Posts Tagged ‘Host plant resistance’

Combining ability of maize (Zea mays) inbred lines resistant to Striga hermonthica (Del.) Benth evaluated under artificial Striga infestation

Posted by Carelia Juarez on , in Journal Articles

Published in African Journal of Agricultural Research 9 (16) : 1287-1295, 2014

Karaya, H.Njoroge, K.Mugo, S.Ariga, E.S.Kanampiu, F.Nderitu, J. 

The parasitic weed Striga affects maize on an estimated 20 million ha in Africa, making it a major cause of maize yield reduction from near world average of 4.2 t/ha few decades ago to the present 1.5 t/ha. The objectives of this study were to examine the combining ability of 20 inbred lines and identify single crosses which can be used to develop other hybrids resistant to Striga hermonthica (Del.) Benth. Fourteen female lines were mated using North Carolina Design II with all six males. The resulting 84 F1s along with six commercial checks were evaluated in four separate trials for two rainy seasons during 2010. The trials were conducted on station under both artificial Striga infestation and Striga free environments using standard procedures at the Kibos and Alupe sites, both in the Kenya’s Lake Victoria Basin. Data were recorded on Striga counts, Striga damage rating (SDR), grain yield and other agronomic traits. General combining ability (GCA) and specific combining ability (SCA) effects were computed using SAS. The new F1 hybrids outperformed the commercial checks in grain yield and reaction to Striga. Single crosses JI-30-3/TESTR 151, JI-30-18/TESTR 151, CML206//56/44-6-3-7-1/TESTR 149 and JI-30-18/TESTR 156 gave the highest yield while single cross JI10-28-#/TESTR 136 gave the lowest yield. The ratio of GCA: SCA mean squares exhibited a predominance of additive gene effects in the inheritance of Striga resistance traits as opposed to dominance gene effects. Inbred lines with good GCA for yield and Striga resistance traits were identified as TESTR 151, TESTR 156 and OSU231//56/44-6-4-17-3. The high GCA inbred lines and the superior single crosses will provide a basis for future use perse and also development of three-way and double cross hybrids to be grown in Striga prone areas of the Lake Victoria Basin in eastern Africa.

Confirming quantitative trait loci for aflatoxin resistance from Mp313E in different genetic backgrounds

Posted by Carelia Juarez on , in Journal Articles

Published in Molecular Breeding, 2013

Martha C. Willcox, Georgia L. Davis,  Marilyn L. Warburton,  Gary L. Windham, Hamed K. Abbas,  Javier Betrán, James B. Holland and W. Paul Williams

The fungus Aspergillus flavus (Link:Fr) causes ear rot of maize (Zea mays L.) and produces the toxic metabolic product aflatoxin. One particularly effective method of controlling the fungus is via host plant resistance, but while several resistant breeding lines have been identified, transferring the resistance genes from these lines into elite cultivars has been less effective than needed. A high number of genes involved with resistance, each with a small effect, and some only found under certain environmental conditions, has hampered resistance breeding. The identification of markers linked to genomic regions associated with resistance would aid in this effort. The goals of this study were to identify and characterize quantitative trait loci (QTL) conferring resistance to aflatoxin accumulation from resistant maize donor Mp313E in a background of the susceptible inbred line Va35; to compare them to the QTL identified from Mp313E in a background of B73; and to test the stability of the QTL identified in Mp313E × Va35 in multiple environments by remapping the phenotypic tails of the Mp313E × Va35 mapping population in new locations. Twenty different QTL were found in this study, 11 of which were also found in different environments using the phenotypic tail subset mapping population, and five of which were likely the same as those reported in the Mp313E × B73 mapping population. This indicates that many of the QTL are stable over the environments and genetic backgrounds tested, which will make them more valuable in breeding efforts.

Phenotypic and genotypic variation in tropical maize inbred lines for resistance to the maize weevil and larger grain borer

Posted by Carelia Juarez on , in Journal Articles

Published in International Journal of Agricultural Science and Research 2 (4) : 41-52, 2012

J.K. Mwololo, P. Okori, S.N. Mugo, Tadele Tefera, B. Yoseph, M. Otim and S.W. Munyiri

