Phenology and growth traits response of maize ( Zea mays L . ) genotypes to semi-arid conditions

Erratic rainfall and extreme weather have put the maize crop at risk in semi-arid regions of Khyber Pakhtunkhwa (KP), Pakistan in the recent past. To this extent a field experiment was carried out to identify tolerance of maize genotypes to semi-arid conditions at different growth stages of crop development. Eight maize genotypes (8003-4*66211, Babar, Azam, Iqbal, Jalal, Pahari, Pop-2009, and Sarhad White) were screened in a Randomized Complete Block (RCB) Design with three replications. Significant variations were found for days to 50% silk emergence, days to 50% tasseling, anthesis silking interval (ASI), plant height (cm), tassel length (cm), and number of plants plot. The genotype 8003-4*66211 was best for all the studied traits followed by Pop-2009 and Babar. Keeping in view the results of this study, it is concluded that genotype 8003-4*66211 delayed taselling and silking and reduced ASI under water limiting conditions and therefore, is recommended to be grown under semi-arid conditions while fulfilling the required agronomic practices.


Introduction
Maize (Zea mays) being a member of the Poaceae family is an important cereal crop of Pakistan after wheat & rice.In Pakistan, it is cultivated on an area of 1,142 thousand hectares with total production of 4,937 thousand tonnes and yield of 4,323 kg ha -1 .It contributes 2.2 % to the value added in agriculture and 0.4 % to gross domestic product [1].
Water is one of the main yield reducing factors in agriculture.An adequate quantity of water is essential for crop growth, development, transpiration and also for transport of nutrients to source (leaves) and prepared food materials for consumption in the development of new tissues (sink).Scarcity of water (drought stress) is one of the major contributors which affect crop growth and ultimately reduces yield

Materials and methods
An experiment titled "Phenology and growth traits response of maize genotypes to semi-arid conditions" was conducted at Agricultural Research Institute (ARI) Tarnab, Khyber Pakhtunkhwa, Pakistan during summer 2015.The experiment was laid out in randomized complete block (RCB) design with three replications.Eight maize genotypes i.e. 8003-4*66211, Babar, Azam, Iqbal, Jalal, Pahari, Sarhad white and Pop-2009 were sown at uniformed seed rate of 100 kg ha -1 .Plot size were consists of 3 *5 m 2 .Each plot consisted of four rows each of 5m length.Row to row and plant to plant distance were kept 75 and 25 cm respectively.Recommended dose of NPK fertilizer were applied from their respective sources (Urea, Single Super Phosphate and Sulphate of Potash) at the rate of 150, 125, and 100 kg ha -1 .Field was irrigated after 20 days of sowing, at grand growth stage, at pollination and grain filling stage.All other agronomic practices were applied uniformly throughout the growing season.The collected data were subjected to analysis of variance (ANOVA) [9].After getting the significant variation among genotypes performance for various parameters, the means for each parameter were further separated and compared by using the least significant difference (LSD) test at 5% level of probability.

Results and discussion
Phenological response of maize genotypes to semi-arid conditions Maize phenology i.e. days to 50% tasseling, silking, and ASI responded significantly and showed a significantly delayed response for genotype 8003-4*66211 under semi-arid conditions however, ASI were decreased as compare to other genotypes (Table 1).Maximum days to 50% tasseling (64.6) were observed for 8003-4*66211 which was different from rest of genotypes (59.67 to 56.66).Similarly, maximum days to 50% silking (65.3) were observed for 8003-4*66211 followed by Jalal (64.0) and Sarhad white (61.6) while the rest of the genotypes had resulted statistically similar values.However, maximum days to ASI (6.0) were observed for genotype Sarhad white followed by Pop-2009 (5.0) and Azam (4.3) while the rest of the genotypes were statistically similar values for days to ASI.The most prominent effect observed during drought was the variations in plant phenological growth stages.Semi-arid conditions reduced the time for days to 50%

Conclusion and recommendation
On the basis of our experimental results, maize genotype 8003-4*66211 due to its stay green and drought resistant characteristics was suggested to be grown under semi-arid conditions.

Response of morphological growth traits of maize genotypes to semi-arid conditions
No. of plants plot-1had not been significantly affected under semi-arid conditions however, maximum no. of plants (81.6) were observed for Sarhad white followed by Pop-2009 (76.6) and Babar (74.0) while the rest of the genotypes had resulted almost similar values.Initially the conditions for seed emergence were conducive for all genotypes and therefor, similar no. of plants plot-1was emerged in all plots.