John Derera

Consumer acceptance of yellow, provitamin A-biofortified maize in KwaZulu-Natal

Abstract Objectives: To assess the acceptance of popular maize food products (phutu, thin porridge and samp), prepared with yellow, provitamin A-biofortified maize varieties, in 212 subjects between the ages of three and 55 years, from rural KwaZulu-Natal. Design: A cross-sectional study. Method: Preschool, primary school and secondary school subjects were randomly selected from two primary schools and one secondary school, respectively, while adult subjects constituted a convenience sample. Pre- and primary school children completed a paired preference test. Secondary school and adult subjects completed a five-point facial hedonic and a preference ranking test. Focus group discussions were conducted using adult subjects. Results: Preschool children preferred yellow maize to white maize food products: phutu (81% vs. 19%; p-value < 0.001), thin porridge (75% vs. 25%; p-value < 0.001) and samp (73% vs. 27%; p-value < 0.001). There was no statistically significant difference in preference for white and yellow maize by primary school children. Secondary school and adult subjects preferred white maize to yellow maize. Focus group discussions confirmed the preference for white maize by the adults. Conclusion: The study findings suggest that yellow, provitamin A-biofortified maize has the potential to succeed as a new strategy of dealing with the serious problem of vitamin A deficiency, especially among children of preschool age. However, in older groups, this strategy is unlikely to be successful, unless other strategies are implemented, including intensive nutrition education programmes on the nutritional benefits of the maize, targeting the market price at which yellow maize is sold, increasing its availability in local grocery stores, and improving its sensory properties through breeding.

Provitamin A carotenoids in biofortified maize and their retention during processing and preparation of South African maize foods

Provitamin A-biofortified maize may contribute to alleviating vitamin A deficiency (VAD), in developing countries. However, processing the maize into food products may reduce its provitamin A content. The aims of this study were to determine the composition of provitamin A carotenoids in biofortified maize varieties as well as to assess their retention during processing of popular maize foods consumed in KwaZulu-Natal, South Africa. The non-provitamin A carotenoid, zeaxanthin and the provitamin A carotenoids, β-cryptoxanthin, and trans and cis isomers of β-carotene, and other unidentified trans and cis isomers of β-carotene were detected in varying concentrations in the maize. Milling provitamin A-biofortified maize into mealie meal resulted in a higher retention of carotenoids compared to milling into samp. The highest retention of provitamin A carotenoids was observed in cooked phutu and cooked samp, whilst cooking into thin porridge resulted in the lowest retention of provitamin A carotenoids. In phutu, 96.6 ± 20.3% β-cryptoxanthin and 95.5 ± 13.6% of the β-carotene were retained after cooking. In samp, 91.9 ± 12.0% β-cryptoxanthin and 100.1 ± 8.8% β-carotene; and in thin porridge, 65.8 ± 4.6% β-cryptoxanthin and 74.7 ± 3.0% β-carotene were retained after cooking. This study demonstrates that provitamin A retention in maize is affected by the cooking method (and hence cooked food form) and therefore cooking methods that result in a good retention of provitamin A need to be identified and recommended.

Gene action determining Phaeosphaeria leaf spot disease resistance in experimental maize hybrids

Phaeosphaeria leaf spot (Phaeosphaeria maydis Henn.) has the potential to cause substantial yield losses in maize. Maize is grown by small-scale farmers without fungicides; hence there is need to breed for resistance in regionally adapted germplasm. Little information about the gene action determining Phaeosphaeria leaf spot disease (PLS) resistance in African maize germplasm is currently available. This study was therefore conducted to determine the gene action controlling resistance to PLS in African maize germplasm. Seventy-two experimental hybrids were generated in eight sets according to a North Carolina Design II mating scheme. Experimental and check hybrids were evaluated in an 8 × 8 simple lattice design during the 2003/4 season, and in an 8 × 10 α-lattice design, with two replications, during the 2004/5 seasons at the Cedara and Rattray Arnold Research Stations, in South Africa and Zimbabwe, respectively. There was significant variation among hybrids for resistance. General combining ability (GCA) due to both male and female inbred parents were highly significant (P<0.01), whereas specific combining ability effects were not significant for PLS scores, indicating that mainly additive gene action conditioned PLS resistance in experimental hybrids. Significant differences between male and female GCA variances, suggested the importance of cytoplasmic inheritance for PLS resistance. Resistance was highly heritable indicating that selection could be used to improve the resistance in this germplasm.

