Responses of east African highland banana (EAHB-AAA) cultivars to drought stress

Abstract

Banana (Musa spp.) yields are estimated at 5-30 t ha-1yr-1, lower than the potential 60 t ha-1yr-1
,
with the cause being drought stress. Much evidence among stakeholders shows little understanding
about banana cultivar sensitivity, escape and avoidance mechanisms to drought due to un-attempted
measures of retaining plant growth during escalating dry spell. This study aimed at determining
cultivar expression as a way of dealing with drought. Triploid cooking cultivars of Mpologoma and
Kisansa (AAA) versus the considered drought tolerant cultivars of Kayinja (ABB), Sukali ndiizi
(AAB) and a low land cultivar Yangambi Km5 (AAA) were grown under a semi-micro environment,
with controlled soil evapo-transpiration. Cultivars were grown on three sandy loam soil water
regimes under pF- curves of 10log matrix head of Wet: 2.0-2.1 (0.1 - 0.13 bar) equivalent to 90%
moisture availability (M.A.); Semi-moist: 2.5-2.7 (0.32 - 0.51 bars) equivalent to 60% M.A. and
Dry: 2.8-2.9 (0.64 - 0.8 bars) for 30% M.A., respectively. Results showed that an increase in soil
moisture deficit from moist to dry condition caused a proportional loss in fresh biomass of up to
50% among cooking cultivars, and less than 40% to dessert cultivars. Leaf orientation was
significant to folding with cooking variety type opening leaves widely (up to 100o
), and enhancing
excessive leaf plant dehydration, even during stressful conditions. Soil evapo-transpiration showed
that cvs. Kisansa and Mpologoma transpired up to 1.125L 48 hr-1, exhibiting a trait for water
spending than saving. Thus, cultivars comprising of genome (B) expressed crucial mechanisms of
avoiding excessive effect of drought stress. Therefore, under high moisture deficits, Kayinja and
Sukali ndiizi cultivars express drought avoidance mechanisms through leaf folding. But, the
cooking type of cultivars Kisansa and Mpologoma (genome A), develop extensive rooting system
important in search for moisture; and large leaf surface characterised by high rate of transpiration
for water spending