Abstract
BackgroundThe low grain water content (GWC) at harvest is a prerequisite to mechanical harvesting in maize, or otherwise would cause massive broken kernels and increase drying costs. The GWC at harvest in turn depends on GWC at the physiological maturity (PM) stage and grain dehydration rate (GDR). Both GWC and GDR are very complex traits, governed by multiple quantitative trait loci (QTL) and easily influenced by environmental conditions. So far, a number of experiments have been conducted to reveal numbers of GWC and GDR QTL, however, very few QTL have been confirmed, and no QTL has been fine-mapped or even been cloned.ResultsWe demonstrated that GWCs after PM were positively correlated with GWC at PM, whereas negatively with GDRs after PM. With a recombinant inbred line (RIL) population, we identified totally 31 QTL related to GWC and 17 QTL related to GDR in three field trials. Seven GWC QTL were consistently detected in at least two of the three field trials, each of which could explain 6.92–24.78% of the total GWC variation. Similarly, one GDR QTL was consistently detected, accounting for 9.44–14.46% of the total GDR variation. Three major GWC QTL were found to overlap with three GDR QTL in bins 1.05/06, 2.06/07, and 3.05, respectively. One of the consistent GWC QTL, namely qGwc1.1, was fine-mapped from a 27.22 Mb to a 2.05 Mb region by using recombinant-derived progeny test. The qGwc1.1 acted in a semi-dominant manner to reduce GWC by 1.49–3.31%.ConclusionsA number of consistent GWC and GDR QTL have been identified, and one of them, QTL-qGwc1.1, was successfully refined into a 2.05 Mb region. Hence, it is realistic to clone the genes underlying the GWC and GDR QTL and to make use of them in breeding of maize varieties with low GWC at harvest.
Highlights
The low grain water content (GWC) at harvest is a prerequisite to mechanical harvesting in maize, or otherwise would cause massive broken kernels and increase drying costs
Thereafter, four recombinant inbred line (RIL) differed with respect to the changing curves of dry weight/100-kernel and GWC
The RIL1 ceased an accumulation of the dry matter and slowed down the dehydration rate, while the other three RILs showed a continuous slow increase in the dry matter and a slow decrease in the GWC (Fig. 2)
Summary
The low grain water content (GWC) at harvest is a prerequisite to mechanical harvesting in maize, or otherwise would cause massive broken kernels and increase drying costs. The GWC at harvest in turn depends on GWC at the physiological maturity (PM) stage and grain dehydration rate (GDR). High GWC kernels can delay the harvest and lead to ear dropping, plant lodging, and bird pecking [8, 9]. Discovery of genetic factors controlling GWC could be the most costeffective way for breeding maize cultivars with low GWC to reduce the kernel breakage and drying costs. Before PM, the decrease in GWC is due to successive accumulation of dry matter via grain filling and the water loss rate is constant and highly dependent on genetic factors, which has been interpreted as a “developmental loss of water”. Maize varieties with a fast dry-down rate generally have low ear moisture at harvest [19, 20]
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