Maize grain soluble sugar and protein contents in response to simulated hail damage

Abstract

Production of grain of high nutritional quality is essential in maize (Zea mays L.) as a food grain crop. Grain quality may be influenced by environmental and management factors, such as hail, plant density and grain selection. A study was conducted to determine the effect of hail damage on maize grain contents of soluble sugars and total proteins in relation to grain position on the cob and planting density. Maize was grown at three planting densities (65 000 plants ha⁻¹ [high], 46 000 plants ha⁻¹ [moderate] and 28 000 plants ha⁻¹ [low]) at two sites (Baynesfield and Swayimane) in KwaZulu-Natal, South Africa. Approximately 80% hail damage was simulated on the leaves at the seventh leaf (V7) and tasseling (VT) stages of development of three maize cultivars (‘SC701’, ‘Mac Medium Pearl’ and ‘Zama Star’), whereas undamaged plants served as the control. After harvest at maturity, grains from the proximal and distal portions of the cob were divided and analysed for grain nutritional quality, i.e. soluble sugars and proteins. Soluble sugar analysis focused on the predominant sugars, namely glucose, fructose and sucrose. Although not significant, hail damage typically at VT reduced grain soluble sugar and protein contents by at least 3.2% and 3.8%, respectively, and grains produced at Baynesfield were more resilient to damage compared with those produced at Swayimane. Selection of seeds from the distal cob portion, especially for ‘SC701’, and low plant density reduced the detrimental effect of hail damage on grain sugar and protein content. The present results indicate that in areas prone to hail ‘SC701’ is a cultivar of choice, and a low plant density and selection of grains from the distal cob portion can mitigate the detrimental effects of hail on grain nutritional quality.

Keywords:

• fructose
• glucose
• grain
• proteins
• sucrose