Physico-chemical changes in “Xiem” banana cultivar (cultivated in Vietnam) during ripening and storage at different temperatures

There are changes in chemical and physical characteristics involved in the ripening of bananas. This study evaluated the changes in physico-chemical and nutritional characteristics of the "Xiêm" banana cultivar at the harvesting (unripe fruit) and ripe stages (ripe fruit). As the pulp to peel ratio and titrable acidity increased, the firmness decreased with an increase in ripening time. A significant increase in total polyphenol content and decrease in beta-carotene and vitamin C content was observed at climacteric peak during ripening. During ripening, the banana peel colour changed from green to yellow, the pulp softened, the flavour develops, and the moisture is lost. "Xiem" banana variety was fully mature after 7 and 22 days of storage at 28-30oC and 13-15oC, respectively. The correlation between various stages of ripeness and these properties were determined and the correlation coefficients were calculated. A very high coefficient of determination (r2 >0.937) was recorded between physical properties (pulp firmness/peel colour) and chemical properties (starch/sugar) of banana fruit with the stage of ripeness.

Standardization of surface sterilization protocols for culture establishment in banana cv. Karpurachakkarakeli(AAB) male flower budsin vitro

Plant tissue culture is a proven technique for producing banana seeds in large quantities, uniformly and in a short time to support good quality banana seeds. The banana flower meristem can be a potential explant. The banana flower meristem offers the opportunity to regenerate plants with agronomic characteristics. This study aimed to regenerate banana flowers in vitro with different sucrose and BA (Benzyladenine) concentrations after standardized surface sterilization protocols. The study used a Completely Randomized Design (CRD), two factorial designwith surface sterilents and gelling agents. The results showed that the treatmentT15 (Sodium hypochlorite (1%) + HgCl2 (0.1%)) in G1 (0.25% gelrite) recorded the lowest fungal and bacterial contamination (0.00, 0.00) & (0.73, 0.53) respectively, in in vitro cultures of male flower buds of banana cultivar KarpuraChakkarakeli (AAB). While, the combination of BA (4 mgL-1) and sucrose (30 mgL-1) concentration had directly induced organogenesis in banana male flower explants.

Banana Cultivar Field Screening for Resistance to Fusarium oxysporum f.sp. cubense Tropical Race 4 in the Northern Territory

Fusarium oxysporum f.sp. cubense, causal agent of Panama disease, is one of the biggest threats to global banana production, particularly the Cavendish competent tropical race 4 (Foc TR4). It continues to spread globally with detections occurring in regions of the Middle East and new continents such as Africa and South America in the last decade. As the search was on for new management strategies and resistant cultivars to combat the disease, a banana cultivar-screening trial took place in the Northern Territory of Australia, which examined the responses of 24 banana cultivars to the soil borne fungus. These cultivars included material from TBRI, FHIA and selections from Thailand, Indonesia and Australia and evaluated for their resistance to tropical race 4 for two cropping cycles. Several cultivars displayed considerable resistance to Foc TR4, including several FHIA parental lines and hybrids, the Cavendish (AAA) selections GCTCV 215 and GCTCV 247 from TBRI and an Indonesian selection CJ19 showed either very little to no plant death due to the disease.

Comparative transcriptome analysis of unripe and ripe banana (cv. Nendran) unraveling genes involved in ripening and other related processes

Banana is one of the most important fruit crops consumed globally owing to its high nutritional value. Previously, we demonstrated that the ripe pulp of the banana cultivar (cv.) Nendran (AAB) contained a high amount of pro-vitamin A carotenoids. However, the molecular factors involved in the ripening process in Nendran fruit are unexplored. Hence, we commenced a transcriptome study by using the Illumina HiSeq 2500 at two stages i.e. unripe and ripe fruit-pulp of Nendran. Overall, 3474 up and 4727 down-regulated genes were obtained. A large number of identified transcripts were related to genes involved in ripening, cell wall degradation and aroma formation. Gene ontology analysis highlighted differentially expressed genes that play a key role in various pathways. These pathways were mainly linked to cellular, molecular and biological processes. The present transcriptome study also reveals a crucial role of up-regulated carotenoid biosynthesis pathway genes namely, lycopene beta cyclase and geranylgeranyl pyrophosphate synthase at the ripening stage. Genes related to the ripening and other processes like aroma and flavor were highly expressed in the ripe pulp. Expression of numerous transcription factor family genes was also identified. This study lays a path towards understanding the ripening, carotenoid accumulation and other related processes in banana.

