The effect of water stress on growth and development of mango (Mangifera indica L.) varieties in lower Eastern region of Kenya

The relationship between the plasticity of different mango (Mangifera indica L.) varieties to soil water stress conditions needs a better  understanding as a potential crop adaptation to changing climate. This study was investigated the effects of different water regimes on  growth and development of different mango varieties. Measurements of mango plants' morphological and physiological variables during  the progressive imposition of soil water stress were performed within a controlled environment. Eight mango varieties were  grown under water stress treatments of 90%, 65% and 35% of field capacity (FC) on split plots in a randomized complete block design with  three replications. Data on shoot height and diameter, leaf chlorophyll content, temperature and water potential were collected  fortnightly, for nine months and means computed to reflect varietal response under increasing water stress (90% FC to 35% FC level).  Results showed significant (p=0.001) reduction in shoot height by 32.1% and shoot diameter by 29.05%. A significant (p=0.05) reduction in  leaf chlorophyll content and leafwater potential by 13.5% and 90% respectively was observed, while leaf temperature significantly (p=0.05)  increased by 20.8%. From the results; Keitt, Sabine, Tommy Atkins and VanDyke showed better performance in shoot growth  and leaf parameters under high water stress. For all varieties, high water stress significantly suppressed shoot growth, leaf chlorophyll  content production and increased leaf temperature and leaf water potential. None of the varieties showed optimal phenotypic plasticity  on both leaf growth and physiological parameters under highest soil water stress. We emphasize the considerable need of investigating,  over a period of at least five years, the effect of water stress on mango yield in the farms located in mango-growing areas.