The aim of this study was to improve resistance to DM and MSVD in three QPM populations. Two cycles of S1 recurrent selection significantly improved DM and MSVD resistance in the three QPM populations although the basic levels of resistance differed.
Importance of Maize in Africa
Unfortunately, QPM varieties are susceptible to DM and MSVD which reduce their grain yield potential and also affect their production in the country. However, no studies have been conducted on the response to selection for resistance to DM and MSVD in these QPM varieties.
Downy Mildew
Farmers' preferences should be considered when improving existing popular varieties and when developing new QPM populations in Mozambique. This was realized by identifying farmers' key production constraints, special preferences and perceptions about QPM cultivars, and determining the utility of recurrent selection method to improve three QPM populations Sussuma, ZM521Q and Pop62SRQ for DM and MSVD resistance.
Literature Review
- The spread of maize into Mozambique
- Quality protein maize
- Genetics and Breeding Strategies of QPM
- Downy Mildew
- Epidemiology of Downy Mildews
- Disease symptoms
- Source of resistance to Downy Mildew and Breeding Progress
- The Maize Streak Virus in Africa
- Epidemiology of maize streak virus
- Sources of Resistance
- Progress on breeding maize streak virus in QPM
- Recurrent Selection in maize
- Participatory Rural Appraisal
- Summary
Zeins, especially alpha-zein, have been found to be abundant in maize endosperm (Gibbon et al., 2005). Maize belt disease (MSVD) is caused by a geminivirus that is transmitted by viruliferous leaf borers (Cicadulina mbila) in Africa (van Rensburg et al., 1991; Welz, 1998; Pratt and Gordon, 2006).
Farmer perceptions on maize production constraints and the status of
Introduction
Farmers' requirements are not uniform and depend on their niches, yet growers usually select cultivars for broad adaptation (Sthapit et al., 1996). An appropriate maize breeding strategy should address the demands of the smallholder farmers in the marginal environments.
Objectives and Research hypothesis of the study
Material and Methods
- Study Area
- Selection of farmers
- Data collection
- Data analyses
The selection was made in such a way that all socio-economic classes of farmers were adequately represented in the study. During the discussions, farmers were asked to list and rank the biggest constraints to maize production in the area.
Results
- Maize consumption
- Household Characteristics
- Production Constraints
- Importance of downy mildew and maize streak virus disease
Average land holdings varied significantly between districts, ranging from 0.8 ha in Manica to 2.0 ha in Angonia. Although farmers in Manica district have accepted the new, precocious OPVs, they have shown great appreciation for their local varieties. Twenty-five percent of farmers interviewed in Angonia district reported that maize streak virus (MSV) was the main disease, followed by gray leaf spot (GLS).
In Manica district, 23% of farmers reported that swine downy mildew (DM) was the most important disease followed by MSV.
Discussion
Pingali (2001) reported that DM was considered one of the major barriers contributing to the yield gap in sub-Saharan Africa. The study results show that control measures for DM and MSVD applied by farmers included early planting and removal of growing tips from young affected plants, a practice similar to rouging. DeVries and Toenniessen (2001) reported that for subsistence farmers, a more effective and practical solution to yield losses is high-yielding corn cultivars resistant to DM and MSVD.
These farmers, although growing hybrids, still mentioned that these hybrids suffered from DM and MSV damage resulting in yield losses.
Conclusions
To obtain an overview of the main constraints and farmers' preferences for high-quality protein corn-resistant cultivars. How many seed dealers are there in your district and which ones do you know are marketing QPM varieties? Resistance to storage pests (e.g. grain beetle) 5. Number of cobs per plant 9. Which of these factors are most important?
Response to selection for downy mildew resistance, grain yield, and
Introduction
Recurrent selection (RS) methods have been widely used to improve the yield and agronomic performance of maize populations (Ceballos et al., 1991). The RS, which has been proven to be efficient in exploiting additive effects (Moll and Smith, 1981), would thus be used to improve three QPM populations for resistance to DM in Mozambique. A review of the available literature revealed that very little, if any, RS has been performed to improve QPM, especially for DM resistance.
However, some improvement in DM resistance has been reported in normal maize (CIMMYT, 2001), especially when S1 selection was used in combination with full sibling selection (Ajala, 1992).
Objectives and Research hypothesis
The QPM populations under cultivation in Mozambique have not been studied for genetic variability for DM resistance and their response to selection for DM resistance. This study was therefore based on the premise that DM resistance is polygenically controlled by predominantly additive gene action and can be improved by recurrent selection.
Materials and methods
- Location of the study
- Germplasm
- Establishment of screening nurseries and artificial inoculation of spreader
- Formation of the cycles
- Selection method
- Experimental layout of yield trial
- Data collection
The progeny of plants selected from the selfed generation (S1) were planted in an ear-by-row method, in which the progeny of each plant was planted in only one row 5 m long. Second, the self-pollinated progeny of each population were selected again at harvest time and sent to the laboratory for final analysis of tryptophan content to maintain the protein quality of the selected progeny for the next generation of selection. Selection for grain texture was based on grain kernel levels and was made after harvest.
Downy mildew incidence and severity were assessed twice after planting, as infection occurs approximately three weeks after planting, based on visual assessment of the entire plot.