Magnesium may be a key nutrient mechanism related to Fusarium wilt resistance: a new banana cultivar (Zhongjiao No. 9)

Zhongjiao No. 9 (Musa spp.), a new Fusarium wilt-resistant banana cultivar, has shown considerable promise in the field. However, the growth, nutrient budgets, and key nutrient mechanisms related to Fusarium wilt resistance have not been explicitly examined. Here, the plant growth, yield, fruit quality, and nutrient budgets of Zhongjiao No. 9 were investigated. The results showed that Zhongjiao No. 9 has a large biomass with a high yield (54.65 t ha−1). The concentrations of N, P, K, Ca, Mg, Mn, B, and Mo were mainly high in the leaves and bunches of mother plants as well as in the leaves and pseudostems of daughter plants, while Cu and Fe were enriched in the roots of both mother plants and daughter plants. Linear discriminant analysis revealed that K, Ca, and Fe were important for plant growth in both the mother plants and daughter plants; S, Zn, and Mn were important for the mother plants, and N, P, and B for were important for the daughter plants. The nutrient uptake ratio of N:P:K:Ca:Mg:S was 1:0.13:3.86:0.68:0.40:0.07. Compared with local cultivars, there was a higher Mg concentration in pseudostems and a higher Mg uptake ratio were observed in Zhongjiao No. 9. Together, our results provide insight into the importance of Mg accumulation in relation to Fusarium wilt resistance, and we provide information on nutrient demands and fertilization application.

Identification of MaWRKY40 and MaDLO1 as effective marker genes for tracking the salicylic acid-mediated immune response in bananas

Bananas lie among the world’s most important cash and staple crops but are threatened by various devastating pathogens. The phytohormone salicylic acid (SA) plays a key role in the regulation of plant immune response. Tracking the expression of SA-responsive marker genes under pathogen infection is important in pathogenesis elucidation. However, the common SA-responsive marker genes are not consistently induced in different banana cultivars or different organs. Here, we conducted transcriptome analysis for SA response of a banana cultivar, ‘Pei-Chiao’ (Cavendish, AAA genome), and identified three genes, MaWRKY40, MaWRKY70, and Downy Mildew Resistant 6 (DMR6)-Like Oxygenase 1 (MaDLO1) that are robustly induced upon SA treatment in both the leaves and roots. Consistent induction of these three genes by SA treatment was also detected in both the leaves and roots of bananas belonging to different genome types such as ‘Tai-Chiao No. 7’ (Cavendish, AAA genome), ‘Pisang Awak’ (ABB genome), and ‘Lady Finger’ (AA genome). Furthermore, the biotrophic pathogen cucumber mosaic virus elicited the expression of MaWRKY40 and MaDLO1 in infected-leaves of susceptible cultivars. The hemi-biotrophic fungal pathogen Fusarium oxysporum f. sp. cubense tropical race 4 (Foc TR4) also consistently induced the expression of MaWRKY40 and MaDLO1 in the infected-roots of the Foc TR4-resistant cultivar. These results indicate that MaWRKY40 and MaDLO1 can serve as reliable SA-responsive marker genes for the study of plant immunity in banana. Revealing SA-responsive marker genes provides a stepping-stone for further studies in banana resistance to pathogens.

In Vitro Shoot Induction of Musa acuminata cv. Mas Kirana

The availability of �mother plants� used for source of explants is one of the most important limitations for the development of in vitro culture in new banana cultivar�s. To increase produce large quantities of uniform and healthy seedlings, induction of multiplication has been carried out on Musa acuminata cv. Mas Kirana. Plant regeneration were obtained by culturing sucker on MS medium supplemented with PGRs BAP and NAA (1 mg/l + 0.5 mg/l, 2 mg/l + 0.5 mg/l, and 3 mg/l + 0.5 mg/l) and TDZ (0.25 mg/l, 0.5 mg/l, and 0.75 mg/l). The highest shoot formation was found in 0.25 mg/l TDZ with average shoots of 13.67 � 3.16 and primary shoot height is 20 cm. TDZ induction tends to form somatic embryos, while induction of BAP and NAA leads to organogenesis. The rate of contaminants occurrence from bacteria is 87.50% and 12.50% from fungus. In histological observation, TDZ, BAP, and NAA affect the development of many new meristematic zones seen in the scalps.