Response to selection for downy mildew (Peronosclerospora sorghi) and maize streak virus resistance in three quality protein maize populations in Mozambique.

Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2007.Quality protein maize (QPM) has high nutritional value, but production is threatened by downy mildew (DM) and maize streak virus disease (MSVD) among other constraints. There are few studies of DM and MSVD resistance in QPM cultivars. The objective of this study was to improve resistance to DM and MSVD in three QPM populations. This was realized through ascertaining farmers’ key production constraints and special preferences for cultivars; determining the utility of recurrent selection method for improvement of three QPM populations (SussumaS2, ZM521Q and Pop62SRQ); and determining grain yield potential. The study was conducted in Mozambique for DM and in Zimbabwe for MSV, during 2003 to 2006. Surveys were conducted in Manica and Angonia districts in Mozambique to ascertain farmers’ perceptions and preferences for maize varieties, especially QPM. Participatory rural appraisal tools that included semi-structured questionnaires and focus group discussions were used to collect data. Results showed that farmers predominantly grew open pollinated varieties and fewer normal maize hybrids (non-QPM), and grain yield was estimated to be very low (0.2 to 0.6 t ha-1). Results showed that drought and insect pests were the dominant constraints to maize productivity in Mozambique, while diseases were ranked third. Downy mildew disease and MSVD were considered to be the most important diseases reducing maize productivity. Farmers also showed high preference for high yielding and early maturity cultivars in all areas. Predominantly, farmers were still using their local landraces because of sweet taste, particularly for home consumption and flint grain for storage. Farmers’ access to improved cultivars was limited due to high seed prices on the local market. Research priorities as perceived by the farmers included breeding for resistance to drought, grain weevils and diseases and sweetness. Generally, farmers showed little knowledge of QPM varieties and the importance of this trait, but they observed that the few QPM varieties they knew had some weaknesses such as poor storability and susceptibility to DM and MSVD which required improvement. These results should be considered in breeding new cultivars, both normal and QPM. To improve DM and MSV disease resistance in QPM varieties, S1 recurrent selection was conducted in three QPM populations, Sussuma, ZM521Q and Pop62SRQ at Umbeluzi Research Station in Mozambique and at CIMMYT-Harare Research Quality protein maize (QPM) has high nutritional value, but production is threatened by downy mildew (DM) and maize streak virus disease (MSVD) among other constraints. There are few studies of DM and MSVD resistance in QPM cultivars. The objective of this study was to improve resistance to DM and MSVD in three QPM populations. This was realized through ascertaining farmers’ key production constraints and special preferences for cultivars; determining the utility of recurrent selection method for improvement of three QPM populations (SussumaS2, ZM521Q and Pop62SRQ); and determining grain yield potential. The study was conducted in Mozambique for DM and in Zimbabwe for MSV, during 2003 to 2006. Surveys were conducted in Manica and Angonia districts in Mozambique to ascertain farmers’ perceptions and preferences for maize varieties, especially QPM. Participatory rural appraisal tools that included semi-structured questionnaires and focus group discussions were used to collect data. Results showed that farmers predominantly grew open pollinated varieties and fewer normal maize hybrids (non-QPM), and grain yield was estimated to be very low (0.2 to 0.6 t ha-1). Results showed that drought and insect pests were the dominant constraints to maize productivity in Mozambique, while diseases were ranked third. Downy mildew disease and MSVD were considered to be the most important diseases reducing maize productivity. Farmers also showed high preference for high yielding and early maturity cultivars in all areas. Predominantly, farmers were still using their local landraces because of sweet taste, particularly for home consumption and flint grain for storage. Farmers’ access to improved cultivars was limited due to high seed prices on the local market. Research priorities as perceived by the farmers included breeding for resistance to drought, grain weevils and diseases and sweetness. Generally, farmers showed little knowledge of QPM varieties and the importance of this trait, but they observed that the few QPM varieties they knew had some weaknesses such as poor storability and susceptibility to DM and MSVD which required improvement. These results should be considered in breeding new cultivars, both normal and QPM. To improve DM and MSV disease resistance in QPM varieties, S1 recurrent selection was conducted in three QPM populations, Sussuma, ZM521Q and Pop62SRQ at Umbeluzi Research Station in Mozambique and at CIMMYT-Harare Research

Approaches in breeding for high quality protein maize

Maize is the principal crop and major staple food in the most African and South American countries. The main problem in human nutrition in developing countries, and in livestock feed in developed countries, is insufficient production and poor quality of cereal proteins. In the case of maize, due to the very low content of essential amino acids lysine and tryptophan in grain endosperm, biological value is very low, which is main limiting factor of common maize in human nutrition and feeding of monogastric animals. Quality protein maize (QPM) can help in solving of this problem. Maize production also faces serious constraints caused by agro-ecological conditions and poor socio-economic situation. To alleviate the effect of the constraints, selected genotypes with more desirable traits and appropriate field-plot techniques to create multiple-stress conditions, were used. It was found that, in downy mildew nursery distance up to 35 m from spreader plot is providing sufficient down load of spores for plant infection, provided that the testing breeding materials are planted towards to down-stream direction of the dominant wind. Using these breeding approaches large number of early, white and flint synthetics, composites and inbred lines were created with resistance or tolerance to downy mildew (DMR), maize streak virus (SR) and drought (DT). Created genotypes exhibited very good kernel modification and yield potential under low and normal inputs. In the case of synthetics and composites, besides tolerance to multiple stress factors, they were competing in yield with local QPM and normal maize checks. In the case of created inbred lines high combining ability was exhibited both in non-conventional and conventional maize hybrids. Trial data revealed that in the most cases the best entries were over-yielding the best checks

