Banca de QUALIFICAÇÃO: MARIANA CAROLINE GUIMARÃES XAVIER

Uma banca de QUALIFICAÇÃO de DOUTORADO foi cadastrada pelo programa.
STUDENT : MARIANA CAROLINE GUIMARÃES XAVIER
DATE: 28/04/2025
TIME: 14:00
LOCAL: Webconferência
TITLE:

Pollen viability and anther culture in hybrids obtained from crossing red and white rice genotypes

KEY WORDS:

Oryza sativa L., hybridization, palynology.

PAGES: 38
BIG AREA: Ciências Agrárias
AREA: Agronomia
SUBÁREA: Fitotecnia
SPECIALTY: Melhoramento Vegetal
SUMMARY:

Biotic and abiotic stresses in different periods of reproductive growth have detrimental effects on rice (Oryza sativa L.) productivity, mainly by reducing pollen viability, spikelet fertility and grain filling percentage. In plant breeding programs, in vitro cultivation technology is important for the production of lines. Anther culture is a technique used in several crops to produce homozygous plants in a short period of time. However, rice has characteristics that affect androgenesis, and the success of this technique depends on several factors such as genotype, conditions of the pollen donor plant, microspore development stage and in vitro cultivation conditions. In addition, the development of new hybrid cultivars is a challenge that requires assertive strategies and methodologies in order to obtain promising results. Therefore, the objective of this study will be to analyze pollen viability, via colorimetric and pollen tube germination tests, as well as its palynological characterization. After this characterization, define, for the in vitro cultivation of anthers, responsive protocols for the induction of callus and regeneration of plants from hybrids obtained from the crossing between white and red rice genotypes. The genotypes used will be three parents (one cultivar of white rice (BRS Esmeralda) and two of red rice (ENA 1601 and ‘Vermelho Virgínia’) and two hybrid combinations between the genotypes BRS Esmeralda x ENA1601 and BRS Esmeralda x ‘Vermelho Virgínia’). The palynological characterization will be performed through microscopic observation of preserved pollen grains of the genotypes to describe the morphology and dimensions of the pollen grains. The pollen grains will be subjected to the acetolysis process, and subsequently, 25 measurements of each pollen characteristic will be taken. Characteristics such as size, shape and type of opening will be evaluated, based on previously established parameters. In the analysis of pollen viability, collections will be carried out between 10:30 am and 4:30 pm, with an interval of one and a half hours between collections. Pollen viability will be determined by colorimetric techniques, using dyes Lugol, acetic carmine and Alexander. Eight slides per genotype will be prepared, counting 250 pollen grains per slide; the pollen grains will be classified as viable or nonviable. Three culture media will be used to assess in vitro viability: the culture medium adapted from Krishnamurthi, Traub & O’Rork and that from Cohen et al. (1989). After the incubation period, pollen grains will be stained and pollen that shows a pollen tube emission longer than the diameter of the pollen itself will be considered germinated. In the second stage, 50 anthers will be excised and inoculated into Petri dishes containing N6 culture medium supplemented with growth regulators (2,4-D, ANA and CIN), kept in a dark room for 40 days at 25 ± 1°C. A completely randomized design will be used, with 5 genotypes and 10 replicates each. Callus formation will be evaluated at 10, 20, 30 and 40 days. Callus with diameter ≥ 2 mm will be transferred to enriched MS medium, under controlled conditions of photoperiod and temperature, for plant regeneration. After 30 days of root development in semi-solid MS medium, the regenerated plants will be kept for 15 days in the growth room, supplemented with diluted MS nutrient solution and then acclimated in a greenhouse, remaining until the end of the cycle. Evaluations will include frequency of callus formation, viable callus and regeneration of green or albino plants. Pollen viability means will be subjected to analysis of variance (ANOVA) and compared by Tukey's test at 5% significance. For anther culture, percentage data will be subjected to analysis of variance (ANOVA). Means will be compared by Tukey's test at 5% significance.

COMMITTEE MEMBERS:
Presidente - 2271445 - BRUNA RAFAELA DA SILVA MENEZES
Externa ao Programa - 2147409 - MARILENE HILMA DOS SANTOS - UFRRJExterna ao Programa - 1604274 - SHARON SANTOS DE LIMA - UFRRJ