUT 22 (2.50 ng / g ), ICGV 91317 (6.31 ng / g ) and ICGV 91324 (12.23 ng / g ) recorded lowest aflatoxin accumulation value of less than 20.00 ng / g and the crosses: SAMNUT 26 x ICGV 91317 (0.8 ng / g ), SAMNUT 26 x ICGV 91328 (1.2 ng / g ), SAMNUT 25 x ICGV 91324 (3.92ng/g), SAMNUT 22 x ICGV 91328 (4.4 ng / g ) and SAMNUT 22 x ICGV 91324 (12.3 ng / g ), as the best for resistance to A. flavus infection and aflatoxin accumulation under the United States Food and Drug Administration, which sets the limit of aflatoxin in food and feeds at 20 ng/g. The general (GCA) and specific (SCA) combining abilities were significant (P≤0.05) for most characters indicating the role of both additive and non-additive gene effects in the expression of most characters. High broad-sense heritability values were obtained for days to 50% flowering (88.9%), plant height (84.0%), haulm weight (86.8%), kernel infection (85.3%) and aflatoxin accumulation (99.7%). The parental genotypes, SAMNUT 23, SAMNUT 24, SAMNUT 25, SAMNUT 26, ICGV 91324, ICGV 91328 were good general combiners for aflatoxin B1 accumulation. Among the progenies, SAMNUT 22 x ICGV 91324 and SAMNUT 23 x ICGV 91317 with positive SCA effects for haulm weight and negative SCA effects for kernel infection and aflatoxin accumulation. A. flavus infection among the parents and progenies correlates poorly to aflatoxin contamination. The study revealed that non-additive gene action was more important than additive gene action for resistance to A. flavus infection, while additive gene action was more predominant for resistance to aflatoxin accumulation. The information provided from this study could be utilized in planning breeding programme for the development of groundnuts with improved pod yield, haulm yield, resistance to A. flavus infection and aflatoxin accumulation.
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    GENETIC ANALYSIS OF MORPHOLOGICAL AND PHYSIOLOGICAL TRAITS RELATED TO DROUGHT TOLERANCE IN GROUNDNUT (ARACHIS HYPOGAEA L.)
    (2020-07) ABDURRASHEED, Nafisa
    Drought stress is one of the major constraints in groundnut producing areas of Sub-Sahara Africa as its yield is reduced by 56-85%. Mitigating this constraint requires the selection of resilient genotypes that withstand drought threats to groundnut production. The objectives of this study were to identify drought tolerant genotypes to be used for groundnut breeding program, to assess the mode of gene action controlling drought tolerance in groundnut and to determine the association of pod yield with morphological and physiological traits related to drought tolerance in groundnut. One hundred and seven (107) groundnut genotypes were screened for drought tolerance during 2018 dry season in a split-plot design arranged in a randomized complete block design under non-stress and water-stress conditions. The mean squares for the morphological and physiological traits showed a highly significant (P≤0.01) difference between the genotypes under water-stress and combined analysis. Based on the PCA ranking under water-stress condition, genotypes ICGV-IS-13115, RS006F4B1-45®, ICGV-IS-07853, ICGV-IS-13989 and RS006F4B-534 were the top 5 drought tolerant while genotypes ICGV-IS-07828, 12CS-010, ICGV-IS-07809, RS006F4B1-45(B) and ICGV-IS-07904 were the least 5 drought susceptible. Seven groundnut genotypes comprising of four drought susceptible and three drought tolerant were randomly selected from the results of screening experiment. The seven genotypes were crossed in a half diallel mating design to obtain 21 F1 progenies. The parents, 21 F1 progenies and two checks were evaluated in a randomized complete block design with two replications under both conditions. Data were collected on days to 50% flowering, plant height, pod yield, 100-seed weight SCMR at 40, 60 and 80 days after sowing (DAS) and harvest index (HI). The analysis of variance showed a highly significant (P≤0.01) difference among the genotypes for viii plant height, number of pods per plant, pod yield and SCMR at 60 DAS under both conditions while a significant (P≤0.05) difference for seed weight under water-stress condition, 100-seed weight and HI under non-stress and water-stress condition was observed. Broad-sense heritability was high (67.45%) for plant height, moderate (46.23%) for 100 seed weight and (42.54%) for SCMR at 60 DAS under water-stress condition. General Combining Ability (GCA) effect for all the traits were significant (P≤0.05) in both non-stress and water-stress conditions, while Specific Combining Ability (SCA) effects were significant (P≤0.05) for all the traits in both non-stress and water-stress conditions. Highly significant GCA effects for all the traits were observed for ICG 5195 (P6) under water-stress condition, while ICGV-IS-07841 (P3) was a poor general combiner under the same condition. Highly significant positive SCA effects for number of pods per plant, seed weight and pod yield were observed with P1 x P6 and P3 x P6 crosses under water-stress condition. SCMR at 60 DAS had a moderate positive and significant ( r =0.45, P≤0.01) relationship with pod yield; HI recorded a strong positive and highly significant ( r =0.59, P≤0.01 and r =0.83 P≤0.01) relationship with number of pods per plant and pod yield. Although both additive and non-additive gene actions were involved in the expression of most traits, non-additive was more important than additive gene action under water-stress condition. The importance of non-additive effect under water-stress suggests the need to achieve acceptable progeny performance under drought stress condition. Therefore, cross P1 x P6 and P3 x P6 exhibit highest SCA effects for number of pods per plant, seed weight and pod yield which can be improved through pedigree selection. SCMR at 60 DAS and HI could also be used as an indirect selection for pod yield under drought stress condition.