Data analysis
Results
- Downy Mildew
- Grain yield
- Plant height
- Anthesis-Silking Interval (ASI)
- Grain Moisture
- Correlation Coefficients
Mean squares for grain moisture among volsib families were significant in all populations (Appendix 3.1, 3.2 and 3.3). In Sussuma, significant correlations were observed between DM and ASI, and grain yield with ears per plant and grain moisture. In ZM521Q, correlations were shown between DM with grain per plant and plant height with grain yield (Table 3.12).
In Pop62SRQ, DM showed high correlation with ASI, and grain structure was related to grain moisture.
Discussion
- ZM521Q and Pop62SRQ
Highly significant increase in grain yield (507 kg cycle-1) in four populations was detected by De Leon et al. 1993), after three cycles of recurrent S1 selection for downy mildew resistance. 1991) reported 19% cycle-1 gain in early and 7% cycle-1 gain in intermediate populations for wheat yield under disease pressure. 1998) experienced significant increase in grain yield in maize population BS 11. 1986) reported early flowering with a 4.4% increase in wheat yield cycle-1 after performing 15 cycles of full replicate selection in a lowland tropical maize population, Tuxpeno Crema1. These findings are consistent with those reported by Ceballos et al. 1991) who observed a similar relationship between disease resistance and higher wheat yield. 1991) reported 19% initial cycle-1 gain and 7% cycle-1 gain under intermediate disease pressure trials for grain yield in maize populations.
1986) reported early flowering with a 4.4% increase in wheat yield cycle-1 after performing 15 cycles of complete repeated selection in a lowland tropical maize population, Tuxpeno Crema1.
Conclusions
Reciprocal selection in BSSS and BSCB1 maize populations and half-sib selection in BSSS. Genetic variation and selection responses in an advanced generation of a widely divergent maize hybrid population. Genetic analysis of resistance to downy mildew and Rajasthan downy mildew in maize (Zea mays L.).
Grain yield stability, endosperm modification and protein quality of hybrid and open pollinated quality protein maize (QPM) cultivars.
Response to selection for maize streak resistance, grain yield, and
Introduction
Maize virus disease (MSVD) is one of the most important diseases affecting quality protein maize (QPM) in Mozambique. Breeding maize for resistance to MSVD is therefore important in northern and central Mozambique (DINA, 1995), where it is most widespread. However, resistance to MSVD can be improved by recurrent selection (RS) methods, which have led to significant increases in yield and other traits in maize populations (Efron et al., 1989) without compromising the genetic variation necessary for future improvements (Moll and Smith, 1981).
High-quality protein maize (QPM) varieties have been introduced in Mozambique, but are highly susceptible to MSVD.
Objective and research hypothesis of the study
Material and Methods
- Location of the experiment
- Germplasm
- Selection method
- Experimental layout of yield trial
- Data collection
Establishment of screening nurseries, artificial inoculation for Maize stripe virus disease and formation of the cycles. The population size of plants was fixed and was equal to that used for screening to DM, approximately 5000 plants for each population. The progeny of the selected plants were planted in an over-to-row method in which progeny of each plant was planted in one row only. Selection for grain texture is based on levels of flintyness of the grain using a scale of 1 (flinty) to 5 (completely plunging).
For yield evaluation and other agronomic characteristics, full-sib families formed through cross-pollination of the selected progeny were used.
Data analysis
Grain weight and moisture content per plot were obtained at harvest and the values obtained were used to estimate grain yield (t ha-1) adjusted to a moisture content of 13.5%.
Results
- Maize Streak Virus
- Grain yield
- Plant height
- Anthesis-Silking Interval
- Correlations
Mean squares for grain yield were highly significant (P≤0.01) among full-sib families in all populations (Appendices 4.1, 4.2 and 4.3). Corresponding estimates of heritability for plant height were higher and are presented in Tables 4.3, 4.4 and 4.5. In the ZM521Q population, significant correlation coefficients were observed between grain moisture and ASI and grain texture with ear per plant.
In the Pop62SRQ population, grain yield was highly correlated with ear per plant and grain moisture.
Discussion
- Sussuma, ZM521Q and Pop62SRQ populations
Mean square values for grain yield in MSVD were highly significant (P≤ 0.01) for cycles and high correlation was observed between MSVD and grain moisture. It can be argued that improvement in grain yield is related to increased resistance to MSVD. Heritability estimates for grain yield were high indicating that an improvement would be achieved from field selection for grain yield.
Highly significant correlation coefficients between grain moisture and MSVD; MSVD and ASI and grain yield with grain moisture in Sussuma were observed.
Conclusions
A gene for resistance to maize stripe virus in the African CIMMYT maize inbred line CML 202, Mol. The correlation coefficients in the Sussuma population showed grain yield highly correlated with ear per head. plant and grain texture. The correlation coefficients in the ZM521Q population showed grain yield highly correlated with ear per plant.
Correlation coefficients in the Pop62SRQ population showed grain yield highly correlated with grain moisture and plant height with grain structure and grain yield.
General Overview
Introduction
Research findings
However, as in Manica district, some of the preferences of farmers in Angonia are not part of the breeding objectives in Mozambique. These preferences are part of the reason why farmers do not immediately adopt improved varieties, even if they have important traits such as disease resistance. A way to achieve higher adoption rates of new cultivars is to involve farmers from the beginning of the breeding program.
Yield and other correlated traits improved due to selection that showed these traits were not compromised as a result of improvements in disease resistance of the populations.