Screening early-generation progenies of interspecific rice genotypes for drought-stress tolerance during vegetative phase.

Drought is an important production constraint in rice (Oryza sativa L.) in Africa. A breeding approach is needed to improve traditional rice by introgression of new genes for drought tolerance and high yield at early generation to enhance production. This study was conducted to identify drought-tolerant progenies in early generations and to establish a relationship between drought tolerance and some morphological and physiological traits. Interspecific progenies were generated using North Carolina II mating design and were advanced to F3 and F4 generations. Progenies were evaluated in 8 × 8 and 9 × 9 simple-lattice designs under managed drought stress and fully irrigated conditions, respectively. Overhead sprinkler irrigation was applied till maximum tillering stage (35 d after sowing) and stopped in the stress experiment for 50 d to induce stress and resumed thereafter until maturity. Significant differences were detected among genotypes for drought tolerance, and tillering and flowering dates. Selection indices ranging from –42.74 to 20.70 were therefore used to rank the progenies. Drought stress delayed flowering and was more pronounced in early- than late-flowering progenies. High-tillering progenies had larger reduction in tiller number than low-tillering progenies under stress. Drought tolerance (little leaf drying), taller plants and less leaf rolling were significantly associated with rapid ability to recover at 3 d and 10 d after drought-stress relief. The putative traits identified could be used as indicators of drought stress tolerance in a breeding program.

Genetic interrelationships among medium to late maturing tropical maize inbred lines using selected SSR markers

Understanding the genetic relationships among breeding lines is fundamental in crop improvement programs. The objectives of this study were to apply selected polymorphic single sequence repeat (SSR) DNA markers and cluster medium to late maturing tropical elite maize inbred lines for effective hybrid breeding. Twenty elite inbred lines were genotyped with 20 SSR markers. The analysis detected a total of 108 alleles. The unweighted pair group method with arithmetic mean allocated the inbred lines into five clusters consistent with the known pedigrees. The tested inbred lines that were adapted to mid-altitude, sub-humid agro-ecologies were classified in different clusters, except for a few discrepancies. The greatest genetic distance was identified between the clusters of lines CML-202 and Gibe-1-91-1-1-1-1. The analysis determined the genetic grouping present in the source population, which will assist in effective utilization of the lines in tropical hybrid maize breeding programs to exploit heterosis.

Marker-assisted selection for low phytic acid (lpa1-1) with single nucleotide polymorphism marker and amplified fragment length polymorphisms for background selection in a maize backcross breeding programme

The level of phytic acid is difficult to assess in a maize breeding programme, therefore a co-dominant single nucleotide polymorphism (SNP) marker was used to detect the single recessive low phytic acid (lpa1-1) gene in a BC2F1 population developed from a locally adapted tropical normal inbred line (P 16) and CM 32 (lpa1-1 donor). High-resolution melt analysis of the lpa1-1 SNP marker was able to identify 11 homozygous recessive and 17 heterozygote genotypes for the lpa1-1 mutation. The SNP R2 values for the heterozygotes were higher (90.95–99.59%) than the lpa1-1 recessives (82.81–99.58%). The selected BC2F1 lines were fingerprinted with six amplified fragment length polymorphism (AFLP) EcoRI/MseI primer combinations to determine the amount of recurrent parent genome present. The 277 AFLP markers were clearly able to differentiate all the BC2F1 lines from each other and the parental controls with a similarity range from 62.12 to 92.15%. It is expected in the BC2 generation to find 87.5% similarity to the recurrent parent, however in this study higher levels of similarity in 13 BC2F1 lines (six heterozygotes and seven homozygous recessive) with 92.15–83.33% similarity were observed. The use of marker-assisted selection for foreground and background selection greatly increased the efficiency of detection of the homozygous recessive (99.58%) and heterozygous (99.59%) genotypes as well as improving the recovery of the recurrent parent (92.15%) in the BC2F1 generation of the maize backcross breeding programme.

