Grain yield is a quantitatively inherited trait in groundnut (Arachis hypogea L.) and subject to genotype by environment interactions. Groundnut varieties show wide variation in grain yield across different agro-ecologies. The objectives of this study were to evaluate Valencia groundnut genotypes for yield stability and classify environments to devise appropriate breeding strategies. Seventeen multi-location trials were conducted in six countries, viz., Malawi, Tanzania, Uganda, Zimbabwe, Mozambique and Zambia, from 2013 to 2016. The experiments were laid out following a resolvable incomplete block design, with two replications at each location (hereafter referred to as ‘environments’) using 14 test lines and two standard checks. The additive main effects and multiplicative interaction (AMMI) analysis was conducted. Variation attributable to environments, genotypes and genotype × environment interaction for grain yield was highly significant (P<0.001). Genotype, environment and genotype × environment interactions accounted for 7%, 53 % and 40% of the total sum of squares respectively. Superior-performing genotypes possessing high to moderate adaptability and stability levels included ICGV-SM 0154, ICGV-SM 07539, ICGV-SM 07536, ICGV-SM 7501, ICGV-SM 99568 and ICGV SM 07520. Nachingwea 2013 in Tanzania, Nakabango 2014 in Uganda and Chitedze 2015 in Malawi were the most representative and discriminative environments. Considering the implications of interactions for Valencia groundnut breeding in East and Southern Africa we propose that different varieties should be targeted for production in different environments and at the same time used for breeding in specific environments.
Schubert' (Reg. No. CV-121, PI 669508) is a high-yielding, high-oleic, early-maturing spanish-type peanut (Arachis hypogaea L. subsp. fastigiata var. vulgaris) cultivar with improved shellout. Schubert was tested under the experimental designation TxL054520-34. Replicated yield tests began in the F 8 generation in 2007 and ran through 2010. Schubert matures approximately 1 to 2 wk earlier than 'OLin' and has significantly higher yield and grade than OLin. Yield averaged 526 kg ha −1 higher than for OLin, and total sound mature kernels grade was 2.2% points higher. Seed size was significantly larger than for the checks, 51.8 g 100 sound mature kernels −1 (SMK), compared with 50.2 and 48.1 g 100 SMK −1 for OLin and Tamspan 90, respectively. Schubert produces a higher proportion of medium seed than does either check cultivar, as well as a smaller proportion of split seeds. Resistance to Sclerotinia minor Jagger was not different for Schubert compared with Tamspan 90. The objectives of releasing this line are to provide growers with a higheryielding, high-oleic cultivar for the spanish market, along with earlier maturity.
TAMVal OL14' (Reg. No. CV-138, PI 689039) is a high-yielding, high-oleic, early-maturing valencia-type peanut (Arachis hypogaea L. subsp. fastigiata var. fastigiata) cultivar with reduced susceptibility to Sclerotinia blight. TAMVal OL14 was tested under the experimental designation TxL054529-33. Replicated line yield tests began in the F 8 generation in 2007 and ran through 2010. TAMVal OL14 is the irst high-oleic valencia peanut released by Texas A&M AgriLife Research and had a maturity (approximately 135 d after planting) similar to 'New Mexico Valencia C'. Yield in breeding trials averaged 706 kg ha −1 higher than for New Mexico Valencia C; in extension trials, the yield advantage ranged from 19 to 33%. Shellout was not statistically diferent from New Mexico Valencia C, but seed size was larger, 53.7 g 100 sound mature kernels −1 compared with 49.9 g 100 sound mature kernels −1 for New Mexico Valencia C. The frequency of pods with three to ive seeds was 37%, not signiicantly diferent than the 43% for New Mexico Valencia C. Susceptibility to Sclerotinia minor Jagger was signiicantly less than New Mexico Valencia C, with a disease incidence of 5.0 to 6.7 for TAMVal OL14 compared with 7.7 to 8.3 for New Mexico Valencia C, on a scale from 0 to 10. The objectives of releasing this line are to provide growers with a higher-yielding and high-oleic cultivar for the valencia market, as well as to reduce the susceptibility of valencia peanut to Sclerotinia blight.
The lack of disease and pest resistance in higholeic varieties has limited their cultivation until additional resistance can be incorporated. Crosses were made among two high-oleic varieties and one nematode-resistant variety, and individual plants possessing both root-knot nematode resistance and high oleic fatty acid composition were identified. Data agreed with previous studies that the high-oleic trait is controlled by two genes; however, segregation of progeny confirmed the existence of a mid-oleic class, and segregation ratios suggested that inheritance followed an additive genetic model in one cross and an epistatic model in the other. Segregation ratios were consistent with presence of one dominant gene for root-knot nematode resistance as reported previously.
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