Genetic analysis of tolerance to combined drought and heat stress in tropical maize.

Simultaneous occurrences of heat and drought stresses have a detrimental effect on growth, development and yield of maize. Heat and drought is expected to worsen maize yield losses under climate change. Selecting CDHS tolerant maize hybrids creates great opportunity for sustainable maize improvement in the tropics. The objective of current investigation was to dissect the genetic basis of CDHS tolerance in tropical maize and to determine performance of single cross hybrids under CDHS. Ninety six single-cross hybrids resulted from crossing 12 tassel blast tolerant and 12 tassel blast susceptible lines along with two Striga resistant commercial hybrids, a heat tolerant and a heat susceptible check hybrids were evaluated under FIRR, MDRTS and CDHS using 25x4 alpha lattice design with two replications. The results showed significant genetic variation for FIRR, MDRTS and CDHS tolerance among maize hybrids. The majority of single crosses that showed improved grain yield over their respective standard checks under MDRTS also exhibited improved grain yield over the same checks under CHDS, indicating development of CHDS tolerance hybrids. Significant and positive genotypic and phenotypic correlation of grain yield under MDRTS and CDHS implicated common genetic mechanisms controlling yield under MDRTS and CDHS. Stress tolerance indices YI, GMP, MP, HM and STI were identified as best selecting indices under both stresses. GCA variances were larger than SCA variances in each testing environment for most studied traits indicating the impotence of additive gene action than non-additive gene action to control these traits. Majority of stress indices and SCA effects demonstrated that hybrids HB18, HB41, HB91 and HB95 were high yielder under MDRTS and CDHS. Hybrids HB41, HB91 and HB95 and their parents' scored minimum tassel blast. Parents 19 and 7 were well general combiner for grain yield and early maturity under MDRTS and CDHS indicting their valuable source of genes for hybridization. The current findings revealed that CDHS tolerance hybrids can reduce expected yield losses and maintain maize productivity in CDHS prone areas. Promising hybrids should be tested further under various drought and CHDS for commercialization.

Perinatal outcome of oligohydramnios in academic hospitals in a low resource setting.

Oligohydramnios has been a topical issue in obstetrics. The prevalence of oligohydramnios ranges from 1 to 5%. Conflicting data exists concerning its effects on adverse perinatal outcome. This study aims to assess perinatal outcomes of oligohydramnios at the Mekelle Public Hospitals from April 1, 2018 - March 31, 2019. This was a cross-sectional study and a total population purposive sampling method was employed to collect data prospectively. During the study period, there were a total of 10,451 deliveries in both hospitals. Oligohydramnios complicated 332 pregnancies (3.2%, 95%CI: 2.9%, 3.5%) across all gestations and 273 pregnancies (2.6%, 95% CI: 2.3%, 2.9%) at term. The composite adverse perinatal outcome rate was 29.7% (95% CI, 24.5, 35.4). Primigravidity and presenting at post-term gestation were associated with adverse perinatal outcome. Nearly 70% of mothers gave birth via Cesarean delivery. Oligohydramnios was found to be associated with a significant increase in adverse newborn and maternal outcomes in the study setting. Although a significant proportion of mothers underwent Cesarean delivery for a perceived increased complications associated with vaginal delivery in this population of patients, Cesarean delivery was found to not improve perinatal outcome. Primigravids and postdated pregnancies must receive increased surveillance to detect oligohydramnios early and to institute appropriate and timely interventions. Indications for Cesarean delivery in patients complicated by oligohydramnios must be carefully examined to balance the benefit on the perinatal outcome on the one hand and to avoid unnecessary major surgery with potential fatal maternal complications on the other.