The maize weevil (Sitophilus zeamais) and larger grain borer (Prostephanus truncatus) are economicallyimportant postharvest insect pests that cause severe losses in stored grain. The use of host-plant resistance is the most effective and benign way of overcoming storage-pest damage. The objectives of this study were to estimate heritability and to identify maize inbred lines with dual resistance to weevil and larger grain borer (LGB). One hundred and twenty (120) inbred lines were evaluated in the field for adaptation and tested in the laboratory for resistance to the LGB and weevil. Insect-damage parameters namely grain damage, weight loss, flour weight and number of insects, were measured. Heritability, genotypic and phenotypic variances for the damage traits were determined. Genotype stability for insect pest resistance was determined based on genotypic variance and coefficient of variation (CVi) for each genotype. There were significant differences (P<0.001) among the lines for all the traits measured. Heritability values were high (ranging from 0.7-0.9) in all the traits, and the genotypic variance was higher (ranging from 0.012-0.04) than the environmental variances (0.007-0.033) for all the traits. Dual resistance and stability were observed in CKSPL10028, CKSPL10035, CKSPL10088, CKSPL10021, CKSPL10042, CKSPL10295 and CKSPL10112.


Downy mildew resistance in maize (Zea mays L.) across Peronosclerospora species in lowland tropical Asia

Posted by Carelia Juarez on , in Journal Articles

Published in Crop Protection 43: 183-191, 2012

Zerka Rashid, P.H. Zaidi, M.T. Vinayan,  S.S. Sharma and T.A. Srirama Setty

Downy mildew (DM) is one of the most destructive diseases of maize in the humid sub-tropical and tropical regions of Asia. The most effective and efficient way of managing losses due to DM is to develop durable host-plant resistance in Asian maize across different DM pathogens. We assessed resistance in released DM (P. zeae) resistant CIMMYT maize lines (CMLs) against Peronosclerospora sorghi and Perenosclerospora heteropogoni to develop DM resistant (DMR) maize germplasm with a broad-spectrum of resistance, and identify and further improve new sources of DMR maize germplasm for use in regional breeding programs targeting DM-prone environments. Data indicated that out of 19 DM resistant CMLs, four (CML-433, 465, 466 and 472) were resistant and 15 susceptible to P. sorghi. Screening of new inbred lines from CIMMYT-Asia (CA) resulted in identification of a set of yellow maize lines with good level of DM resistance (disease score – 0.0–25%). However, the high quality protein maize (QPM) lines derived from CIMMYT Population 61 and bi-parental pedigree crosses between elite QPM lines showed very poor resistance to DM. Progenies of the bi-parental population developed by crossing DMR (P. sorghi) CA lines showed further enhanced levels of resistance to both P. sorghi and P. heteropogoni. The study resulted in identification of 10 new inbred lines, in addition to the 4 released CMLs, offering consistent high resistance to both the DM pathogens. Promising bi-parental populations (13) with combined DM resistance and other desirable agronomic traits were identified for the extraction of a new generation of DMR lines with broad-spectrum DM resistance and other commercial traits. Comparison of genotypic response under different screening methods/DM species clearly indicated that the glasshouse-based sandwich method of screening against P. sorghi was the best method for identifying promising genotypes with a high level of DM resistance that were also resistant to DM under field conditions for both the species. However, the highly controlled conditions used for sandwich screening, which is most favourable for disease development, resulted in high disease pressure potentially masking the identification of genotypes with a moderate level of DM resistance.

Grain yield, stem borer and disease resistance of new maize hybrids in Kenya

Posted by on , in Journal Articles

Published in African Journal of Biotechnology 10(23): 4777-4783, 2011

Grain yield, stem borer and disease resistance of new maize hybrids in Kenya

Tadele Tefera, Stephen Mugo, Yoseph Beyene, Haron Karaya and Regina Tende

Evaluation of 30 maize hybrids for yield and resistance to stem borers and foliar diseases in four agro-ecologies in Kenya was conducted in 2009. There were significant differences among the hybrids in leaf damage, number of exit holes, tunnel length and grain yield in Kiboko. The maize hybrids CKPH08014, CKPH08025, and CKPH08026 showed the least leaf damage, exit holes and tunnel length, similar to the resistant check.  Although ten hybrids yielded over 8 t/ha, two hybrids, CKPH09001 and CKPH08033, gave the highest yield of 8.99 and 8.86 t/ha, respectively, in Kiboko. There were significant differences among the hybrids in resistance to leaf rust and maize streak virus in Kakamega. The intensity of foliar diseases was high in Kakamega compared to the other sites. All hybrids appeared resistant to the foliar diseases at Kakamega. On the average, the highest yield of the hybrids was recorded in Kiboko (7.5 t/ha) followed by Kakamega (6.1 t/ha), and the least at Embu (3.5 t/ha), and Mtwapa (3.14 t/ha). The performance of the hybrids varied from site to site, with CKPH09002 and CKPH09003 performing well at Mtwapa, CKPH09001 at Kiboko, CKPH08039 at Embu, CKPH 08002 and CKPH08010 at Kakamega.