Genetics of Morpho-Physiological Traits in Segregating Populations of Interspecific Hybrid Rice Under Stress and Non-Stress Conditions

Drought is one of the major constraints for rice (Oryza sativa L.) production in the rainfed ecologies in Sub-Saharan Africa. The objectives of this study were to investigate the genetic effects of morpho-physiological traits controlling drought-stress tolerance. Five Oryza glaberrima genotypes, four interspecific inbred lines, two interspecific hybrids, and two O. sativa lines and their progenies from a North Carolina II mating design were evaluated at ICRISAT in Mali under drought and fully irrigated conditions in 8 × 8 lattice designs. Data were collected on morpho-physiological traits, such as plant height, leaf rolling and stress recovery ability. General combining ability (GCA) effects for females and males were significant for all traits. Female GCA and specific combining ability (SCA) effects were significant for tiller number, plant height, and specific leaf dry weight. Heritability estimates based on variance ratios ranged from 47% to 67% for plant height, leaf area, specific leaf dry weight, and SPAD (chlorophyll); these were not significant for tiller number, which was controlled by overdominance. Heritability estimates based on regression were significant and ranged from 22% to 72% for drought-tolerance scores and leaf rolling scores. Highly significant positive relationships were observed between F3 and F4 generations for drought tolerance and leaf-rolling scores in all the populations examined. Both additive and non-additive genetic affects were important in controlling morpho-physiological traits; hence breeding procedures that exploit both GCA and SCA should be considered to improve drought tolerance in this rice germplasm.

Acceptance of a complementary food prepared with yellow, provitamin A-biofortified maize by black caregivers in rural KwaZulu-Natal

Abstract Objectives: The objective was to assess the sensory acceptability and consumer perceptions of soft porridge made with yellow, provitamin A-biofortified maize by black African female infant caregivers from rural KwaZulu-Natal. Design: This was a cross-sectional study. Setting: The study was conducted at Edendale Hospital, located in the uMgungundlovu District, KwaZulu-Natal province. The hospital serves a high proportion of people from rural areas in this district. Subjects: Sixty black African female infant caregivers participated in the study. Outcome measures: The sensory acceptability of soft porridge made from two varieties of provitamin-A biofortified maize and one variety of white maize were evaluated by black African female infant caregivers (n = 60) using a five-point facial hedonic scale. Some of the subjects (n = 21) participated in focus group discussions to assess consumer perceptions. Results: There was no significant difference in the sensory acceptability of the biofortified maize porridge and the white maize porridge, irrespective of caregiver age (p-value > 0.05). The caregivers expressed a willingness to give their infants porridge made with provitamin A-biofortified maize if it was more affordable, readily available and beneficial to health. Conclusion: The biofortified maize soft porridge was found to be as acceptable as the white maize soft porridge to black African female infant caregivers from rural KwaZulu-Natal. Provitamin A-biofortified maize has the potential to be used as a complementary food item that would contribute to the alleviation of vitamin A deficiency.

Effects of amaranth addition on the pro-vitamin A content, and physical and antioxidant properties of extruded pro-vitamin A-biofortified maize snacks

BACKGROUND Pro-vitamin A-biofortified maize snacks with added leafy vegetable may have a potential as nutritious and health-promoting products, especially in addressing vitamin A deficiency, which is prevalent in developing regions. The objective of the study was to determine the effects of adding amaranth leaf powder on the physical, antioxidant properties and pro-vitamin A content of extruded pro-vitamin A-biofortified maize snacks. Extruded snacks were processed using four pro-vitamin A-biofortified maize varieties that were composited with amaranth leaf powder at 0%, 1% and 3% (w/w) substitution levels. RESULTS At higher amaranth concentration, the expansion ratio of the snacks decreased, while their hardness increased by as much as 93%. The physical quality of the snacks may therefore need improvement. As amaranth was increased, the phenolic content and antioxidant activity of the snacks increased as well as the pro-vitamin A content. CONCLUSION Pro-vitamin A-biofortified maize with added amaranth has a potential for use in nutritious and healthy extruded snacks. There are limited studies reporting on processing pro-vitamin A maize with complementary plant foods, which is common with white maize in southern Africa; thus the current study serves as a baseline.

Development of a single nucleotide polymorphism (SNP) marker for detection of the low phytic acid ( lpa1-1 ) gene used during maize breeding

Three in vitro experiments were conducted to study the effect of different concentrations of carbon source, salinity and gelling agent on number of new shoots, shoot length, fresh weight, and dry weight of fig (Ficus carica L.) to develop an efficient in vitro propagation method. The results show that there were no significant differences between the three carbon sources regarding number of newly formed shoots and their shoot lengths. However, there were some differences regarding fresh and dry weights. On the other hand, increased salinity concentrations reduced the number of the newly formed shoots, as well as, their shoot lengths. In addition, liquid media produced more shoots compared with the three solidifying agents used. However, there were significant differences among the concentrations of solidifying agents used.