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Pixley, K.V.

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Pixley
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K.V.
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Pixley, K.V.

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Now showing 1 - 10 of 11
  • Eastern Africa regional maize nursery: project report for 1997 and 1998
    (CIMMYT, 2000) Ngwira, P.; Pixley, K.V.
    A Regional Eastern Africa collaborative maize nursery project was initiated with funding from the Rockefeller Foundation in 1998. The project facilitates development of disease resistant maize varieties for eastern Africa. It·also encourages sharing of information and breeding materials, particularly those developed through the project.
    Publication
  • Combining ability and heterotic grouping of highland transition maize inbred lines
    (Consiglio per la Ricerca e la sperimentazione in Agricoltura, Unità di Ricerca per la Maiscoltura, 2009) Legesse, B.W.; Pixley, K.V.; Botha, A.M.
    The objectives of the present study were to examine combining ability of highland transition maize inbred lines for grain yield and other desirable traits, to determine heterotic groups of germplasm of the inbred lines and to identify promising hybrid crosses. Twenty-six inbred lines were factorially mated (Design II) with six testers and the resulting F1s along with two checks and the parents were evaluated in separate trials at five locations namely: Ambo, Awassa, Bako, Holeta and Kulumsa, all in Ethiopia during 2002. General combining ability (GCA) and specific combining ability (SCA) effects were calculated using line x tester analysis. GCA mean squares due to lines and, testers were highly significant (P < 0.01) for all the traits. Similarly SCA mean squares for most traits except for days to physiological maturity and for northern leaf blight (NLB, caused by Exserohilum turcicum) were found highly significant (P < 0.001). The ratio of GCA/SCA mean square further exhibited the preponderance of additive gene effects in the inheritance of all traits. Estimates of GCA effects indicated that three inbred lines showed good combiners for grain yield. For days to silking four, for grey leaf spot (GLS caused by Cercospora zeae-maydis Tehon), three, and for NLB one inbred lines revealed significantly negative GCA effects. These inbred lines can be a good source of variability for the improvement of the traits in the breeding program. Significantly different SCA effects were revealed for crosses involving most traits. A number of single crosses out-yielded the hybrid checks (BH660 and BH 540) and also revealed desirable plant height performances. Moreover, two best contrasting heterotic group (Pool 9A-MHM x 142-1-e) composed of 13 and 10 inbred lines, respectively, have been determine to initiate heterotic source germplasm. This heterotic group may have wide applicability in the east African highland maize breeding programs, as well.
    Publication
  • Enhancing introgression of the Opaque-2 trait into elite maize lines using simple sequence repeats
    (African Crop Science Society, 2005) Manna, R.; Okello, D.K.; Imanywoha, J.; Pixley, K.V.; Edema, R.
    To improve on the efficiency of Quality Protein Maize (QPM) breeding in Uganada, the utility of three simple sequence repeats (SSR) markers (phi057, phi112 and umc1066) in selection and introgression of the opaque-2 (o2) gene was investigated. Genomic DNA of six normal and seven (QPM) lines was analysed using a standard PCR protocol. Polymorphisms were detected in the Opaque-2 locus among all the maize lines when using the SSR primers, phi057 and phi112, while no polymorphism was detected with primer umc1066. To facilitate background selection in the heterozygous BC2 progeny, key phenotypic characters of the recurrent parent (136R) were used as additional markers. The SSR marker phi057 was co-dominant while phi112 was dominant. The polymorphic SSR markers correctly predicted the expression of tryptophan in kernels of all QPM inbreds and five of the six non-QPM inbred lines. However, one non-QPM inbred line (PED49B) had a tryptophan content that is characteristic of the o2 mutation (0.090), suggesting that another genetic system may be responsible for the expression of tryptophan in this maize line. Phi057 was employed to monitor the introgression of the o2 allele from CML176 to 136R. Of the 200 BC1F1 (136R/CML176/136R) plants genotyped, 104 were found to be heterozygous, producing products corresponding to both alleles (o2 and O2), while 96 produced a single band corresponding to the homozygous dominant (O2O2) condition. The ratio of the two groups in the backcross (BC) population was consistent with proportion 1 :1 accorded by the Chi-square rest (X2=0.16
    Publication
  • Selection for drought tolerance in two tropical maize populations
    (African Crop Science Society, 2003) Magorokosho, C.; Pixley, K.V.; Tongoona, P.
    Drought is a major factor limiting maize ( Zea mays check for this species in other resources L.) yield in much of the world. The need to breed maize cultivars with improved drought tolerance is apparent. This study compared two maize populations, ZM601 and ZM607 for drought tolerance during flowering, the most drought-vulnerable period for the maize plant. Cultivar ZM601 had been improved through recurrent selection for two cycles for drought tolerance at flowering plus one cycle under rainfed ("random") drought stress, while ZM607 had been improved for high yield for three cycles under favorable growing conditions. A set of 143 random S1 lines from ZM601 was compared with 94 from ZM607 at two drought stressed and one well-watered environment for yield and secondary traits. The results did not show much difference in drought tolerance between ZM601 and ZM607. Differences between population means for grain yield, anthesis-silking interval (ASI), and number of ears per plant (EPP) were small. Frequency distributions for ASI and leaf rolling were different for the two populations. However, ZM601 had more lines with shorter ASI and less leaf rolling as compared to ZM607. Broad sense heritability of ASI was larger,while that of grain yield smaller, and the correlation between ASI and grain yield was larger at drought-stressed compared to unstressed sites. Absence of large differences in grain yield between ZM601 and ZM607 lines was attributed to little effect of the selection completed prior to this evaluation, to genetic similarities of the two populations prior to selection, and to large genotype-by-environment interaction between Mexico, where drought screening was conducted, and Zimbabwe, where this evaluation was conducted. Results confirmed the value of ASI (measured at drought-stressed sites) as an indirect selection criterion for improving grain yield under drought stress conditions.
    Publication
  • Characterization of maize germplasm grown in Eastern and Southern Africa: results of the 2004 regional trials coordinated by CIMMYT
    (CIMMYT, 2005) Vivek, B.; Banziger, M.; Pixley, K.V.
    The Summary Tables present grain yields averaged across sites with significant differences between entries, for each of the five to six environments. Data on agronomic performance such as anthesis date, plant and ear height, ear position, root and stem lodging, husk cover, ear rot, leaf diseases, grain weevil and stem borer damage, grain texture and grain moisture were averaged across all sites that provided results with significant differences between entries. If no data are presented for these traits, no trial data demonstrating significant differences for these traits was available.
    Publication
  • Maize productivity gains through research and technology dissemination
    (CIMMYT, 1997) Ransom, J.K.; Palmer, A.F.E.; Zambezi, B.T.; Waddington, S.R.; Pixley, K.V.; Jewell, D.C.
    This publication contains papers presented at the fifth Eastern and Southern Africa Regional Maize Conference held in Arusha, Tanzania, June, 1996, documenting advances in maize productivity achieved through research and technology dissemination. Topics covered include the dissemination of maize farming technology and related impacts and challenges; productivity gains though genetic improvement and through identifying and integrating key management practices; stress tolerance for greater yield stability; soil fertility enhancing technologies; and disease management
    Publication
  • Maize research for stress environments: proceedings of the Fourth Eastern and Southern Africa Regional maize conference
    (CIMMYT, 1995) Jewell, D.C.; Waddington, S.R.; Ransom, J.K.; Pixley, K.V.
    This maize conference has come at an opportune time. The papers/presentations on the different aspects of maize research for stress environments will enable us to revisit our workplan if necessary and assess whether we are addressing the key problems faci
    Publication