Relationship of Some Morpho-physiological Traits with Grain Yield in Maize

Maize is sensitive to drought and suffers a serious setback in yield due to high temperature stress. There is need to evaluate maize inbred lines, which are resistant to drought conditions. Ten maize inbred lines namely MO-17, DK-656, lZI-7103, SYP-31, AYP-17, H-93, B-73, A-6660, IZI-4001 and KLI-2301 were exposed to water stress in drought chamber. Genotypic and phenotypic correlation coefficients of various plant morpho-physiological traits with grain yield were ascertained. Survival rate treat-II, root-shoot ratio, stomatal frequency and photosynthetically active rations showed significant correlation at genotypic level with grain yield. The study emphasized that these morpho-physiological traits have underlying genetic basis. Once these basis are understood precisely, breeders will be able to tailor maize varieties with better yield potential. Introduction Maize being C4 plant has an efficient energy capturing system and is capable of rapid growth. Being a short duration crop, it has attained top priority in hilly areas where snowfall and chilling conditions limit the growing period of other cereals. With the possibility of raising two crops in a year, it could contribute significantly to overall food production programme of the country. The adaptation of a particular genotype to a particular environment is determined by its response to effects of heat, cold, drought and soil nutrients. The plant breeder in collaboration with plant physiologist strives to make inherent modifications in plant physiological processes so as to enable them function more efficiently. In this connection various worker like Sen and Misra (1981), Dai et al. (1990), Metha and Sarkar (1991) and Ali (1994) have tried to establish relationship among different plant traits and grain yield. Koscielniak and Dubert (1985) discussed the significance of seedling traits in predicting grain yield in maize breeding programmes. The main objective of the present study was to determine the extent and nature of correlation between various maize plant morpho-physiological traits under drought conditions. The information derived from this study will be helpful in tailoring maize genotypes with better photosynthetic ability and efficiency to survive under drought conditions. Materials and Methods The experimental material comprised of ten elite maize inbred lines viz., MO-17, DK-656, IZI-7103, SYP-31, AYP-17, H-93, B-73, A-6660, IZI-4001 and KLI-2301. The experiment was conducted both in the drought chamber and in the experimental area of the department of Plant Breeding and Genetics, University of Agriculture, Faisalabad, during 1994-95. The inbred lines were grown in drought chamber during Oct. 1994. Polythene bags (18 x 9 cm) were filled with fresh river sand washed distilled water to make it free form nutrients. One seed of each inbred line was sown in each bag at a uniform depth of 3 cm. A completely randomized design with three replications was followed. Each replication consisted of ten seedlings of each inbred line. At three-leaf stage, the seedlings were placed in drought chamber. The soil moisture was replenished to the desired level by weighing the individual bag and restoring the deficit if any by adding water. The combinations of drought components (temperature, relative humidity and soil moisture) were used as follows. Treatments Temp. Moisture Humidity (EC) (% FC) (%) l 48 25 12 ll 48 25 50-70 Ill 48 50 12 IV 48 50 60-70 FC = Field capacity When there was 50 percent mortality, survived seedlings were taken out from drought chamber and Hogland's solution was applied to the seedlings and their survival rate counted after 15 days. The number of survived seedlings was counted in each replication. The survival rate was calculated as, Seedlings Survived after 15 days×100 Total Number of Seedlings Five seedlings of each inbred line from each treatment were chosen which survived drought shock. Polythene bags were carefully torn off, seedlings were shaken gently to shed off the sand, washed under tap water taking care that their shoots and roots were not damaged. Fresh roots and shoots were placed in kraft paper bags at 60EC in an electronic oven till they became dry. Thereafter, samples were weighed in milligrams using an electronic balance. Root-shoot ratio was determined as: