Several methods of evaluating stalk quality in maize have been developed and evaluated, but most breeders still rely on naturally occurring stalk lodging. We evaluated the effectiveness of a penetrometer device for stalk strength improvement by phenotypic recurrent selection.
B(K)RRS, from the Nebraska Agriculture Experiment Station, was planted and the 2nd elongated internodes of at least 300 plants were punched to obtain rind puncture values approximately one week pre-flowering. Ten percent, or approximately 30 plants, were intermated to complete a selection cycle.
Progress through three cycles of selection by the rind penetrometer technique was evaluated by growing the original population (C0) and the first (C1) through third (C3) cycles of selection. For comparison purposes, the original (C0), C1, C2, and C3 of MoSQA and MoSQB that had undergone cyclic selection for stalk strength improvement by the crushing strength method were included in the evaluation test.
Mature stalks from the 2nd elongated internode above the ground level were harvested. Crushing strength, weight of 5.1 cm stalk section and rind thickness were measured.
Gain in stalk crushing strength per cycle as the result of selection for high rind puncture values in synthetic B(K)RRS is shown in Table 1. Comparable values resulting from selection for crushing strength in MoSQA and MoSQB are also given. Three cycles of selection in B(K)RRS for high rind puncture values resulted in significant gains of 25 kg per cycle higher crushing strength, 0.10 g per cycle increase in stalk weight and 0.115 mm thicker rind per cycle. For comparison, MoSQA did not show a significant increase in stalk strength or rind thickness in three cycles of selection for crushing strength, whereas MoSQB had significant increases for crushing strength (58 kg) and stalk weight (0.19 g) but no significant change in rind thickness. From this preliminary study, we suggest that recurrent selection for high rind puncture values in the pre-flowering stage may be an effective method of improving stalk strength, with the advantage that one cycle of selection could be completed each season.
T. R. Colbert, L. L. Darrah and M. S. Zuber
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