Testcrosses for Selection of Sweet Corn Inbred Lines.

Sweet corn is a special type of corn, with high nutritional value. What differentiates it from other corns is the presence of a gene(s) that alters starch biosynthesis, causing accumulation of soluble polysaccharides in the endosperm, so it is sweeter than other types of corn. The consumption is increasing in Brazil. Being one of the major producers of corn in the world, there is also an enormous potential for the production of sweet corn. Nowadays, there are 46 varieties in Brazil, but only two of these are planted. There is a demand for new cultivars adapted to tropical conditions with high yields and superior grain quality. Additionally there is not enough information about evaluations and how to obtain new varieties for the Brazilian conditions. The main goal of this project is investigating different testers for selection of sweet corn inbred lines aimed at obtaining superior hybrids. Two populations of tropical germoplasm, where one is the tester of the other, were evaluated. In each cycle of selection testers were obtained from a mixture of selected lines in the previous generation, leading to three levels of selection and inbreeding. Testcrosses were evaluated in randomized complete blocks with three replications in two sowing seasons. The traits ear length, ear diameter and commercial quality, grain yield, plant height and days to flowering were evaluated and considered for selecting the inbred lines. The same traits were considered for evaluation of testcrosses derived from crosses between lines and testers. We concluded that the tester stemming from more selected inbred lines was as good as testers derived from less selected lines. We also verified that the level of selection underlying the constitution of a tester did not affect the genetic variance among testcrosses of evaluated lines.