An ideotype of maize for conditions of high temperature and low moisture

Among the agronondcally impoitant grasses, maize is unusually suscq>tible to drought at flowering. Drou^t stimulates a protandrous pattern of development, w^ch lengthens the anthesis-silking interval Because maize has a short period of flowenng and pollen remains viable for small periods of time, each day of delay between pollen shed and silk emergence translates into a reduction in the rate of sexual fertilization, and an increase in barrenness. An ideotype of nuiize is proposed to overcome this problem The purpose is to reduce sensitivity to vvater deficit throu^ a series of morphological and anatomical modifications, inchiding: transference of the site of grain production from the axil of a leaf to the apex of the plant; condensation of the upper intemodes of the stem; and reduction of plant height and leaf number. The research efforts were concentrated in two areas; selection to integrate in one plant aH desired traits. Genetic diversty was found for all characters of mterest It was possible to identify and select mutants that exhibited in a single phenotype the proposed changes. However, several unde^able characteristics, such as lack of vigor and disease susceptibility, were also associated with the mutants and need to be in:q)roved. evahiation of the inq)act of proposed modifications on the performance of current cuhivars. Since tassel suppression and reduction in plant height are two in^portant characteristics of the ideotype, field e?q)eriments were conducted to evaluate their effect on maize tolerance to high plant population and drought stress.