Značaj genetičkih resursa iz različitih geografskih i klimatskih regiona u simultanom oplemenjivanju kukuruza na visok kvalitet proteina (VKP) i tolerantnost na stres

Due to the low biological value of proteins of common maize, it was reinitiated breeding for high protein quality maize (HQPM) using three genetic systems, namely: opaque-2 gene, endosperm modifier genes and enhancer genes, which are increasing lysine and tryptophan content in opaque-2 background In order to alleviate effect of abiotic and biotic stress factors, the genotypes with tolerance to those factors were included. Genetic resources originating from North, Central and South America, then West, Central and Southern Africa and gene bank of Maize Research Institute 'Zemun Polje' were used. Combining breeding approaches in selection of genetic resources, field plot techniques and laboratory analysis, it was created large number of early QPM varieties, inbred lines and hybrids with modified endosperm and high yield potential under poor and good growing conditions. Created lines exhibited high combining ability in conventional and non-conventional hybrids. Yield trials showed that QPM hybrids are competing with commercial hybrids of common maize.Zbog niske biološke vrednosti proteina zrna standardnog tipa kukuruza se pristupilo stvaranju sorata i linija kukuruza visokog kvaliteta proteina (VKP) korišćenjem tri genetička sistema: opaque-2 gena, gena modifikatora endosperma i gena enhansera koji povećavaju sadržaj lizina i triptofana u opaque-2 osnovi. Da bi se istovremeno ublažilo i delovanje abiotskih i biotskih faktora stresa uključeni su i genotipovi sa tolerantnošću na ove faktore. Korišćeni su genetički resursi poreklom iz Severne, Centralne i Južne Amerike, zatim Zapadne, Centralne i Južne Afrike i resursi iz banke gena Instituta za kukuruz 'Zemun polje'. Kombinovanjem selekcionih pristupa u izboru genetičkih resursa, tehnika u poljskim i laboratorijskim uslovima stvoren je veliki broj ranih sorata, inbred linija i hibrida VKP, modifikikovanog endosperma i visokog potencijala rodnosti pod lošim i normalnim uslovima gajenja. Takođe, stvorene inbred linije su ispoljile visoku kombinacionu sposobnost u nekonvencionalnim i konvencionalnim hibridima. Poljski ogledi su pokazali da VKP hibridi konkurišu po prinosu najboljim komercijalnim hibridima standardnog tipa kukuruza

Evaluation of the genetic potential of two maize populations (Zea mays L.) and the breeding implications for oil content in the seed kernel

O presente trabalho teve por objetivo avaliar a potencialidade genética de duas populações de milho (IG-1 e IG-2) para o melhoramento de teor de óleo na semente. Foram avaliadas progênies de meios irmãos das duas populações, utilizando-se de duas testemunhas intercalares (híbridos triplo e simples P3232 e P3072) a cada 50 progênies. Foram tomados dados de peso da espiga, altura da planta, altura da espiga, teor de óleo nos grãos, comprimento da espiga, diâmetro da espiga, número de fileiras de grãos da espiga e número de grãos por fileira da espiga de uma amostra de 5 espigas de cada parcela e produção total de cada parcela. Os dados foram submetidos às análises de variância conforme modelo proposto por VENCOVSKY (1969) e análise de covariância. A partir destas, foram estimadas a variância genética aditiva (σ2A), variância de interação (σ2A1), variância genética entre progênies (σ2p), variância de interação com local (σ2p1), variância ambiental entre parcelas (σ2e), variância fenotípica entre plantas dentro de progênies (σ2d), variância fenotípica da progênie (σ2F). Estimaram-se também o coeficiente de herdabilidade, correlações genéticas e fenotípicas, progressos genéticos esperados e respostas correlacionadas com a seleção. As duas populações em estudo apresentaram suficiente variabilidade genética para a obtenção de progressos significativos, em programas de melhoramento, para os caracteres avaliados. Os valores dos coeficientes de herdabilidade obtidos para os oito caracteres em estudo foram considerados médios, sendo que o IG-1 apresentou valores de herdabilidade maiores que o IG-2. As estimativas das correlações genéticas entre os caracteres altura da planta, altura da espiga e peso das espigas para as duas populações com o teor de óleo, foram todas positivas, exceção para o teor de óleo x peso da espiga na população IG-1. As respostas correlacionadas indicam que a seleção para aumentar o teor de óleo nos grãos poderá causar algum aumento na altura da planta e da espiga na população IG-1, e para o caráter peso de espiga não ocorre influência da seleção para o teor de óleo.The present work was done in order to evaluate the genetic potential of two maize populations (IG-1 and IG-2) when selected for the oil content in the seed kernel. Half sib families from both populations were evaluated through a single hybrids (P3232 and P3072) placed in between as an environmental check. Data from the following characteristics are reported: the yielding per plot, plant and ear height, the oil content in each ear, the cob diameter, the ear length, the kernels row number, and the kernels number per row. The statistical analysis of variance for each trait was done following the approaches proposed by VENCOVSKY (1969) and by covariances. Estimates were obtained for genetic additive variance (σ2A), genetic variance among progenies (σ2p), environmental variance among plots (σ2e), phenotypic variance among plants within progenies (σ2d), phenotypic progeny variance (σ2F). Also, were estimated the coefficient of heritability, the coefficient of genetic and phenotypic correlations, the expected genetic progress and the coefficient for expected correlated response. Based on the results it can be concluded that both populations have enough genetic variability in order to permit a significant progress with the selection. Medium values for the coefficient of heritability were obtained to all eight traits under study, and it can be shown that the IG-1 population has a higher value for this coefficient when compared to the IG-2. The estimates of genetic additive correlations among plant height, ear height, and ear weight with oil content for both populations had a positive value except in IG-1 type for oil content by ear weight. Correlated response are indicative that if selection is done in order to increase the oil content it will also increase the plant and ear weight at the IG-1 population, on the other side ear weight will be not affected during the selection

