Root Shallowness Of Common Bean Phaseolus Vulgaris L Effects On Low Input Agroecosystems Productivity In The Tropics

Author : Claire Lorts
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (959 download)

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Download or read book Parental Effects and Provisioning Under Drought and Phosphorus Stress in Common Bean written by Claire Lorts and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Low soil fertility and drought are primary constraints in common bean (Phaseolus vulgaris) production in low input agricultural systems, and a threat to food security in many developing nations. Common bean genotypes tolerant to drought or low phosphorus conditions have been identified, and root traits associated with tolerance to such stress have been examined. The utility of these root traits in tolerant genotypes is usually tested using seed from a well-watered and high-nutrient parental environment. However, many farmers in developing nations collect seed for the next years crop from parent plants grown in low phosphorus and/or drought conditions. Thus, it is important to understand how progeny from a stressed parental environment perform under similar stressful conditions. This study investigates the impact of a low phosphorus and/or drought parental environment on progeny seed and root traits. To test whether differences in progeny seed and root traits from stressed parental environments could be explained by differences in parental provisioning of seeds during seed development, we also examined seed and root traits in seeds from different pod positions (stylar versus peduncular) and pod developmental times on the parent plant. Greenhouse, field, and seedling experiments were used to evaluate seed, seedling, and mature root traits in progeny from stressed and non-stressed parental conditions. In parental drought studies, progeny from drought stressed parents had lower individual seed weight, lower basal root number (BRN) in both seedlings and plants at growth stage R2, and lighter total seedling dry weight, shorter seedling basal roots, shorter lateral roots borne on seedling tap roots. The length and density of root hairs borne on seedling tap and basal roots also differed between progeny from parental drought and well-watered environments. At growth stage R2 progeny from parental drought had a smaller basal root diameter, lighter shoot dry weight, fewer shoot-borne roots, and fewer dominant shoot-borne roots. In parental phosphorus (P) studies, progeny from a low P parental environment had lower individual seed P content, fewer shoot-borne roots at R2, and greater BRWN at R2. In studies comparing root traits between seeds from the peduncular (closest to the petiole) versus stylar (farthest from the petiole) positions in the pod, and between seeds from early versus late developing pods, seeds from the peduncular position in the pod at growth stage R2 had lower individual seed weight, lower BRN, lighter root dry weight, smaller tap root diameter, and fewer lateral roots borne on basal roots. In all studies, responses to parental effects varied across genotypes. Seed and seedling root traits had greater consistency across genotypes compared to mature root traits, whereas stronger genotypic effects were seen in mature root traits. Seeds and seedlings showed more consistency in parental effects across genotypes likely due to the exposure to fewer environmental factors, resulting in less variability among measured traits. Overall, progeny from drought stressed parents, progeny from a low P parental environment, and seeds from the peduncular position within the pod had root traits that were lighter, shorter, smaller in diameter, or fewer in number. Parent plants grown under stressful conditions such as low P and drought during seed fill may have had less resources available to allocate into seeds during seed fill, relative to parent plants in well-watered and high fertility environments. Seeds from the peduncular position may have had root traits that were lighter, shorter, or smaller in diameter due to later fertilization within the pod compared to seeds from the stylar position. Thus, most differences in root traits from stressed parents or seeds from the peduncular position were likely explained by lower parental provisioning of seeds during seed fill. In addition to parental effects that suggest lower parental provisioning, possible adaptive parental effects were found in both parental drought and parental low P studies. Greater BRWN in progeny from P stressed parents may be adaptive to low P conditions by increasing the area of soil explored, assisting in potentially greater acquisition of P in low P soils. Longer basal roots in seedlings from parental drought may assist in greater exploration of deeper soil where water is more available under drought conditions. Results from this study may be used to help improve food security in developing nations by assisting the selection of genotypes that thrive in nutrient and water deprived soils in current and subsequent generations. This thesis demonstrated profound differences in root phenotypes in response to parental stress, seed position in the pod, and pod developmental time, depending on the genotype. Thus, the parental environment in which seeds are collected must be a factor that is considered in breeding programs and phenotyping initiatives. Genotypes displaying potential adaptations to stress in response to the previous generation should be considered in breeding programs, but genotypes displaying relatively greater reduction in provisioning of progeny in response to parental stress should be avoided.