ABSTRACT
BRS Caipira variety, internationally known as 'Yangambi km 5', is an alternative to meet the demand of 'Maçã'-type fruit due to its resistance to Panama disease. This study had the objective of generating information about 'BRS Caipira' fruit ripening and cold storage potential. For the ripening study fruits were stored under room temperature conditions (25±2°C / 58±6% U.R.) and assessed for postharvest life evaluation and characterization of seven maturity stages based on peel color: completely green - MS1; green with yellow traces - MS2; more green than yellow - MS3; more yellow than green - MS4; yellow with green tips - MS5; completely yellow - MS6; yellow with brown spots - MS7. For the cold storage potential study, fruits at MS1 were cold stored (14±1°C / 53±2% U.R.) for 28 days. Weekly, fruits were transferred to room temperature to ripen until MS6 when were assessed for quality attributes. Ripening of 'BRS Caipira' fruit was characterized as slow between MS1 and MS2 (averaging five days), then fast between MS2 and MS6 (up to four days in average), and undergoing determinant changes between MS6 and MS7: pulp yield reached 80%, titratable acidity reduced by 50% and ratio increased by 78%. Cold storage extended shelf life by up to 19 days as compared with control, without visible symptoms of chilling injury, although tends to reduce soluble solids in ripe fruit. Maximum recommended time for storage of 'BRS Caipira' fruit at 14°C is 21 days, since it allows a few more days under room temperature until fruit reach MS6.
A variedade BRS Caipira, internacionalmente conhecida como 'Yangambi km 5', é uma alternativa para atender a demanda de frutos do tipo Maçã, devido à sua resistência ao mal-do-Panamá. Este estudo objetivou gerar informações sobre o amadurecimento e o potencial de armazenamento refrigerado de frutos de 'BRS Caipira'. Para o estudo do amadurecimento, frutos foram armazenados sob temperatura ambiente (25±2°C / 58±6% U.R.) e avaliados para vida pós-colheita e caracterização de sete estádios de maturação baseados na cor da casca: completamente verde - MS1; verde com traços amarelos - MS2; mais verde que amarelo - MS3; mais amarelo que verde - MS4; amarelo com pontas verdes - MS5; completamente amarelo - MS6; amarelo com manchas marrons - MS7. Para o estudo de potencial de armazenamento refrigerado, frutos em MS1 foram armazenados em câmara fria (14±1°C / 53±2% U.R.) por 28 dias. Semanalmente, uma amostra de frutos era retirada para a temperatura ambiente e avaliados para atributos de qualidade. O amadurecimento de frutos de 'BRS Caipira' foi caracterizado como lento entre MS1 e MS2 (cinco dias em média), rápido entre MS2 e MS6 (até quatro dias em média), e que passa por alterações determinantes entre MS6 e MS7: rendimento em polpa atingiu 80%; acidez reduziu pela metade; e ratio aumentou 78%. A refrigeração prolongou a vida útil dos frutos em até 19 dias em relação ao controle, sem sintomas visíveis de danos por frio, embora tenda a reduzir o teor de sólidos solúveis nos frutos maduros. O período máximo recomendado para armazenagem de frutos de 'BRS Caipira' a 14°C é de 21 dias, tempo que permitiria mais alguns dias em temperatura ambiente para os frutos atingirem o estádio MS6.
ABSTRACT
Activity differences of the first (phenylalanine ammonia lyase, PAL) and the last (cinnamyl alcohol dehydrogenase, CAD) enzymes of phenylpropanoid pathway in the roots of resistant (Yangambi Km5 and Anaikomban) and susceptible (Nendran and Robusta) banana cultivars caused by root lesion nematode, Pratylenchus coffeae, were investigated. Also, the accumulation of phenolics and deposition of lignin polymers in cell walls in relation to resistance of the banana cultivars to the nematode were analyzed. Compared to the susceptible cultivars, the resistant cultivars had constitutively significantly higher PAL activity and total soluble and cell wall-bound phenolics than in susceptible cultivars. The resistant cultivars responded strongly to the infection of the nematode by induction of several-time higher PAL and CAD enzymes activities, soluble and wall-bound phenolics and enrichment of lignin polymers in cell wall and these biochemical parameters reached maximum at 7th day postinoculation. In addition, profiles of phenolic acid metabolites in roots of Yangambi Km5 and Nendran were analyzed by HPLC to ascertain the underlying biochemical mechanism of bananas resistance to the nematode. Identification and quantification of soluble and cell wall-bound phenolic acids showed six metabolites and only quantitative, no qualitative, differences occurred between the resistant and susceptible cvs. and between constitutive and induced contents. A very prominent increase of p-coumaric, ferulic and sinapic acids, which are precursors of monolignols of lignin, in resistant cv. was found. These constitutive and induced biochemical alterations are definitely the chemical defenses of resistant cvs. to the nematode infection.