Physiological and Biochemical Responses of Cowpea Genotypes to Water Stress Under Glasshouse and Field Conditions

Abstract

Five cowpea genotypes, Gorom local (Go), KVX61‐1 (KV), Mouride (Mo), Bambey 21 (B21) and TN88‐63 (TN), differing in their susceptibility to water stress, were studied under glasshouse and field conditions, to determine their physiological, biochemical and agronomic responses to water deficit at flowering stage. Effect of water deficit on leaf water potential (ψl), canopy temperature, gaseous exchange, leaf proline content, total protein and starch contents, maximal quantum yield (ϕp0) and yield components was examined. Water deficit significantly increased the canopy temperature and the proline content of the five genotypes while ψl, gaseous exchanges, ϕp0 and starch content decreased significantly. Yield components, with the exception of seed number per pod, of the five genotypes, were also significantly affected. Under glasshouse and field conditions, the results showed that stomatal closure is the common strategy used by the five genotypes to avoid dehydration. Go, Mo and TN tolerated water stress better than B21 and KV. Furthermore, Go and Mo recovered more rapidly after rewatering than B21 and KV. These latter genotypes are revealed to be sensitive with low recovery capacity. The results suggest that the maintenance of net photosynthesis and solute accumulation seem to be traits conferring water stress tolerance in Go, Mo and TN. These traits and recovery capacity could be valuable selection criteria for higher yields under water deficit conditions.

Leaf Photosynthetic Metabolism and N2 Fixation at the Flowering Stage in Three Genotypes of Cowpea [Vigna unguiculata (L.) Walp.]

“…Previous studies have shown that a dose of nitrogen at planting or coverage benefits the development of bean plants (Hungria et al, 2003;Xavier et al, 2008); hence the absence of the conventional treatment in this study, involving BNF alone, without any source of mineral nitrogen. In this study, seeding in pots with only sand as substrate was also avoided, since previous studies have shown that the bean is strongly hindered by this substrate without organic matter (Melo et al, 2005); moreover, this condition can easily lead to water deficit or high temperature in nodulated roots, which is harmful (Hamidou et al, 2007;Simões-Araújo et al, 2008). Under field conditions plants of all three cultivars exhibited similar behavior regarding gas exchange and photochemical efficiency for both treatments with BNF and not (Fig.…”

“…This feature, a short period of peak photosynthesis in the preflowering phase, a common physiological behavior of bean, is perhaps the main reason that the culture responds to a small amount of mineral nitrogen while under BNF Hungary et al, 2003;Xavier et al, 2008;Pelegrin et al, 2009). Another determining factor for the low efficiency of BNF in bean is the occurrence of water stress (Figueiredo et al, 2007;Hamidou et al, 2007), even in Vigna, which is more tolerant of water shortage than Phaseolus (Pimentel and Hébert, 1999). This is especially true if these stressful conditions occur between vegetative and early reproductive stages, when the production of new nodules is stabilizing in cowpea (Senanayake et al, 1987), leading to low efficiency of BNF during the reproductive stage when a high amount of nitrogen is required by the leaves in legumes (Neves et al, 1982;Kaschuk et al, 2010).…”

“…Although drought is the main abiotic factor responsible for the reduction in BNF efficiency (Hamidou et al, 2007), in tropical areas, high soil temperature also limits the process (Simões-Araújo et al, 2008). The degree of specificity of certain species of tropical legumes and of tropical strains of rhizobia has been previously discussed (Thies et al, 1991;Simões-Araújo et al, 2008); however, for cowpea, the ease with which this plant is nodulated by several types of rhizobia has discouraged the selection of strains for crop.…”

Response of coleoptiles to water deficit: growth, turgor maintenance and osmotic adjustment in barley plants (Hordeum vulgare L.)

“…The expression of these genes is differentially affected by the drought stress applied [2]. Heat-stress was associated with a decrease in the rate of growth and in the final length of barley and wheat coleoptiles [3,4] Osmotic adjustment is becoming increasingly recognised as an efficient drought tolerance mechanism in cultivated plants [5,6], exerting a positive effect-either directly or indirectly-on the productivity of plants that grow under drought conditions [7]. Genotypes with the ability to make osmotic adjustments produce greater yields; for example in chickpea [8,9], pea [10], sorghum [11,12], wheat [13,14], barley [15,16], sunflower [17] and potato [18] .…”

Evaluation of four Mozambican cowpea landraces for drought tolerance

“…However, significant differences exist among cowpea genotypes in their response to drought (Watanabe et al 1997;Mai-Kodomi et al 1999). Stomatal closure has been identified as a common response to drought in cowpea (Ogbannaya et al 2003;Anya and Herzog 2004;Souza et al 2004;Hamidou et al 2007). 3 The Mozambican National Gene Bank has recently started collecting the country's national heritage of plant genetic resources.…”