Review on Integrated Plant Breeding Approaches for Moisture Stress Tolerance in Maize (Zea mays L.)

Abstract

Maize being grown throughout the world due to its adaptability with range of environments and occupies third largest area under cultivation. It can be used as fodder, poultry feed and human staple food crop. It also serves as raw material for more than five hundred food products. Therefore, maize has huge demand in both national and international markets. At the same time, it faces serious problems viz., abiotic and biotic stresses which reduces production greatly. Among the stresses, moisture stress is the one that can decrease yield up to 79-80% (Monneveux et al. 2005). Maize varieties or hybrids have to be developed to meet the present demand by applying suitable breeding approaches.

Studies are being conducted, to explore germplasm, develop breeding material, understand genetics of moisture stress tolerance and to determine the physiological, biochemical, molecular, agronomical as well as phenotypic traits associated with tolerance to moisture stress. There are many reports confirming, moisture stress tolerance a complex trait, controlled by poly genes and highly influenced by environmental factors. Researchers employed different breeding approaches and physio-biochemical along with agronomic parameters to assess the moisture stress tolerance and to develop a variety tolerant to stress.

Mahmood et al. 2013, evaluated six maize cultivars for tolerance based on physiological traits associated with cell wall plasticity and found two (EV-1097 & Agaiti 2002) as tolerant, based on higher values of LGR, Chlorophyll, TSP, Proline, SLW and TSS. In addition to above physiological traits, Canopy Temperature is also a trait which is directly associated with stress tolerance as reported by Abbas et al. 2014. Root is the organ which senses the water limitation and signals the above ground canopy to run adoptive mechanisms thus, study of root features is essential to develop a drought tolerant cultivar as suggested by Rangyao Li, 2015.

Drought tolerant indices are mathematical ratios calculated based on yield data from stress and non stress field. Researchers have concluded the significant and positive association of tolerant indices (DTI, MP, GMP, TOL, SSPI, K1STI and K2STI) with grain yield in stress condition. Zahra& Jahad (2012) evaluated the maize cultivars using tolerant indices and find out best indices and cultivars for determining tolerance and moisture stress tolerant respectively. Yanli Lu et al. 2011 screened 551 lines for drought tolerance by considering multiple selection criteria among which NDVI, chlorophyll content and leaf senescence are the major traits. This study confirmed the NDVI as an effective parameter to determine stress tolerance.

Identification of morpho-physiological traits and QTLs linked with tolerance and stay green can serve as effective strategy to improve stress tolerance via MAS, as confirmed by Zhu et al. (2011) and Ai-Yu et al. 2012. MABC breeding could be employed to select and develop hybrids tolerant to moisture stress as confirmed by jean and Mic 2007. Among various breeding approaches described, integrated breeding approach would be the best technique to develop variety resistant to moisture stress.