Effects of environment on pollen-silk synchronisation in maize hybrid seed production
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Date
2012-10-11
Authors
Chanda, Richard
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Abstract
In maize hybrid seed production, the objective is to maximise seed yield of desirable seed grade that is saleable and genetically pure. To achieve this, the timing of pollen shed of the male and silking of the female should be well synchronised. Currently, maize hybrid seed production is based on limited information on the quantity of pollen produced by the male and practical experience synchronising pollen-shed with silking. Therefore, the objective of the research was to look into the aspects of synchronisation as related to hybrid seed maize production, specifically to study the effect of environment on male - female synchrony. Nine inbred lines, used as males and nine single cross hybrids,used as females, producing hybrids of different maturities were used in the study. The parents were grown under optimal, sub-optimal conditions relative to soil nitrogen level and under water stress in the dry season. Irrigation water was withheld for four weeks during flowering. The recommended agronomic practices were used at all the trial sites. During the growing season, the rate of silking and pollen-shedding were collected on each plant daily. In addition, seed yield components and other important agronomic traits were recorded. Significant (p<0.05) genotype x environment interactions were observed on grain yield, 100 seed weight, ear leaf area, plant stand, average tassel length, days to 50% anthesis, anthesis-silking interval and number of tassel branches. The main effects of the environment and hybrids were significant (p<0.05) in most of the traits measured. There was considerable variation in the response of parents to varying environmental conditions. Generally, the onset of flowering was delayed, with water stress having the greatest influence on the onset of silking, tasselling and pollen shedding, compared to optimal conditions. On average, BIPASI and desychronisation increased under nitrogen stress. Low nitrogen and high plant population with optimal nitrogen increased the duration of pollination and duration of pollen shedding. BIPASI explained only 22% of the observed variation in number of grains per plant. The number of grains per plant were strongly associated to ears per plant (R'^ = 0.84), sheddays (R'^ = 0.75) and silk spread (R- = 0.75); moderately associated to duration of anthesis (R'-^ = 0.66) and to low extent associated to 50% silking (R^ - 0.52). Therefore, it was concluded that seed set depends on the dynamics of silking and pollen shedding. Multiple regression analysis revealed that traits responsible for moderating seed set differed from environment to environment-, but averaged across all environments and parents, one hundred seed weight, ears per plant and shelling percentage were the most common traits. Ears per plant had the highest impact, again proving the robustness of this trait in influencing seed yield. Generally, most parents that had BIPASI of +5days, had high seed set, except under low N conditions were N deficiency limited yield. Despite synchronisation being affected by environment, seed production was economically viable for parents planted on the same day when grown in various environments. However, this depended on parental combination. Therefore, in order to maximise seed set, synchronisation studies should be done to simulate actual field production to take care of the differential response of parents to stress conditions.
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Keywords
Environment , Acclimatization (Plants) , Seed industry and trade , Pollen -- Dispersal -- Climatic factors , Corn