Maize quality Breeding: plant and prolificity traits of single-crosses obtained and tested in Argentina

--Bernatené, EA, Corcuera, VR, Naranjo, CA

A maize quality breeding programme has been conducted at the Instituto Fitotecnico de Santa Catalina since 1990. Several inbreds have been developed and used to obtain single-cross hybrids, which have been tested in multi-location field trials since 2001/02. These hybrids can be classified by the nature of their endosperm into 3 categories: 1) waxy, 2) high quality protein and 3) waxy and high quality protein (double recessive) hybrids. Waxy hybrids have a naturally modified starch (high amylopectin) that constitutes an excellent staple to be transformed for technological objectives and it is also partially useful for feed, and the textile, paper and adhesive industries. In turn, high quality protein hybrids differ from the rest by the high content of lysine and tryptophan that enhances their biological value. As a result, they are excellent for use in pig and poultry feed as a partial solution to starvation in humans.

Several single-cross hybrids and their parent inbreds were tested during the growing season of 2002/03. Of these, fifteen hybrids (five of each category) and their parents were studied using some plant and prolificity traits. The trial was sown in a 3-replicate completely randomized block design at a density of 71,500 plants/ha on October 22 at Llavallol (35 ºS, 58 ºW), province of Buenos Aires (Argentina).

Measurements for each trait were taken on the basis of the individual plant. Each plot consisted of a row of 5.5 m. Three plant traits were considered: a) plant height (PH), b) ear insertion height (EIH) and c) number of leaves above the uppermost ear (LUE) as well as one prolificity trait: number of ears/plant (EP). Routine statistical analysis was done according to the classical methodology proposed by Falconer. Degree of heterosis was calculated on the basis of the highest parent value (HP-heterosis).

If data obtained for each descriptor in each group of hybrids are averaged, the high quality protein hybrids are 204.3 cm tall, waxy hybrids are 210.8 cm tall and the double recessive 239.6 cm tall. Waxy hybrids are more prolific (1.5 ears/plant) than high quality protein hybrids (1.1 ears/plant) but similar to double recessive hybrids (1.4 ears/plant). Detailed information is shown in Tables 1, 2, and 3.

Degree of heterosis is also presented in the attached tables. All hybrids evaluated showed lower LUE and EP than their respective parents. On the other hand, hybrid vigor is strongly expressed, as expected, through PH and EIH.

In summary, it can be said that the hybrids studied showed regular size and adequate ear insertion height that will facilitate their cultivation. Waxy and double recessive hybrids studied differed because of their prolificity, which is higher than in current maizes commonly grown in Argentina.

P1: Female parentPH: Plant height (cm)
P2: Male parentEIH: Ear insertion height (cm)
MP: Mid-parent valueLUE: Leaves above the uppermost ear
F1: Hybrid valueEP: Ears per plant
HP-Heterosis: High-parent heterosis %