Evaluation of the genetic potential of two maize populations (Zea mays L.) and the breeding implications for oil content in the seed kernel

O presente trabalho teve por objetivo avaliar a potencialidade genética de duas populações de milho (IG-1 e IG-2) para o melhoramento de teor de óleo na semente. Foram avaliadas progênies de meios irmãos das duas populações, utilizando-se de duas testemunhas intercalares (híbridos triplo e simples P3232 e P3072) a cada 50 progênies. Foram tomados dados de peso da espiga, altura da planta, altura da espiga, teor de óleo nos grãos, comprimento da espiga, diâmetro da espiga, número de fileiras de grãos da espiga e número de grãos por fileira da espiga de uma amostra de 5 espigas de cada parcela e produção total de cada parcela. Os dados foram submetidos às análises de variância conforme modelo proposto por VENCOVSKY (1969) e análise de covariância. A partir destas, foram estimadas a variância genética aditiva (σ2A), variância de interação (σ2A1), variância genética entre progênies (σ2p), variância de interação com local (σ2p1), variância ambiental entre parcelas (σ2e), variância fenotípica entre plantas dentro de progênies (σ2d), variância fenotípica da progênie (σ2F). Estimaram-se também o coeficiente de herdabilidade, correlações genéticas e fenotípicas, progressos genéticos esperados e respostas correlacionadas com a seleção. As duas populações em estudo apresentaram suficiente variabilidade genética para a obtenção de progressos significativos, em programas de melhoramento, para os caracteres avaliados. Os valores dos coeficientes de herdabilidade obtidos para os oito caracteres em estudo foram considerados médios, sendo que o IG-1 apresentou valores de herdabilidade maiores que o IG-2. As estimativas das correlações genéticas entre os caracteres altura da planta, altura da espiga e peso das espigas para as duas populações com o teor de óleo, foram todas positivas, exceção para o teor de óleo x peso da espiga na população IG-1. As respostas correlacionadas indicam que a seleção para aumentar o teor de óleo nos grãos poderá causar algum aumento na altura da planta e da espiga na população IG-1, e para o caráter peso de espiga não ocorre influência da seleção para o teor de óleo.The present work was done in order to evaluate the genetic potential of two maize populations (IG-1 and IG-2) when selected for the oil content in the seed kernel. Half sib families from both populations were evaluated through a single hybrids (P3232 and P3072) placed in between as an environmental check. Data from the following characteristics are reported: the yielding per plot, plant and ear height, the oil content in each ear, the cob diameter, the ear length, the kernels row number, and the kernels number per row. The statistical analysis of variance for each trait was done following the approaches proposed by VENCOVSKY (1969) and by covariances. Estimates were obtained for genetic additive variance (σ2A), genetic variance among progenies (σ2p), environmental variance among plots (σ2e), phenotypic variance among plants within progenies (σ2d), phenotypic progeny variance (σ2F). Also, were estimated the coefficient of heritability, the coefficient of genetic and phenotypic correlations, the expected genetic progress and the coefficient for expected correlated response. Based on the results it can be concluded that both populations have enough genetic variability in order to permit a significant progress with the selection. Medium values for the coefficient of heritability were obtained to all eight traits under study, and it can be shown that the IG-1 population has a higher value for this coefficient when compared to the IG-2. The estimates of genetic additive correlations among plant height, ear height, and ear weight with oil content for both populations had a positive value except in IG-1 type for oil content by ear weight. Correlated response are indicative that if selection is done in order to increase the oil content it will also increase the plant and ear weight at the IG-1 population, on the other side ear weight will be not affected during the selection