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Fusarium wilt of banana is a devastating disease that has decimated banana production worldwide. Host resistance to Fusarium oxysporum f. sp. Cubense (Foc), the causal agent of this disease, is genetically dissected in this study using two Musa acuminata ssp. Malaccensis segregating populations, segregating for Foc Tropical (TR4) and Subtropical (STR4) race 4 resistance. Marker loci and trait association using 11 SNP-based PCR markers allowed the candidate region to be delimited to a 12.9 cM genetic interval corresponding to a 959 kb region on chromosome 3 of 'DH-Pahang' reference assembly v4. Within this region, there was a cluster of pattern recognition receptors, namely leucine-rich repeat ectodomain containing receptor-like protein kinases, cysteine-rich cell-wall-associated protein kinases, and leaf rust 10 disease-resistance locus receptor-like proteins, positioned in an interspersed arrangement. Their transcript levels were rapidly upregulated in the resistant progenies but not in the susceptible F2 progenies at the onset of infection. This suggests that one or several of these genes may control resistance at this locus. To confirm the segregation of single-gene resistance, we generated an inter-cross between the resistant parent 'Ma850' and a susceptible line 'Ma848', to show that the STR4 resistance co-segregated with marker '28820' at this locus. Finally, an informative SNP marker 29730 allowed the locus-specific resistance to be assessed in a collection of diploid and polyploid banana plants. Of the 60 lines screened, 22 lines were predicted to carry resistance at this locus, including lines known to be TR4-resistant, such as 'Pahang', 'SH-3362', 'SH-3217', 'Ma-ITC0250', and 'DH-Pahang/CIRAD 930'. Additional screening in the International Institute for Tropical Agriculture's collection suggests that the dominant allele is common among the elite 'Matooke' NARITA hybrids, as well as in other triploid or tetraploid hybrids derived from East African highland bananas. Fine mapping and candidate gene identification will allow characterization of molecular mechanisms underlying the TR4 resistance. The markers developed in this study can now aid the marker-assisted selection of TR4 resistance in breeding programs around the world. [ABSTRACT FROM AUTHOR]

Panama wilt, caused by Fusarium oxysporum f. sp. cubense (Foc) is considered one of the most devastating banana diseases in recorded history. The disease threatens the banana industry due to Tropical Race 4 (TR4) infecting the Cavendish cultivar. Forty-two of the 45 representative isolates from Luzon were pathogenic, based on leaf symptom index and vascular discoloration rating. Accurate, fast and reliable identification are pre-requisites for effective management considering there are yet no proven effective chemicals to control the disease, thus the confirmation by a PCR-based diagnostic tool is essential. Using race-specific primers, FocTr4-F/FocTr4-R and Foc-1/Foc-2, the absence of TR4 in Luzon has been confirmed, however, the occurrence of Race 4 has been reported, which should also be taken in consideration as the latter can also cause severe damage under favorable conditions. Furthermore, to examine genetic diversity of Foc in bananas, 55 of the 164 isolates collected from Regions I, II, III, IV and Cordillera Administrative Region (CAR) were analyzed by fingerprinting techniques using M13, ERIC and REP primers. Twenty-two reference isolates from Mindanao were also analyzed using the same primers. Foc isolates were differentiated into two clades at 25% similarity level, classifying all Mindanao isolates to clade A. Consistently high genetic variation was obtained from Luzon isolates using M13, an arbitrarily primed fingerprinting technique and repetitive elements, REP and ERIC-PCR, while low genetic variation was obtained from Mindanao isolates. ERIC-PCR was the most informative and predictive fingerprinting method as the TR4 isolates from Mindanao were grouped together. No grouping of Foc isolates was observed with respect to geographical origin, except isolates from Mindanao. In addition, grouping of Foc4 is also regardless of host variety in all analyses conducted. Overall, high genetic variability was recorded in Foc Philippine population for the three primers used, which might render host resistance vulnerable.

Panama wilt, caused by Fusarium oxysporum f. sp. cubense (Foc) is considered one of the most devastating banana diseases in recorded history. The disease threatens the banana industry due to Tropical Race 4 (TR4) infecting the Cavendish cultivar. Forty-two of the 45 representative isolates from Luzon were pathogenic, based on leaf symptom index and vascular discoloration rating. Accurate, fast and reliable identification are pre-requisites for effective management considering there are yet no proven effective chemicals to control the disease, thus the confirmation by a PCR-based diagnostic tool is essential. Using race-specific primers, FocTr4-F/FocTr4-R and Foc-1/Foc-2, the absence of TR4 in Luzon has been confirmed, however, the occurrence of Race 4 has been reported, which should also be taken in consideration as the latter can also cause severe damage under favorable conditions. Furthermore, to examine genetic diversity of Foc in bananas, 55 of the 164 isolates collected from Regions I, II, III, IV and Cordillera Administrative Region (CAR) were analyzed by fingerprinting techniques using M13, ERIC and REP primers. Twenty-two reference isolates from Mindanao were also analyzed using the same primers. Foc isolates were differentiated into two clades at 25% similarity level, classifying all Mindanao isolates to clade A. Consistently high genetic variation was obtained from Luzon isolates using M13, an arbitrarily primed fingerprinting technique and repetitive elements, REP and ERIC-PCR, while low genetic variation was obtained from Mindanao isolates. ERIC-PCR was the most informative and predictive fingerprinting method as the TR4 isolates from Mindanao were grouped together. No grouping of Foc isolates was observed with respect to geographical origin, except isolates from Mindanao. In addition, grouping of Foc4 is also regardless of host variety in all analyses conducted. Overall, high genetic variability was recorded in Foc Philippine population for the three primers used, which might render host resistance vulnerable. [ABSTRACT FROM AUTHOR]