Aspectos ecofisiológicos y moleculares de la incorporación de las características hoja lanceolada y alto porcentaje de vainas de cuatro semillas a germoplasma elite de soja
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2018
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El rendimiento del cultivo de soja es función del número de semillas por unidad de
superficie (NSS) y del peso unitario de las semillas. El componente más asociado con el
rendimiento es el NSS, el cual depende a su vez del número de vainas por unidad de
superficie y del número promedio de semillas por vaina (NPSV). Existen evidencias que
sugieren que la radiación fotomorfogénica, especialmente la relación rojo/rojo lejano R/RL,
participaría de la regulación del número de vainas en canopeos de soja. La radiación
fotomorfogénica es muy afectada por cambios en la arquitectura del canopeo. La estructura
de un canopeo puede modificarse por las prácticas de manejo o genéticamente a través de
caracteres morfológicos como la forma de los folíolos. Canopeos de folíolos lanceolados
permiten que la luz penetre hasta estratos más profundos en comparación con canopeos de
folíolos oblongos. A su vez, genotipos con forma de hoja lanceolada tienden a tener mayor
NPSV (debido a la presencia de una mayor frecuencia de vainas con cuatro semillas) en
relación a genotipos con forma de hoja oblonga.
El objetivo de la presente Tesis fue estudiar aspectos ecofisiológicos y moleculares
de la incorporación de las características hoja lanceolada y alto porcentaje de vainas de
cuatro semillas a germoplasma elite de soja. En los experimentos ecofisiológicos se
utilizaron pares de isolíneas que diferían en la morfología foliar y en el NPSV sembradas en
dos densidades. Canopeos con hojas lanceoladas presentaron mayor relación R/RL en su
interior en relación a canopeos con hojas oblongas. El número de vainas estuvo asociado en
forma lineal y directa con la relación R/RL; no presentó asociación con la TCCR2-R5, y mostró
una relación inversa con el índice de área foliar y con el porcentaje de radiación
interceptada. Estos resultados soportan la hipótesis de que la regulación del número de
estructuras reproductivas en canopeos de soja responde a estímulos fotomorfogénicos. Por
otra parte, incrementos en el porcentaje de vainas de cuatro semillas y por consiguiente, del
NPSV aumentó en forma directa el NSS.
Para el estudio genético y molecular se obtuvieron poblaciones segregantes y líneas
endocriadas recombinantes. Respecto del carácter forma de hoja lanceolada, se corroboró
que el gen que regula dicha característica en los parentales utilizados es un alelo del gen ln,
localizado en el grupo de ligamiento molecular (GLM) I de la soja. Además, se validaron y se
encontraron nuevos marcadores microsatélites estrechamente ligados a dicho gen en un
contexto genético de buen comportamiento agronómico. Respecto del carácter alto
porcentaje de vainas de cuatro semillas, evaluado a través del NPSV, se identificaron
cuatro QTLs estables, con efecto mayor que explican una alta proporción de la variabilidad
fenotípica observada para dicho carácter en los GLM F, L e I. Los marcadores microsatélites
ligados a hoja lanceolada y a alto porcentaje de vainas de cuatro semillas permitirán, en
caso de ser validados, disponer de herramientas moleculares para facilitar la introgresión
rápida de ambos caracteres a germoplasma elite de soja.
Soybean seed yield is function of seed number (per unit land area, SN) and seed size. Seed yield is highly associated with SN. SN is the result of pod number times seeds per pod (SPP). Evidences suggests that photomorphogenic radiation, especially red/far red (R/FR) ratio, could regulate the SN in soybean canopies. Photomorphogenic radiations are affected by changes in canopy structure. Canopy structure is modified by management practices or by morphological traits as leaflet shape. Lanceolate leaflet leaves genotypes (L) allowed better light penetration into deeper strata of the canopy compare to ovate leaflet leaves genotypes (O). Moreover, L tend to have more SPP than O, due to an increase in the four-seeded pods frequency. The aim of this thesis was to study the ecophysiological and molecular features of introgressing the traits lanceolate leaflet and high number of four-seeded pods into soybean elite germplasm, and their contribution to crop improvement. For the ecophysiological study, the effect of different canopy structures on SN were evaluated using isolines differing in leaf shape (L and O) and seed per pod, sown in two densities. Results show that L canopies had higher R/FR ratio than O canopies. Moreover, a linear and direct association between R/FR ratio with the pod number was observed. On the contrary, no association of these components with CGRR2-R5 was found. These results support the hypothesis that the regulation of the pod number in soybean canopies respond to photomorphogenic stimuli. Also, increase in four-seeded pods directly improved SN. Segregant populations and recombinant inbred lines (RILs) populations were used for the molecular approach. For the L parental genotypes, an ln gene allele, located in soybean molecular linkage group (MLG) I was verified as the gene that control the trait. Besides, new microsatellite markers tightly linked to the gene controlling this trait were found and validated in a genetic background of good agronomic performance. Regarding the four-seeded pods trait, four genomic regions (QTLs) that explained a high proportion of the phenotypic variance located in MLG F, L and I were identified. Molecular markers linked to lanceolate leaf shape and high four seed per pod frequency (high SPP) could be used as a tool to introgression both traits in soybean elite germoplasm.
Soybean seed yield is function of seed number (per unit land area, SN) and seed size. Seed yield is highly associated with SN. SN is the result of pod number times seeds per pod (SPP). Evidences suggests that photomorphogenic radiation, especially red/far red (R/FR) ratio, could regulate the SN in soybean canopies. Photomorphogenic radiations are affected by changes in canopy structure. Canopy structure is modified by management practices or by morphological traits as leaflet shape. Lanceolate leaflet leaves genotypes (L) allowed better light penetration into deeper strata of the canopy compare to ovate leaflet leaves genotypes (O). Moreover, L tend to have more SPP than O, due to an increase in the four-seeded pods frequency. The aim of this thesis was to study the ecophysiological and molecular features of introgressing the traits lanceolate leaflet and high number of four-seeded pods into soybean elite germplasm, and their contribution to crop improvement. For the ecophysiological study, the effect of different canopy structures on SN were evaluated using isolines differing in leaf shape (L and O) and seed per pod, sown in two densities. Results show that L canopies had higher R/FR ratio than O canopies. Moreover, a linear and direct association between R/FR ratio with the pod number was observed. On the contrary, no association of these components with CGRR2-R5 was found. These results support the hypothesis that the regulation of the pod number in soybean canopies respond to photomorphogenic stimuli. Also, increase in four-seeded pods directly improved SN. Segregant populations and recombinant inbred lines (RILs) populations were used for the molecular approach. For the L parental genotypes, an ln gene allele, located in soybean molecular linkage group (MLG) I was verified as the gene that control the trait. Besides, new microsatellite markers tightly linked to the gene controlling this trait were found and validated in a genetic background of good agronomic performance. Regarding the four-seeded pods trait, four genomic regions (QTLs) that explained a high proportion of the phenotypic variance located in MLG F, L and I were identified. Molecular markers linked to lanceolate leaf shape and high four seed per pod frequency (high SPP) could be used as a tool to introgression both traits in soybean elite germoplasm.
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Keywords
Rendimiento de cultivos, Soja, Canopeo, Hoja lanceolada, Vainas, Germoplasma